75 files changed, 1632 insertions, 1062 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 74e5a8273..49022502d 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -82,9 +82,9 @@ checksum = "cdb031dd78e28731d87d56cc8ffef4a8f36ca26c38fe2de700543e627f8a464a"
 
 [[package]]
 name = "backtrace"
-version = "0.3.50"
+version = "0.3.51"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "46254cf2fdcdf1badb5934448c1bcbe046a56537b3987d96c51a7afc5d03f293"
+checksum = "ec1931848a574faa8f7c71a12ea00453ff5effbb5f51afe7f77d7a48cace6ac1"
 dependencies = [
  "addr2line",
  "cfg-if",
@@ -214,9 +214,9 @@ dependencies = [
 
 [[package]]
 name = "chrono"
-version = "0.4.18"
+version = "0.4.19"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d021fddb7bd3e734370acfa4a83f34095571d8570c039f1420d77540f68d5772"
+checksum = "670ad68c9088c2a963aaa298cb369688cf3f9465ce5e2d4ca10e6e0098a1ce73"
 dependencies = [
  "libc",
  "num-integer",
@@ -365,9 +365,9 @@ checksum = "37ab347416e802de484e4d03c7316c48f1ecb56574dfd4a46a80f173ce1de04d"
 
 [[package]]
 name = "flate2"
-version = "1.0.17"
+version = "1.0.18"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "766d0e77a2c1502169d4a93ff3b8c15a71fd946cd0126309752104e5f3c46d94"
+checksum = "da80be589a72651dcda34d8b35bcdc9b7254ad06325611074d9cc0fbb19f60ee"
 dependencies = [
  "cfg-if",
  "crc32fast",
@@ -453,9 +453,9 @@ dependencies = [
 
 [[package]]
 name = "hashbrown"
-version = "0.9.0"
+version = "0.9.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "00d63df3d41950fb462ed38308eea019113ad1508da725bbedcd0fa5a85ef5f7"
+checksum = "d7afe4a420e3fe79967a00898cc1f4db7c8a49a9333a29f8a4bd76a253d5cd04"
 
 [[package]]
 name = "heck"
@@ -725,9 +725,9 @@ checksum = "830d08ce1d1d941e6b30645f1a0eb5643013d835ce3779a5fc208261dbe10f55"
 
 [[package]]
 name = "libc"
-version = "0.2.77"
+version = "0.2.78"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f2f96b10ec2560088a8e76961b00d47107b3a625fecb76dedb29ee7ccbf98235"
+checksum = "aa7087f49d294270db4e1928fc110c976cd4b9e5a16348e0a1df09afa99e6c98"
 
 [[package]]
 name = "libloading"
@@ -1070,6 +1070,12 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "28b9b4df73455c861d7cbf8be42f01d3b373ed7f02e378d55fa84eafc6f638b1"
 
 [[package]]
+name = "pin-project-lite"
+version = "0.1.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e555d9e657502182ac97b539fb3dae8b79cda19e3e4f8ffb5e8de4f18df93c95"
+
+[[package]]
 name = "plain"
 version = "0.2.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -1077,9 +1083,9 @@ checksum = "b4596b6d070b27117e987119b4dac604f3c58cfb0b191112e24771b2faeac1a6"
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.23"
+version = "1.0.24"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "51ef7cd2518ead700af67bf9d1a658d90b6037d77110fd9c0445429d0ba1c6c9"
+checksum = "1e0704ee1a7e00d7bb417d0770ea303c1bccbabf0ef1667dae92b5967f5f8a71"
 dependencies = [
  "unicode-xid",
 ]
@@ -1180,9 +1186,9 @@ dependencies = [
 
 [[package]]
 name = "rayon"
-version = "1.4.0"
+version = "1.4.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cfd016f0c045ad38b5251be2c9c0ab806917f82da4d36b2a327e5166adad9270"
+checksum = "dcf6960dc9a5b4ee8d3e4c5787b4a112a8818e0290a42ff664ad60692fdf2032"
 dependencies = [
  "autocfg",
  "crossbeam-deque",
@@ -1294,9 +1300,9 @@ dependencies = [
 
 [[package]]
 name = "rustc-ap-rustc_lexer"
-version = "673.0.0"
+version = "681.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f6b71fa1285bdefe5fb61e59b63d6cc246abf337f4acafdd620d721bc488e671"
+checksum = "01e579a90506e9d9c9a098f380cad55b9ecf9e7be9fa96cb67b31f52045f41a8"
 dependencies = [
  "unicode-xid",
 ]
@@ -1427,9 +1433,9 @@ dependencies = [
 
 [[package]]
 name = "serde_json"
-version = "1.0.57"
+version = "1.0.58"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "164eacbdb13512ec2745fb09d51fd5b22b0d65ed294a1dcf7285a360c80a675c"
+checksum = "a230ea9107ca2220eea9d46de97eddcb04cd00e92d13dda78e478dd33fa82bd4"
 dependencies = [
  "itoa",
  "ryu",
@@ -1623,11 +1629,12 @@ dependencies = [
 
 [[package]]
 name = "tracing"
-version = "0.1.19"
+version = "0.1.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6d79ca061b032d6ce30c660fded31189ca0b9922bf483cd70759f13a2d86786c"
+checksum = "b0987850db3733619253fe60e17cb59b82d37c7e6c0236bb81e4d6b87c879f27"
 dependencies = [
  "cfg-if",
+ "pin-project-lite",
  "tracing-attributes",
  "tracing-core",
 ]
@@ -1645,9 +1652,9 @@ dependencies = [
 
 [[package]]
 name = "tracing-core"
-version = "0.1.16"
+version = "0.1.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5bcf46c1f1f06aeea2d6b81f3c863d0930a596c86ad1920d4e5bad6dd1d7119a"
+checksum = "f50de3927f93d202783f4513cda820ab47ef17f624b03c096e86ef00c67e6b5f"
 dependencies = [
  "lazy_static",
 ]
@@ -1696,9 +1703,9 @@ dependencies = [
 
 [[package]]
 name = "tracing-tree"
-version = "0.1.5"
+version = "0.1.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e1a3dc4774db3a6b2d66a4f8d8de670e874ec3ed55615860c994927419b32c5f"
+checksum = "43aac8afb493b08e1e1904956f7407c1e671b9c83b26a17e1bd83d6a3520e350"
 dependencies = [
  "ansi_term",
  "atty",
diff --git a/crates/assists/src/ast_transform.rs b/crates/assists/src/ast_transform.rs
index 835da3bb2..4307e0191 100644
--- a/crates/assists/src/ast_transform.rs
+++ b/crates/assists/src/ast_transform.rs
@@ -5,12 +5,13 @@ use hir::{HirDisplay, PathResolution, SemanticsScope};
 use syntax::{
     algo::SyntaxRewriter,
     ast::{self, AstNode},
+    SyntaxNode,
 };
 
 pub fn apply<'a, N: AstNode>(transformer: &dyn AstTransform<'a>, node: N) -> N {
     SyntaxRewriter::from_fn(|element| match element {
         syntax::SyntaxElement::Node(n) => {
-            let replacement = transformer.get_substitution(&n)?;
+            let replacement = transformer.get_substitution(&n, transformer)?;
             Some(replacement.into())
         }
         _ => None,
@@ -47,32 +48,35 @@ pub fn apply<'a, N: AstNode>(transformer: &dyn AstTransform<'a>, node: N) -> N {
 /// We'd want to somehow express this concept simpler, but so far nobody got to
 /// simplifying this!
 pub trait AstTransform<'a> {
-    fn get_substitution(&self, node: &syntax::SyntaxNode) -> Option<syntax::SyntaxNode>;
+    fn get_substitution(
+        &self,
+        node: &SyntaxNode,
+        recur: &dyn AstTransform<'a>,
+    ) -> Option<SyntaxNode>;
 
-    fn chain_before(self, other: Box<dyn AstTransform<'a> + 'a>) -> Box<dyn AstTransform<'a> + 'a>;
     fn or<T: AstTransform<'a> + 'a>(self, other: T) -> Box<dyn AstTransform<'a> + 'a>
     where
         Self: Sized + 'a,
     {
-        self.chain_before(Box::new(other))
+        Box::new(Or(Box::new(self), Box::new(other)))
     }
 }
 
-struct NullTransformer;
+struct Or<'a>(Box<dyn AstTransform<'a> + 'a>, Box<dyn AstTransform<'a> + 'a>);
 
-impl<'a> AstTransform<'a> for NullTransformer {
-    fn get_substitution(&self, _node: &syntax::SyntaxNode) -> Option<syntax::SyntaxNode> {
-        None
-    }
-    fn chain_before(self, other: Box<dyn AstTransform<'a> + 'a>) -> Box<dyn AstTransform<'a> + 'a> {
-        other
+impl<'a> AstTransform<'a> for Or<'a> {
+    fn get_substitution(
+        &self,
+        node: &SyntaxNode,
+        recur: &dyn AstTransform<'a>,
+    ) -> Option<SyntaxNode> {
+        self.0.get_substitution(node, recur).or_else(|| self.1.get_substitution(node, recur))
     }
 }
 
 pub struct SubstituteTypeParams<'a> {
     source_scope: &'a SemanticsScope<'a>,
     substs: FxHashMap<hir::TypeParam, ast::Type>,
-    previous: Box<dyn AstTransform<'a> + 'a>,
 }
 
 impl<'a> SubstituteTypeParams<'a> {
@@ -111,11 +115,7 @@ impl<'a> SubstituteTypeParams<'a> {
                 }
             })
             .collect();
-        return SubstituteTypeParams {
-            source_scope,
-            substs: substs_by_param,
-            previous: Box::new(NullTransformer),
-        };
+        return SubstituteTypeParams { source_scope, substs: substs_by_param };
 
         // FIXME: It would probably be nicer if we could get this via HIR (i.e. get the
         // trait ref, and then go from the types in the substs back to the syntax).
@@ -140,7 +140,14 @@ impl<'a> SubstituteTypeParams<'a> {
             Some(result)
         }
     }
-    fn get_substitution_inner(&self, node: &syntax::SyntaxNode) -> Option<syntax::SyntaxNode> {
+}
+
+impl<'a> AstTransform<'a> for SubstituteTypeParams<'a> {
+    fn get_substitution(
+        &self,
+        node: &SyntaxNode,
+        _recur: &dyn AstTransform<'a>,
+    ) -> Option<SyntaxNode> {
         let type_ref = ast::Type::cast(node.clone())?;
         let path = match &type_ref {
             ast::Type::PathType(path_type) => path_type.path()?,
@@ -154,27 +161,23 @@ impl<'a> SubstituteTypeParams<'a> {
     }
 }
 
-impl<'a> AstTransform<'a> for SubstituteTypeParams<'a> {
-    fn get_substitution(&self, node: &syntax::SyntaxNode) -> Option<syntax::SyntaxNode> {
-        self.get_substitution_inner(node).or_else(|| self.previous.get_substitution(node))
-    }
-    fn chain_before(self, other: Box<dyn AstTransform<'a> + 'a>) -> Box<dyn AstTransform<'a> + 'a> {
-        Box::new(SubstituteTypeParams { previous: other, ..self })
-    }
-}
-
 pub struct QualifyPaths<'a> {
     target_scope: &'a SemanticsScope<'a>,
     source_scope: &'a SemanticsScope<'a>,
-    previous: Box<dyn AstTransform<'a> + 'a>,
 }
 
 impl<'a> QualifyPaths<'a> {
     pub fn new(target_scope: &'a SemanticsScope<'a>, source_scope: &'a SemanticsScope<'a>) -> Self {
-        Self { target_scope, source_scope, previous: Box::new(NullTransformer) }
+        Self { target_scope, source_scope }
     }
+}
 
-    fn get_substitution_inner(&self, node: &syntax::SyntaxNode) -> Option<syntax::SyntaxNode> {
+impl<'a> AstTransform<'a> for QualifyPaths<'a> {
+    fn get_substitution(
+        &self,
+        node: &SyntaxNode,
+        recur: &dyn AstTransform<'a>,
+    ) -> Option<SyntaxNode> {
         // FIXME handle value ns?
         let from = self.target_scope.module()?;
         let p = ast::Path::cast(node.clone())?;
@@ -191,7 +194,7 @@ impl<'a> QualifyPaths<'a> {
                 let type_args = p
                     .segment()
                     .and_then(|s| s.generic_arg_list())
-                    .map(|arg_list| apply(self, arg_list));
+                    .map(|arg_list| apply(recur, arg_list));
                 if let Some(type_args) = type_args {
                     let last_segment = path.segment().unwrap();
                     path = path.with_segment(last_segment.with_generic_args(type_args))
@@ -208,15 +211,6 @@ impl<'a> QualifyPaths<'a> {
     }
 }
 
-impl<'a> AstTransform<'a> for QualifyPaths<'a> {
-    fn get_substitution(&self, node: &syntax::SyntaxNode) -> Option<syntax::SyntaxNode> {
-        self.get_substitution_inner(node).or_else(|| self.previous.get_substitution(node))
-    }
-    fn chain_before(self, other: Box<dyn AstTransform<'a> + 'a>) -> Box<dyn AstTransform<'a> + 'a> {
-        Box::new(QualifyPaths { previous: other, ..self })
-    }
-}
-
 pub(crate) fn path_to_ast(path: hir::ModPath) -> ast::Path {
     let parse = ast::SourceFile::parse(&path.to_string());
     parse
diff --git a/crates/assists/src/handlers/add_missing_impl_members.rs b/crates/assists/src/handlers/add_missing_impl_members.rs
index 1ac5fefd6..51b5a2eb0 100644
--- a/crates/assists/src/handlers/add_missing_impl_members.rs
+++ b/crates/assists/src/handlers/add_missing_impl_members.rs
@@ -146,7 +146,7 @@ fn add_missing_impl_members_inner(
 
     let target = impl_def.syntax().text_range();
     acc.add(AssistId(assist_id, AssistKind::QuickFix), label, target, |builder| {
-        let impl_item_list = impl_def.assoc_item_list().unwrap_or(make::assoc_item_list());
+        let impl_item_list = impl_def.assoc_item_list().unwrap_or_else(make::assoc_item_list);
 
         let n_existing_items = impl_item_list.assoc_items().count();
         let source_scope = ctx.sema.scope_for_def(trait_);
diff --git a/crates/assists/src/handlers/extract_struct_from_enum_variant.rs b/crates/assists/src/handlers/extract_struct_from_enum_variant.rs
index d1eadaa99..f5f03ef36 100644
--- a/crates/assists/src/handlers/extract_struct_from_enum_variant.rs
+++ b/crates/assists/src/handlers/extract_struct_from_enum_variant.rs
@@ -91,7 +91,7 @@ fn existing_struct_def(db: &RootDatabase, variant_name: &str, variant: &EnumVari
         .module(db)
         .scope(db, None)
         .into_iter()
-        .any(|(name, _)| name.to_string() == variant_name.to_string())
+        .any(|(name, _)| name.to_string() == variant_name)
 }
 
 #[allow(dead_code)]
diff --git a/crates/assists/src/utils/insert_use.rs b/crates/assists/src/utils/insert_use.rs
index 5719b06af..f6025c99a 100644
--- a/crates/assists/src/utils/insert_use.rs
+++ b/crates/assists/src/utils/insert_use.rs
@@ -4,13 +4,14 @@ use std::{
     iter::{self, successors},
 };
 
-use ast::{
-    edit::{AstNodeEdit, IndentLevel},
-    PathSegmentKind, VisibilityOwner,
-};
+use itertools::{EitherOrBoth, Itertools};
 use syntax::{
     algo,
-    ast::{self, make, AstNode},
+    ast::{
+        self,
+        edit::{AstNodeEdit, IndentLevel},
+        make, AstNode, PathSegmentKind, VisibilityOwner,
+    },
     InsertPosition, SyntaxElement, SyntaxNode,
 };
 
@@ -174,7 +175,7 @@ pub(crate) fn try_merge_trees(
     let (lhs_prefix, rhs_prefix) = common_prefix(&lhs_path, &rhs_path)?;
     let lhs = lhs.split_prefix(&lhs_prefix);
     let rhs = rhs.split_prefix(&rhs_prefix);
-    recursive_merge(&lhs, &rhs, merge).map(|(merged, _)| merged)
+    recursive_merge(&lhs, &rhs, merge)
 }
 
 /// Recursively "zips" together lhs and rhs.
@@ -182,22 +183,24 @@ fn recursive_merge(
     lhs: &ast::UseTree,
     rhs: &ast::UseTree,
     merge: MergeBehaviour,
-) -> Option<(ast::UseTree, bool)> {
+) -> Option<ast::UseTree> {
     let mut use_trees = lhs
         .use_tree_list()
         .into_iter()
         .flat_map(|list| list.use_trees())
-        // check if any of the use trees are nested, if they are and the behaviour is `last` we are not allowed to merge this
-        // so early exit the iterator by using Option's Intoiterator impl
-        .map(|tree| match merge == MergeBehaviour::Last && tree.use_tree_list().is_some() {
-            true => None,
-            false => Some(tree),
+        // we use Option here to early return from this function(this is not the same as a `filter` op)
+        .map(|tree| match merge.is_tree_allowed(&tree) {
+            true => Some(tree),
+            false => None,
         })
         .collect::<Option<Vec<_>>>()?;
-    use_trees.sort_unstable_by(|a, b| path_cmp_opt(a.path(), b.path()));
+    use_trees.sort_unstable_by(|a, b| path_cmp_for_sort(a.path(), b.path()));
     for rhs_t in rhs.use_tree_list().into_iter().flat_map(|list| list.use_trees()) {
+        if !merge.is_tree_allowed(&rhs_t) {
+            return None;
+        }
         let rhs_path = rhs_t.path();
-        match use_trees.binary_search_by(|p| path_cmp_opt(p.path(), rhs_path.clone())) {
+        match use_trees.binary_search_by(|p| path_cmp_bin_search(p.path(), rhs_path.clone())) {
             Ok(idx) => {
                 let lhs_t = &mut use_trees[idx];
                 let lhs_path = lhs_t.path()?;
@@ -239,17 +242,9 @@ fn recursive_merge(
                 }
                 let lhs = lhs_t.split_prefix(&lhs_prefix);
                 let rhs = rhs_t.split_prefix(&rhs_prefix);
-                let this_has_children = use_trees.len() > 0;
                 match recursive_merge(&lhs, &rhs, merge) {
-                    Some((_, has_multiple_children))
-                        if merge == MergeBehaviour::Last
-                            && this_has_children
-                            && has_multiple_children =>
-                    {
-                        return None
-                    }
-                    Some((use_tree, _)) => use_trees[idx] = use_tree,
-                    None => use_trees.insert(idx, rhs_t),
+                    Some(use_tree) => use_trees[idx] = use_tree,
+                    None => return None,
                 }
             }
             Err(_)
@@ -264,8 +259,7 @@ fn recursive_merge(
             }
         }
     }
-    let has_multiple_children = use_trees.len() > 1;
-    Some((lhs.with_use_tree_list(make::use_tree_list(use_trees)), has_multiple_children))
+    Some(lhs.with_use_tree_list(make::use_tree_list(use_trees)))
 }
 
 /// Traverses both paths until they differ, returning the common prefix of both.
@@ -308,41 +302,83 @@ fn segment_iter(path: &ast::Path) -> impl Iterator<Item = ast::PathSegment> + Cl
     successors(first_segment(path), |p| p.parent_path().parent_path().and_then(|p| p.segment()))
 }
 
+fn path_len(path: ast::Path) -> usize {
+    segment_iter(&path).count()
+}
+
 /// Orders paths in the following way:
 /// the sole self token comes first, after that come uppercase identifiers, then lowercase identifiers
-// FIXME: rustfmt sort lowercase idents before uppercase, in general we want to have the same ordering rustfmt has
+// FIXME: rustfmt sorts lowercase idents before uppercase, in general we want to have the same ordering rustfmt has
 // which is `self` and `super` first, then identifier imports with lowercase ones first, then glob imports and at last list imports.
 // Example foo::{self, foo, baz, Baz, Qux, *, {Bar}}
-fn path_cmp(a: &ast::Path, b: &ast::Path) -> Ordering {
-    match (path_is_self(a), path_is_self(b)) {
-        (true, true) => Ordering::Equal,
-        (true, false) => Ordering::Less,
-        (false, true) => Ordering::Greater,
-        (false, false) => {
-            let a = segment_iter(a);
-            let b = segment_iter(b);
-            // cmp_by would be useful for us here but that is currently unstable
-            // cmp doesnt work due the lifetimes on text's return type
-            a.zip(b)
-                .flat_map(|(seg, seg2)| seg.name_ref().zip(seg2.name_ref()))
-                .find_map(|(a, b)| match a.text().cmp(b.text()) {
-                    ord @ Ordering::Greater | ord @ Ordering::Less => Some(ord),
-                    Ordering::Equal => None,
-                })
-                .unwrap_or(Ordering::Equal)
-        }
+fn path_cmp_for_sort(a: Option<ast::Path>, b: Option<ast::Path>) -> Ordering {
+    match (a, b) {
+        (None, None) => Ordering::Equal,
+        (None, Some(_)) => Ordering::Less,
+        (Some(_), None) => Ordering::Greater,
+        (Some(ref a), Some(ref b)) => match (path_is_self(a), path_is_self(b)) {
+            (true, true) => Ordering::Equal,
+            (true, false) => Ordering::Less,
+            (false, true) => Ordering::Greater,
+            (false, false) => path_cmp_short(a, b),
+        },
     }
 }
 
-fn path_cmp_opt(a: Option<ast::Path>, b: Option<ast::Path>) -> Ordering {
-    match (a, b) {
+/// Path comparison func for binary searching for merging.
+fn path_cmp_bin_search(lhs: Option<ast::Path>, rhs: Option<ast::Path>) -> Ordering {
+    match (lhs, rhs) {
         (None, None) => Ordering::Equal,
         (None, Some(_)) => Ordering::Less,
         (Some(_), None) => Ordering::Greater,
-        (Some(a), Some(b)) => path_cmp(&a, &b),
+        (Some(ref a), Some(ref b)) => path_cmp_short(a, b),
     }
 }
 
+/// Short circuiting comparison, if both paths are equal until one of them ends they are considered
+/// equal
+fn path_cmp_short(a: &ast::Path, b: &ast::Path) -> Ordering {
+    let a = segment_iter(a);
+    let b = segment_iter(b);
+    // cmp_by would be useful for us here but that is currently unstable
+    // cmp doesnt work due the lifetimes on text's return type
+    a.zip(b)
+        .find_map(|(a, b)| match path_segment_cmp(&a, &b) {
+            Ordering::Equal => None,
+            ord => Some(ord),
+        })
+        .unwrap_or(Ordering::Equal)
+}
+
+/// Compares to paths, if one ends earlier than the other the has_tl parameters decide which is
+/// greater as a a path that has a tree list should be greater, while one that just ends without
+/// a tree list should be considered less.
+fn use_tree_path_cmp(a: &ast::Path, a_has_tl: bool, b: &ast::Path, b_has_tl: bool) -> Ordering {
+    let a_segments = segment_iter(a);
+    let b_segments = segment_iter(b);
+    // cmp_by would be useful for us here but that is currently unstable
+    // cmp doesnt work due the lifetimes on text's return type
+    a_segments
+        .zip_longest(b_segments)
+        .find_map(|zipped| match zipped {
+            EitherOrBoth::Both(ref a, ref b) => match path_segment_cmp(a, b) {
+                Ordering::Equal => None,
+                ord => Some(ord),
+            },
+            EitherOrBoth::Left(_) if !b_has_tl => Some(Ordering::Greater),
+            EitherOrBoth::Left(_) => Some(Ordering::Less),
+            EitherOrBoth::Right(_) if !a_has_tl => Some(Ordering::Less),
+            EitherOrBoth::Right(_) => Some(Ordering::Greater),
+        })
+        .unwrap_or(Ordering::Equal)
+}
+
+fn path_segment_cmp(a: &ast::PathSegment, b: &ast::PathSegment) -> Ordering {
+    let a = a.name_ref();
+    let b = b.name_ref();
+    a.as_ref().map(ast::NameRef::text).cmp(&b.as_ref().map(ast::NameRef::text))
+}
+
 /// What type of merges are allowed.
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub enum MergeBehaviour {
@@ -352,6 +388,19 @@ pub enum MergeBehaviour {
     Last,
 }
 
+impl MergeBehaviour {
+    #[inline]
+    fn is_tree_allowed(&self, tree: &ast::UseTree) -> bool {
+        match self {
+            MergeBehaviour::Full => true,
+            // only simple single segment paths are allowed
+            MergeBehaviour::Last => {
+                tree.use_tree_list().is_none() && tree.path().map(path_len) <= Some(1)
+            }
+        }
+    }
+}
+
 #[derive(Eq, PartialEq, PartialOrd, Ord)]
 enum ImportGroup {
     // the order here defines the order of new group inserts
@@ -379,7 +428,6 @@ impl ImportGroup {
             PathSegmentKind::Name(name) => match name.text().as_str() {
                 "std" => ImportGroup::Std,
                 "core" => ImportGroup::Std,
-                // FIXME: can be ThisModule as well
                 _ => ImportGroup::ExternCrate,
             },
             PathSegmentKind::Type { .. } => unreachable!(),
@@ -405,30 +453,30 @@ fn find_insert_position(
         .as_syntax_node()
         .children()
         .filter_map(|node| ast::Use::cast(node.clone()).zip(Some(node)))
-        .flat_map(|(use_, node)| use_.use_tree().and_then(|tree| tree.path()).zip(Some(node)));
+        .flat_map(|(use_, node)| {
+            let tree = use_.use_tree()?;
+            let path = tree.path()?;
+            let has_tl = tree.use_tree_list().is_some();
+            Some((path, has_tl, node))
+        });
     // Iterator that discards anything thats not in the required grouping
     // This implementation allows the user to rearrange their import groups as this only takes the first group that fits
     let group_iter = path_node_iter
         .clone()
-        .skip_while(|(path, _)| ImportGroup::new(path) != group)
-        .take_while(|(path, _)| ImportGroup::new(path) == group);
+        .skip_while(|(path, ..)| ImportGroup::new(path) != group)
+        .take_while(|(path, ..)| ImportGroup::new(path) == group);
 
