24 files changed, 731 insertions, 197 deletions

diff --git a/Cargo.lock b/Cargo.lock
index c5645b2d2..494011068 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -139,9 +139,9 @@ dependencies = [
 
 [[package]]
 name = "cc"
-version = "1.0.61"
+version = "1.0.62"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ed67cbde08356238e75fc4656be4749481eeffb09e19f320a25237d5221c985d"
+checksum = "f1770ced377336a88a67c473594ccc14eca6f4559217c34f64aac8f83d641b40"
 
 [[package]]
 name = "cfg"
@@ -398,11 +398,11 @@ dependencies = [
 
 [[package]]
 name = "filetime"
-version = "0.2.12"
+version = "0.2.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3ed85775dcc68644b5c950ac06a2b23768d3bc9390464151aaf27136998dcf9e"
+checksum = "0c122a393ea57648015bf06fbd3d372378992e86b9ff5a7a497b076a28c79efe"
 dependencies = [
- "cfg-if 0.1.10",
+ "cfg-if 1.0.0",
  "libc",
  "redox_syscall",
  "winapi 0.3.9",
@@ -439,6 +439,16 @@ dependencies = [
 ]
 
 [[package]]
+name = "form_urlencoded"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ece68d15c92e84fa4f19d3780f1294e5ca82a78a6d515f1efaabcc144688be00"
+dependencies = [
+ "matches",
+ "percent-encoding",
+]
+
+[[package]]
 name = "fsevent"
 version = "2.0.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -715,9 +725,9 @@ dependencies = [
 
 [[package]]
 name = "inotify-sys"
-version = "0.1.3"
+version = "0.1.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e74a1aa87c59aeff6ef2cc2fa62d41bc43f54952f55652656b18a02fd5e356c0"
+checksum = "c4563555856585ab3180a5bf0b2f9f8d301a728462afffc8195b3f5394229c55"
 dependencies = [
  "libc",
 ]
@@ -1384,9 +1394,9 @@ dependencies = [
 
 [[package]]
 name = "rustc-ap-rustc_lexer"
-version = "686.0.0"
+version = "688.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a5b04cd2159495584d976d501c5394498470c2e94e4f0cebb8186562d407a678"
+checksum = "ebbdcc99bd015349093fcbae4780fda21416fec5d8843acfb3d1733e130cd4db"
 dependencies = [
  "unicode-xid",
 ]
@@ -1889,10 +1899,11 @@ checksum = "f7fe0bb3479651439c9112f72b6c505038574c9fbb575ed1bf3b797fa39dd564"
 
 [[package]]
 name = "url"
-version = "2.1.1"
+version = "2.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "829d4a8476c35c9bf0bbce5a3b23f4106f79728039b726d292bb93bc106787cb"
+checksum = "5909f2b0817350449ed73e8bcd81c8c3c8d9a7a5d8acba4b27db277f1868976e"
 dependencies = [
+ "form_urlencoded",
  "idna",
  "matches",
  "percent-encoding",
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 84662d832..067afabf2 100644
--- a/crates/assists/src/handlers/extract_struct_from_enum_variant.rs
+++ b/crates/assists/src/handlers/extract_struct_from_enum_variant.rs
@@ -5,10 +5,9 @@ use hir::{AsName, EnumVariant, Module, ModuleDef, Name};
 use ide_db::{defs::Definition, search::Reference, RootDatabase};
 use rustc_hash::{FxHashMap, FxHashSet};
 use syntax::{
-    algo::find_node_at_offset,
-    algo::SyntaxRewriter,
-    ast::{self, edit::IndentLevel, make, ArgListOwner, AstNode, NameOwner, VisibilityOwner},
-    SourceFile, SyntaxElement,
+    algo::{find_node_at_offset, SyntaxRewriter},
+    ast::{self, edit::IndentLevel, make, AstNode, NameOwner, VisibilityOwner},
+    SourceFile, SyntaxElement, SyntaxNode, T,
 };
 