-    let segments = segment_iter(&insert_path);
     // track the last element we iterated over, if this is still None after the iteration then that means we never iterated in the first place
     let mut last = None;
     // find the element that would come directly after our new import
-    let post_insert =
-        group_iter.inspect(|(_, node)| last = Some(node.clone())).find(|(path, _)| {
-            let check_segments = segment_iter(&path);
-            segments
-                .clone()
-                .zip(check_segments)
-                .flat_map(|(seg, seg2)| seg.name_ref().zip(seg2.name_ref()))
-                .all(|(l, r)| l.text() <= r.text())
-        });
+    let post_insert = group_iter.inspect(|(.., node)| last = Some(node.clone())).find(
+        |&(ref path, has_tl, _)| {
+            use_tree_path_cmp(&insert_path, false, path, has_tl) != Ordering::Greater
+        },
+    );
     match post_insert {
         // insert our import before that element
-        Some((_, node)) => (InsertPosition::Before(node.into()), AddBlankLine::After),
+        Some((.., node)) => (InsertPosition::Before(node.into()), AddBlankLine::After),
         // there is no element after our new import, so append it to the end of the group
         None => match last {
             Some(node) => (InsertPosition::After(node.into()), AddBlankLine::Before),
@@ -438,10 +486,10 @@ fn find_insert_position(
                 let mut last = None;
                 // find the group that comes after where we want to insert
                 let post_group = path_node_iter
-                    .inspect(|(_, node)| last = Some(node.clone()))
-                    .find(|(p, _)| ImportGroup::new(p) > group);
+                    .inspect(|(.., node)| last = Some(node.clone()))
+                    .find(|(p, ..)| ImportGroup::new(p) > group);
                 match post_group {
-                    Some((_, node)) => {
+                    Some((.., node)) => {
                         (InsertPosition::Before(node.into()), AddBlankLine::AfterTwice)
                     }
                     // there is no such group, so append after the last one
@@ -676,6 +724,11 @@ use std::io;",
     }
 
     #[test]
+    fn merge_last_into_self() {
+        check_last("foo::bar::baz", r"use foo::bar;", r"use foo::bar::{self, baz};");
+    }
+
+    #[test]
     fn merge_groups_full() {
         check_full(
             "std::io",
@@ -819,8 +872,23 @@ use std::io;",
     }
 
     #[test]
-    fn merge_last_too_long() {
-        check_last("foo::bar", r"use foo::bar::baz::Qux;", r"use foo::bar::{self, baz::Qux};");
+    fn skip_merge_last_too_long() {
+        check_last(
+            "foo::bar",
+            r"use foo::bar::baz::Qux;",
+            r"use foo::bar;
+use foo::bar::baz::Qux;",
+        );
+    }
+
+    #[test]
+    fn skip_merge_last_too_long2() {
+        check_last(
+            "foo::bar::baz::Qux",
+            r"use foo::bar;",
+            r"use foo::bar;
+use foo::bar::baz::Qux;",
+        );
     }
 
     #[test]
diff --git a/crates/base_db/src/change.rs b/crates/base_db/src/change.rs
new file mode 100644
index 000000000..043e03bba
--- /dev/null
+++ b/crates/base_db/src/change.rs
@@ -0,0 +1,97 @@
+//! Defines a unit of change that can applied to the database to get the next
+//! state. Changes are transactional.
+
+use std::{fmt, sync::Arc};
+
+use rustc_hash::FxHashSet;
+use salsa::Durability;
+use vfs::FileId;
+
+use crate::{CrateGraph, SourceDatabaseExt, SourceRoot, SourceRootId};
+
+/// Encapsulate a bunch of raw `.set` calls on the database.
+#[derive(Default)]
+pub struct Change {
+    pub roots: Option<Vec<SourceRoot>>,
+    pub files_changed: Vec<(FileId, Option<Arc<String>>)>,
+    pub crate_graph: Option<CrateGraph>,
+}
+
+impl fmt::Debug for Change {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        let mut d = fmt.debug_struct("AnalysisChange");
+        if let Some(roots) = &self.roots {
+            d.field("roots", roots);
+        }
+        if !self.files_changed.is_empty() {
+            d.field("files_changed", &self.files_changed.len());
+        }
+        if self.crate_graph.is_some() {
+            d.field("crate_graph", &self.crate_graph);
+        }
+        d.finish()
+    }
+}
+
+impl Change {
+    pub fn new() -> Change {
+        Change::default()
+    }
+
+    pub fn set_roots(&mut self, roots: Vec<SourceRoot>) {
+        self.roots = Some(roots);
+    }
+
+    pub fn change_file(&mut self, file_id: FileId, new_text: Option<Arc<String>>) {
+        self.files_changed.push((file_id, new_text))
+    }
+
+    pub fn set_crate_graph(&mut self, graph: CrateGraph) {
+        self.crate_graph = Some(graph);
+    }
+
+    pub fn apply(self, db: &mut dyn SourceDatabaseExt) {
+        let _p = profile::span("RootDatabase::apply_change");
+        // db.request_cancellation();
+        // log::info!("apply_change {:?}", change);
+        if let Some(roots) = self.roots {
+            let mut local_roots = FxHashSet::default();
+            let mut library_roots = FxHashSet::default();
+            for (idx, root) in roots.into_iter().enumerate() {
+                let root_id = SourceRootId(idx as u32);
+                let durability = durability(&root);
+                if root.is_library {
+                    library_roots.insert(root_id);
+                } else {
+                    local_roots.insert(root_id);
+                }
+                for file_id in root.iter() {
+                    db.set_file_source_root_with_durability(file_id, root_id, durability);
+                }
+                db.set_source_root_with_durability(root_id, Arc::new(root), durability);
+            }
+            // db.set_local_roots_with_durability(Arc::new(local_roots), Durability::HIGH);
+            // db.set_library_roots_with_durability(Arc::new(library_roots), Durability::HIGH);
+        }
+
+        for (file_id, text) in self.files_changed {
+            let source_root_id = db.file_source_root(file_id);
+            let source_root = db.source_root(source_root_id);
+            let durability = durability(&source_root);
+            // XXX: can't actually remove the file, just reset the text
+            let text = text.unwrap_or_default();
+            db.set_file_text_with_durability(file_id, text, durability)
+        }
+        if let Some(crate_graph) = self.crate_graph {
+            db.set_crate_graph_with_durability(Arc::new(crate_graph), Durability::HIGH)
+        }
+    }
+}
+
+fn durability(source_root: &SourceRoot) -> Durability {
+    if source_root.is_library {
+        Durability::HIGH
+    } else {
+        Durability::LOW
+    }
+}
diff --git a/crates/base_db/src/fixture.rs b/crates/base_db/src/fixture.rs
index 5ff8ead0e..b7286fc7d 100644
--- a/crates/base_db/src/fixture.rs
+++ b/crates/base_db/src/fixture.rs
@@ -65,24 +65,26 @@ use test_utils::{extract_range_or_offset, Fixture, RangeOrOffset, CURSOR_MARKER}
 use vfs::{file_set::FileSet, VfsPath};
 
 use crate::{
-    input::CrateName, CrateGraph, CrateId, Edition, Env, FileId, FilePosition, SourceDatabaseExt,
-    SourceRoot, SourceRootId,
+    input::CrateName, Change, CrateGraph, CrateId, Edition, Env, FileId, FilePosition,
+    SourceDatabaseExt, SourceRoot, SourceRootId,
 };
 
 pub const WORKSPACE: SourceRootId = SourceRootId(0);
 
 pub trait WithFixture: Default + SourceDatabaseExt + 'static {
     fn with_single_file(text: &str) -> (Self, FileId) {
+        let fixture = ChangeFixture::parse(text);
         let mut db = Self::default();
-        let (_, files) = with_files(&mut db, text);
-        assert_eq!(files.len(), 1);
-        (db, files[0])
+        fixture.change.apply(&mut db);
+        assert_eq!(fixture.files.len(), 1);
+        (db, fixture.files[0])
     }
 
     fn with_files(ra_fixture: &str) -> Self {
+        let fixture = ChangeFixture::parse(ra_fixture);
         let mut db = Self::default();
-        let (pos, _) = with_files(&mut db, ra_fixture);
-        assert!(pos.is_none());
+        fixture.change.apply(&mut db);
+        assert!(fixture.file_position.is_none());
         db
     }
 
@@ -96,9 +98,10 @@ pub trait WithFixture: Default + SourceDatabaseExt + 'static {
     }
 
     fn with_range_or_offset(ra_fixture: &str) -> (Self, FileId, RangeOrOffset) {
+        let fixture = ChangeFixture::parse(ra_fixture);
         let mut db = Self::default();
-        let (pos, _) = with_files(&mut db, ra_fixture);
-        let (file_id, range_or_offset) = pos.unwrap();
+        fixture.change.apply(&mut db);
+        let (file_id, range_or_offset) = fixture.file_position.unwrap();
         (db, file_id, range_or_offset)
     }
 
@@ -113,89 +116,95 @@ pub trait WithFixture: Default + SourceDatabaseExt + 'static {
 
 impl<DB: SourceDatabaseExt + Default + 'static> WithFixture for DB {}
 
-fn with_files(
-    db: &mut dyn SourceDatabaseExt,
-    fixture: &str,
-) -> (Option<(FileId, RangeOrOffset)>, Vec<FileId>) {
-    let fixture = Fixture::parse(fixture);
-
-    let mut files = Vec::new();
-    let mut crate_graph = CrateGraph::default();
-    let mut crates = FxHashMap::default();
-    let mut crate_deps = Vec::new();
-    let mut default_crate_root: Option<FileId> = None;
-
-    let mut file_set = FileSet::default();
-    let source_root_id = WORKSPACE;
-    let source_root_prefix = "/".to_string();
-    let mut file_id = FileId(0);
-
-    let mut file_position = None;
-
-    for entry in fixture {
-        let text = if entry.text.contains(CURSOR_MARKER) {
-            let (range_or_offset, text) = extract_range_or_offset(&entry.text);
-            assert!(file_position.is_none());
-            file_position = Some((file_id, range_or_offset));
-            text.to_string()
-        } else {
-            entry.text.clone()
-        };
+pub struct ChangeFixture {
+    pub file_position: Option<(FileId, RangeOrOffset)>,
+    pub files: Vec<FileId>,
+    pub change: Change,
+}
 
-        let meta = FileMeta::from(entry);
-        assert!(meta.path.starts_with(&source_root_prefix));
+impl ChangeFixture {
+    pub fn parse(ra_fixture: &str) -> ChangeFixture {
+        let fixture = Fixture::parse(ra_fixture);
+        let mut change = Change::new();
+
+        let mut files = Vec::new();
+        let mut crate_graph = CrateGraph::default();
+        let mut crates = FxHashMap::default();
+        let mut crate_deps = Vec::new();
+        let mut default_crate_root: Option<FileId> = None;
+        let mut default_cfg = CfgOptions::default();
+
+        let mut file_set = FileSet::default();
+        let source_root_prefix = "/".to_string();
+        let mut file_id = FileId(0);
+
+        let mut file_position = None;
+
+        for entry in fixture {
+            let text = if entry.text.contains(CURSOR_MARKER) {
+                let (range_or_offset, text) = extract_range_or_offset(&entry.text);
+                assert!(file_position.is_none());
+                file_position = Some((file_id, range_or_offset));
+                text.to_string()
+            } else {
+                entry.text.clone()
+            };
+
+            let meta = FileMeta::from(entry);
+            assert!(meta.path.starts_with(&source_root_prefix));
+
+            if let Some(krate) = meta.krate {
+                let crate_id = crate_graph.add_crate_root(
+                    file_id,
+                    meta.edition,
+                    Some(krate.clone()),
+                    meta.cfg,
+                    meta.env,
+                    Default::default(),
+                );
+                let crate_name = CrateName::new(&krate).unwrap();
+                let prev = crates.insert(crate_name.clone(), crate_id);
+                assert!(prev.is_none());
+                for dep in meta.deps {
+                    let dep = CrateName::new(&dep).unwrap();
+                    crate_deps.push((crate_name.clone(), dep))
+                }
+            } else if meta.path == "/main.rs" || meta.path == "/lib.rs" {
+                assert!(default_crate_root.is_none());
+                default_crate_root = Some(file_id);
+                default_cfg = meta.cfg;
+            }
+
+            change.change_file(file_id, Some(Arc::new(text)));
+            let path = VfsPath::new_virtual_path(meta.path);
+            file_set.insert(file_id, path.into());
+            files.push(file_id);
+            file_id.0 += 1;
+        }
 
-        if let Some(krate) = meta.krate {
-            let crate_id = crate_graph.add_crate_root(
-                file_id,
-                meta.edition,
-                Some(krate.clone()),
-                meta.cfg,
-                meta.env,
+        if crates.is_empty() {
+            let crate_root = default_crate_root.unwrap();
+            crate_graph.add_crate_root(
+                crate_root,
+                Edition::Edition2018,
+                Some("test".to_string()),
+                default_cfg,
+                Env::default(),
                 Default::default(),
             );
-            let crate_name = CrateName::new(&krate).unwrap();
-            let prev = crates.insert(crate_name.clone(), crate_id);
-            assert!(prev.is_none());
-            for dep in meta.deps {
-                let dep = CrateName::new(&dep).unwrap();
-                crate_deps.push((crate_name.clone(), dep))
+        } else {
+            for (from, to) in crate_deps {
+                let from_id = crates[&from];
+                let to_id = crates[&to];
+                crate_graph.add_dep(from_id, CrateName::new(&to).unwrap(), to_id).unwrap();
             }
-        } else if meta.path == "/main.rs" || meta.path == "/lib.rs" {
-            assert!(default_crate_root.is_none());
-            default_crate_root = Some(file_id);
         }
 
-        db.set_file_text(file_id, Arc::new(text));
-        db.set_file_source_root(file_id, source_root_id);
-        let path = VfsPath::new_virtual_path(meta.path);
-        file_set.insert(file_id, path.into());
-        files.push(file_id);
-        file_id.0 += 1;
-    }
+        change.set_roots(vec![SourceRoot::new_local(file_set)]);
+        change.set_crate_graph(crate_graph);
 
-    if crates.is_empty() {
-        let crate_root = default_crate_root.unwrap();
-        crate_graph.add_crate_root(
-            crate_root,
-            Edition::Edition2018,
-            None,
-            CfgOptions::default(),
-            Env::default(),
-            Default::default(),
-        );
-    } else {
-        for (from, to) in crate_deps {
-            let from_id = crates[&from];
-            let to_id = crates[&to];
-            crate_graph.add_dep(from_id, CrateName::new(&to).unwrap(), to_id).unwrap();
-        }
+        ChangeFixture { file_position, files, change }
     }
-
-    db.set_source_root(source_root_id, Arc::new(SourceRoot::new_local(file_set)));
-    db.set_crate_graph(Arc::new(crate_graph));
-
-    (file_position, files)
 }
 
 struct FileMeta {
diff --git a/crates/base_db/src/lib.rs b/crates/base_db/src/lib.rs
index ee3415850..e38aa7257 100644
--- a/crates/base_db/src/lib.rs
+++ b/crates/base_db/src/lib.rs
@@ -1,6 +1,7 @@
 //! base_db defines basic database traits. The concrete DB is defined by ide.
 mod cancellation;
 mod input;
+mod change;
 pub mod fixture;
 
 use std::{panic, sync::Arc};
@@ -10,6 +11,7 @@ use syntax::{ast, Parse, SourceFile, TextRange, TextSize};
 
 pub use crate::{
     cancellation::Canceled,
+    change::Change,
     input::{
         CrateData, CrateGraph, CrateId, CrateName, Dependency, Edition, Env, FileId, ProcMacroId,
         SourceRoot, SourceRootId,
diff --git a/crates/hir/src/code_model.rs b/crates/hir/src/code_model.rs
index 567fd91af..5721a66c4 100644
--- a/crates/hir/src/code_model.rs
+++ b/crates/hir/src/code_model.rs
@@ -145,7 +145,7 @@ impl Crate {
             }
         }).flat_map(|t| t).next();
 
-        doc_url.map(|s| s.trim_matches('"').trim_end_matches("/").to_owned() + "/")
+        doc_url.map(|s| s.trim_matches('"').trim_end_matches('/').to_owned() + "/")
     }
 }
 
diff --git a/crates/hir_def/src/nameres/collector.rs b/crates/hir_def/src/nameres/collector.rs
index 100e25ffc..c8cd04264 100644
--- a/crates/hir_def/src/nameres/collector.rs
+++ b/crates/hir_def/src/nameres/collector.rs
@@ -1229,9 +1229,10 @@ impl ModCollector<'_, '_> {
         } else {
             let derive = attrs.by_key("proc_macro_derive");
             if let Some(arg) = derive.tt_values().next() {
-                if let [TokenTree::Leaf(Leaf::Ident(trait_name))] = &*arg.token_trees {
+                if let [TokenTree::Leaf(Leaf::Ident(trait_name)), ..] = &*arg.token_trees {
                     trait_name.as_name()
                 } else {
+                    log::trace!("malformed `#[proc_macro_derive]`: {}", arg);
                     return;
                 }
             } else {
diff --git a/crates/hir_def/src/nameres/tests/macros.rs b/crates/hir_def/src/nameres/tests/macros.rs
index 0851c3b7d..305fca0f9 100644
--- a/crates/hir_def/src/nameres/tests/macros.rs
+++ b/crates/hir_def/src/nameres/tests/macros.rs
@@ -688,13 +688,20 @@ fn resolves_proc_macros() {
         pub fn derive_macro(_item: TokenStream) -> TokenStream {
             TokenStream
         }
+
+        #[proc_macro_derive(AnotherTrait, attributes(helper_attr))]
+        pub fn derive_macro_2(_item: TokenStream) -> TokenStream {
+            TokenStream
+        }
         ",
         expect![[r#"
             crate
+            AnotherTrait: m
             DummyTrait: m
             TokenStream: t v
             attribute_macro: v m
             derive_macro: v
+            derive_macro_2: v
             function_like_macro: v m
         "#]],
     );
diff --git a/crates/ide/src/call_hierarchy.rs b/crates/ide/src/call_hierarchy.rs
index 58e26b94c..d2cf2cc7d 100644
--- a/crates/ide/src/call_hierarchy.rs
+++ b/crates/ide/src/call_hierarchy.rs
@@ -139,7 +139,7 @@ impl CallLocations {
 mod tests {
     use base_db::FilePosition;
 
-    use crate::mock_analysis::analysis_and_position;
+    use crate::fixture;
 
     fn check_hierarchy(
         ra_fixture: &str,
@@ -147,7 +147,7 @@ mod tests {
         expected_incoming: &[&str],
         expected_outgoing: &[&str],
     ) {
-        let (analysis, pos) = analysis_and_position(ra_fixture);
+        let (analysis, pos) = fixture::position(ra_fixture);
 
         let mut navs = analysis.call_hierarchy(pos).unwrap().unwrap().info;
         assert_eq!(navs.len(), 1);
@@ -181,8 +181,8 @@ fn caller() {
     call<|>ee();
 }
 "#,
-            "callee FN FileId(1) 0..14 3..9",
-            &["caller FN FileId(1) 15..44 18..24 : [33..39]"],
+            "callee FN FileId(0) 0..14 3..9",
+            &["caller FN FileId(0) 15..44 18..24 : [33..39]"],
             &[],
         );
     }
@@ -197,8 +197,8 @@ fn caller() {
     callee();
 }
 "#,
-            "callee FN FileId(1) 0..14 3..9",
-            &["caller FN FileId(1) 15..44 18..24 : [33..39]"],
+            "callee FN FileId(0) 0..14 3..9",
+            &["caller FN FileId(0) 15..44 18..24 : [33..39]"],
             &[],
         );
     }
@@ -214,8 +214,8 @@ fn caller() {
     callee();
 }
 "#,
-            "callee FN FileId(1) 0..14 3..9",
-            &["caller FN FileId(1) 15..58 18..24 : [33..39, 47..53]"],
+            "callee FN FileId(0) 0..14 3..9",
+            &["caller FN FileId(0) 15..58 18..24 : [33..39, 47..53]"],
             &[],
         );
     }
@@ -234,10 +234,10 @@ fn caller2() {
     callee();
 }
 "#,
-            "callee FN FileId(1) 0..14 3..9",
+            "callee FN FileId(0) 0..14 3..9",
             &[
-                "caller1 FN FileId(1) 15..45 18..25 : [34..40]",
-                "caller2 FN FileId(1) 47..77 50..57 : [66..72]",
+                "caller1 FN FileId(0) 15..45 18..25 : [34..40]",
+                "caller2 FN FileId(0) 47..77 50..57 : [66..72]",
             ],
             &[],
         );
@@ -263,10 +263,10 @@ mod tests {
     }
 }
 "#,
-            "callee FN FileId(1) 0..14 3..9",
+            "callee FN FileId(0) 0..14 3..9",
             &[
-                "caller1 FN FileId(1) 15..45 18..25 : [34..40]",
-                "test_caller FN FileId(1) 95..149 110..121 : [134..140]",
+                "caller1 FN FileId(0) 15..45 18..25 : [34..40]",
+                "test_caller FN FileId(0) 95..149 110..121 : [134..140]",
             ],
             &[],
         );
@@ -287,8 +287,8 @@ fn caller() {
 //- /foo/mod.rs
 pub fn callee() {}
 "#,
-            "callee FN FileId(2) 0..18 7..13",
-            &["caller FN FileId(1) 27..56 30..36 : [45..51]"],
+            "callee FN FileId(1) 0..18 7..13",
+            &["caller FN FileId(0) 27..56 30..36 : [45..51]"],
             &[],
         );
     }
@@ -304,9 +304,9 @@ fn call<|>er() {
     callee();
 }
 "#,
-            "caller FN FileId(1) 15..58 18..24",
+            "caller FN FileId(0) 15..58 18..24",
             &[],
-            &["callee FN FileId(1) 0..14 3..9 : [33..39, 47..53]"],
+            &["callee FN FileId(0) 0..14 3..9 : [33..39, 47..53]"],
         );
     }
 
@@ -325,9 +325,9 @@ fn call<|>er() {
 //- /foo/mod.rs
 pub fn callee() {}
 "#,
-            "caller FN FileId(1) 27..56 30..36",
+            "caller FN FileId(0) 27..56 30..36",
             &[],
-            &["callee FN FileId(2) 0..18 7..13 : [45..51]"],
+            &["callee FN FileId(1) 0..18 7..13 : [45..51]"],
         );
     }
 
@@ -348,9 +348,9 @@ fn caller3() {
 
 }
 "#,
-            "caller2 FN FileId(1) 33..64 36..43",
-            &["caller1 FN FileId(1) 0..31 3..10 : [19..26]"],
-            &["caller3 FN FileId(1) 66..83 69..76 : [52..59]"],
+            "caller2 FN FileId(0) 33..64 36..43",
+            &["caller1 FN FileId(0) 0..31 3..10 : [19..26]"],
+            &["caller3 FN FileId(0) 66..83 69..76 : [52..59]"],
         );
     }
 
@@ -368,9 +368,9 @@ fn main() {
     a<|>()
 }
 "#,
-            "a FN FileId(1) 0..18 3..4",
-            &["main FN FileId(1) 31..52 34..38 : [47..48]"],
-            &["b FN FileId(1) 20..29 23..24 : [13..14]"],
+            "a FN FileId(0) 0..18 3..4",
+            &["main FN FileId(0) 31..52 34..38 : [47..48]"],
+            &["b FN FileId(0) 20..29 23..24 : [13..14]"],
         );
 
         check_hierarchy(
@@ -385,8 +385,8 @@ fn main() {
     a()
 }
 "#,
-            "b FN FileId(1) 20..29 23..24",
-            &["a FN FileId(1) 0..18 3..4 : [13..14]"],
+            "b FN FileId(0) 20..29 23..24",
+            &["a FN FileId(0) 0..18 3..4 : [13..14]"],
             &[],
         );
     }
diff --git a/crates/ide/src/call_info.rs b/crates/ide/src/call_info.rs
index 7e99c6b72..d7b2b926e 100644
--- a/crates/ide/src/call_info.rs
+++ b/crates/ide/src/call_info.rs
@@ -232,10 +232,10 @@ mod tests {
     use expect_test::{expect, Expect};
     use test_utils::mark;
 
-    use crate::mock_analysis::analysis_and_position;
+    use crate::fixture;
 
     fn check(ra_fixture: &str, expect: Expect) {
-        let (analysis, position) = analysis_and_position(ra_fixture);
+        let (analysis, position) = fixture::position(ra_fixture);
         let call_info = analysis.call_info(position).unwrap();
         let actual = match call_info {
             Some(call_info) => {
diff --git a/crates/ide/src/completion.rs b/crates/ide/src/completion.rs
index daea2aa95..697f691b0 100644
--- a/crates/ide/src/completion.rs
+++ b/crates/ide/src/completion.rs
@@ -133,7 +133,7 @@ pub(crate) fn completions(
 #[cfg(test)]
 mod tests {
     use crate::completion::completion_config::CompletionConfig;
-    use crate::mock_analysis::analysis_and_position;
+    use crate::fixture;
 
     struct DetailAndDocumentation<'a> {
         detail: &'a str,
@@ -141,7 +141,7 @@ mod tests {
     }
 
     fn check_detail_and_documentation(ra_fixture: &str, expected: DetailAndDocumentation) {
-        let (analysis, position) = analysis_and_position(ra_fixture);
+        let (analysis, position) = fixture::position(ra_fixture);
         let config = CompletionConfig::default();
         let completions = analysis.completions(&config, position).unwrap().unwrap();
         for item in completions {
diff --git a/crates/ide/src/completion/complete_keyword.rs b/crates/ide/src/completion/complete_keyword.rs
index 5645b41fa..e59747095 100644
--- a/crates/ide/src/completion/complete_keyword.rs
+++ b/crates/ide/src/completion/complete_keyword.rs
@@ -495,13 +495,13 @@ Some multi-line comment<|>
     fn test_completion_await_impls_future() {
         check(
             r#"
-//- /main.rs
+//- /main.rs crate:main deps:std
 use std::future::*;
 struct A {}
 impl Future for A {}
 fn foo(a: A) { a.<|> }
 
-//- /std/lib.rs
+//- /std/lib.rs crate:std
 pub mod future {
     #[lang = "future_trait"]
     pub trait Future {}
@@ -514,14 +514,14 @@ pub mod future {
 
         check(
             r#"
-//- /main.rs
+//- /main.rs crate:main deps:std
 use std::future::*;
 fn foo() {
     let a = async {};
     a.<|>
 }
 
-//- /std/lib.rs
+//- /std/lib.rs crate:std
 pub mod future {
     #[lang = "future_trait"]
     pub trait Future {
diff --git a/crates/ide/src/completion/complete_mod.rs b/crates/ide/src/completion/complete_mod.rs
index 3cfc2e131..c7a99bdc3 100644
--- a/crates/ide/src/completion/complete_mod.rs
+++ b/crates/ide/src/completion/complete_mod.rs
@@ -300,7 +300,7 @@ mod tests {
     //     "#,
     //         expect![[r#"
     //             md bar;
-    //         "#]],
+    //         "#]],foo
     //     );
     // }
 
@@ -308,7 +308,7 @@ mod tests {
     fn already_declared_bin_module_completion_omitted() {
         check(
             r#"
-            //- /src/bin.rs
+            //- /src/bin.rs crate:main
             fn main() {}
             //- /src/bin/foo.rs
             mod <|>
diff --git a/crates/ide/src/completion/complete_postfix.rs b/crates/ide/src/completion/complete_postfix.rs
index 26a5af5b9..db5319618 100644
--- a/crates/ide/src/completion/complete_postfix.rs
+++ b/crates/ide/src/completion/complete_postfix.rs
@@ -1,11 +1,15 @@
 //! FIXME: write short doc here
+
+mod format_like;
+
 use assists::utils::TryEnum;
 use syntax::{
-    ast::{self, AstNode},
+    ast::{self, AstNode, AstToken},
     TextRange, TextSize,
 };
 use text_edit::TextEdit;
 
+use self::format_like::add_format_like_completions;
 use crate::{
     completion::{
         completion_config::SnippetCap,
@@ -207,6 +211,12 @@ pub(super) fn complete_postfix(acc: &mut Completions, ctx: &CompletionContext) {
         &format!("${{1}}({})", receiver_text),
     )
     .add_to(acc);
+
+    if let ast::Expr::Literal(literal) = dot_receiver.clone() {
+        if let Some(literal_text) = ast::String::cast(literal.token()) {
+            add_format_like_completions(acc, ctx, &dot_receiver, cap, &literal_text);
+        }
+    }
 }
 
 fn get_receiver_text(receiver: &ast::Expr, receiver_is_ambiguous_float_literal: bool) -> String {
@@ -392,4 +402,53 @@ fn main() {
         check_edit("dbg", r#"fn main() { &&42.<|> }"#, r#"fn main() { dbg!(&&42) }"#);
         check_edit("refm", r#"fn main() { &&42.<|> }"#, r#"fn main() { &&&mut 42 }"#);
     }
+
+    #[test]
+    fn postfix_completion_for_format_like_strings() {
+        check_edit(
+            "fmt",
+            r#"fn main() { "{some_var:?}".<|> }"#,
+            r#"fn main() { format!("{:?}", some_var) }"#,
+        );
+        check_edit(
+            "panic",
+            r#"fn main() { "Panic with {a}".<|> }"#,
+            r#"fn main() { panic!("Panic with {}", a) }"#,
+        );
+        check_edit(
+            "println",
+            r#"fn main() { "{ 2+2 } { SomeStruct { val: 1, other: 32 } :?}".<|> }"#,
+            r#"fn main() { println!("{} {:?}", 2+2, SomeStruct { val: 1, other: 32 }) }"#,
+        );
+        check_edit(
+            "loge",
+            r#"fn main() { "{2+2}".<|> }"#,
+            r#"fn main() { log::error!("{}", 2+2) }"#,
+        );
+        check_edit(
+            "logt",
+            r#"fn main() { "{2+2}".<|> }"#,
+            r#"fn main() { log::trace!("{}", 2+2) }"#,
+        );
+        check_edit(
+            "logd",
+            r#"fn main() { "{2+2}".<|> }"#,
+            r#"fn main() { log::debug!("{}", 2+2) }"#,
+        );
+        check_edit(
+            "logi",
+            r#"fn main() { "{2+2}".<|> }"#,
+            r#"fn main() { log::info!("{}", 2+2) }"#,
+        );
+        check_edit(
+            "logw",
+            r#"fn main() { "{2+2}".<|> }"#,
+            r#"fn main() { log::warn!("{}", 2+2) }"#,
+        );
+        check_edit(
+            "loge",
+            r#"fn main() { "{2+2}".<|> }"#,
+            r#"fn main() { log::error!("{}", 2+2) }"#,
+        );
+    }
 }
diff --git a/crates/ide/src/completion/complete_postfix/format_like.rs b/crates/ide/src/completion/complete_postfix/format_like.rs
new file mode 100644
index 000000000..81c33bf3a
--- /dev/null
+++ b/crates/ide/src/completion/complete_postfix/format_like.rs
@@ -0,0 +1,277 @@
+// Feature: Format String Completion.
+//
+// `"Result {result} is {2 + 2}"` is expanded to the `"Result {} is {}", result, 2 + 2`.
+//
+// The following postfix snippets are available:
+//
+// - `format` -> `format!(...)`
+// - `panic` -> `panic!(...)`
+// - `println` -> `println!(...)`
+// - `log`:
+//   + `logd` -> `log::debug!(...)`
+//   + `logt` -> `log::trace!(...)`
+//   + `logi` -> `log::info!(...)`
+//   + `logw` -> `log::warn!(...)`
+//   + `loge` -> `log::error!(...)`
+
+use crate::completion::{
+    complete_postfix::postfix_snippet, completion_config::SnippetCap,
+    completion_context::CompletionContext, completion_item::Completions,
+};
+use syntax::ast::{self, AstToken};
+
+/// Mapping ("postfix completion item" => "macro to use")
+static KINDS: &[(&str, &str)] = &[
+    ("fmt", "format!"),
+    ("panic", "panic!"),
+    ("println", "println!"),
+    ("logd", "log::debug!"),
+    ("logt", "log::trace!"),
+    ("logi", "log::info!"),
+    ("logw", "log::warn!"),
+    ("loge", "log::error!"),
+];
+
+pub(super) fn add_format_like_completions(
+    acc: &mut Completions,
+    ctx: &CompletionContext,
+    dot_receiver: &ast::Expr,
+    cap: SnippetCap,
+    receiver_text: &ast::String,
+) {
+    let input = match string_literal_contents(receiver_text) {
+        // It's not a string literal, do not parse input.
+        Some(input) => input,
+        None => return,
+    };
+
+    let mut parser = FormatStrParser::new(input);
+
+    if parser.parse().is_ok() {
+        for (label, macro_name) in KINDS {
+            let snippet = parser.into_suggestion(macro_name);
+
+            postfix_snippet(ctx, cap, &dot_receiver, label, macro_name, &snippet).add_to(acc);
+        }
+    }
+}
+
+/// Checks whether provided item is a string literal.
+fn string_literal_contents(item: &ast::String) -> Option<String> {
+    let item = item.text();
+    if item.len() >= 2 && item.starts_with("\"") && item.ends_with("\"") {
+        return Some(item[1..item.len() - 1].to_owned());
+    }
+
+    None
+}
+
+/// Parser for a format-like string. It is more allowing in terms of string contents,
+/// as we expect variable placeholders to be filled with expressions.
+#[derive(Debug)]
+pub struct FormatStrParser {
+    input: String,
+    output: String,
+    extracted_expressions: Vec<String>,
+    state: State,
+    parsed: bool,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq)]
+enum State {
+    NotExpr,
+    MaybeExpr,
+    Expr,
+    MaybeIncorrect,
+    FormatOpts,
+}
+
+impl FormatStrParser {
+    pub fn new(input: String) -> Self {
+        Self {
+            input: input.into(),
+            output: String::new(),
+            extracted_expressions: Vec::new(),
+            state: State::NotExpr,
+            parsed: false,
+        }
+    }
+
+    pub fn parse(&mut self) -> Result<(), ()> {
+        let mut current_expr = String::new();
+
+        let mut placeholder_id = 1;
+
+        // Count of open braces inside of an expression.
+        // We assume that user knows what they're doing, thus we treat it like a correct pattern, e.g.
+        // "{MyStruct { val_a: 0, val_b: 1 }}".
+        let mut inexpr_open_count = 0;
+
+        for chr in self.input.chars() {
+            match (self.state, chr) {
+                (State::NotExpr, '{') => {
+                    self.output.push(chr);
+                    self.state = State::MaybeExpr;
+                }
+                (State::NotExpr, '}') => {
+                    self.output.push(chr);
+                    self.state = State::MaybeIncorrect;
+                }
+                (State::NotExpr, _) => {
+                    self.output.push(chr);
+                }
+                (State::MaybeIncorrect, '}') => {
+                    // It's okay, we met "}}".
+                    self.output.push(chr);
+                    self.state = State::NotExpr;
+                }
+                (State::MaybeIncorrect, _) => {
+                    // Error in the string.
+                    return Err(());
+                }
+                (State::MaybeExpr, '{') => {
+                    self.output.push(chr);
+                    self.state = State::NotExpr;
+                }
+                (State::MaybeExpr, '}') => {
+                    // This is an empty sequence '{}'. Replace it with placeholder.
+                    self.output.push(chr);
+                    self.extracted_expressions.push(format!("${}", placeholder_id));
+                    placeholder_id += 1;
+                    self.state = State::NotExpr;
+                }
+                (State::MaybeExpr, _) => {
+                    current_expr.push(chr);
+                    self.state = State::Expr;
+                }
+                (State::Expr, '}') => {
+                    if inexpr_open_count == 0 {
+                        self.output.push(chr);
+                        self.extracted_expressions.push(current_expr.trim().into());
+                        current_expr = String::new();
+                        self.state = State::NotExpr;
+                    } else {
+                        // We're closing one brace met before inside of the expression.
+                        current_expr.push(chr);
+                        inexpr_open_count -= 1;
+                    }
+                }
+                (State::Expr, ':') => {
+                    if inexpr_open_count == 0 {
+                        // We're outside of braces, thus assume that it's a specifier, like "{Some(value):?}"
+                        self.output.push(chr);
+                        self.extracted_expressions.push(current_expr.trim().into());
+                        current_expr = String::new();
+                        self.state = State::FormatOpts;
+                    } else {
+                        // We're inside of braced expression, assume that it's a struct field name/value delimeter.
+                        current_expr.push(chr);
+                    }
+                }
+                (State::Expr, '{') => {
+                    current_expr.push(chr);
+                    inexpr_open_count += 1;
+                }
+                (State::Expr, _) => {
+                    current_expr.push(chr);
+                }
+                (State::FormatOpts, '}') => {
+                    self.output.push(chr);
+                    self.state = State::NotExpr;
+                }
+                (State::FormatOpts, _) => {
+                    self.output.push(chr);
+                }
+            }
+        }
+
+        if self.state != State::NotExpr {
+            return Err(());
+        }
+
+        self.parsed = true;
+        Ok(())
+    }
+
+    pub fn into_suggestion(&self, macro_name: &str) -> String {
+        assert!(self.parsed, "Attempt to get a suggestion from not parsed expression");
+
+        let expressions_as_string = self.extracted_expressions.join(", ");
+        format!(r#"{}("{}", {})"#, macro_name, self.output, expressions_as_string)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use expect_test::{expect, Expect};
+
+    fn check(input: &str, expect: &Expect) {
+        let mut parser = FormatStrParser::new((*input).to_owned());
+        let outcome_repr = if parser.parse().is_ok() {
+            // Parsing should be OK, expected repr is "string; expr_1, expr_2".
+            if parser.extracted_expressions.is_empty() {
+                parser.output
+            } else {
+                format!("{}; {}", parser.output, parser.extracted_expressions.join(", "))
+            }
+        } else {
+            // Parsing should fail, expected repr is "-".
+            "-".to_owned()
+        };
+
+        expect.assert_eq(&outcome_repr);
+    }
+
+    #[test]
+    fn format_str_parser() {
+        let test_vector = &[
+            ("no expressions", expect![["no expressions"]]),
+            ("{expr} is {2 + 2}", expect![["{} is {}; expr, 2 + 2"]]),
+            ("{expr:?}", expect![["{:?}; expr"]]),
+            ("{malformed", expect![["-"]]),
+            ("malformed}", expect![["-"]]),
+            ("{{correct", expect![["{{correct"]]),
+            ("correct}}", expect![["correct}}"]]),
+            ("{correct}}}", expect![["{}}}; correct"]]),
+            ("{correct}}}}}", expect![["{}}}}}; correct"]]),
+            ("{incorrect}}", expect![["-"]]),
+            ("placeholders {} {}", expect![["placeholders {} {}; $1, $2"]]),
+            ("mixed {} {2 + 2} {}", expect![["mixed {} {} {}; $1, 2 + 2, $2"]]),
+            (
+                "{SomeStruct { val_a: 0, val_b: 1 }}",
+                expect![["{}; SomeStruct { val_a: 0, val_b: 1 }"]],
+            ),
+            ("{expr:?} is {2.32f64:.5}", expect![["{:?} is {:.5}; expr, 2.32f64"]]),
+            (
+                "{SomeStruct { val_a: 0, val_b: 1 }:?}",
+                expect![["{:?}; SomeStruct { val_a: 0, val_b: 1 }"]],
+            ),
+            ("{     2 + 2        }", expect![["{}; 2 + 2"]]),
+        ];
+
+        for (input, output) in test_vector {
+            check(input, output)
+        }
+    }
+
+    #[test]
+    fn test_into_suggestion() {
+        let test_vector = &[
+            ("println!", "{}", r#"println!("{}", $1)"#),
+            (
+                "log::info!",
+                "{} {expr} {} {2 + 2}",
+                r#"log::info!("{} {} {} {}", $1, expr, $2, 2 + 2)"#,
+            ),
+            ("format!", "{expr:?}", r#"format!("{:?}", expr)"#),
+        ];
+
+        for (kind, input, output) in test_vector {
+            let mut parser = FormatStrParser::new((*input).to_owned());
+            parser.parse().expect("Parsing must succeed");
+
+            assert_eq!(&parser.into_suggestion(*kind), output);
+        }
+    }
+}
diff --git a/crates/ide/src/completion/complete_qualified_path.rs b/crates/ide/src/completion/complete_qualified_path.rs
index 00e89f0fd..2fafedd47 100644
--- a/crates/ide/src/completion/complete_qualified_path.rs
+++ b/crates/ide/src/completion/complete_qualified_path.rs
@@ -422,10 +422,10 @@ fn foo() { let _ = U::<|> }
     fn completes_use_paths_across_crates() {
         check(
             r#"
-//- /main.rs
+//- /main.rs crate:main deps:foo
 use foo::<|>;
 
-//- /foo/lib.rs
+//- /foo/lib.rs crate:foo
 pub mod bar { pub struct S; }
 "#,
             expect![[r#"
diff --git a/crates/ide/src/completion/complete_unqualified_path.rs b/crates/ide/src/completion/complete_unqualified_path.rs
index 8eda4b64d..8b6757195 100644
--- a/crates/ide/src/completion/complete_unqualified_path.rs
+++ b/crates/ide/src/completion/complete_unqualified_path.rs
@@ -267,14 +267,34 @@ fn quux() { <|> }
         );
     }
 
+    /// Regression test for issue #6091.
+    #[test]
+    fn correctly_completes_module_items_prefixed_with_underscore() {
+        check_edit(
+            "_alpha",
+            r#"
+fn main() {
+    _<|>
+}
+fn _alpha() {}
+"#,
+            r#"
+fn main() {
+    _alpha()$0
+}
+fn _alpha() {}
+"#,
+        )
+    }
+
     #[test]
     fn completes_extern_prelude() {
         check(
             r#"
-//- /lib.rs
+//- /lib.rs crate:main deps:other_crate
 use <|>;
 
-//- /other_crate/lib.rs
+//- /other_crate/lib.rs crate:other_crate
 // nothing here
 "#,
             expect![[r#"
@@ -350,10 +370,10 @@ fn foo() {
     fn completes_prelude() {
         check(
             r#"
-//- /main.rs
+//- /main.rs crate:main deps:std
 fn foo() { let x: <|> }
 
-//- /std/lib.rs
+//- /std/lib.rs crate:std
 #[prelude_import]
 use prelude::*;
 
@@ -371,16 +391,16 @@ mod prelude { struct Option; }
     fn completes_std_prelude_if_core_is_defined() {
         check(
             r#"
-//- /main.rs
+//- /main.rs crate:main deps:core,std
 fn foo() { let x: <|> }
 
-//- /core/lib.rs
+//- /core/lib.rs crate:core
 #[prelude_import]
 use prelude::*;
 
 mod prelude { struct Option; }
 
-//- /std/lib.rs
+//- /std/lib.rs crate:std deps:core
 #[prelude_import]
 use prelude::*;
 
diff --git a/crates/ide/src/completion/completion_context.rs b/crates/ide/src/completion/completion_context.rs
index 671b13328..8dea8a4bf 100644
--- a/crates/ide/src/completion/completion_context.rs
+++ b/crates/ide/src/completion/completion_context.rs
@@ -221,10 +221,11 @@ impl<'a> CompletionContext<'a> {
         Some(ctx)
     }
 
-    // The range of the identifier that is being completed.
+    /// The range of the identifier that is being completed.
     pub(crate) fn source_range(&self) -> TextRange {
         // check kind of macro-expanded token, but use range of original token
-        if self.token.kind() == IDENT || self.token.kind().is_keyword() {
+        let kind = self.token.kind();
+        if kind == IDENT || kind == UNDERSCORE || kind.is_keyword() {
             mark::hit!(completes_if_prefix_is_keyword);
             self.original_token.text_range()
         } else {
@@ -469,7 +470,7 @@ impl<'a> CompletionContext<'a> {
                     }
                 } else {
                     false
-                }
+                };
         }
         if let Some(method_call_expr) = ast::MethodCallExpr::cast(parent) {
             // As above
diff --git a/crates/ide/src/completion/presentation.rs b/crates/ide/src/completion/presentation.rs
index 987cbfa7a..a5172b87e 100644
--- a/crates/ide/src/completion/presentation.rs
+++ b/crates/ide/src/completion/presentation.rs
@@ -1172,9 +1172,9 @@ fn foo(xs: Vec<i128>)
         check_edit(
             "frobnicate!",
             r#"
-//- /main.rs
+//- /main.rs crate:main deps:foo
 use foo::<|>;
-//- /foo/lib.rs
+//- /foo/lib.rs crate:foo
 #[macro_export]
 macro_rules frobnicate { () => () }
 "#,
diff --git a/crates/ide/src/completion/test_utils.rs b/crates/ide/src/completion/test_utils.rs
index 1452d7e9e..feb8cd2a6 100644
--- a/crates/ide/src/completion/test_utils.rs
+++ b/crates/ide/src/completion/test_utils.rs
@@ -8,8 +8,7 @@ use test_utils::assert_eq_text;
 
 use crate::{
     completion::{completion_item::CompletionKind, CompletionConfig},
-    mock_analysis::analysis_and_position,
-    CompletionItem,
+    fixture, CompletionItem,
 };
 
 pub(crate) fn do_completion(code: &str, kind: CompletionKind) -> Vec<CompletionItem> {
@@ -80,7 +79,7 @@ pub(crate) fn check_edit_with_config(
     ra_fixture_after: &str,
 ) {
     let ra_fixture_after = trim_indent(ra_fixture_after);
-    let (analysis, position) = analysis_and_position(ra_fixture_before);
+    let (analysis, position) = fixture::position(ra_fixture_before);
     let completions: Vec<CompletionItem> =
         analysis.completions(&config, position).unwrap().unwrap().into();
     let (completion,) = completions
@@ -94,7 +93,7 @@ pub(crate) fn check_edit_with_config(
 }
 
 pub(crate) fn check_pattern_is_applicable(code: &str, check: fn(SyntaxElement) -> bool) {
-    let (analysis, pos) = analysis_and_position(code);
+    let (analysis, pos) = fixture::position(code);
     analysis
         .with_db(|db| {
             let sema = Semantics::new(db);
@@ -109,6 +108,6 @@ pub(crate) fn get_all_completion_items(
     config: CompletionConfig,
     code: &str,
 ) -> Vec<CompletionItem> {
-    let (analysis, position) = analysis_and_position(code);
+    let (analysis, position) = fixture::position(code);
     analysis.completions(&config, position).unwrap().unwrap().into()
 }
diff --git a/crates/ide/src/diagnostics.rs b/crates/ide/src/diagnostics.rs
index dc815a483..f5d627b6e 100644
--- a/crates/ide/src/diagnostics.rs
+++ b/crates/ide/src/diagnostics.rs
@@ -218,10 +218,7 @@ mod tests {
     use stdx::trim_indent;
     use test_utils::assert_eq_text;
 
-    use crate::{
-        mock_analysis::{analysis_and_position, single_file, MockAnalysis},
-        DiagnosticsConfig,
-    };
+    use crate::{fixture, DiagnosticsConfig};
 
     /// Takes a multi-file input fixture with annotated cursor positions,
     /// and checks that:
@@ -231,7 +228,7 @@ mod tests {
     fn check_fix(ra_fixture_before: &str, ra_fixture_after: &str) {
         let after = trim_indent(ra_fixture_after);
 
-        let (analysis, file_position) = analysis_and_position(ra_fixture_before);
+        let (analysis, file_position) = fixture::position(ra_fixture_before);
         let diagnostic = analysis
             .diagnostics(&DiagnosticsConfig::default(), file_position.file_id)
             .unwrap()
@@ -260,7 +257,7 @@ mod tests {
     /// which has a fix that can apply to other files.
     fn check_apply_diagnostic_fix_in_other_file(ra_fixture_before: &str, ra_fixture_after: &str) {
         let ra_fixture_after = &trim_indent(ra_fixture_after);
-        let (analysis, file_pos) = analysis_and_position(ra_fixture_before);
+        let (analysis, file_pos) = fixture::position(ra_fixture_before);
         let current_file_id = file_pos.file_id;
         let diagnostic = analysis
             .diagnostics(&DiagnosticsConfig::default(), current_file_id)
@@ -282,9 +279,7 @@ mod tests {
     /// Takes a multi-file input fixture with annotated cursor position and checks that no diagnostics
     /// apply to the file containing the cursor.
     fn check_no_diagnostics(ra_fixture: &str) {
-        let mock = MockAnalysis::with_files(ra_fixture);
-        let files = mock.files().map(|(it, _)| it).collect::<Vec<_>>();
-        let analysis = mock.analysis();
+        let (analysis, files) = fixture::files(ra_fixture);
         let diagnostics = files
             .into_iter()
             .flat_map(|file_id| {
@@ -295,7 +290,7 @@ mod tests {
     }
 
     fn check_expect(ra_fixture: &str, expect: Expect) {
-        let (analysis, file_id) = single_file(ra_fixture);
+        let (analysis, file_id) = fixture::file(ra_fixture);
         let diagnostics = analysis.diagnostics(&DiagnosticsConfig::default(), file_id).unwrap();
         expect.assert_debug_eq(&diagnostics)
     }
@@ -304,7 +299,7 @@ mod tests {
     fn test_wrap_return_type() {
         check_fix(
             r#"
-//- /main.rs
+//- /main.rs crate:main deps:core
 use core::result::Result::{self, Ok, Err};
 
 fn div(x: i32, y: i32) -> Result<i32, ()> {
@@ -313,7 +308,7 @@ fn div(x: i32, y: i32) -> Result<i32, ()> {
     }
     x / y<|>
 }
-//- /core/lib.rs
+//- /core/lib.rs crate:core
 pub mod result {
     pub enum Result<T, E> { Ok(T), Err(E) }
 }
@@ -335,7 +330,7 @@ fn div(x: i32, y: i32) -> Result<i32, ()> {
     fn test_wrap_return_type_handles_generic_functions() {
         check_fix(
             r#"
-//- /main.rs
+//- /main.rs crate:main deps:core
 use core::result::Result::{self, Ok, Err};
 
 fn div<T>(x: T) -> Result<T, i32> {
@@ -344,7 +339,7 @@ fn div<T>(x: T) -> Result<T, i32> {
     }
     <|>x
 }
-//- /core/lib.rs
+//- /core/lib.rs crate:core
 pub mod result {
     pub enum Result<T, E> { Ok(T), Err(E) }
 }
@@ -366,7 +361,7 @@ fn div<T>(x: T) -> Result<T, i32> {
     fn test_wrap_return_type_handles_type_aliases() {
         check_fix(
             r#"
-//- /main.rs
+//- /main.rs crate:main deps:core
 use core::result::Result::{self, Ok, Err};
 
 type MyResult<T> = Result<T, ()>;
@@ -377,7 +372,7 @@ fn div(x: i32, y: i32) -> MyResult<i32> {
     }
     x <|>/ y
 }
-//- /core/lib.rs
+//- /core/lib.rs crate:core
 pub mod result {
     pub enum Result<T, E> { Ok(T), Err(E) }
 }
@@ -401,12 +396,12 @@ fn div(x: i32, y: i32) -> MyResult<i32> {
     fn test_wrap_return_type_not_applicable_when_expr_type_does_not_match_ok_type() {
         check_no_diagnostics(
             r#"
-//- /main.rs
+//- /main.rs crate:main deps:core
 use core::result::Result::{self, Ok, Err};
 
 fn foo() -> Result<(), i32> { 0 }
 
-//- /core/lib.rs
+//- /core/lib.rs crate:core
 pub mod result {
     pub enum Result<T, E> { Ok(T), Err(E) }
 }
@@ -418,14 +413,14 @@ pub mod result {
     fn test_wrap_return_type_not_applicable_when_return_type_is_not_result() {
         check_no_diagnostics(
             r#"
-//- /main.rs
+//- /main.rs crate:main deps:core
 use core::result::Result::{self, Ok, Err};
 
 enum SomeOtherEnum { Ok(i32), Err(String) }
 
 fn foo() -> SomeOtherEnum { 0 }
 
-//- /core/lib.rs
+//- /core/lib.rs crate:core
 pub mod result {
     pub enum Result<T, E> { Ok(T), Err(E) }
 }
@@ -567,7 +562,7 @@ fn test_fn() {
                                     file_system_edits: [
                                         CreateFile {
                                             anchor: FileId(
-                                                1,
+                                                0,
                                             ),
                                             dst: "foo.rs",
                                         },
@@ -787,7 +782,7 @@ struct Foo {
         let mut config = DiagnosticsConfig::default();
         config.disabled.insert("unresolved-module".into());
 