 use crate::{
@@ -130,17 +129,21 @@ fn existing_definition(db: &RootDatabase, variant_name: &ast::Name, variant: &En
 fn insert_import(
     ctx: &AssistContext,
     rewriter: &mut SyntaxRewriter,
-    path: &ast::PathExpr,
+    scope_node: &SyntaxNode,
     module: &Module,
     enum_module_def: &ModuleDef,
     variant_hir_name: &Name,
 ) -> Option<()> {
     let db = ctx.db();
-    let mod_path = module.find_use_path(db, enum_module_def.clone());
+    let mod_path = module.find_use_path_prefixed(
+        db,
+        enum_module_def.clone(),
+        ctx.config.insert_use.prefix_kind,
+    );
     if let Some(mut mod_path) = mod_path {
         mod_path.segments.pop();
         mod_path.segments.push(variant_hir_name.clone());
-        let scope = ImportScope::find_insert_use_container(path.syntax(), ctx)?;
+        let scope = ImportScope::find_insert_use_container(scope_node, ctx)?;
 
         *rewriter += insert_use(&scope, mod_path_to_ast(&mod_path), ctx.config.insert_use.merge);
     }
@@ -204,27 +207,31 @@ fn update_reference(
     variant_hir_name: &Name,
     visited_modules_set: &mut FxHashSet<Module>,
 ) -> Option<()> {
-    let path_expr: ast::PathExpr = find_node_at_offset::<ast::PathExpr>(
-        source_file.syntax(),
-        reference.file_range.range.start(),
-    )?;
-    let call = path_expr.syntax().parent().and_then(ast::CallExpr::cast)?;
-    let list = call.arg_list()?;
-    let segment = path_expr.path()?.segment()?;
-    let module = ctx.sema.scope(&path_expr.syntax()).module()?;
+    let offset = reference.file_range.range.start();
+    let (segment, expr) = if let Some(path_expr) =
+        find_node_at_offset::<ast::PathExpr>(source_file.syntax(), offset)
+    {
+        // tuple variant
+        (path_expr.path()?.segment()?, path_expr.syntax().parent()?.clone())
+    } else if let Some(record_expr) =
+        find_node_at_offset::<ast::RecordExpr>(source_file.syntax(), offset)
+    {
+        // record variant
+        (record_expr.path()?.segment()?, record_expr.syntax().clone())
+    } else {
+        return None;
+    };
+
+    let module = ctx.sema.scope(&expr).module()?;
     if !visited_modules_set.contains(&module) {
-        if insert_import(ctx, rewriter, &path_expr, &module, enum_module_def, variant_hir_name)
-            .is_some()
+        if insert_import(ctx, rewriter, &expr, &module, enum_module_def, variant_hir_name).is_some()
         {
             visited_modules_set.insert(module);
         }
     }
-
-    let lparen = syntax::SyntaxElement::from(list.l_paren_token()?);
-    let rparen = syntax::SyntaxElement::from(list.r_paren_token()?);
-    rewriter.insert_after(&lparen, segment.syntax());
-    rewriter.insert_after(&lparen, &lparen);
-    rewriter.insert_before(&rparen, &rparen);
+    rewriter.insert_after(segment.syntax(), &make::token(T!['(']));
+    rewriter.insert_after(segment.syntax(), segment.syntax());
+    rewriter.insert_after(&expr, &make::token(T![')']));
     Some(())
 }
 
@@ -320,7 +327,7 @@ fn another_fn() {
             r#"use my_mod::my_other_mod::MyField;
 
 mod my_mod {
-    use my_other_mod::MyField;
+    use self::my_other_mod::MyField;
 
     fn another_fn() {
         let m = my_other_mod::MyEnum::MyField(MyField(1, 1));
@@ -346,6 +353,33 @@ fn another_fn() {
     }
 
     #[test]
+    fn extract_record_fix_references() {
+        check_assist(
+            extract_struct_from_enum_variant,
+            r#"
+enum E {
+    <|>V { i: i32, j: i32 }
+}
+
+fn f() {
+    let e = E::V { i: 9, j: 2 };
+}
+"#,
+            r#"
+struct V{ pub i: i32, pub j: i32 }
+
+enum E {
+    V(V)
+}
+
+fn f() {
+    let e = E::V(V { i: 9, j: 2 });
+}
+"#,
+        )
+    }
+
+    #[test]
     fn test_several_files() {
         check_assist(
             extract_struct_from_enum_variant,
@@ -372,9 +406,7 @@ enum E {
 mod foo;
 