-        let (analysis, file_id) = single_file(r#"mod foo;"#);
+        let (analysis, file_id) = fixture::file(r#"mod foo;"#);
 
         let diagnostics = analysis.diagnostics(&config, file_id).unwrap();
         assert!(diagnostics.is_empty());
diff --git a/crates/ide/src/display/navigation_target.rs b/crates/ide/src/display/navigation_target.rs
index 1ee80c2dd..cf9d617dc 100644
--- a/crates/ide/src/display/navigation_target.rs
+++ b/crates/ide/src/display/navigation_target.rs
@@ -423,11 +423,11 @@ pub(crate) fn description_from_symbol(db: &RootDatabase, symbol: &FileSymbol) ->
 mod tests {
     use expect_test::expect;
 
-    use crate::{mock_analysis::single_file, Query};
+    use crate::{fixture, Query};
 
     #[test]
     fn test_nav_for_symbol() {
-        let (analysis, _) = single_file(
+        let (analysis, _) = fixture::file(
             r#"
 enum FooInner { }
 fn foo() { enum FooInner { } }
@@ -439,7 +439,7 @@ fn foo() { enum FooInner { } }
             [
                 NavigationTarget {
                     file_id: FileId(
-                        1,
+                        0,
                     ),
                     full_range: 0..17,
                     focus_range: Some(
@@ -455,7 +455,7 @@ fn foo() { enum FooInner { } }
                 },
                 NavigationTarget {
                     file_id: FileId(
-                        1,
+                        0,
                     ),
                     full_range: 29..46,
                     focus_range: Some(
@@ -478,7 +478,7 @@ fn foo() { enum FooInner { } }
 
     #[test]
     fn test_world_symbols_are_case_sensitive() {
-        let (analysis, _) = single_file(
+        let (analysis, _) = fixture::file(
             r#"
 fn foo() {}
 struct Foo;
diff --git a/crates/ide/src/expand_macro.rs b/crates/ide/src/expand_macro.rs
index 8a285bcf7..8d75e0f05 100644
--- a/crates/ide/src/expand_macro.rs
+++ b/crates/ide/src/expand_macro.rs
@@ -122,10 +122,10 @@ fn insert_whitespaces(syn: SyntaxNode) -> String {
 mod tests {
     use expect_test::{expect, Expect};
 
-    use crate::mock_analysis::analysis_and_position;
+    use crate::fixture;
 
     fn check(ra_fixture: &str, expect: Expect) {
-        let (analysis, pos) = analysis_and_position(ra_fixture);
+        let (analysis, pos) = fixture::position(ra_fixture);
         let expansion = analysis.expand_macro(pos).unwrap().unwrap();
         let actual = format!("{}\n{}", expansion.name, expansion.expansion);
         expect.assert_eq(&actual);
diff --git a/crates/ide/src/extend_selection.rs b/crates/ide/src/extend_selection.rs
index 34563a026..3ee0af8ad 100644
--- a/crates/ide/src/extend_selection.rs
+++ b/crates/ide/src/extend_selection.rs
@@ -315,12 +315,12 @@ fn adj_comments(comment: &ast::Comment, dir: Direction) -> ast::Comment {
 
 #[cfg(test)]
 mod tests {
-    use crate::mock_analysis::analysis_and_position;
+    use crate::fixture;
 
     use super::*;
 
     fn do_check(before: &str, afters: &[&str]) {
-        let (analysis, position) = analysis_and_position(&before);
+        let (analysis, position) = fixture::position(&before);
         let before = analysis.file_text(position.file_id).unwrap();
         let range = TextRange::empty(position.offset);
         let mut frange = FileRange { file_id: position.file_id, range };
diff --git a/crates/ide/src/fixture.rs b/crates/ide/src/fixture.rs
new file mode 100644
index 000000000..ed06689f0
--- /dev/null
+++ b/crates/ide/src/fixture.rs
@@ -0,0 +1,70 @@
+//! Utilities for creating `Analysis` instances for tests.
+use base_db::fixture::ChangeFixture;
+use test_utils::{extract_annotations, RangeOrOffset};
+
+use crate::{Analysis, AnalysisHost, FileId, FilePosition, FileRange};
+
+/// Creates analysis for a single file.
+pub(crate) fn file(ra_fixture: &str) -> (Analysis, FileId) {
+    let mut host = AnalysisHost::default();
+    let change_fixture = ChangeFixture::parse(ra_fixture);
+    host.db.apply_change(change_fixture.change);
+    (host.analysis(), change_fixture.files[0])
+}
+
+/// Creates analysis for many files.
+pub(crate) fn files(ra_fixture: &str) -> (Analysis, Vec<FileId>) {
+    let mut host = AnalysisHost::default();
+    let change_fixture = ChangeFixture::parse(ra_fixture);
+    host.db.apply_change(change_fixture.change);
+    (host.analysis(), change_fixture.files)
+}
+
+/// Creates analysis from a multi-file fixture, returns positions marked with <|>.
+pub(crate) fn position(ra_fixture: &str) -> (Analysis, FilePosition) {
+    let mut host = AnalysisHost::default();
+    let change_fixture = ChangeFixture::parse(ra_fixture);
+    host.db.apply_change(change_fixture.change);
+    let (file_id, range_or_offset) = change_fixture.file_position.expect("expected a marker (<|>)");
+    let offset = match range_or_offset {
+        RangeOrOffset::Range(_) => panic!(),
+        RangeOrOffset::Offset(it) => it,
+    };
+    (host.analysis(), FilePosition { file_id, offset })
+}
+
+/// Creates analysis for a single file, returns range marked with a pair of <|>.
+pub(crate) fn range(ra_fixture: &str) -> (Analysis, FileRange) {
+    let mut host = AnalysisHost::default();
+    let change_fixture = ChangeFixture::parse(ra_fixture);
+    host.db.apply_change(change_fixture.change);
+    let (file_id, range_or_offset) = change_fixture.file_position.expect("expected a marker (<|>)");
+    let range = match range_or_offset {
+        RangeOrOffset::Range(it) => it,
+        RangeOrOffset::Offset(_) => panic!(),
+    };
+    (host.analysis(), FileRange { file_id, range })
+}
+
+/// Creates analysis from a multi-file fixture, returns positions marked with <|>.
+pub(crate) fn annotations(ra_fixture: &str) -> (Analysis, FilePosition, Vec<(FileRange, String)>) {
+    let mut host = AnalysisHost::default();
+    let change_fixture = ChangeFixture::parse(ra_fixture);
+    host.db.apply_change(change_fixture.change);
+    let (file_id, range_or_offset) = change_fixture.file_position.expect("expected a marker (<|>)");
+    let offset = match range_or_offset {
+        RangeOrOffset::Range(_) => panic!(),
+        RangeOrOffset::Offset(it) => it,
+    };
+
+    let annotations = change_fixture
+        .files
+        .iter()
+        .flat_map(|&file_id| {
+            let file_text = host.analysis().file_text(file_id).unwrap();
+            let annotations = extract_annotations(&file_text);
+            annotations.into_iter().map(move |(range, data)| (FileRange { file_id, range }, data))
+        })
+        .collect();
+    (host.analysis(), FilePosition { file_id, offset }, annotations)
+}
diff --git a/crates/ide/src/fn_references.rs b/crates/ide/src/fn_references.rs
index 1989a562b..459f201ed 100644
--- a/crates/ide/src/fn_references.rs
+++ b/crates/ide/src/fn_references.rs
@@ -25,15 +25,14 @@ fn method_range(item: SyntaxNode, file_id: FileId) -> Option<FileRange> {
 
 #[cfg(test)]
 mod tests {
-    use crate::mock_analysis::analysis_and_position;
+    use crate::fixture;
     use crate::{FileRange, TextSize};
     use std::ops::RangeInclusive;
 
     #[test]
     fn test_find_all_methods() {
-        let (analysis, pos) = analysis_and_position(
+        let (analysis, pos) = fixture::position(
             r#"
-            //- /lib.rs
             fn private_fn() {<|>}
 
             pub fn pub_fn() {}
@@ -48,9 +47,8 @@ mod tests {
 
     #[test]
     fn test_find_trait_methods() {
-        let (analysis, pos) = analysis_and_position(
+        let (analysis, pos) = fixture::position(
             r#"
-            //- /lib.rs
             trait Foo {
                 fn bar() {<|>}
                 fn baz() {}
@@ -64,7 +62,7 @@ mod tests {
 
     #[test]
     fn test_skip_tests() {
-        let (analysis, pos) = analysis_and_position(
+        let (analysis, pos) = fixture::position(
             r#"
             //- /lib.rs
             #[test]
diff --git a/crates/ide/src/goto_definition.rs b/crates/ide/src/goto_definition.rs
index 15e9b7fad..582bf4837 100644
--- a/crates/ide/src/goto_definition.rs
+++ b/crates/ide/src/goto_definition.rs
@@ -103,12 +103,11 @@ mod tests {
     use base_db::FileRange;
     use syntax::{TextRange, TextSize};
 
-    use crate::mock_analysis::MockAnalysis;
+    use crate::fixture;
 
     fn check(ra_fixture: &str) {
-        let (mock, position) = MockAnalysis::with_files_and_position(ra_fixture);
-        let (mut expected, data) = mock.annotation();
-        let analysis = mock.analysis();
+        let (analysis, position, mut annotations) = fixture::annotations(ra_fixture);
+        let (mut expected, data) = annotations.pop().unwrap();
         match data.as_str() {
             "" => (),
             "file" => {
@@ -133,9 +132,9 @@ mod tests {
     fn goto_def_for_extern_crate() {
         check(
             r#"
-            //- /main.rs
+            //- /main.rs crate:main deps:std
             extern crate std<|>;
-            //- /std/lib.rs
+            //- /std/lib.rs crate:std
             // empty
             //^ file
             "#,
@@ -146,9 +145,9 @@ mod tests {
     fn goto_def_for_renamed_extern_crate() {
         check(
             r#"
-            //- /main.rs
+            //- /main.rs crate:main deps:std
             extern crate std as abc<|>;
-            //- /std/lib.rs
+            //- /std/lib.rs crate:std
             // empty
             //^ file
             "#,
@@ -342,10 +341,10 @@ fn bar() {
     fn goto_def_for_use_alias() {
         check(
             r#"
-//- /lib.rs
+//- /lib.rs crate:main deps:foo
 use foo as bar<|>;
 
-//- /foo/lib.rs
+//- /foo/lib.rs crate:foo
 // empty
 //^ file
 "#,
@@ -356,10 +355,10 @@ use foo as bar<|>;
     fn goto_def_for_use_alias_foo_macro() {
         check(
             r#"
-//- /lib.rs
+//- /lib.rs crate:main deps:foo
 use foo::foo as bar<|>;
 
-//- /foo/lib.rs
+//- /foo/lib.rs crate:foo
 #[macro_export]
 macro_rules! foo { () => { () } }
            //^^^
@@ -371,7 +370,6 @@ macro_rules! foo { () => { () } }
     fn goto_def_for_methods() {
         check(
             r#"
-//- /lib.rs
 struct Foo;
 impl Foo {
     fn frobnicate(&self) { }
diff --git a/crates/ide/src/goto_implementation.rs b/crates/ide/src/goto_implementation.rs
index f503f4ec5..6c586bbd1 100644
--- a/crates/ide/src/goto_implementation.rs
+++ b/crates/ide/src/goto_implementation.rs
@@ -76,12 +76,10 @@ fn impls_for_trait(
 mod tests {
     use base_db::FileRange;
 
-    use crate::mock_analysis::MockAnalysis;
+    use crate::fixture;
 
     fn check(ra_fixture: &str) {
-        let (mock, position) = MockAnalysis::with_files_and_position(ra_fixture);
-        let annotations = mock.annotations();
-        let analysis = mock.analysis();
+        let (analysis, position, annotations) = fixture::annotations(ra_fixture);
 
         let navs = analysis.goto_implementation(position).unwrap().unwrap().info;
 
diff --git a/crates/ide/src/goto_type_definition.rs b/crates/ide/src/goto_type_definition.rs
index 4a151b150..6d0df04dd 100644
--- a/crates/ide/src/goto_type_definition.rs
+++ b/crates/ide/src/goto_type_definition.rs
@@ -56,13 +56,12 @@ fn pick_best(tokens: TokenAtOffset<SyntaxToken>) -> Option<SyntaxToken> {
 mod tests {
     use base_db::FileRange;
 
-    use crate::mock_analysis::MockAnalysis;
+    use crate::fixture;
 
     fn check(ra_fixture: &str) {
-        let (mock, position) = MockAnalysis::with_files_and_position(ra_fixture);
-        let (expected, data) = mock.annotation();
+        let (analysis, position, mut annotations) = fixture::annotations(ra_fixture);
+        let (expected, data) = annotations.pop().unwrap();
         assert!(data.is_empty());
-        let analysis = mock.analysis();
 
         let mut navs = analysis.goto_type_definition(position).unwrap().unwrap().info;
         assert_eq!(navs.len(), 1);
diff --git a/crates/ide/src/hover.rs b/crates/ide/src/hover.rs
index bb9f12cd3..9cf02f0a3 100644
--- a/crates/ide/src/hover.rs
+++ b/crates/ide/src/hover.rs
@@ -377,17 +377,17 @@ mod tests {
     use base_db::FileLoader;
     use expect_test::{expect, Expect};
 
-    use crate::mock_analysis::analysis_and_position;
+    use crate::fixture;
 
     use super::*;
 
     fn check_hover_no_result(ra_fixture: &str) {
-        let (analysis, position) = analysis_and_position(ra_fixture);
+        let (analysis, position) = fixture::position(ra_fixture);
         assert!(analysis.hover(position, true).unwrap().is_none());
     }
 
     fn check(ra_fixture: &str, expect: Expect) {
-        let (analysis, position) = analysis_and_position(ra_fixture);
+        let (analysis, position) = fixture::position(ra_fixture);
         let hover = analysis.hover(position, true).unwrap().unwrap();
 
         let content = analysis.db.file_text(position.file_id);
@@ -398,7 +398,7 @@ mod tests {
     }
 
     fn check_hover_no_links(ra_fixture: &str, expect: Expect) {
-        let (analysis, position) = analysis_and_position(ra_fixture);
+        let (analysis, position) = fixture::position(ra_fixture);
         let hover = analysis.hover(position, false).unwrap().unwrap();
 
         let content = analysis.db.file_text(position.file_id);
@@ -409,7 +409,7 @@ mod tests {
     }
 
     fn check_actions(ra_fixture: &str, expect: Expect) {
-        let (analysis, position) = analysis_and_position(ra_fixture);
+        let (analysis, position) = fixture::position(ra_fixture);
         let hover = analysis.hover(position, true).unwrap().unwrap();
         expect.assert_debug_eq(&hover.info.actions)
     }
@@ -963,7 +963,7 @@ impl Thing {
             "#]],
         )
     } /* FIXME: revive these tests
-              let (analysis, position) = analysis_and_position(
+              let (analysis, position) = fixture::position(
                   "
                   struct Thing { x: u32 }
                   impl Thing {
@@ -977,7 +977,7 @@ impl Thing {
               let hover = analysis.hover(position).unwrap().unwrap();
               assert_eq!(trim_markup(&hover.info.markup.as_str()), ("Thing"));
 
-              let (analysis, position) = analysis_and_position(
+              let (analysis, position) = fixture::position(
                   "
                   enum Thing { A }
                   impl Thing {
@@ -990,7 +990,7 @@ impl Thing {
               let hover = analysis.hover(position).unwrap().unwrap();
               assert_eq!(trim_markup(&hover.info.markup.as_str()), ("enum Thing"));
 
-              let (analysis, position) = analysis_and_position(
+              let (analysis, position) = fixture::position(
                   "
                   enum Thing { A }
                   impl Thing {
@@ -1275,7 +1275,7 @@ fn bar() { fo<|>o(); }
                     Implementaion(
                         FilePosition {
                             file_id: FileId(
-                                1,
+                                0,
                             ),
                             offset: 13,
                         },
@@ -1289,9 +1289,9 @@ fn bar() { fo<|>o(); }
     fn test_hover_extern_crate() {
         check(
             r#"
-//- /main.rs
+//- /main.rs crate:main deps:std
 extern crate st<|>d;
-//- /std/lib.rs
+//- /std/lib.rs crate:std
 //! Standard library for this test
 //!
 //! Printed?
@@ -1307,9 +1307,9 @@ extern crate st<|>d;
         );
         check(
             r#"
-//- /main.rs
+//- /main.rs crate:main deps:std
 extern crate std as ab<|>c;
-//- /std/lib.rs
+//- /std/lib.rs crate:std
 //! Standard library for this test
 //!
 //! Printed?
@@ -1989,7 +1989,7 @@ fn foo() { let bar = Bar; bar.fo<|>o(); }
                     Implementaion(
                         FilePosition {
                             file_id: FileId(
-                                1,
+                                0,
                             ),
                             offset: 6,
                         },
@@ -2008,7 +2008,7 @@ fn foo() { let bar = Bar; bar.fo<|>o(); }
                     Implementaion(
                         FilePosition {
                             file_id: FileId(
-                                1,
+                                0,
                             ),
                             offset: 7,
                         },
@@ -2027,7 +2027,7 @@ fn foo() { let bar = Bar; bar.fo<|>o(); }
                     Implementaion(
                         FilePosition {
                             file_id: FileId(
-                                1,
+                                0,
                             ),
                             offset: 6,
                         },
@@ -2046,7 +2046,7 @@ fn foo() { let bar = Bar; bar.fo<|>o(); }
                     Implementaion(
                         FilePosition {
                             file_id: FileId(
-                                1,
+                                0,
                             ),
                             offset: 5,
                         },
@@ -2069,7 +2069,7 @@ fn foo_<|>test() {}
                         Runnable {
                             nav: NavigationTarget {
                                 file_id: FileId(
-                                    1,
+                                    0,
                                 ),
                                 full_range: 0..24,
                                 focus_range: Some(
@@ -2112,7 +2112,7 @@ mod tests<|> {
                         Runnable {
                             nav: NavigationTarget {
                                 file_id: FileId(
-                                    1,
+                                    0,
                                 ),
                                 full_range: 0..46,
                                 focus_range: Some(
@@ -2151,7 +2151,7 @@ fn main() { let s<|>t = S{ f1:0 }; }
                                 mod_path: "test::S",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 0..19,
                                     focus_range: Some(
@@ -2190,7 +2190,7 @@ fn main() { let s<|>t = S{ f1:Arg(0) }; }
                                 mod_path: "test::S",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 17..37,
                                     focus_range: Some(
@@ -2209,7 +2209,7 @@ fn main() { let s<|>t = S{ f1:Arg(0) }; }
                                 mod_path: "test::Arg",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 0..16,
                                     focus_range: Some(
@@ -2248,7 +2248,7 @@ fn main() { let s<|>t = S{ f1: S{ f1: Arg(0) } }; }
                                 mod_path: "test::S",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 17..37,
                                     focus_range: Some(
@@ -2267,7 +2267,7 @@ fn main() { let s<|>t = S{ f1: S{ f1: Arg(0) } }; }
                                 mod_path: "test::Arg",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 0..16,
                                     focus_range: Some(
@@ -2309,7 +2309,7 @@ fn main() { let s<|>t = (A(1), B(2), M::C(3) ); }
                                 mod_path: "test::A",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 0..14,
                                     focus_range: Some(
@@ -2328,7 +2328,7 @@ fn main() { let s<|>t = (A(1), B(2), M::C(3) ); }
                                 mod_path: "test::B",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 15..29,
                                     focus_range: Some(
@@ -2347,7 +2347,7 @@ fn main() { let s<|>t = (A(1), B(2), M::C(3) ); }
                                 mod_path: "test::M::C",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 42..60,
                                     focus_range: Some(
@@ -2386,7 +2386,7 @@ fn main() { let s<|>t = foo(); }
                                 mod_path: "test::Foo",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 0..12,
                                     focus_range: Some(
@@ -2426,7 +2426,7 @@ fn main() { let s<|>t = foo(); }
                                 mod_path: "test::Foo",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 0..15,
                                     focus_range: Some(
@@ -2445,7 +2445,7 @@ fn main() { let s<|>t = foo(); }
                                 mod_path: "test::S",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 16..25,
                                     focus_range: Some(
@@ -2485,7 +2485,7 @@ fn main() { let s<|>t = foo(); }
                                 mod_path: "test::Foo",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 0..12,
                                     focus_range: Some(
@@ -2504,7 +2504,7 @@ fn main() { let s<|>t = foo(); }
                                 mod_path: "test::Bar",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 13..25,
                                     focus_range: Some(
@@ -2547,7 +2547,7 @@ fn main() { let s<|>t = foo(); }
                                 mod_path: "test::Foo",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 0..15,
                                     focus_range: Some(
@@ -2566,7 +2566,7 @@ fn main() { let s<|>t = foo(); }
                                 mod_path: "test::Bar",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 16..31,
                                     focus_range: Some(
@@ -2585,7 +2585,7 @@ fn main() { let s<|>t = foo(); }
                                 mod_path: "test::S1",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 32..44,
                                     focus_range: Some(
@@ -2604,7 +2604,7 @@ fn main() { let s<|>t = foo(); }
                                 mod_path: "test::S2",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 45..57,
                                     focus_range: Some(
@@ -2641,7 +2641,7 @@ fn foo(ar<|>g: &impl Foo) {}
                                 mod_path: "test::Foo",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 0..12,
                                     focus_range: Some(
@@ -2681,7 +2681,7 @@ fn foo(ar<|>g: &impl Foo + Bar<S>) {}
                                 mod_path: "test::Foo",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 0..12,
                                     focus_range: Some(
@@ -2700,7 +2700,7 @@ fn foo(ar<|>g: &impl Foo + Bar<S>) {}
                                 mod_path: "test::Bar",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 13..28,
                                     focus_range: Some(
@@ -2719,7 +2719,7 @@ fn foo(ar<|>g: &impl Foo + Bar<S>) {}
                                 mod_path: "test::S",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 29..39,
                                     focus_range: Some(
@@ -2764,7 +2764,7 @@ mod future {
                                 mod_path: "test::future::Future",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 101..163,
                                     focus_range: Some(
@@ -2783,7 +2783,7 @@ mod future {
                                 mod_path: "test::S",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 0..9,
                                     focus_range: Some(
@@ -2821,7 +2821,7 @@ fn foo(ar<|>g: &impl Foo<S>) {}
                                 mod_path: "test::Foo",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 0..15,
                                     focus_range: Some(
@@ -2840,7 +2840,7 @@ fn foo(ar<|>g: &impl Foo<S>) {}
                                 mod_path: "test::S",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 16..27,
                                     focus_range: Some(
@@ -2883,7 +2883,7 @@ fn main() { let s<|>t = foo(); }
                                 mod_path: "test::B",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 42..55,
                                     focus_range: Some(
@@ -2902,7 +2902,7 @@ fn main() { let s<|>t = foo(); }
                                 mod_path: "test::Foo",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 0..12,
                                     focus_range: Some(
@@ -2939,7 +2939,7 @@ fn foo(ar<|>g: &dyn Foo) {}
                                 mod_path: "test::Foo",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 0..12,
                                     focus_range: Some(
@@ -2977,7 +2977,7 @@ fn foo(ar<|>g: &dyn Foo<S>) {}
                                 mod_path: "test::Foo",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 0..15,
                                     focus_range: Some(
@@ -2996,7 +2996,7 @@ fn foo(ar<|>g: &dyn Foo<S>) {}
                                 mod_path: "test::S",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 16..27,
                                     focus_range: Some(
@@ -3037,7 +3037,7 @@ fn foo(a<|>rg: &impl ImplTrait<B<dyn DynTrait<B<S>>>>) {}
                                 mod_path: "test::ImplTrait",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 0..21,
                                     focus_range: Some(
@@ -3056,7 +3056,7 @@ fn foo(a<|>rg: &impl ImplTrait<B<dyn DynTrait<B<S>>>>) {}
                                 mod_path: "test::B",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 43..57,
                                     focus_range: Some(
@@ -3075,7 +3075,7 @@ fn foo(a<|>rg: &impl ImplTrait<B<dyn DynTrait<B<S>>>>) {}
                                 mod_path: "test::DynTrait",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 22..42,
                                     focus_range: Some(
@@ -3094,7 +3094,7 @@ fn foo(a<|>rg: &impl ImplTrait<B<dyn DynTrait<B<S>>>>) {}
                                 mod_path: "test::S",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 58..69,
                                     focus_range: Some(
@@ -3142,7 +3142,7 @@ fn main() { let s<|>t = test().get(); }
                                 mod_path: "test::Foo",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        1,
+                                        0,
                                     ),
                                     full_range: 0..62,
                                     focus_range: Some(
diff --git a/crates/ide/src/inlay_hints.rs b/crates/ide/src/inlay_hints.rs
index 583f39d85..1d7e8de56 100644
--- a/crates/ide/src/inlay_hints.rs
+++ b/crates/ide/src/inlay_hints.rs
@@ -189,7 +189,7 @@ fn get_bind_pat_hints(
 
     let ty = sema.type_of_pat(&pat.clone().into())?;
 
-    if should_not_display_type_hint(sema.db, &pat, &ty) {
+    if should_not_display_type_hint(sema, &pat, &ty) {
         return None;
     }
 
@@ -215,10 +215,12 @@ fn pat_is_enum_variant(db: &RootDatabase, bind_pat: &ast::IdentPat, pat_ty: &Typ
 }
 
 fn should_not_display_type_hint(
-    db: &RootDatabase,
+    sema: &Semantics<RootDatabase>,
     bind_pat: &ast::IdentPat,
     pat_ty: &Type,
 ) -> bool {
+    let db = sema.db;
+
     if pat_ty.is_unknown() {
         return true;
     }
@@ -249,6 +251,15 @@ fn should_not_display_type_hint(
                     return it.condition().and_then(|condition| condition.pat()).is_some()
                         && pat_is_enum_variant(db, bind_pat, pat_ty);
                 },
+                ast::ForExpr(it) => {
+                    // We *should* display hint only if user provided "in {expr}" and we know the type of expr (and it's not unit).
+                    // Type of expr should be iterable.
+                    return it.in_token().is_none() ||
+                        it.iterable()
+                            .and_then(|iterable_expr|sema.type_of_expr(&iterable_expr))
+                            .map(|iterable_ty| iterable_ty.is_unknown() || iterable_ty.is_unit())
+                            .unwrap_or(true)
+                },
                 _ => (),
             }
         }
@@ -339,14 +350,14 @@ mod tests {
     use expect_test::{expect, Expect};
     use test_utils::extract_annotations;
 
-    use crate::{inlay_hints::InlayHintsConfig, mock_analysis::single_file};
+    use crate::{fixture, inlay_hints::InlayHintsConfig};
 
     fn check(ra_fixture: &str) {
         check_with_config(InlayHintsConfig::default(), ra_fixture);
     }
 
     fn check_with_config(config: InlayHintsConfig, ra_fixture: &str) {
-        let (analysis, file_id) = single_file(ra_fixture);
+        let (analysis, file_id) = fixture::file(ra_fixture);
         let expected = extract_annotations(&*analysis.file_text(file_id).unwrap());
         let inlay_hints = analysis.inlay_hints(file_id, &config).unwrap();
         let actual =
@@ -355,7 +366,7 @@ mod tests {
     }
 
     fn check_expect(config: InlayHintsConfig, ra_fixture: &str, expect: Expect) {
-        let (analysis, file_id) = single_file(ra_fixture);
+        let (analysis, file_id) = fixture::file(ra_fixture);
         let inlay_hints = analysis.inlay_hints(file_id, &config).unwrap();
         expect.assert_debug_eq(&inlay_hints)
     }
@@ -496,19 +507,6 @@ fn main() {
     }
 
     #[test]
-    fn for_expression() {
-        check(
-            r#"
-fn main() {
-    let mut start = 0;
-      //^^^^^^^^^ i32
-    for increment in 0..2 { start += increment; }
-      //^^^^^^^^^ i32
-}"#,
-        );
-    }
-
-    #[test]
     fn if_expr() {
         check(
             r#"
@@ -924,4 +922,108 @@ fn main() {
             "#]],
         );
     }
+
+    #[test]
+    fn incomplete_for_no_hint() {
+        check(
+            r#"
+fn main() {
+    let data = &[1i32, 2, 3];
+      //^^^^ &[i32; _]
+    for i
+}"#,
+        );
+        check(
+            r#"
+//- /main.rs crate:main deps:core
+pub struct Vec<T> {}
+
+impl<T> Vec<T> {
+    pub fn new() -> Self { Vec {} }
+    pub fn push(&mut self, t: T) {}
+}
+
+impl<T> IntoIterator for Vec<T> {
+    type Item=T;
+}
+
+fn main() {
+    let mut data = Vec::new();
+      //^^^^^^^^ Vec<&str>
+    data.push("foo");
+    for i in
+
+    println!("Unit expr");
+}
+
+//- /core.rs crate:core
+#[prelude_import] use iter::*;
+mod iter {
+    trait IntoIterator {
+        type Item;
+    }
+}
+//- /alloc.rs crate:alloc deps:core
+mod collections {
+    struct Vec<T> {}
+    impl<T> Vec<T> {
+        fn new() -> Self { Vec {} }
+        fn push(&mut self, t: T) { }
+    }
+    impl<T> IntoIterator for Vec<T> {
+        type Item=T;
+    }
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn complete_for_hint() {
+        check(
+            r#"
+//- /main.rs crate:main deps:core
+pub struct Vec<T> {}
+
+impl<T> Vec<T> {
+    pub fn new() -> Self { Vec {} }
+    pub fn push(&mut self, t: T) {}
+}
+
+impl<T> IntoIterator for Vec<T> {
+    type Item=T;
+}
+
+fn main() {
+    let mut data = Vec::new();
+      //^^^^^^^^ Vec<&str>
+    data.push("foo");
+    for i in data {
+      //^ &str
+      let z = i;
+        //^ &str
+    }
+}
+
+//- /core.rs crate:core
+#[prelude_import] use iter::*;
+mod iter {
+    trait IntoIterator {
+        type Item;
+    }
+}
+//- /alloc.rs crate:alloc deps:core
+mod collections {
+    struct Vec<T> {}
+    impl<T> Vec<T> {
+        fn new() -> Self { Vec {} }
+        fn push(&mut self, t: T) { }
+    }
+    impl<T> IntoIterator for Vec<T> {
+        type Item=T;
+    }
+}
+"#,
+        );
+    }
 }
diff --git a/crates/ide/src/lib.rs b/crates/ide/src/lib.rs
index 31f2bcba3..1aa673cf8 100644
--- a/crates/ide/src/lib.rs
+++ b/crates/ide/src/lib.rs
@@ -15,7 +15,8 @@ macro_rules! eprintln {
     ($($tt:tt)*) => { stdx::eprintln!($($tt)*) };
 }
 
-pub mod mock_analysis;
+#[cfg(test)]
+mod fixture;
 
 mod markup;
 mod prime_caches;
@@ -86,12 +87,11 @@ pub use assists::{
     utils::MergeBehaviour, Assist, AssistConfig, AssistId, AssistKind, ResolvedAssist,
 };
 pub use base_db::{
-    Canceled, CrateGraph, CrateId, Edition, FileId, FilePosition, FileRange, SourceRoot,
+    Canceled, Change, CrateGraph, CrateId, Edition, FileId, FilePosition, FileRange, SourceRoot,
     SourceRootId,
 };
 pub use hir::{Documentation, Semantics};
 pub use ide_db::{
-    change::AnalysisChange,
     label::Label,
     line_index::{LineCol, LineIndex},
     search::SearchScope,
@@ -140,14 +140,10 @@ impl AnalysisHost {
 
     /// Applies changes to the current state of the world. If there are
     /// outstanding snapshots, they will be canceled.
-    pub fn apply_change(&mut self, change: AnalysisChange) {
+    pub fn apply_change(&mut self, change: Change) {
         self.db.apply_change(change)
     }
 
-    pub fn maybe_collect_garbage(&mut self) {
-        self.db.maybe_collect_garbage();
-    }
-
     pub fn collect_garbage(&mut self) {
         self.db.collect_garbage();
     }
@@ -198,7 +194,7 @@ impl Analysis {
         file_set.insert(file_id, VfsPath::new_virtual_path("/main.rs".to_string()));
         let source_root = SourceRoot::new_local(file_set);
 
-        let mut change = AnalysisChange::new();
+        let mut change = Change::new();
         change.set_roots(vec![source_root]);
         let mut crate_graph = CrateGraph::default();
         // FIXME: cfg options
@@ -220,8 +216,8 @@ impl Analysis {
     }
 
     /// Debug info about the current state of the analysis.
-    pub fn status(&self) -> Cancelable<String> {
-        self.with_db(|db| status::status(&*db))
+    pub fn status(&self, file_id: Option<FileId>) -> Cancelable<String> {
+        self.with_db(|db| status::status(&*db, file_id))
     }
 
     pub fn prime_caches(&self, files: Vec<FileId>) -> Cancelable<()> {
diff --git a/crates/ide/src/link_rewrite.rs b/crates/ide/src/link_rewrite.rs
index 107787bb9..a16f90e17 100644
--- a/crates/ide/src/link_rewrite.rs
+++ b/crates/ide/src/link_rewrite.rs
@@ -120,7 +120,7 @@ fn rewrite_intra_doc_link(
 
 /// Try to resolve path to local documentation via path-based links (i.e. `../gateway/struct.Shard.html`).
 fn rewrite_url_link(db: &RootDatabase, def: ModuleDef, target: &str) -> Option<String> {
-    if !(target.contains("#") || target.contains(".html")) {
+    if !(target.contains('#') || target.contains(".html")) {
         return None;
     }
 
@@ -190,7 +190,7 @@ fn strip_prefixes_suffixes(mut s: &str) -> &str {
         prefixes.clone().for_each(|prefix| s = s.trim_start_matches(*prefix));
         suffixes.clone().for_each(|suffix| s = s.trim_end_matches(*suffix));
     });
-    s.trim_start_matches("@").trim()
+    s.trim_start_matches('@').trim()
 }
 
 static TYPES: ([&str; 7], [&str; 0]) =
diff --git a/crates/ide/src/mock_analysis.rs b/crates/ide/src/mock_analysis.rs
deleted file mode 100644
index 235796dbc..000000000
--- a/crates/ide/src/mock_analysis.rs
+++ /dev/null
@@ -1,176 +0,0 @@
-//! FIXME: write short doc here
-use std::sync::Arc;
-
-use base_db::{CrateName, FileSet, SourceRoot, VfsPath};
-use cfg::CfgOptions;
-use test_utils::{
-    extract_annotations, extract_range_or_offset, Fixture, RangeOrOffset, CURSOR_MARKER,
-};
-
-use crate::{
-    Analysis, AnalysisChange, AnalysisHost, CrateGraph, Edition, FileId, FilePosition, FileRange,
-};
-
-/// Mock analysis is used in test to bootstrap an AnalysisHost/Analysis
-/// from a set of in-memory files.
-#[derive(Debug, Default)]
-pub struct MockAnalysis {
-    files: Vec<Fixture>,
-}
-
-impl MockAnalysis {
-    /// Creates `MockAnalysis` using a fixture data in the following format:
-    ///
-    /// ```not_rust
-    /// //- /main.rs
-    /// mod foo;
-    /// fn main() {}
-    ///
-    /// //- /foo.rs
-    /// struct Baz;
-    /// ```
-    pub fn with_files(ra_fixture: &str) -> MockAnalysis {
-        let (res, pos) = MockAnalysis::with_fixture(ra_fixture);
-        assert!(pos.is_none());
-        res
-    }
-
-    /// Same as `with_files`, but requires that a single file contains a `<|>` marker,
-    /// whose position is also returned.
-    pub fn with_files_and_position(fixture: &str) -> (MockAnalysis, FilePosition) {
-        let (res, position) = MockAnalysis::with_fixture(fixture);
-        let (file_id, range_or_offset) = position.expect("expected a marker (<|>)");
-        let offset = match range_or_offset {
-            RangeOrOffset::Range(_) => panic!(),
-            RangeOrOffset::Offset(it) => it,
-        };
-        (res, FilePosition { file_id, offset })
-    }
-
-    fn with_fixture(fixture: &str) -> (MockAnalysis, Option<(FileId, RangeOrOffset)>) {
-        let mut position = None;
-        let mut res = MockAnalysis::default();
-        for mut entry in Fixture::parse(fixture) {
-            if entry.text.contains(CURSOR_MARKER) {
-                assert!(position.is_none(), "only one marker (<|>) per fixture is allowed");
-                let (range_or_offset, text) = extract_range_or_offset(&entry.text);
-                entry.text = text;
-                let file_id = res.add_file_fixture(entry);
-                position = Some((file_id, range_or_offset));
-            } else {
-                res.add_file_fixture(entry);
-            }
-        }
-        (res, position)
-    }
-
-    fn add_file_fixture(&mut self, fixture: Fixture) -> FileId {
-        let file_id = FileId((self.files.len() + 1) as u32);
-        self.files.push(fixture);
-        file_id
-    }
-
-    pub fn id_of(&self, path: &str) -> FileId {
-        let (file_id, _) =
-            self.files().find(|(_, data)| path == data.path).expect("no file in this mock");
-        file_id
-    }
-    pub fn annotations(&self) -> Vec<(FileRange, String)> {
-        self.files()
-            .flat_map(|(file_id, fixture)| {
-                let annotations = extract_annotations(&fixture.text);
-                annotations
-                    .into_iter()
-                    .map(move |(range, data)| (FileRange { file_id, range }, data))
-            })
-            .collect()
-    }
-    pub fn files(&self) -> impl Iterator<Item = (FileId, &Fixture)> + '_ {
-        self.files.iter().enumerate().map(|(idx, fixture)| (FileId(idx as u32 + 1), fixture))
-    }
-    pub fn annotation(&self) -> (FileRange, String) {
-        let mut all = self.annotations();
-        assert_eq!(all.len(), 1);
-        all.pop().unwrap()
-    }
-    pub fn analysis_host(self) -> AnalysisHost {
-        let mut host = AnalysisHost::default();
-        let mut change = AnalysisChange::new();
-        let mut file_set = FileSet::default();
-        let mut crate_graph = CrateGraph::default();
-        let mut root_crate = None;
-        for (i, data) in self.files.into_iter().enumerate() {
-            let path = data.path;
-            assert!(path.starts_with('/'));
-
-            let mut cfg = CfgOptions::default();
-            data.cfg_atoms.iter().for_each(|it| cfg.insert_atom(it.into()));
-            data.cfg_key_values.iter().for_each(|(k, v)| cfg.insert_key_value(k.into(), v.into()));
-            let edition: Edition =
-                data.edition.and_then(|it| it.parse().ok()).unwrap_or(Edition::Edition2018);
-
-            let file_id = FileId(i as u32 + 1);
-            let env = data.env.into_iter().collect();
-            if path == "/lib.rs" || path == "/main.rs" {
-                root_crate = Some(crate_graph.add_crate_root(
-                    file_id,
-                    edition,
-                    Some("test".to_string()),
-                    cfg,
-                    env,
-                    Default::default(),
-                ));
-            } else if path.ends_with("/lib.rs") {
-                let base = &path[..path.len() - "/lib.rs".len()];
-                let crate_name = &base[base.rfind('/').unwrap() + '/'.len_utf8()..];
-                let other_crate = crate_graph.add_crate_root(
-                    file_id,
-                    edition,
-                    Some(crate_name.to_string()),
-                    cfg,
-                    env,
-                    Default::default(),
-                );
-                if let Some(root_crate) = root_crate {
-                    crate_graph
-                        .add_dep(root_crate, CrateName::new(crate_name).unwrap(), other_crate)
-                        .unwrap();
-                }
-            }
-            let path = VfsPath::new_virtual_path(path.to_string());
-            file_set.insert(file_id, path);
-            change.change_file(file_id, Some(Arc::new(data.text).to_owned()));
-        }
-        change.set_crate_graph(crate_graph);
-        change.set_roots(vec![SourceRoot::new_local(file_set)]);
-        host.apply_change(change);
-        host
-    }
-    pub fn analysis(self) -> Analysis {
-        self.analysis_host().analysis()
-    }
-}
-
-/// Creates analysis from a multi-file fixture, returns positions marked with <|>.
-pub fn analysis_and_position(ra_fixture: &str) -> (Analysis, FilePosition) {
-    let (mock, position) = MockAnalysis::with_files_and_position(ra_fixture);
-    (mock.analysis(), position)
-}
-
-/// Creates analysis for a single file.
-pub fn single_file(ra_fixture: &str) -> (Analysis, FileId) {
-    let mock = MockAnalysis::with_files(ra_fixture);
-    let file_id = mock.id_of("/main.rs");
-    (mock.analysis(), file_id)
-}
-
-/// Creates analysis for a single file, returns range marked with a pair of <|>.
-pub fn analysis_and_range(ra_fixture: &str) -> (Analysis, FileRange) {
-    let (res, position) = MockAnalysis::with_fixture(ra_fixture);
-    let (file_id, range_or_offset) = position.expect("expected a marker (<|>)");
-    let range = match range_or_offset {
-        RangeOrOffset::Range(it) => it,
-        RangeOrOffset::Offset(_) => panic!(),
-    };
-    (res.analysis(), FileRange { file_id, range })
-}
diff --git a/crates/ide/src/parent_module.rs b/crates/ide/src/parent_module.rs
index 59ed2967c..ef94acfec 100644
--- a/crates/ide/src/parent_module.rs
+++ b/crates/ide/src/parent_module.rs
@@ -63,19 +63,13 @@ pub(crate) fn crate_for(db: &RootDatabase, file_id: FileId) -> Vec<CrateId> {
 
 #[cfg(test)]
 mod tests {
-    use base_db::Env;
-    use cfg::CfgOptions;
     use test_utils::mark;
 
-    use crate::{
-        mock_analysis::{analysis_and_position, MockAnalysis},
-        AnalysisChange, CrateGraph,
-        Edition::Edition2018,
-    };
+    use crate::fixture::{self};
 
     #[test]
     fn test_resolve_parent_module() {
-        let (analysis, pos) = analysis_and_position(
+        let (analysis, pos) = fixture::position(
             "
             //- /lib.rs
             mod foo;
@@ -84,13 +78,13 @@ mod tests {
             ",
         );
         let nav = analysis.parent_module(pos).unwrap().pop().unwrap();
-        nav.assert_match("foo MODULE FileId(1) 0..8");
+        nav.assert_match("foo MODULE FileId(0) 0..8");
     }
 
     #[test]
     fn test_resolve_parent_module_on_module_decl() {
         mark::check!(test_resolve_parent_module_on_module_decl);
-        let (analysis, pos) = analysis_and_position(
+        let (analysis, pos) = fixture::position(
             "
             //- /lib.rs
             mod foo;
@@ -103,12 +97,12 @@ mod tests {
             ",
         );
         let nav = analysis.parent_module(pos).unwrap().pop().unwrap();
-        nav.assert_match("foo MODULE FileId(1) 0..8");
+        nav.assert_match("foo MODULE FileId(0) 0..8");
     }
 
     #[test]
     fn test_resolve_parent_module_for_inline() {
-        let (analysis, pos) = analysis_and_position(
+        let (analysis, pos) = fixture::position(
             "
             //- /lib.rs
             mod foo {
@@ -119,37 +113,19 @@ mod tests {
             ",
         );
         let nav = analysis.parent_module(pos).unwrap().pop().unwrap();
-        nav.assert_match("baz MODULE FileId(1) 32..44");
+        nav.assert_match("baz MODULE FileId(0) 32..44");
     }
 
     #[test]
     fn test_resolve_crate_root() {
-        let mock = MockAnalysis::with_files(
+        let (analysis, file_id) = fixture::file(
             r#"
-//- /bar.rs
+//- /main.rs
 mod foo;
 //- /foo.rs
-// empty
+<|>
 "#,
         );
-        let root_file = mock.id_of("/bar.rs");
-        let mod_file = mock.id_of("/foo.rs");
-        let mut host = mock.analysis_host();
-        assert!(host.analysis().crate_for(mod_file).unwrap().is_empty());
-
-        let mut crate_graph = CrateGraph::default();
-        let crate_id = crate_graph.add_crate_root(
-            root_file,
-            Edition2018,
-            None,
-            CfgOptions::default(),
-            Env::default(),
-            Default::default(),
-        );
-        let mut change = AnalysisChange::new();
-        change.set_crate_graph(crate_graph);
-        host.apply_change(change);
-
-        assert_eq!(host.analysis().crate_for(mod_file).unwrap(), vec![crate_id]);
+        assert_eq!(analysis.crate_for(file_id).unwrap().len(), 1);
     }
 }
diff --git a/crates/ide/src/references.rs b/crates/ide/src/references.rs
index 722c8f406..e0830eb4f 100644
--- a/crates/ide/src/references.rs
+++ b/crates/ide/src/references.rs
@@ -190,14 +190,15 @@ fn get_struct_def_name_for_struct_literal_search(
 
 #[cfg(test)]
 mod tests {
-    use crate::{
-        mock_analysis::{analysis_and_position, MockAnalysis},
-        Declaration, Reference, ReferenceSearchResult, SearchScope,
-    };
+    use base_db::FileId;
+    use expect_test::{expect, Expect};
+    use stdx::format_to;
+
+    use crate::{fixture, SearchScope};
 
     #[test]
     fn test_struct_literal_after_space() {
-        let refs = get_all_refs(
+        check(
             r#"
 struct Foo <|>{
     a: i32,
@@ -210,17 +211,17 @@ fn main() {
     f = Foo {a: Foo::f()};
 }
 "#,
-        );
-        check_result(
-            refs,
-            "Foo STRUCT FileId(1) 0..26 7..10 Other",
-            &["FileId(1) 101..104 StructLiteral"],
+            expect![[r#"
+                Foo STRUCT FileId(0) 0..26 7..10 Other
+
+                FileId(0) 101..104 StructLiteral
+            "#]],
         );
     }
 
     #[test]
     fn test_struct_literal_before_space() {
-        let refs = get_all_refs(
+        check(
             r#"
 struct Foo<|> {}
     fn main() {
@@ -228,17 +229,18 @@ struct Foo<|> {}
     f = Foo {};
 }
 "#,
-        );
-        check_result(
-            refs,
-            "Foo STRUCT FileId(1) 0..13 7..10 Other",
-            &["FileId(1) 41..44 Other", "FileId(1) 54..57 StructLiteral"],
+            expect![[r#"
+                Foo STRUCT FileId(0) 0..13 7..10 Other
+
+                FileId(0) 41..44 Other
+                FileId(0) 54..57 StructLiteral
+            "#]],
         );
     }
 
     #[test]
     fn test_struct_literal_with_generic_type() {
-        let refs = get_all_refs(
+        check(
             r#"
 struct Foo<T> <|>{}
     fn main() {
@@ -246,17 +248,17 @@ struct Foo<T> <|>{}
     f = Foo {};
 }
 "#,
-        );
-        check_result(
-            refs,
-            "Foo STRUCT FileId(1) 0..16 7..10 Other",
-            &["FileId(1) 64..67 StructLiteral"],
+            expect![[r#"
+                Foo STRUCT FileId(0) 0..16 7..10 Other
+
+                FileId(0) 64..67 StructLiteral
+            "#]],
         );
     }
 
     #[test]
     fn test_struct_literal_for_tuple() {
-        let refs = get_all_refs(
+        check(
             r#"
 struct Foo<|>(i32);
 
@@ -265,17 +267,17 @@ fn main() {
     f = Foo(1);
 }
 "#,
-        );
-        check_result(
-            refs,
-            "Foo STRUCT FileId(1) 0..16 7..10 Other",
-            &["FileId(1) 54..57 StructLiteral"],
+            expect![[r#"
+                Foo STRUCT FileId(0) 0..16 7..10 Other
+
+                FileId(0) 54..57 StructLiteral
+            "#]],
         );
     }
 
     #[test]
     fn test_find_all_refs_for_local() {
-        let refs = get_all_refs(
+        check(
             r#"
 fn main() {
     let mut i = 1;
@@ -288,22 +290,20 @@ fn main() {
 
     i = 5;
 }"#,
-        );
-        check_result(
-            refs,
-            "i IDENT_PAT FileId(1) 24..25 Other Write",
-            &[
-                "FileId(1) 50..51 Other Write",
-                "FileId(1) 54..55 Other Read",
-                "FileId(1) 76..77 Other Write",
-                "FileId(1) 94..95 Other Write",
-            ],
+            expect![[r#"
+                i IDENT_PAT FileId(0) 24..25 Other Write
+
+                FileId(0) 50..51 Other Write
+                FileId(0) 54..55 Other Read
+                FileId(0) 76..77 Other Write
+                FileId(0) 94..95 Other Write
+            "#]],
         );
     }
 
     #[test]
     fn search_filters_by_range() {
-        let refs = get_all_refs(
+        check(
             r#"
 fn foo() {
     let spam<|> = 92;
@@ -314,41 +314,46 @@ fn bar() {
     spam + spam
 }
 "#,
-        );
-        check_result(
-            refs,
-            "spam IDENT_PAT FileId(1) 19..23 Other",
-            &["FileId(1) 34..38 Other Read", "FileId(1) 41..45 Other Read"],
+            expect![[r#"
+                spam IDENT_PAT FileId(0) 19..23 Other
+
+                FileId(0) 34..38 Other Read
+                FileId(0) 41..45 Other Read
+            "#]],
         );
     }
 
     #[test]
     fn test_find_all_refs_for_param_inside() {
-        let refs = get_all_refs(
+        check(
             r#"
-fn foo(i : u32) -> u32 {
-    i<|>
-}
+fn foo(i : u32) -> u32 { i<|> }
 "#,
+            expect![[r#"
+                i IDENT_PAT FileId(0) 7..8 Other
+
+                FileId(0) 25..26 Other Read
+            "#]],
         );
-        check_result(refs, "i IDENT_PAT FileId(1) 7..8 Other", &["FileId(1) 29..30 Other Read"]);
     }
 
     #[test]
     fn test_find_all_refs_for_fn_param() {
-        let refs = get_all_refs(
+        check(
             r#"
-fn foo(i<|> : u32) -> u32 {
-    i
-}
+fn foo(i<|> : u32) -> u32 { i }
 "#,
+            expect![[r#"
+                i IDENT_PAT FileId(0) 7..8 Other
+
+                FileId(0) 25..26 Other Read
+            "#]],
         );
-        check_result(refs, "i IDENT_PAT FileId(1) 7..8 Other", &["FileId(1) 29..30 Other Read"]);
     }
 
     #[test]
     fn test_find_all_refs_field_name() {
-        let refs = get_all_refs(
+        check(
             r#"
 //- /lib.rs
 struct Foo {
@@ -359,30 +364,33 @@ fn main(s: Foo) {
     let f = s.spam;
 }
 "#,
-        );
-        check_result(
-            refs,
-            "spam RECORD_FIELD FileId(1) 17..30 21..25 Other",
-            &["FileId(1) 67..71 Other Read"],
+            expect![[r#"
+                spam RECORD_FIELD FileId(0) 17..30 21..25 Other
+
+                FileId(0) 67..71 Other Read
+            "#]],
         );
     }
 
     #[test]
     fn test_find_all_refs_impl_item_name() {
-        let refs = get_all_refs(
+        check(
             r#"
 struct Foo;
 impl Foo {
     fn f<|>(&self) {  }
 }
 "#,
+            expect![[r#"
+                f FN FileId(0) 27..43 30..31 Other
+
+            "#]],
         );
-        check_result(refs, "f FN FileId(1) 27..43 30..31 Other", &[]);
     }
 