 //- /foo.rs
-use V;
-
-use crate::E;
+use crate::{E, V};
 fn f() {
     let e = E::V(V(9, 2));
 }
@@ -384,7 +416,6 @@ fn f() {
 
     #[test]
     fn test_several_files_record() {
-        // FIXME: this should fix the usage as well!
         check_assist(
             extract_struct_from_enum_variant,
             r#"
@@ -401,6 +432,7 @@ fn f() {
 }
 "#,
             r#"
+//- /main.rs
 struct V{ pub i: i32, pub j: i32 }
 
 enum E {
@@ -408,10 +440,42 @@ enum E {
 }
 mod foo;
 
+//- /foo.rs
+use crate::{E, V};
+fn f() {
+    let e = E::V(V { i: 9, j: 2 });
+}
 "#,
         )
     }
 
+    #[test]
+    fn test_extract_struct_record_nested_call_exp() {
+        check_assist(
+            extract_struct_from_enum_variant,
+            r#"
+enum A { <|>One { a: u32, b: u32 } }
+
+struct B(A);
+
+fn foo() {
+    let _ = B(A::One { a: 1, b: 2 });
+}
+"#,
+            r#"
+struct One{ pub a: u32, pub b: u32 }
+
+enum A { One(One) }
+
+struct B(A);
+
+fn foo() {
+    let _ = B(A::One(One { a: 1, b: 2 }));
+}
+"#,
+        );
+    }
+
     fn check_not_applicable(ra_fixture: &str) {
         let fixture =
             format!("//- /main.rs crate:main deps:core\n{}\n{}", ra_fixture, FamousDefs::FIXTURE);
diff --git a/crates/assists/src/handlers/remove_unused_param.rs b/crates/assists/src/handlers/remove_unused_param.rs
index 5fccca54b..1ff5e92b0 100644
--- a/crates/assists/src/handlers/remove_unused_param.rs
+++ b/crates/assists/src/handlers/remove_unused_param.rs
@@ -73,7 +73,8 @@ fn process_usage(
     let source_file = ctx.sema.parse(usage.file_range.file_id);
     let call_expr: ast::CallExpr =
         find_node_at_range(source_file.syntax(), usage.file_range.range)?;
-    if call_expr.expr()?.syntax().text_range() != usage.file_range.range {
+    let call_expr_range = call_expr.expr()?.syntax().text_range();
+    if !call_expr_range.contains_range(usage.file_range.range) {
         return None;
     }
     let arg = call_expr.arg_list()?.args().nth(arg_to_remove)?;
@@ -118,6 +119,53 @@ fn b() { foo(9, ) }
     }
 