     #[test]
     fn test_find_all_refs_enum_var_name() {
-        let refs = get_all_refs(
+        check(
             r#"
 enum Foo {
     A,
@@ -390,13 +398,16 @@ enum Foo {
     C,
 }
 "#,
+            expect![[r#"
+                B VARIANT FileId(0) 22..23 22..23 Other
+
+            "#]],
         );
-        check_result(refs, "B VARIANT FileId(1) 22..23 22..23 Other", &[]);
     }
 
     #[test]
     fn test_find_all_refs_two_modules() {
-        let (analysis, pos) = analysis_and_position(
+        check(
             r#"
 //- /lib.rs
 pub mod foo;
@@ -428,12 +439,12 @@ fn f() {
     let i = foo::Foo<|> { n: 5 };
 }
 "#,
-        );
-        let refs = analysis.find_all_refs(pos, None).unwrap().unwrap();
-        check_result(
-            refs,
-            "Foo STRUCT FileId(2) 17..51 28..31 Other",
-            &["FileId(1) 53..56 StructLiteral", "FileId(3) 79..82 StructLiteral"],
+            expect![[r#"
+                Foo STRUCT FileId(1) 17..51 28..31 Other
+
+                FileId(0) 53..56 StructLiteral
+                FileId(2) 79..82 StructLiteral
+            "#]],
         );
     }
 
@@ -442,7 +453,7 @@ fn f() {
     // which is the whole `foo.rs`, and the second one is in `use foo::Foo`.
     #[test]
     fn test_find_all_refs_decl_module() {
-        let (analysis, pos) = analysis_and_position(
+        check(
             r#"
 //- /lib.rs
 mod foo<|>;
@@ -458,14 +469,17 @@ pub struct Foo {
     pub n: u32,
 }
 "#,
+            expect![[r#"
+                foo SOURCE_FILE FileId(1) 0..35 Other
+
+                FileId(0) 14..17 Other
+            "#]],
         );
-        let refs = analysis.find_all_refs(pos, None).unwrap().unwrap();
-        check_result(refs, "foo SOURCE_FILE FileId(2) 0..35 Other", &["FileId(1) 14..17 Other"]);
     }
 
     #[test]
     fn test_find_all_refs_super_mod_vis() {
-        let (analysis, pos) = analysis_and_position(
+        check(
             r#"
 //- /lib.rs
 mod foo;
@@ -483,12 +497,12 @@ pub(super) struct Foo<|> {
     pub n: u32,
 }
 "#,
-        );
-        let refs = analysis.find_all_refs(pos, None).unwrap().unwrap();
-        check_result(
-            refs,
-            "Foo STRUCT FileId(3) 0..41 18..21 Other",
-            &["FileId(2) 20..23 Other", "FileId(2) 47..50 StructLiteral"],
+            expect![[r#"
+                Foo STRUCT FileId(2) 0..41 18..21 Other
+
+                FileId(1) 20..23 Other
+                FileId(1) 47..50 StructLiteral
+            "#]],
         );
     }
 
@@ -508,29 +522,31 @@ pub(super) struct Foo<|> {
             fn f() { super::quux(); }
         "#;
 
-        let (mock, pos) = MockAnalysis::with_files_and_position(code);
-        let bar = mock.id_of("/bar.rs");
-        let analysis = mock.analysis();
+        check_with_scope(
+            code,
+            None,
+            expect![[r#"
+                quux FN FileId(0) 19..35 26..30 Other
 
-        let refs = analysis.find_all_refs(pos, None).unwrap().unwrap();
-        check_result(
-            refs,
-            "quux FN FileId(1) 19..35 26..30 Other",
-            &["FileId(2) 16..20 StructLiteral", "FileId(3) 16..20 StructLiteral"],
+                FileId(1) 16..20 StructLiteral
+                FileId(2) 16..20 StructLiteral
+            "#]],
         );
 
-        let refs =
-            analysis.find_all_refs(pos, Some(SearchScope::single_file(bar))).unwrap().unwrap();
-        check_result(
-            refs,
-            "quux FN FileId(1) 19..35 26..30 Other",
-            &["FileId(3) 16..20 StructLiteral"],
+        check_with_scope(
+            code,
+            Some(SearchScope::single_file(FileId(2))),
+            expect![[r#"
+                quux FN FileId(0) 19..35 26..30 Other
+
+                FileId(2) 16..20 StructLiteral
+            "#]],
         );
     }
 
     #[test]
     fn test_find_all_refs_macro_def() {
-        let refs = get_all_refs(
+        check(
             r#"
 #[macro_export]
 macro_rules! m1<|> { () => (()) }
@@ -540,34 +556,36 @@ fn foo() {
     m1();
 }
 "#,
-        );
-        check_result(
-            refs,
-            "m1 MACRO_CALL FileId(1) 0..46 29..31 Other",
-            &["FileId(1) 63..65 StructLiteral", "FileId(1) 73..75 StructLiteral"],
+            expect![[r#"
+                m1 MACRO_CALL FileId(0) 0..46 29..31 Other
+
+                FileId(0) 63..65 StructLiteral
+                FileId(0) 73..75 StructLiteral
+            "#]],
         );
     }
 
     #[test]
     fn test_basic_highlight_read_write() {
-        let refs = get_all_refs(
+        check(
             r#"
 fn foo() {
     let mut i<|> = 0;
     i = i + 1;
 }
 "#,
-        );
-        check_result(
-            refs,
-            "i IDENT_PAT FileId(1) 23..24 Other Write",
-            &["FileId(1) 34..35 Other Write", "FileId(1) 38..39 Other Read"],
+            expect![[r#"
+                i IDENT_PAT FileId(0) 23..24 Other Write
+
+                FileId(0) 34..35 Other Write
+                FileId(0) 38..39 Other Read
+            "#]],
         );
     }
 
     #[test]
     fn test_basic_highlight_field_read_write() {
-        let refs = get_all_refs(
+        check(
             r#"
 struct S {
     f: u32,
@@ -578,38 +596,41 @@ fn foo() {
     s.f<|> = 0;
 }
 "#,
-        );
-        check_result(
-            refs,
-            "f RECORD_FIELD FileId(1) 15..21 15..16 Other",
-            &["FileId(1) 55..56 Other Read", "FileId(1) 68..69 Other Write"],
+            expect![[r#"
+                f RECORD_FIELD FileId(0) 15..21 15..16 Other
+
+                FileId(0) 55..56 Other Read
+                FileId(0) 68..69 Other Write
+            "#]],
         );
     }
 
     #[test]
     fn test_basic_highlight_decl_no_write() {
-        let refs = get_all_refs(
+        check(
             r#"
 fn foo() {
     let i<|>;
     i = 1;
 }
 "#,
+            expect![[r#"
+                i IDENT_PAT FileId(0) 19..20 Other
+
+                FileId(0) 26..27 Other Write
+            "#]],
         );
-        check_result(refs, "i IDENT_PAT FileId(1) 19..20 Other", &["FileId(1) 26..27 Other Write"]);
     }
 
     #[test]
     fn test_find_struct_function_refs_outside_module() {
-        let refs = get_all_refs(
+        check(
             r#"
 mod foo {
     pub struct Foo;
 
     impl Foo {
-        pub fn new<|>() -> Foo {
-            Foo
-        }
+        pub fn new<|>() -> Foo { Foo }
     }
 }
 
@@ -617,80 +638,62 @@ fn main() {
     let _f = foo::Foo::new();
 }
 "#,
-        );
-        check_result(
-            refs,
-            "new FN FileId(1) 54..101 61..64 Other",
-            &["FileId(1) 146..149 StructLiteral"],
+            expect![[r#"
+                new FN FileId(0) 54..81 61..64 Other
+
+                FileId(0) 126..129 StructLiteral
+            "#]],
         );
     }
 
     #[test]
     fn test_find_all_refs_nested_module() {
-        let code = r#"
-            //- /lib.rs
-            mod foo {
-                mod bar;
-            }
+        check(
+            r#"
+//- /lib.rs
+mod foo { mod bar; }
 
-            fn f<|>() {}
+fn f<|>() {}
 
-            //- /foo/bar.rs
-            use crate::f;
+//- /foo/bar.rs
+use crate::f;
 
-            fn g() {
-                f();
-            }
-        "#;
+fn g() { f(); }
+"#,
+            expect![[r#"
+                f FN FileId(0) 22..31 25..26 Other
 
-        let (analysis, pos) = analysis_and_position(code);
-        let refs = analysis.find_all_refs(pos, None).unwrap().unwrap();
-        check_result(
-            refs,
-            "f FN FileId(1) 26..35 29..30 Other",
-            &["FileId(2) 11..12 Other", "FileId(2) 28..29 StructLiteral"],
+                FileId(1) 11..12 Other
+                FileId(1) 24..25 StructLiteral
+            "#]],
         );
     }
 
-    fn get_all_refs(ra_fixture: &str) -> ReferenceSearchResult {
-        let (analysis, position) = analysis_and_position(ra_fixture);
-        analysis.find_all_refs(position, None).unwrap().unwrap()
+    fn check(ra_fixture: &str, expect: Expect) {
+        check_with_scope(ra_fixture, None, expect)
     }
 
-    fn check_result(res: ReferenceSearchResult, expected_decl: &str, expected_refs: &[&str]) {
-        res.declaration().assert_match(expected_decl);
-        assert_eq!(res.references.len(), expected_refs.len());
-        res.references()
-            .iter()
-            .enumerate()
-            .for_each(|(i, r)| ref_assert_match(r, expected_refs[i]));
-    }
+    fn check_with_scope(ra_fixture: &str, search_scope: Option<SearchScope>, expect: Expect) {
+        let (analysis, pos) = fixture::position(ra_fixture);
+        let refs = analysis.find_all_refs(pos, search_scope).unwrap().unwrap();
 
-    impl Declaration {
-        fn debug_render(&self) -> String {
-            let mut s = format!("{} {:?}", self.nav.debug_render(), self.kind);
-            if let Some(access) = self.access {
-                s.push_str(&format!(" {:?}", access));
+        let mut actual = String::new();
+        {
+            let decl = refs.declaration;
+            format_to!(actual, "{} {:?}", decl.nav.debug_render(), decl.kind);
+            if let Some(access) = decl.access {
+                format_to!(actual, " {:?}", access)
             }
-            s
+            actual += "\n\n";
         }
 
-        fn assert_match(&self, expected: &str) {
-            let actual = self.debug_render();
-            test_utils::assert_eq_text!(expected.trim(), actual.trim(),);
-        }
-    }
-
-    fn ref_debug_render(r: &Reference) -> String {
-        let mut s = format!("{:?} {:?} {:?}", r.file_range.file_id, r.file_range.range, r.kind);
-        if let Some(access) = r.access {
-            s.push_str(&format!(" {:?}", access));
+        for r in &refs.references {
+            format_to!(actual, "{:?} {:?} {:?}", r.file_range.file_id, r.file_range.range, r.kind);
+            if let Some(access) = r.access {
+                format_to!(actual, " {:?}", access);
+            }
+            actual += "\n";
         }
-        s
-    }
-
-    fn ref_assert_match(r: &Reference, expected: &str) {
-        let actual = ref_debug_render(r);
-        test_utils::assert_eq_text!(expected.trim(), actual.trim(),);
+        expect.assert_eq(&actual)
     }
 }
diff --git a/crates/ide/src/references/rename.rs b/crates/ide/src/references/rename.rs
index 301629763..8cbe1ae5a 100644
--- a/crates/ide/src/references/rename.rs
+++ b/crates/ide/src/references/rename.rs
@@ -275,11 +275,11 @@ mod tests {
     use test_utils::{assert_eq_text, mark};
     use text_edit::TextEdit;
 
-    use crate::{mock_analysis::analysis_and_position, FileId};
+    use crate::{fixture, FileId};
 
     fn check(new_name: &str, ra_fixture_before: &str, ra_fixture_after: &str) {
         let ra_fixture_after = &trim_indent(ra_fixture_after);
-        let (analysis, position) = analysis_and_position(ra_fixture_before);
+        let (analysis, position) = fixture::position(ra_fixture_before);
         let source_change = analysis.rename(position, new_name).unwrap();
         let mut text_edit_builder = TextEdit::builder();
         let mut file_id: Option<FileId> = None;
@@ -297,7 +297,7 @@ mod tests {
     }
 
     fn check_expect(new_name: &str, ra_fixture: &str, expect: Expect) {
-        let (analysis, position) = analysis_and_position(ra_fixture);
+        let (analysis, position) = fixture::position(ra_fixture);
         let source_change = analysis.rename(position, new_name).unwrap().unwrap();
         expect.assert_debug_eq(&source_change)
     }
@@ -314,7 +314,7 @@ mod tests {
 
     #[test]
     fn test_rename_to_invalid_identifier() {
-        let (analysis, position) = analysis_and_position(r#"fn main() { let i<|> = 1; }"#);
+        let (analysis, position) = fixture::position(r#"fn main() { let i<|> = 1; }"#);
         let new_name = "invalid!";
         let source_change = analysis.rename(position, new_name).unwrap();
         assert!(source_change.is_none());
@@ -602,7 +602,7 @@ mod foo<|>;
                         source_file_edits: [
                             SourceFileEdit {
                                 file_id: FileId(
-                                    2,
+                                    1,
                                 ),
                                 edit: TextEdit {
                                     indels: [
@@ -617,10 +617,10 @@ mod foo<|>;
                         file_system_edits: [
                             MoveFile {
                                 src: FileId(
-                                    3,
+                                    2,
                                 ),
                                 anchor: FileId(
-                                    3,
+                                    2,
                                 ),
                                 dst: "foo2.rs",
                             },
@@ -655,7 +655,7 @@ use crate::foo<|>::FooContent;
                         source_file_edits: [
                             SourceFileEdit {
                                 file_id: FileId(
-                                    1,
+                                    0,
                                 ),
                                 edit: TextEdit {
                                     indels: [
@@ -668,7 +668,7 @@ use crate::foo<|>::FooContent;
                             },
                             SourceFileEdit {
                                 file_id: FileId(
-                                    3,
+                                    2,
                                 ),
                                 edit: TextEdit {
                                     indels: [
@@ -683,10 +683,10 @@ use crate::foo<|>::FooContent;
                         file_system_edits: [
                             MoveFile {
                                 src: FileId(
-                                    2,
+                                    1,
                                 ),
                                 anchor: FileId(
-                                    2,
+                                    1,
                                 ),
                                 dst: "quux.rs",
                             },
@@ -715,7 +715,7 @@ mod fo<|>o;
                         source_file_edits: [
                             SourceFileEdit {
                                 file_id: FileId(
-                                    1,
+                                    0,
                                 ),
                                 edit: TextEdit {
                                     indels: [
@@ -730,10 +730,10 @@ mod fo<|>o;
                         file_system_edits: [
                             MoveFile {
                                 src: FileId(
-                                    2,
+                                    1,
                                 ),
                                 anchor: FileId(
-                                    2,
+                                    1,
                                 ),
                                 dst: "../foo2/mod.rs",
                             },
@@ -763,7 +763,7 @@ mod outer { mod fo<|>o; }
                         source_file_edits: [
                             SourceFileEdit {
                                 file_id: FileId(
-                                    1,
+                                    0,
                                 ),
                                 edit: TextEdit {
                                     indels: [
@@ -778,10 +778,10 @@ mod outer { mod fo<|>o; }
                         file_system_edits: [
                             MoveFile {
                                 src: FileId(
-                                    2,
+                                    1,
                                 ),
                                 anchor: FileId(
-                                    2,
+                                    1,
                                 ),
                                 dst: "bar.rs",
                             },
@@ -834,7 +834,7 @@ pub mod foo<|>;
                         source_file_edits: [
                             SourceFileEdit {
                                 file_id: FileId(
-                                    2,
+                                    1,
                                 ),
                                 edit: TextEdit {
                                     indels: [
@@ -847,7 +847,7 @@ pub mod foo<|>;
                             },
                             SourceFileEdit {
                                 file_id: FileId(
-                                    1,
+                                    0,
                                 ),
                                 edit: TextEdit {
                                     indels: [
@@ -862,10 +862,10 @@ pub mod foo<|>;
                         file_system_edits: [
                             MoveFile {
                                 src: FileId(
-                                    3,
+                                    2,
                                 ),
                                 anchor: FileId(
-                                    3,
+                                    2,
                                 ),
                                 dst: "foo2.rs",
                             },
diff --git a/crates/ide/src/runnables.rs b/crates/ide/src/runnables.rs
index cfeff40c1..752ef2f21 100644
--- a/crates/ide/src/runnables.rs
+++ b/crates/ide/src/runnables.rs
@@ -292,7 +292,7 @@ fn has_test_function_or_multiple_test_submodules(module: &ast::Module) -> bool {
 mod tests {
     use expect_test::{expect, Expect};
 
-    use crate::mock_analysis::analysis_and_position;
+    use crate::fixture;
 
     use super::{RunnableAction, BENCH, BIN, DOCTEST, TEST};
 
@@ -302,7 +302,7 @@ mod tests {
         actions: &[&RunnableAction],
         expect: Expect,
     ) {
-        let (analysis, position) = analysis_and_position(ra_fixture);
+        let (analysis, position) = fixture::position(ra_fixture);
         let runnables = analysis.runnables(position.file_id).unwrap();
         expect.assert_debug_eq(&runnables);
         assert_eq!(
@@ -335,7 +335,7 @@ fn bench() {}
                     Runnable {
                         nav: NavigationTarget {
                             file_id: FileId(
-                                1,
+                                0,
                             ),
                             full_range: 1..13,
                             focus_range: Some(
@@ -353,7 +353,7 @@ fn bench() {}
                     Runnable {
                         nav: NavigationTarget {
                             file_id: FileId(
-                                1,
+                                0,
                             ),
                             full_range: 15..39,
                             focus_range: Some(
@@ -378,7 +378,7 @@ fn bench() {}
                     Runnable {
                         nav: NavigationTarget {
                             file_id: FileId(
-                                1,
+                                0,
                             ),
                             full_range: 41..75,
                             focus_range: Some(
@@ -403,7 +403,7 @@ fn bench() {}
                     Runnable {
                         nav: NavigationTarget {
                             file_id: FileId(
-                                1,
+                                0,
                             ),
                             full_range: 77..99,
                             focus_range: Some(
@@ -494,7 +494,7 @@ fn should_have_no_runnable_6() {}
                     Runnable {
                         nav: NavigationTarget {
                             file_id: FileId(
-                                1,
+                                0,
                             ),
                             full_range: 1..13,
                             focus_range: Some(
@@ -512,7 +512,7 @@ fn should_have_no_runnable_6() {}
                     Runnable {
                         nav: NavigationTarget {
                             file_id: FileId(
-                                1,
+                                0,
                             ),
                             full_range: 15..74,
                             focus_range: None,
@@ -532,7 +532,7 @@ fn should_have_no_runnable_6() {}
                     Runnable {
                         nav: NavigationTarget {
                             file_id: FileId(
-                                1,
+                                0,
                             ),
                             full_range: 76..148,
                             focus_range: None,
@@ -552,7 +552,7 @@ fn should_have_no_runnable_6() {}
                     Runnable {
                         nav: NavigationTarget {
                             file_id: FileId(
-                                1,
+                                0,
                             ),
                             full_range: 150..254,
                             focus_range: None,
@@ -596,7 +596,7 @@ impl Data {
                     Runnable {
                         nav: NavigationTarget {
                             file_id: FileId(
-                                1,
+                                0,
                             ),
                             full_range: 1..13,
                             focus_range: Some(
@@ -614,7 +614,7 @@ impl Data {
                     Runnable {
                         nav: NavigationTarget {
                             file_id: FileId(
-                                1,
+                                0,
                             ),
                             full_range: 44..98,
                             focus_range: None,
@@ -653,7 +653,7 @@ mod test_mod {
                     Runnable {
                         nav: NavigationTarget {
                             file_id: FileId(
-                                1,
+                                0,
                             ),
                             full_range: 1..51,
                             focus_range: Some(
@@ -673,7 +673,7 @@ mod test_mod {
                     Runnable {
                         nav: NavigationTarget {
                             file_id: FileId(
-                                1,
+                                0,
                             ),
                             full_range: 20..49,
                             focus_range: Some(
@@ -733,7 +733,7 @@ mod root_tests {
                     Runnable {
                         nav: NavigationTarget {
                             file_id: FileId(
-                                1,
+                                0,
                             ),
                             full_range: 22..323,
                             focus_range: Some(
@@ -753,7 +753,7 @@ mod root_tests {
                     Runnable {
                         nav: NavigationTarget {
                             file_id: FileId(
-                                1,
+                                0,
                             ),
                             full_range: 51..192,
                             focus_range: Some(
@@ -773,7 +773,7 @@ mod root_tests {
                     Runnable {
                         nav: NavigationTarget {
                             file_id: FileId(
-                                1,
+                                0,
                             ),
                             full_range: 84..126,
                             focus_range: Some(
@@ -798,7 +798,7 @@ mod root_tests {
                     Runnable {
                         nav: NavigationTarget {
                             file_id: FileId(
-                                1,
+                                0,
                             ),
                             full_range: 140..182,
                             focus_range: Some(
@@ -823,7 +823,7 @@ mod root_tests {
                     Runnable {
                         nav: NavigationTarget {
                             file_id: FileId(
-                                1,
+                                0,
                             ),
                             full_range: 202..286,
                             focus_range: Some(
@@ -843,7 +843,7 @@ mod root_tests {
                     Runnable {
                         nav: NavigationTarget {
                             file_id: FileId(
-                                1,
+                                0,
                             ),
                             full_range: 235..276,
                             focus_range: Some(
@@ -886,7 +886,7 @@ fn test_foo1() {}
                     Runnable {
                         nav: NavigationTarget {
                             file_id: FileId(
-                                1,
+                                0,
                             ),
                             full_range: 1..50,
                             focus_range: Some(
@@ -934,7 +934,7 @@ fn test_foo1() {}
                     Runnable {
                         nav: NavigationTarget {
                             file_id: FileId(
-                                1,
+                                0,
                             ),
                             full_range: 1..72,
                             focus_range: Some(
diff --git a/crates/ide/src/status.rs b/crates/ide/src/status.rs
index c23708181..0af84daa0 100644
--- a/crates/ide/src/status.rs
+++ b/crates/ide/src/status.rs
@@ -2,19 +2,19 @@ use std::{fmt, iter::FromIterator, sync::Arc};
 
 use base_db::{
     salsa::debug::{DebugQueryTable, TableEntry},
-    FileTextQuery, SourceRootId,
+    CrateId, FileId, FileTextQuery, SourceDatabase, SourceRootId,
 };
 use hir::MacroFile;
 use ide_db::{
     symbol_index::{LibrarySymbolsQuery, SymbolIndex},
     RootDatabase,
 };
+use itertools::Itertools;
 use profile::{memory_usage, Bytes};
 use rustc_hash::FxHashMap;
+use stdx::format_to;
 use syntax::{ast, Parse, SyntaxNode};
 
-use crate::FileId;
-
 fn syntax_tree_stats(db: &RootDatabase) -> SyntaxTreeStats {
     base_db::ParseQuery.in_db(db).entries::<SyntaxTreeStats>()
 }
@@ -31,20 +31,36 @@ fn macro_syntax_tree_stats(db: &RootDatabase) -> SyntaxTreeStats {
 //
 // | VS Code | **Rust Analyzer: Status**
 // |===
-pub(crate) fn status(db: &RootDatabase) -> String {
-    let files_stats = FileTextQuery.in_db(db).entries::<FilesStats>();
-    let syntax_tree_stats = syntax_tree_stats(db);
-    let macro_syntax_tree_stats = macro_syntax_tree_stats(db);
-    let symbols_stats = LibrarySymbolsQuery.in_db(db).entries::<LibrarySymbolsStats>();
-    format!(
-        "{}\n{}\n{}\n{} (macros)\n\n\nmemory:\n{}\ngc {:?} seconds ago",
-        files_stats,
-        symbols_stats,
-        syntax_tree_stats,
-        macro_syntax_tree_stats,
-        memory_usage(),
-        db.last_gc.elapsed().as_secs(),
-    )
+pub(crate) fn status(db: &RootDatabase, file_id: Option<FileId>) -> String {
+    let mut buf = String::new();
+    format_to!(buf, "{}\n", FileTextQuery.in_db(db).entries::<FilesStats>());
+    format_to!(buf, "{}\n", LibrarySymbolsQuery.in_db(db).entries::<LibrarySymbolsStats>());
+    format_to!(buf, "{}\n", syntax_tree_stats(db));
+    format_to!(buf, "{} (macros)\n", macro_syntax_tree_stats(db));
+    format_to!(buf, "{} total\n", memory_usage());
+
+    if let Some(file_id) = file_id {
+        format_to!(buf, "\nfile info:\n");
+        let krate = crate::parent_module::crate_for(db, file_id).pop();
+        match krate {
+            Some(krate) => {
+                let crate_graph = db.crate_graph();
+                let display_crate = |krate: CrateId| match &crate_graph[krate].display_name {
+                    Some(it) => format!("{}({:?})", it, krate),
+                    None => format!("{:?}", krate),
+                };
+                format_to!(buf, "crate: {}\n", display_crate(krate));
+                let deps = crate_graph[krate]
+                    .dependencies
+                    .iter()
+                    .map(|dep| format!("{}={:?}", dep.name, dep.crate_id))
+                    .format(", ");
+                format_to!(buf, "deps: {}\n", deps);
+            }
+            None => format_to!(buf, "does not belong to any crate"),
+        }
+    }
+    buf
 }
 
 #[derive(Default)]
@@ -121,7 +137,7 @@ struct LibrarySymbolsStats {
 
 impl fmt::Display for LibrarySymbolsStats {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
-        write!(fmt, "{} ({}) symbols", self.total, self.size)
+        write!(fmt, "{} ({}) index symbols", self.total, self.size)
     }
 }
 
diff --git a/crates/ide/src/syntax_highlighting/tests.rs b/crates/ide/src/syntax_highlighting/tests.rs
index 211e62ea1..694c4b7fa 100644
--- a/crates/ide/src/syntax_highlighting/tests.rs
+++ b/crates/ide/src/syntax_highlighting/tests.rs
@@ -3,7 +3,7 @@ use std::fs;
 use expect_test::{expect_file, ExpectFile};
 use test_utils::project_dir;
 