     #[test]
+    fn remove_unused_qualified_call() {
+        check_assist(
+            remove_unused_param,
+            r#"
+mod bar { pub fn foo(x: i32, <|>y: i32) { x; } }
+fn b() { bar::foo(9, 2) }
+"#,
+            r#"
+mod bar { pub fn foo(x: i32) { x; } }
+fn b() { bar::foo(9) }
+"#,
+        );
+    }
+
+    #[test]
+    fn remove_unused_turbofished_func() {
+        check_assist(
+            remove_unused_param,
+            r#"
+pub fn foo<T>(x: T, <|>y: i32) { x; }
+fn b() { foo::<i32>(9, 2) }
+"#,
+            r#"
+pub fn foo<T>(x: T) { x; }
+fn b() { foo::<i32>(9) }
+"#,
+        );
+    }
+
+    #[test]
+    fn remove_unused_generic_unused_param_func() {
+        check_assist(
+            remove_unused_param,
+            r#"
+pub fn foo<T>(x: i32, <|>y: T) { x; }
+fn b() { foo::<i32>(9, 2) }
+fn b2() { foo(9, 2) }
+"#,
+            r#"
+pub fn foo<T>(x: i32) { x; }
+fn b() { foo::<i32>(9) }
+fn b2() { foo(9) }
+"#,
+        );
+    }
+
+    #[test]
     fn keep_used() {
         mark::check!(keep_used);
         check_assist_not_applicable(
@@ -128,4 +176,37 @@ fn main() { foo(9, 2) }
 "#,
         );
     }
+
+    #[test]
+    fn remove_across_files() {
+        check_assist(
+            remove_unused_param,
+            r#"
+//- /main.rs
+fn foo(x: i32, <|>y: i32) { x; }
+
+mod foo;
+
+//- /foo.rs
+use super::foo;
+
+fn bar() {
+    let _ = foo(1, 2);
+}
+"#,
+            r#"
+//- /main.rs
+fn foo(x: i32) { x; }
+
+mod foo;
+
+//- /foo.rs
+use super::foo;
+
+fn bar() {
+    let _ = foo(1);
+}
+"#,
+        )
+    }
 }
diff --git a/crates/assists/src/utils/insert_use.rs b/crates/assists/src/utils/insert_use.rs
index 84a0dffdd..af3fc96b6 100644
--- a/crates/assists/src/utils/insert_use.rs
+++ b/crates/assists/src/utils/insert_use.rs
@@ -9,7 +9,7 @@ use syntax::{
         edit::{AstNodeEdit, IndentLevel},
         make, AstNode, PathSegmentKind, VisibilityOwner,
     },
-    InsertPosition, SyntaxElement, SyntaxNode,
+    AstToken, InsertPosition, NodeOrToken, SyntaxElement, SyntaxNode, SyntaxToken,
 };
 use test_utils::mark;
 
@@ -63,27 +63,30 @@ impl ImportScope {
         }
     }
 
-    fn insert_pos_after_inner_attribute(&self) -> (InsertPosition<SyntaxElement>, AddBlankLine) {
-        // check if the scope has inner attributes, we dont want to insert in front of them
-        match self
-            .as_syntax_node()
-            .children()
-            // no flat_map here cause we want to short circuit the iterator
-            .map(ast::Attr::cast)
-            .take_while(|attr| {
-                attr.as_ref().map(|attr| attr.kind() == ast::AttrKind::Inner).unwrap_or(false)
+    fn insert_pos_after_last_inner_element(&self) -> (InsertPosition<SyntaxElement>, AddBlankLine) {
+        self.as_syntax_node()
+            .children_with_tokens()
+            .filter(|child| match child {
+                NodeOrToken::Node(node) => is_inner_attribute(node.clone()),
+                NodeOrToken::Token(token) => is_inner_comment(token.clone()),
             })
             .last()
-            .flatten()
-        {
-            Some(attr) => {
-                (InsertPosition::After(attr.syntax().clone().into()), AddBlankLine::BeforeTwice)
-            }
-            None => self.first_insert_pos(),
-        }
+            .map(|last_inner_element| {
+                (InsertPosition::After(last_inner_element.into()), AddBlankLine::BeforeTwice)
+            })
+            .unwrap_or_else(|| self.first_insert_pos())
     }
 }
 
+fn is_inner_attribute(node: SyntaxNode) -> bool {
+    ast::Attr::cast(node).map(|attr| attr.kind()) == Some(ast::AttrKind::Inner)
+}
+
+fn is_inner_comment(token: SyntaxToken) -> bool {
+    ast::Comment::cast(token).and_then(|comment| comment.kind().doc)
+        == Some(ast::CommentPlacement::Inner)
+}
+
 /// Insert an import path into the given file/node. A `merge` value of none indicates that no import merging is allowed to occur.
 pub(crate) fn insert_use<'a>(
     scope: &ImportScope,
@@ -558,7 +561,7 @@ fn find_insert_position(
                             (InsertPosition::After(node.into()), AddBlankLine::BeforeTwice)
                         }
                         // there are no imports in this file at all
-                        None => scope.insert_pos_after_inner_attribute(),
+                        None => scope.insert_pos_after_last_inner_element(),
                     },
                 }
             }
@@ -830,12 +833,67 @@ use foo::bar;",
             "foo::bar",
             r"#![allow(unused_imports)]
 