-use crate::{mock_analysis::single_file, FileRange, TextRange};
+use crate::{fixture, FileRange, TextRange};
 
 #[test]
 fn test_highlighting() {
@@ -178,7 +178,7 @@ fn accidentally_quadratic() {
     let file = project_dir().join("crates/syntax/test_data/accidentally_quadratic");
     let src = fs::read_to_string(file).unwrap();
 
-    let (analysis, file_id) = single_file(&src);
+    let (analysis, file_id) = fixture::file(&src);
 
     // let t = std::time::Instant::now();
     let _ = analysis.highlight(file_id).unwrap();
@@ -187,7 +187,7 @@ fn accidentally_quadratic() {
 
 #[test]
 fn test_ranges() {
-    let (analysis, file_id) = single_file(
+    let (analysis, file_id) = fixture::file(
         r#"
 #[derive(Clone, Debug)]
 struct Foo {
@@ -228,7 +228,7 @@ fn main() {
 
 #[test]
 fn ranges_sorted() {
-    let (analysis, file_id) = single_file(
+    let (analysis, file_id) = fixture::file(
         r#"
 #[foo(bar = "bar")]
 macro_rules! test {}
@@ -462,12 +462,12 @@ macro_rules! noop {
 fn test_extern_crate() {
     check_highlighting(
         r#"
-        //- /main.rs
+        //- /main.rs crate:main deps:std,alloc
         extern crate std;
         extern crate alloc as abc;
-        //- /std/lib.rs
+        //- /std/lib.rs crate:std
         pub struct S;
-        //- /alloc/lib.rs
+        //- /alloc/lib.rs crate:alloc
         pub struct A
         "#,
         expect_file!["./test_data/highlight_extern_crate.html"],
@@ -479,7 +479,7 @@ fn test_extern_crate() {
 /// result as HTML, and compares it with the HTML file given as `snapshot`.
 /// Note that the `snapshot` file is overwritten by the rendered HTML.
 fn check_highlighting(ra_fixture: &str, expect: ExpectFile, rainbow: bool) {
-    let (analysis, file_id) = single_file(ra_fixture);
+    let (analysis, file_id) = fixture::file(ra_fixture);
     let actual_html = &analysis.highlight_as_html(file_id, rainbow).unwrap();
     expect.assert_eq(actual_html)
 }
diff --git a/crates/ide/src/syntax_tree.rs b/crates/ide/src/syntax_tree.rs
index f80044959..0eed2dbd7 100644
--- a/crates/ide/src/syntax_tree.rs
+++ b/crates/ide/src/syntax_tree.rs
@@ -104,12 +104,12 @@ fn syntax_tree_for_token(node: &SyntaxToken, text_range: TextRange) -> Option<St
 mod tests {
     use test_utils::assert_eq_text;
 
-    use crate::mock_analysis::{analysis_and_range, single_file};
+    use crate::fixture;
 
     #[test]
     fn test_syntax_tree_without_range() {
         // Basic syntax
-        let (analysis, file_id) = single_file(r#"fn foo() {}"#);
+        let (analysis, file_id) = fixture::file(r#"fn foo() {}"#);
         let syn = analysis.syntax_tree(file_id, None).unwrap();
 
         assert_eq_text!(
@@ -132,7 +132,7 @@ [email protected]
             .trim()
         );
 
-        let (analysis, file_id) = single_file(
+        let (analysis, file_id) = fixture::file(
             r#"
 fn test() {
     assert!("
@@ -184,7 +184,7 @@ [email protected]
 
     #[test]
     fn test_syntax_tree_with_range() {
-        let (analysis, range) = analysis_and_range(r#"<|>fn foo() {}<|>"#.trim());
+        let (analysis, range) = fixture::range(r#"<|>fn foo() {}<|>"#.trim());
         let syn = analysis.syntax_tree(range.file_id, Some(range.range)).unwrap();
 
         assert_eq_text!(
@@ -206,7 +206,7 @@ [email protected]
             .trim()
         );
 
-        let (analysis, range) = analysis_and_range(
+        let (analysis, range) = fixture::range(
             r#"fn test() {
     <|>assert!("
     fn foo() {
@@ -242,7 +242,7 @@ [email protected]
 
     #[test]
     fn test_syntax_tree_inside_string() {
-        let (analysis, range) = analysis_and_range(
+        let (analysis, range) = fixture::range(
             r#"fn test() {
     assert!("
 <|>fn foo() {
@@ -276,7 +276,7 @@ [email protected]
         );
 
         // With a raw string
-        let (analysis, range) = analysis_and_range(
+        let (analysis, range) = fixture::range(
             r###"fn test() {
     assert!(r#"
 <|>fn foo() {
@@ -310,7 +310,7 @@ [email protected]
         );
 
         // With a raw string
-        let (analysis, range) = analysis_and_range(
+        let (analysis, range) = fixture::range(
             r###"fn test() {
     assert!(r<|>#"
 fn foo() {
diff --git a/crates/ide/src/typing/on_enter.rs b/crates/ide/src/typing/on_enter.rs
index f7d46146c..a0dc4b9df 100644
--- a/crates/ide/src/typing/on_enter.rs
+++ b/crates/ide/src/typing/on_enter.rs
@@ -109,10 +109,10 @@ mod tests {
     use stdx::trim_indent;
     use test_utils::{assert_eq_text, mark};
 
-    use crate::mock_analysis::analysis_and_position;
+    use crate::fixture;
 
     fn apply_on_enter(before: &str) -> Option<String> {
-        let (analysis, position) = analysis_and_position(&before);
+        let (analysis, position) = fixture::position(&before);
         let result = analysis.on_enter(position).unwrap()?;
 
         let mut actual = analysis.file_text(position.file_id).unwrap().to_string();
diff --git a/crates/ide_db/src/change.rs b/crates/ide_db/src/apply_change.rs
index 8b4fd7ab8..da16fa21d 100644
--- a/crates/ide_db/src/change.rs
+++ b/crates/ide_db/src/apply_change.rs
@@ -1,58 +1,16 @@
-//! Defines a unit of change that can applied to a state of IDE to get the next
-//! state. Changes are transactional.
+//! Applies changes to the IDE state transactionally.
 
-use std::{fmt, sync::Arc, time};
+use std::{fmt, sync::Arc};
 
 use base_db::{
     salsa::{Database, Durability, SweepStrategy},
-    CrateGraph, FileId, SourceDatabase, SourceDatabaseExt, SourceRoot, SourceRootId,
+    Change, FileId, SourceRootId,
 };
 use profile::{memory_usage, Bytes};
 use rustc_hash::FxHashSet;
 
 use crate::{symbol_index::SymbolsDatabase, RootDatabase};
 
-#[derive(Default)]
-pub struct AnalysisChange {
-    roots: Option<Vec<SourceRoot>>,
-    files_changed: Vec<(FileId, Option<Arc<String>>)>,
-    crate_graph: Option<CrateGraph>,
-}
-
-impl fmt::Debug for AnalysisChange {
-    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
-        let mut d = fmt.debug_struct("AnalysisChange");
-        if let Some(roots) = &self.roots {
-            d.field("roots", roots);
-        }
-        if !self.files_changed.is_empty() {
-            d.field("files_changed", &self.files_changed.len());
-        }
-        if self.crate_graph.is_some() {
-            d.field("crate_graph", &self.crate_graph);
-        }
-        d.finish()
-    }
-}
-
-impl AnalysisChange {
-    pub fn new() -> AnalysisChange {
-        AnalysisChange::default()
-    }
-
-    pub fn set_roots(&mut self, roots: Vec<SourceRoot>) {
-        self.roots = Some(roots);
-    }
-
-    pub fn change_file(&mut self, file_id: FileId, new_text: Option<Arc<String>>) {
-        self.files_changed.push((file_id, new_text))
-    }
-
-    pub fn set_crate_graph(&mut self, graph: CrateGraph) {
-        self.crate_graph = Some(graph);
-    }
-}
-
 #[derive(Debug)]
 struct AddFile {
     file_id: FileId,
@@ -81,59 +39,31 @@ impl fmt::Debug for RootChange {
     }
 }
 
-const GC_COOLDOWN: time::Duration = time::Duration::from_millis(100);
-
 impl RootDatabase {
     pub fn request_cancellation(&mut self) {
         let _p = profile::span("RootDatabase::request_cancellation");
         self.salsa_runtime_mut().synthetic_write(Durability::LOW);
     }
 
-    pub fn apply_change(&mut self, change: AnalysisChange) {
+    pub fn apply_change(&mut self, change: Change) {
         let _p = profile::span("RootDatabase::apply_change");
         self.request_cancellation();
         log::info!("apply_change {:?}", change);
-        if let Some(roots) = change.roots {
+        if let Some(roots) = &change.roots {
             let mut local_roots = FxHashSet::default();
             let mut library_roots = FxHashSet::default();
-            for (idx, root) in roots.into_iter().enumerate() {
+            for (idx, root) in roots.iter().enumerate() {
                 let root_id = SourceRootId(idx as u32);
-                let durability = durability(&root);
                 if root.is_library {
                     library_roots.insert(root_id);
                 } else {
                     local_roots.insert(root_id);
                 }
-                for file_id in root.iter() {
-                    self.set_file_source_root_with_durability(file_id, root_id, durability);
-                }
-                self.set_source_root_with_durability(root_id, Arc::new(root), durability);
             }
             self.set_local_roots_with_durability(Arc::new(local_roots), Durability::HIGH);
             self.set_library_roots_with_durability(Arc::new(library_roots), Durability::HIGH);
         }
-
-        for (file_id, text) in change.files_changed {
-            let source_root_id = self.file_source_root(file_id);
-            let source_root = self.source_root(source_root_id);
-            let durability = durability(&source_root);
-            // XXX: can't actually remove the file, just reset the text
-            let text = text.unwrap_or_default();
-            self.set_file_text_with_durability(file_id, text, durability)
-        }
-        if let Some(crate_graph) = change.crate_graph {
-            self.set_crate_graph_with_durability(Arc::new(crate_graph), Durability::HIGH)
-        }
-    }
-
-    pub fn maybe_collect_garbage(&mut self) {
-        if cfg!(feature = "wasm") {
-            return;
-        }
-
-        if self.last_gc_check.elapsed() > GC_COOLDOWN {
-            self.last_gc_check = crate::wasm_shims::Instant::now();
-        }
+        change.apply(self);
     }
 
     pub fn collect_garbage(&mut self) {
@@ -142,7 +72,6 @@ impl RootDatabase {
         }
 
         let _p = profile::span("RootDatabase::collect_garbage");
-        self.last_gc = crate::wasm_shims::Instant::now();
 
         let sweep = SweepStrategy::default().discard_values().sweep_all_revisions();
 
@@ -308,11 +237,3 @@ impl RootDatabase {
         acc
     }
 }
-
-fn durability(source_root: &SourceRoot) -> Durability {
-    if source_root.is_library {
-        Durability::HIGH
-    } else {
-        Durability::LOW
-    }
-}
diff --git a/crates/ide_db/src/lib.rs b/crates/ide_db/src/lib.rs
index 70ada02f3..7eff247c7 100644
--- a/crates/ide_db/src/lib.rs
+++ b/crates/ide_db/src/lib.rs
@@ -2,15 +2,14 @@
 //!
 //! It is mainly a `HirDatabase` for semantic analysis, plus a `SymbolsDatabase`, for fuzzy search.
 
+mod apply_change;
 pub mod label;
 pub mod line_index;
 pub mod symbol_index;
-pub mod change;
 pub mod defs;
 pub mod search;
 pub mod imports_locator;
 pub mod source_change;
-mod wasm_shims;
 
 use std::{fmt, sync::Arc};
 
@@ -36,8 +35,6 @@ use crate::{line_index::LineIndex, symbol_index::SymbolsDatabase};
 )]
 pub struct RootDatabase {
     storage: salsa::Storage<RootDatabase>,
-    pub last_gc: crate::wasm_shims::Instant,
-    pub last_gc_check: crate::wasm_shims::Instant,
 }
 
 impl fmt::Debug for RootDatabase {
@@ -99,11 +96,7 @@ impl Default for RootDatabase {
 
 impl RootDatabase {
     pub fn new(lru_capacity: Option<usize>) -> RootDatabase {
-        let mut db = RootDatabase {
-            storage: salsa::Storage::default(),
-            last_gc: crate::wasm_shims::Instant::now(),
-            last_gc_check: crate::wasm_shims::Instant::now(),
-        };
+        let mut db = RootDatabase { storage: salsa::Storage::default() };
         db.set_crate_graph_with_durability(Default::default(), Durability::HIGH);
         db.set_local_roots_with_durability(Default::default(), Durability::HIGH);
         db.set_library_roots_with_durability(Default::default(), Durability::HIGH);
@@ -121,11 +114,7 @@ impl RootDatabase {
 
 impl salsa::ParallelDatabase for RootDatabase {
     fn snapshot(&self) -> salsa::Snapshot<RootDatabase> {
-        salsa::Snapshot::new(RootDatabase {
-            storage: self.storage.snapshot(),
-            last_gc: self.last_gc,
-            last_gc_check: self.last_gc_check,
-        })
+        salsa::Snapshot::new(RootDatabase { storage: self.storage.snapshot() })
     }
 }
 
diff --git a/crates/ide_db/src/wasm_shims.rs b/crates/ide_db/src/wasm_shims.rs
deleted file mode 100644
index 7af9f9d9b..000000000
--- a/crates/ide_db/src/wasm_shims.rs
+++ /dev/null
@@ -1,19 +0,0 @@
-//! A version of `std::time::Instant` that doesn't panic in WASM.
-
-#[cfg(not(feature = "wasm"))]
-pub use std::time::Instant;
-
-#[cfg(feature = "wasm")]
-#[derive(Clone, Copy, Debug)]
-pub struct Instant;
-
-#[cfg(feature = "wasm")]
-impl Instant {
-    pub fn now() -> Self {
-        Self
-    }
-
-    pub fn elapsed(&self) -> std::time::Duration {
-        std::time::Duration::new(0, 0)
-    }
-}
diff --git a/crates/rust-analyzer/src/cli/analysis_bench.rs b/crates/rust-analyzer/src/cli/analysis_bench.rs
index c312e0a2e..d1c095ba5 100644
--- a/crates/rust-analyzer/src/cli/analysis_bench.rs
+++ b/crates/rust-analyzer/src/cli/analysis_bench.rs
@@ -8,8 +8,7 @@ use base_db::{
     FileId,
 };
 use ide::{
-    Analysis, AnalysisChange, AnalysisHost, CompletionConfig, DiagnosticsConfig, FilePosition,
-    LineCol,
+    Analysis, AnalysisHost, Change, CompletionConfig, DiagnosticsConfig, FilePosition, LineCol,
 };
 use vfs::AbsPathBuf;
 
@@ -143,7 +142,7 @@ fn do_work<F: Fn(&Analysis) -> T, T>(host: &mut AnalysisHost, file_id: FileId, w
         {
             let mut text = host.analysis().file_text(file_id).unwrap().to_string();
             text.push_str("\n/* Hello world */\n");
-            let mut change = AnalysisChange::new();
+            let mut change = Change::new();
             change.change_file(file_id, Some(Arc::new(text)));
             host.apply_change(change);
         }
@@ -156,7 +155,7 @@ fn do_work<F: Fn(&Analysis) -> T, T>(host: &mut AnalysisHost, file_id: FileId, w
         {
             let mut text = host.analysis().file_text(file_id).unwrap().to_string();
             text.push_str("\npub fn _dummy() {}\n");
-            let mut change = AnalysisChange::new();
+            let mut change = Change::new();
             change.change_file(file_id, Some(Arc::new(text)));
             host.apply_change(change);
         }
diff --git a/crates/rust-analyzer/src/cli/load_cargo.rs b/crates/rust-analyzer/src/cli/load_cargo.rs
index c47cf6ef3..7ae1c9055 100644
--- a/crates/rust-analyzer/src/cli/load_cargo.rs
+++ b/crates/rust-analyzer/src/cli/load_cargo.rs
@@ -5,7 +5,7 @@ use std::{path::Path, sync::Arc};
 use anyhow::Result;
 use base_db::CrateGraph;
 use crossbeam_channel::{unbounded, Receiver};
-use ide::{AnalysisChange, AnalysisHost};
+use ide::{AnalysisHost, Change};
 use project_model::{CargoConfig, ProcMacroClient, ProjectManifest, ProjectWorkspace};
 use vfs::{loader::Handle, AbsPath, AbsPathBuf};
 
@@ -62,7 +62,7 @@ fn load(
 ) -> AnalysisHost {
     let lru_cap = std::env::var("RA_LRU_CAP").ok().and_then(|it| it.parse::<usize>().ok());
     let mut host = AnalysisHost::new(lru_cap);
-    let mut analysis_change = AnalysisChange::new();
+    let mut analysis_change = Change::new();
 
     // wait until Vfs has loaded all roots
     for task in receiver {
diff --git a/crates/rust-analyzer/src/config.rs b/crates/rust-analyzer/src/config.rs
index 42e1ad376..0ab4c37bf 100644
--- a/crates/rust-analyzer/src/config.rs
+++ b/crates/rust-analyzer/src/config.rs
@@ -38,6 +38,7 @@ pub struct Config {
     pub cargo: CargoConfig,
     pub rustfmt: RustfmtConfig,
     pub flycheck: Option<FlycheckConfig>,
+    pub runnables: RunnablesConfig,
 
     pub inlay_hints: InlayHintsConfig,
     pub completion: CompletionConfig,
@@ -124,6 +125,15 @@ pub enum RustfmtConfig {
     CustomCommand { command: String, args: Vec<String> },
 }
 
+/// Configuration for runnable items, such as `main` function or tests.
+#[derive(Debug, Clone, Default)]
+pub struct RunnablesConfig {
+    /// Custom command to be executed instead of `cargo` for runnables.
+    pub override_cargo: Option<String>,
+    /// Additional arguments for the `cargo`, e.g. `--release`.
+    pub cargo_extra_args: Vec<String>,
+}
+
 #[derive(Debug, Clone, Default)]
 pub struct ClientCapsConfig {
     pub location_link: bool,
@@ -164,6 +174,7 @@ impl Config {
                 extra_args: Vec::new(),
                 features: Vec::new(),
             }),
+            runnables: RunnablesConfig::default(),
 
             inlay_hints: InlayHintsConfig {
                 type_hints: true,
@@ -220,6 +231,10 @@ impl Config {
             load_out_dirs_from_check: data.cargo_loadOutDirsFromCheck,
             target: data.cargo_target.clone(),
         };
+        self.runnables = RunnablesConfig {
+            override_cargo: data.runnables_overrideCargo,
+            cargo_extra_args: data.runnables_cargoExtraArgs,
+        };
 
         self.proc_macro_srv = if data.procMacro_enable {
             std::env::current_exe().ok().map(|path| (path, vec!["proc-macro".into()]))
@@ -474,6 +489,9 @@ config_data! {
         notifications_cargoTomlNotFound: bool      = true,
         procMacro_enable: bool                     = false,
 
+        runnables_overrideCargo: Option<String> = None,
+        runnables_cargoExtraArgs: Vec<String>   = Vec::new(),
+
         rustfmt_extraArgs: Vec<String>               = Vec::new(),
         rustfmt_overrideCommand: Option<Vec<String>> = None,
 
diff --git a/crates/rust-analyzer/src/dispatch.rs b/crates/rust-analyzer/src/dispatch.rs
index 891fdb96d..9c8815e29 100644
--- a/crates/rust-analyzer/src/dispatch.rs
+++ b/crates/rust-analyzer/src/dispatch.rs
@@ -1,5 +1,5 @@
 //! A visitor for downcasting arbitrary request (JSON) into a specific type.
-use std::panic;
+use std::{fmt, panic};
 
 use serde::{de::DeserializeOwned, Serialize};
 
@@ -23,7 +23,7 @@ impl<'a> RequestDispatcher<'a> {
     ) -> Result<&mut Self>
     where
         R: lsp_types::request::Request + 'static,
-        R::Params: DeserializeOwned + panic::UnwindSafe + 'static,
+        R::Params: DeserializeOwned + panic::UnwindSafe + fmt::Debug + 'static,
         R::Result: Serialize + 'static,
     {
         let (id, params) = match self.parse::<R>() {
@@ -34,6 +34,7 @@ impl<'a> RequestDispatcher<'a> {
         };
         let world = panic::AssertUnwindSafe(&mut *self.global_state);
         let response = panic::catch_unwind(move || {
+            stdx::panic_context::enter(format!("request: {} {:#?}", R::METHOD, params));
             let result = f(world.0, params);
             result_to_response::<R>(id, result)
         })
@@ -49,7 +50,7 @@ impl<'a> RequestDispatcher<'a> {
     ) -> Result<&mut Self>
     where
         R: lsp_types::request::Request + 'static,
-        R::Params: DeserializeOwned + Send + 'static,
+        R::Params: DeserializeOwned + Send + fmt::Debug + 'static,
         R::Result: Serialize + 'static,
     {
         let (id, params) = match self.parse::<R>() {
@@ -61,7 +62,10 @@ impl<'a> RequestDispatcher<'a> {
 
         self.global_state.task_pool.handle.spawn({
             let world = self.global_state.snapshot();
+
             move || {
+                let _ctx =
+                    stdx::panic_context::enter(format!("request: {} {:#?}", R::METHOD, params));
                 let result = f(world, params);
                 Task::Response(result_to_response::<R>(id, result))
             }
@@ -156,6 +160,7 @@ impl<'a> NotificationDispatcher<'a> {
                 return Ok(self);
             }
         };
+        stdx::panic_context::enter(format!("notification: {}", N::METHOD));
         f(self.global_state, params)?;
         Ok(self)
     }
diff --git a/crates/rust-analyzer/src/global_state.rs b/crates/rust-analyzer/src/global_state.rs
index 96313aaec..dafab6a6a 100644
--- a/crates/rust-analyzer/src/global_state.rs
+++ b/crates/rust-analyzer/src/global_state.rs
@@ -8,7 +8,7 @@ use std::{sync::Arc, time::Instant};
 use base_db::{CrateId, VfsPath};
 use crossbeam_channel::{unbounded, Receiver, Sender};
 use flycheck::FlycheckHandle;
-use ide::{Analysis, AnalysisChange, AnalysisHost, FileId};
+use ide::{Analysis, AnalysisHost, Change, FileId};
 use lsp_types::{SemanticTokens, Url};
 use parking_lot::{Mutex, RwLock};
 use project_model::{CargoWorkspace, ProcMacroClient, ProjectWorkspace, Target};
@@ -139,7 +139,7 @@ impl GlobalState {
         let mut has_fs_changes = false;
 
         let change = {
-            let mut change = AnalysisChange::new();
+            let mut change = Change::new();
             let (vfs, line_endings_map) = &mut *self.vfs.write();
             let changed_files = vfs.take_changes();
             if changed_files.is_empty() {
diff --git a/crates/rust-analyzer/src/handlers.rs b/crates/rust-analyzer/src/handlers.rs
index 7ac1a30f6..e970abb7c 100644
--- a/crates/rust-analyzer/src/handlers.rs
+++ b/crates/rust-analyzer/src/handlers.rs
@@ -38,10 +38,22 @@ use crate::{
     to_proto, LspError, Result,
 };
 
-pub(crate) fn handle_analyzer_status(snap: GlobalStateSnapshot, _: ()) -> Result<String> {
+pub(crate) fn handle_analyzer_status(
+    snap: GlobalStateSnapshot,
+    params: lsp_ext::AnalyzerStatusParams,
+) -> Result<String> {
     let _p = profile::span("handle_analyzer_status");
 
     let mut buf = String::new();
+
+    let mut file_id = None;
+    if let Some(tdi) = params.text_document {
+        match from_proto::file_id(&snap, &tdi.uri) {
+            Ok(it) => file_id = Some(it),
+            Err(_) => format_to!(buf, "file {} not found in vfs", tdi.uri),
+        }
+    }
+
     if snap.workspaces.is_empty() {
         buf.push_str("no workspaces\n")
     } else {
@@ -52,7 +64,10 @@ pub(crate) fn handle_analyzer_status(snap: GlobalStateSnapshot, _: ()) -> Result
     }
     buf.push_str("\nanalysis:\n");
     buf.push_str(
-        &snap.analysis.status().unwrap_or_else(|_| "Analysis retrieval was cancelled".to_owned()),
+        &snap
+            .analysis
+            .status(file_id)
+            .unwrap_or_else(|_| "Analysis retrieval was cancelled".to_owned()),
     );
     format_to!(buf, "\n\nrequests:\n");
     let requests = snap.latest_requests.read();
@@ -476,6 +491,7 @@ pub(crate) fn handle_runnables(
     }
 
     // Add `cargo check` and `cargo test` for all targets of the whole package
+    let config = &snap.config.runnables;
     match cargo_spec {
         Some(spec) => {
             for &cmd in ["check", "test"].iter() {
@@ -485,12 +501,14 @@ pub(crate) fn handle_runnables(
                     kind: lsp_ext::RunnableKind::Cargo,
                     args: lsp_ext::CargoRunnable {
                         workspace_root: Some(spec.workspace_root.clone().into()),
+                        override_cargo: config.override_cargo.clone(),
                         cargo_args: vec![
                             cmd.to_string(),
                             "--package".to_string(),
                             spec.package.clone(),
                             "--all-targets".to_string(),
                         ],
+                        cargo_extra_args: config.cargo_extra_args.clone(),
                         executable_args: Vec::new(),
                         expect_test: None,
                     },
@@ -504,7 +522,9 @@ pub(crate) fn handle_runnables(
                 kind: lsp_ext::RunnableKind::Cargo,
                 args: lsp_ext::CargoRunnable {
                     workspace_root: None,
+                    override_cargo: config.override_cargo.clone(),
                     cargo_args: vec!["check".to_string(), "--workspace".to_string()],
+                    cargo_extra_args: config.cargo_extra_args.clone(),
                     executable_args: Vec::new(),
                     expect_test: None,
                 },
diff --git a/crates/rust-analyzer/src/lsp_ext.rs b/crates/rust-analyzer/src/lsp_ext.rs
index e1a28b1b4..fee0bb69c 100644
--- a/crates/rust-analyzer/src/lsp_ext.rs
+++ b/crates/rust-analyzer/src/lsp_ext.rs
@@ -11,11 +11,17 @@ use serde::{Deserialize, Serialize};
 pub enum AnalyzerStatus {}
 
 impl Request for AnalyzerStatus {
-    type Params = ();
+    type Params = AnalyzerStatusParams;
     type Result = String;
     const METHOD: &'static str = "rust-analyzer/analyzerStatus";
 }
 
+#[derive(Deserialize, Serialize, Debug)]
+#[serde(rename_all = "camelCase")]
+pub struct AnalyzerStatusParams {
+    pub text_document: Option<TextDocumentIdentifier>,
+}
+
 pub enum MemoryUsage {}
 
 impl Request for MemoryUsage {
@@ -165,10 +171,14 @@ pub enum RunnableKind {
 #[derive(Deserialize, Serialize, Debug)]
 #[serde(rename_all = "camelCase")]
 pub struct CargoRunnable {
+    // command to be executed instead of cargo
+    pub override_cargo: Option<String>,
     #[serde(skip_serializing_if = "Option::is_none")]
     pub workspace_root: Option<PathBuf>,
     // command, --package and --lib stuff
     pub cargo_args: Vec<String>,
+    // user-specified additional cargo args, like `--release`.
+    pub cargo_extra_args: Vec<String>,
     // stuff after --
     pub executable_args: Vec<String>,
     #[serde(skip_serializing_if = "Option::is_none")]
diff --git a/crates/rust-analyzer/src/main_loop.rs b/crates/rust-analyzer/src/main_loop.rs
index 06ab9d508..c2d0ac791 100644
--- a/crates/rust-analyzer/src/main_loop.rs
+++ b/crates/rust-analyzer/src/main_loop.rs
@@ -189,19 +189,16 @@ impl GlobalState {
                 }
                 lsp_server::Message::Response(resp) => self.complete_request(resp),
             },
-            Event::Task(task) => {
-                match task {
-                    Task::Response(response) => self.respond(response),
-                    Task::Diagnostics(diagnostics_per_file) => {
-                        for (file_id, diagnostics) in diagnostics_per_file {
-                            self.diagnostics.set_native_diagnostics(file_id, diagnostics)
-                        }
+            Event::Task(task) => match task {
+                Task::Response(response) => self.respond(response),
+                Task::Diagnostics(diagnostics_per_file) => {
+                    for (file_id, diagnostics) in diagnostics_per_file {
+                        self.diagnostics.set_native_diagnostics(file_id, diagnostics)
                     }
-                    Task::Workspaces(workspaces) => self.switch_workspaces(workspaces),
-                    Task::Unit => (),
                 }
-                self.analysis_host.maybe_collect_garbage();
-            }
+                Task::Workspaces(workspaces) => self.switch_workspaces(workspaces),
+                Task::Unit => (),
+            },
             Event::Vfs(mut task) => {
                 let _p = profile::span("GlobalState::handle_event/vfs");
                 loop {
diff --git a/crates/rust-analyzer/src/reload.rs b/crates/rust-analyzer/src/reload.rs
index de0dbcad4..f7215f129 100644
--- a/crates/rust-analyzer/src/reload.rs
+++ b/crates/rust-analyzer/src/reload.rs
@@ -3,7 +3,7 @@ use std::{mem, sync::Arc};
 
 use base_db::{CrateGraph, SourceRoot, VfsPath};
 use flycheck::{FlycheckConfig, FlycheckHandle};
-use ide::AnalysisChange;
+use ide::Change;
 use project_model::{ProcMacroClient, ProjectWorkspace};
 use vfs::{file_set::FileSetConfig, AbsPath, AbsPathBuf, ChangeKind};
 
@@ -171,7 +171,7 @@ impl GlobalState {
             );
         }
 
-        let mut change = AnalysisChange::new();
+        let mut change = Change::new();
 
         let project_folders = ProjectFolders::new(&workspaces);
 
diff --git a/crates/rust-analyzer/src/to_proto.rs b/crates/rust-analyzer/src/to_proto.rs
index 59e780b7d..aeacde0f7 100644
--- a/crates/rust-analyzer/src/to_proto.rs
+++ b/crates/rust-analyzer/src/to_proto.rs
@@ -740,6 +740,7 @@ pub(crate) fn runnable(
     file_id: FileId,
     runnable: Runnable,
 ) -> Result<lsp_ext::Runnable> {
+    let config = &snap.config.runnables;
     let spec = CargoTargetSpec::for_file(snap, file_id)?;
     let workspace_root = spec.as_ref().map(|it| it.workspace_root.clone());
     let target = spec.as_ref().map(|s| s.target.clone());
@@ -754,7 +755,9 @@ pub(crate) fn runnable(
         kind: lsp_ext::RunnableKind::Cargo,
         args: lsp_ext::CargoRunnable {
             workspace_root: workspace_root.map(|it| it.into()),
+            override_cargo: config.override_cargo.clone(),
             cargo_args,
+            cargo_extra_args: config.cargo_extra_args.clone(),
             executable_args,
             expect_test: None,
         },
diff --git a/crates/rust-analyzer/tests/rust-analyzer/main.rs b/crates/rust-analyzer/tests/rust-analyzer/main.rs
index 06726f957..e51eb2626 100644
--- a/crates/rust-analyzer/tests/rust-analyzer/main.rs
+++ b/crates/rust-analyzer/tests/rust-analyzer/main.rs
@@ -107,6 +107,8 @@ fn main() {}
             "args": {
               "cargoArgs": ["test", "--package", "foo", "--test", "spam"],
               "executableArgs": ["test_eggs", "--exact", "--nocapture"],
+              "cargoExtraArgs": [],
+              "overrideCargo": null,
               "workspaceRoot": server.path().join("foo")
             },
             "kind": "cargo",
@@ -127,6 +129,8 @@ fn main() {}
             "args": {
               "cargoArgs": ["check", "--package", "foo", "--all-targets"],
               "executableArgs": [],
+              "cargoExtraArgs": [],
+              "overrideCargo": null,
               "workspaceRoot": server.path().join("foo")
             },
             "kind": "cargo",
@@ -136,6 +140,8 @@ fn main() {}
             "args": {
               "cargoArgs": ["test", "--package", "foo", "--all-targets"],
               "executableArgs": [],
+              "cargoExtraArgs": [],
+              "overrideCargo": null,
               "workspaceRoot": server.path().join("foo")
             },
             "kind": "cargo",
diff --git a/crates/ssr/src/resolving.rs b/crates/ssr/src/resolving.rs
index 5d2cbec47..347cc4aad 100644
--- a/crates/ssr/src/resolving.rs
+++ b/crates/ssr/src/resolving.rs
@@ -205,7 +205,7 @@ impl<'db> ResolutionScope<'db> {
 
     /// Returns the function in which SSR was invoked, if any.
     pub(crate) fn current_function(&self) -> Option<SyntaxNode> {
-        self.node.ancestors().find(|node| node.kind() == SyntaxKind::FN).map(|node| node.clone())
+        self.node.ancestors().find(|node| node.kind() == SyntaxKind::FN)
     }
 
     fn resolve_path(&self, path: &ast::Path) -> Option<hir::PathResolution> {
diff --git a/crates/stdx/src/lib.rs b/crates/stdx/src/lib.rs
index 273b0f55b..011935cad 100644
--- a/crates/stdx/src/lib.rs
+++ b/crates/stdx/src/lib.rs
@@ -5,6 +5,7 @@ use std::{
 };
 
 mod macros;
+pub mod panic_context;
 
 #[inline(always)]
 pub fn is_ci() -> bool {
diff --git a/crates/stdx/src/panic_context.rs b/crates/stdx/src/panic_context.rs
new file mode 100644
index 000000000..fd232e0cc
--- /dev/null
+++ b/crates/stdx/src/panic_context.rs
@@ -0,0 +1,49 @@
+//! A micro-crate to enhance panic messages with context info.
+//!
+//! FIXME: upstream to https://github.com/kriomant/panic-context ?
+
+use std::{cell::RefCell, panic, sync::Once};
+
+pub fn enter(context: String) -> impl Drop {
+    static ONCE: Once = Once::new();
+    ONCE.call_once(PanicContext::init);
+
+    with_ctx(|ctx| ctx.push(context));
+    PanicContext { _priv: () }
+}
+
+#[must_use]
+struct PanicContext {
+    _priv: (),
+}
+
+impl PanicContext {
+    fn init() {
+        let default_hook = panic::take_hook();
+        let hook = move |panic_info: &panic::PanicInfo<'_>| {
+            with_ctx(|ctx| {
+                if !ctx.is_empty() {
+                    eprintln!("Panic context:");
+                    for frame in ctx.iter() {
+                        eprintln!("> {}\n", frame)
+                    }
+                }
+                default_hook(panic_info)
+            })
+        };
+        panic::set_hook(Box::new(hook))
+    }
+}
+
+impl Drop for PanicContext {
+    fn drop(&mut self) {
+        with_ctx(|ctx| assert!(ctx.pop().is_some()))
+    }
+}
+
+fn with_ctx(f: impl FnOnce(&mut Vec<String>)) {
+    thread_local! {
+        static CTX: RefCell<Vec<String>> = RefCell::new(Vec::new());
+    }
+    CTX.with(|ctx| f(&mut *ctx.borrow_mut()))
+}
diff --git a/crates/syntax/Cargo.toml b/crates/syntax/Cargo.toml
index af61bb658..0b15f10e9 100644
--- a/crates/syntax/Cargo.toml
+++ b/crates/syntax/Cargo.toml
@@ -13,7 +13,7 @@ doctest = false
 [dependencies]
 itertools = "0.9.0"
 rowan = "0.10.0"
-rustc_lexer = { version = "673.0.0", package = "rustc-ap-rustc_lexer" }
+rustc_lexer = { version = "681.0.0", package = "rustc-ap-rustc_lexer" }
 rustc-hash = "1.1.0"
 arrayvec = "0.5.1"
 once_cell = "1.3.1"
diff --git a/crates/syntax/src/ast/edit.rs b/crates/syntax/src/ast/edit.rs
index dda0a0319..77233ab31 100644
--- a/crates/syntax/src/ast/edit.rs
+++ b/crates/syntax/src/ast/edit.rs
@@ -159,7 +159,7 @@ impl ast::AssocItemList {
         let whitespace =
             last_token_before_curly.clone().into_token().and_then(ast::Whitespace::cast)?;
         let text = whitespace.syntax().text();
-        let newline = text.rfind("\n")?;
+        let newline = text.rfind('\n')?;
         let keep = tokens::WsBuilder::new(&text[newline..]);
         Some(self.replace_children(
             first_token_after_items..=last_token_before_curly,
diff --git a/crates/syntax/src/parsing/lexer.rs b/crates/syntax/src/parsing/lexer.rs
index fa3be1016..f1202113b 100644
--- a/crates/syntax/src/parsing/lexer.rs
+++ b/crates/syntax/src/parsing/lexer.rs
@@ -120,10 +120,10 @@ fn rustc_token_kind_to_syntax_kind(
 
     let syntax_kind = {
         match rustc_token_kind {
-            rustc_lexer::TokenKind::LineComment => COMMENT,
+            rustc_lexer::TokenKind::LineComment { doc_style: _ } => COMMENT,
 
-            rustc_lexer::TokenKind::BlockComment { terminated: true } => COMMENT,
-            rustc_lexer::TokenKind::BlockComment { terminated: false } => {
+            rustc_lexer::TokenKind::BlockComment { doc_style: _, terminated: true } => COMMENT,
+            rustc_lexer::TokenKind::BlockComment { doc_style: _, terminated: false } => {
                 return (
                     COMMENT,
                     Some("Missing trailing `*/` symbols to terminate the block comment"),
@@ -164,7 +164,7 @@ fn rustc_token_kind_to_syntax_kind(
             rustc_lexer::TokenKind::Colon => T![:],
             rustc_lexer::TokenKind::Dollar => T![$],
             rustc_lexer::TokenKind::Eq => T![=],
-            rustc_lexer::TokenKind::Not => T![!],
+            rustc_lexer::TokenKind::Bang => T![!],
             rustc_lexer::TokenKind::Lt => T![<],
             rustc_lexer::TokenKind::Gt => T![>],
             rustc_lexer::TokenKind::Minus => T![-],
diff --git a/docs/dev/lsp-extensions.md b/docs/dev/lsp-extensions.md
index 2e3133449..f1160bb1c 100644
--- a/docs/dev/lsp-extensions.md
+++ b/docs/dev/lsp-extensions.md
@@ -390,7 +390,14 @@ rust-analyzer supports only one `kind`, `"cargo"`. The `args` for `"cargo"` look
 
 **Method:** `rust-analyzer/analyzerStatus`
 
-**Request:** `null`
+**Request:**
+
+```typescript
+interface AnalyzerStatusParams {
+    /// If specified, show dependencies of the current file.
+    textDocument?: TextDocumentIdentifier;
+}
+```
 
 **Response:** `string`
 
diff --git a/docs/dev/style.md b/docs/dev/style.md
index bcd86fd3f..fb407afcd 100644
--- a/docs/dev/style.md
+++ b/docs/dev/style.md
@@ -197,7 +197,7 @@ fn frobnicate(walrus: Option<Walrus>) {
 }
 ```
 
-Avoid preconditions that spawn function boundaries:
+Avoid preconditions that span across function boundaries:
 
 
 ```rust
@@ -218,9 +218,8 @@ fn foo() {
 }
 
 // Not as good
-fn is_string_literal(s: &str) -> Option<&str> {
+fn is_string_literal(s: &str) -> bool {
     s.starts_with('"') && s.ends_with('"')
-    Some()
 }
 
 fn foo() {
@@ -231,8 +230,8 @@ fn foo() {
 }
 ```
 
-In the "Not as good" version, the precondition that `1` is a valid char boundary is checked in `is_string_literal` and utilized in `foo`.
-In the "Good" version, precondition check and usage are checked in the same block, and then encoded in the types.
+In the "Not as good" version, the precondition that `1` is a valid char boundary is checked in `is_string_literal` and used in `foo`.
+In the "Good" version, the precondition check and usage are checked in the same block, and then encoded in the types.
 
 # Early Returns
 
@@ -372,3 +371,13 @@ After you are happy with the state of the code, please use [interactive rebase](
 
 Avoid @mentioning people in commit messages and pull request descriptions(they are added to commit message by bors).
 Such messages create a lot of duplicate notification traffic during rebases.
+
+# Clippy
+
+We don't enforce Clippy.
+A number of default lints have high false positive rate.
+Selectively patching false-positives with `allow(clippy)` is considered worse than not using Clippy at all.
+There's `cargo xtask lint` command which runs a subset of low-FPR lints.
+Careful tweaking of `xtask lint` is welcome.
+See also [rust-lang/clippy#5537](https://github.com/rust-lang/rust-clippy/issues/5537).
+Of course, applying Clippy suggestions is welcome as long as they indeed improve the code.
diff --git a/docs/user/manual.adoc b/docs/user/manual.adoc
index 7d85b36cb..c1a778852 100644
--- a/docs/user/manual.adoc
+++ b/docs/user/manual.adoc
@@ -113,8 +113,8 @@ Note that installing via `xtask install` does not work for VS Code Remote, inste
 
 Here are some useful self-diagnostic commands:
 
-* **Rust Analyzer: Show RA Version** shows the version of `rust-analyzer` binary
-* **Rust Analyzer: Status** prints some statistics about the server, like the few latest LSP requests
+* **Rust Analyzer: Show RA Version** shows the version of `rust-analyzer` binary.
+* **Rust Analyzer: Status** prints some statistics about the server, and dependency information for the current file.
 * To enable server-side logging, run with `env RA_LOG=info` and see `Output > Rust Analyzer Language Server` in VS Code's panel.
 * To log all LSP requests, add `"rust-analyzer.trace.server": "verbose"` to the settings and look for `Rust Analyzer Language Server Trace` in the panel.
 * To enable client-side logging, add `"rust-analyzer.trace.extension": true` to the settings and open `Output > Rust Analyzer Client` in the panel.
diff --git a/editors/code/package.json b/editors/code/package.json
index bdd8a0c29..cc2ac3bd2 100644
--- a/editors/code/package.json
+++ b/editors/code/package.json
@@ -651,6 +651,22 @@
                     ],
                     "default": "full",
                     "description": "The strategy to use when inserting new imports or merging imports."
+                },
+                "rust-analyzer.runnables.overrideCargo": {
+                    "type": [
+                        "null",
+                        "string"
+                    ],
+                    "default": null,
+                    "description": "Command to be executed instead of 'cargo' for runnables."
+                },
+                "rust-analyzer.runnables.cargoExtraArgs": {
+                    "type": "array",
+                    "items": {
+                        "type": "string"
+                    },
+                    "default": [],
+                    "description": "Additional arguments to be passed to cargo for runnables such as tests or binaries.\nFor example, it may be '--release'"
                 }
             }
         },
diff --git a/editors/code/src/commands.ts b/editors/code/src/commands.ts
index e9581a9b5..1a90f1b7d 100644
--- a/editors/code/src/commands.ts
+++ b/editors/code/src/commands.ts
@@ -21,7 +21,12 @@ export function analyzerStatus(ctx: Ctx): Cmd {
         provideTextDocumentContent(_uri: vscode.Uri): vscode.ProviderResult<string> {
             if (!vscode.window.activeTextEditor) return '';
 
-            return ctx.client.sendRequest(ra.analyzerStatus);
+            const params: ra.AnalyzerStatusParams = {};
+            const doc = ctx.activeRustEditor?.document;
+            if (doc != null) {
+                params.textDocument = ctx.client.code2ProtocolConverter.asTextDocumentIdentifier(doc);
+            }
+            return ctx.client.sendRequest(ra.analyzerStatus, params);
         }
 
         get onDidChange(): vscode.Event<vscode.Uri> {
@@ -94,7 +99,7 @@ export function matchingBrace(ctx: Ctx): Cmd {
         if (!editor || !client) return;
 
         const response = await client.sendRequest(ra.matchingBrace, {
-            textDocument: { uri: editor.document.uri.toString() },
+            textDocument: ctx.client.code2ProtocolConverter.asTextDocumentIdentifier(editor.document),
             positions: editor.selections.map(s =>
                 client.code2ProtocolConverter.asPosition(s.active),
             ),
@@ -118,7 +123,7 @@ export function joinLines(ctx: Ctx): Cmd {
 
         const items: lc.TextEdit[] = await client.sendRequest(ra.joinLines, {
             ranges: editor.selections.map((it) => client.code2ProtocolConverter.asRange(it)),
-            textDocument: { uri: editor.document.uri.toString() },
+            textDocument: ctx.client.code2ProtocolConverter.asTextDocumentIdentifier(editor.document),
         });
         editor.edit((builder) => {
             client.protocol2CodeConverter.asTextEdits(items).forEach((edit: any) => {
@@ -136,7 +141,7 @@ export function onEnter(ctx: Ctx): Cmd {
         if (!editor || !client) return false;
 
         const lcEdits = await client.sendRequest(ra.onEnter, {
-            textDocument: { uri: editor.document.uri.toString() },
+            textDocument: ctx.client.code2ProtocolConverter.asTextDocumentIdentifier(editor.document),
             position: client.code2ProtocolConverter.asPosition(
                 editor.selection.active,
             ),
@@ -165,7 +170,7 @@ export function parentModule(ctx: Ctx): Cmd {
         if (!editor || !client) return;
 
         const response = await client.sendRequest(ra.parentModule, {
-            textDocument: { uri: editor.document.uri.toString() },
+            textDocument: ctx.client.code2ProtocolConverter.asTextDocumentIdentifier(editor.document),
             position: client.code2ProtocolConverter.asPosition(
                 editor.selection.active,
             ),
@@ -191,7 +196,7 @@ export function ssr(ctx: Ctx): Cmd {
 
         const position = editor.selection.active;
         const selections = editor.selections;
-        const textDocument = { uri: editor.document.uri.toString() };
+        const textDocument = ctx.client.code2ProtocolConverter.asTextDocumentIdentifier(editor.document);
 
         const options: vscode.InputBoxOptions = {
             value: "() ==>> ()",
@@ -339,7 +344,7 @@ export function expandMacro(ctx: Ctx): Cmd {
             const position = editor.selection.active;
 
             const expanded = await client.sendRequest(ra.expandMacro, {
-                textDocument: { uri: editor.document.uri.toString() },
+                textDocument: ctx.client.code2ProtocolConverter.asTextDocumentIdentifier(editor.document),
                 position,
             });
 
diff --git a/editors/code/src/lsp_ext.ts b/editors/code/src/lsp_ext.ts
index d167041c4..f286b68a6 100644
--- a/editors/code/src/lsp_ext.ts
+++ b/editors/code/src/lsp_ext.ts
@@ -4,7 +4,10 @@
 
 import * as lc from "vscode-languageclient";
 
-export const analyzerStatus = new lc.RequestType0<string, void>("rust-analyzer/analyzerStatus");
+export interface AnalyzerStatusParams {
+    textDocument?: lc.TextDocumentIdentifier;
+}
+export const analyzerStatus = new lc.RequestType<AnalyzerStatusParams, string, void>("rust-analyzer/analyzerStatus");
 export const memoryUsage = new lc.RequestType0<string, void>("rust-analyzer/memoryUsage");
 
 export type Status = "loading" | "ready" | "invalid" | "needsReload";
@@ -66,8 +69,10 @@ export interface Runnable {
     args: {
         workspaceRoot?: string;
         cargoArgs: string[];
+        cargoExtraArgs: string[];
         executableArgs: string[];
         expectTest?: boolean;
+        overrideCargo?: string;
     };
 }
 export const runnables = new lc.RequestType<RunnablesParams, Runnable[], void>("experimental/runnables");
diff --git a/editors/code/src/run.ts b/editors/code/src/run.ts
index de68f27ae..459b7f250 100644
--- a/editors/code/src/run.ts
+++ b/editors/code/src/run.ts
@@ -129,6 +129,7 @@ export async function createTask(runnable: ra.Runnable, config: Config): Promise
     }
 
     const args = [...runnable.args.cargoArgs]; // should be a copy!
+    args.push(...runnable.args.cargoExtraArgs); // Append user-specified cargo options.
     if (runnable.args.executableArgs.length > 0) {
         args.push('--', ...runnable.args.executableArgs);
     }
@@ -139,6 +140,7 @@ export async function createTask(runnable: ra.Runnable, config: Config): Promise
         args: args.slice(1),
         cwd: runnable.args.workspaceRoot || ".",
         env: prepareEnv(runnable, config.runnableEnv),
+        overrideCargo: runnable.args.overrideCargo,
     };
 
     const target = vscode.workspace.workspaceFolders![0]; // safe, see main activate()
diff --git a/editors/code/src/tasks.ts b/editors/code/src/tasks.ts
index 14abbd5b7..a3ff15102 100644
--- a/editors/code/src/tasks.ts
+++ b/editors/code/src/tasks.ts
@@ -13,6 +13,7 @@ export interface CargoTaskDefinition extends vscode.TaskDefinition {
     args?: string[];
     cwd?: string;
     env?: { [key: string]: string };
+    overrideCargo?: string;
 }
 
 class CargoTaskProvider implements vscode.TaskProvider {
@@ -98,7 +99,14 @@ export async function buildCargoTask(
     }
 
     if (!exec) {
-        exec = new vscode.ShellExecution(toolchain.cargoPath(), args, definition);
+        // Check whether we must use a user-defined substitute for cargo.
+        const cargoCommand = definition.overrideCargo ? definition.overrideCargo : toolchain.cargoPath();
+
+        // Prepare the whole command as one line. It is required if user has provided override command which contains spaces,
+        // for example "wrapper cargo". Without manual preparation the overridden command will be quoted and fail to execute.
+        const fullCommand = [cargoCommand, ...args].join(" ");
+
+        exec = new vscode.ShellExecution(fullCommand, definition);
     }
 
     return new vscode.Task(
diff --git a/editors/code/tests/unit/runnable_env.test.ts b/editors/code/tests/unit/runnable_env.test.ts
index f2f53e91a..c5600cf64 100644
--- a/editors/code/tests/unit/runnable_env.test.ts
+++ b/editors/code/tests/unit/runnable_env.test.ts
@@ -9,7 +9,8 @@ function makeRunnable(label: string): ra.Runnable {
         kind: "cargo",
         args: {
             cargoArgs: [],
-            executableArgs: []
+            executableArgs: [],
+            cargoExtraArgs: []
         }
     };
 }
diff --git a/xtask/src/codegen/gen_feature_docs.rs b/xtask/src/codegen/gen_feature_docs.rs
index 3f0013e82..341e67c73 100644
--- a/xtask/src/codegen/gen_feature_docs.rs
+++ b/xtask/src/codegen/gen_feature_docs.rs
@@ -38,7 +38,9 @@ impl Feature {
 
             for block in comment_blocks {
                 let id = block.id;
-                assert!(is_valid_feature_name(&id), "invalid feature name: {:?}", id);
+                if let Err(msg) = is_valid_feature_name(&id) {
+                    panic!("invalid feature name: {:?}:\n  {}", id, msg)
+                }
                 let doc = block.contents.join("\n");
                 let location = Location::new(path.clone(), block.line);
                 acc.push(Feature { id, location, doc })
@@ -49,7 +51,7 @@ impl Feature {
     }
 }
 
-fn is_valid_feature_name(feature: &str) -> bool {
+fn is_valid_feature_name(feature: &str) -> Result<(), String> {
     'word: for word in feature.split_whitespace() {
         for &short in ["to", "and"].iter() {
             if word == short {
@@ -58,14 +60,14 @@ fn is_valid_feature_name(feature: &str) -> bool {
         }
         for &short in ["To", "And"].iter() {
             if word == short {
-                return false;
+                return Err(format!("Don't capitalize {:?}", word));
             }
         }
         if !word.starts_with(char::is_uppercase) {
-            return false;
+            return Err(format!("Capitalize {:?}", word));
         }
     }
-    true
+    Ok(())
 }
 
 impl fmt::Display for Feature {