+#![no_std]
 fn main() {}",
             r"#![allow(unused_imports)]
 
-use foo::bar;
+#![no_std]
 
+use foo::bar;
 fn main() {}",
+        );
+    }
+
+    #[test]
+    fn inserts_after_single_line_inner_comments() {
+        check_none(
+            "foo::bar::Baz",
+            "//! Single line inner comments do not allow any code before them.",
+            r#"//! Single line inner comments do not allow any code before them.
+
+use foo::bar::Baz;"#,
+        );
+    }
+
+    #[test]
+    fn inserts_after_multiline_inner_comments() {
+        check_none(
+            "foo::bar::Baz",
+            r#"/*! Multiline inner comments do not allow any code before them. */
+
+/*! Still an inner comment, cannot place any code before. */
+fn main() {}"#,
+            r#"/*! Multiline inner comments do not allow any code before them. */
+
+/*! Still an inner comment, cannot place any code before. */
+
+use foo::bar::Baz;
+fn main() {}"#,
+        )
+    }
+
+    #[test]
+    fn inserts_after_all_inner_items() {
+        check_none(
+            "foo::bar::Baz",
+            r#"#![allow(unused_imports)]
+/*! Multiline line comment 2 */
+
+
+//! Single line comment 1
+#![no_std]
+//! Single line comment 2
+fn main() {}"#,
+            r#"#![allow(unused_imports)]
+/*! Multiline line comment 2 */
+
+
+//! Single line comment 1
+#![no_std]
+//! Single line comment 2
+
+use foo::bar::Baz;
+fn main() {}"#,
         )
     }
 
diff --git a/crates/project_model/src/cargo_workspace.rs b/crates/project_model/src/cargo_workspace.rs
index d5f6a4025..608a031d4 100644
--- a/crates/project_model/src/cargo_workspace.rs
+++ b/crates/project_model/src/cargo_workspace.rs
@@ -64,6 +64,9 @@ pub struct CargoConfig {
 
     /// rustc target
     pub target: Option<String>,
+
+    /// rustc private crate source
+    pub rustc_source: Option<AbsPathBuf>,
 }
 
 pub type Package = Idx<PackageData>;
diff --git a/crates/project_model/src/lib.rs b/crates/project_model/src/lib.rs
index e92cfea59..4531b1928 100644
--- a/crates/project_model/src/lib.rs
+++ b/crates/project_model/src/lib.rs
@@ -9,6 +9,7 @@ use std::{
     fmt,
     fs::{self, read_dir, ReadDir},
     io,
+    path::Component,
     process::Command,
 };
 
@@ -31,7 +32,7 @@ pub use proc_macro_api::ProcMacroClient;
 #[derive(Clone, Eq, PartialEq)]
 pub enum ProjectWorkspace {
     /// Project workspace was discovered by running `cargo metadata` and `rustc --print sysroot`.
-    Cargo { cargo: CargoWorkspace, sysroot: Sysroot },
+    Cargo { cargo: CargoWorkspace, sysroot: Sysroot, rustc: Option<CargoWorkspace> },
     /// Project workspace was manually specified using a `rust-project.json` file.
     Json { project: ProjectJson, sysroot: Option<Sysroot> },
 }
@@ -39,10 +40,14 @@ pub enum ProjectWorkspace {
 impl fmt::Debug for ProjectWorkspace {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
-            ProjectWorkspace::Cargo { cargo, sysroot } => f
+            ProjectWorkspace::Cargo { cargo, sysroot, rustc } => f
                 .debug_struct("Cargo")
                 .field("n_packages", &cargo.packages().len())
                 .field("n_sysroot_crates", &sysroot.crates().len())
+                .field(
+                    "n_rustc_compiler_crates",
+                    &rustc.as_ref().map_or(0, |rc| rc.packages().len()),
+                )
                 .finish(),
             ProjectWorkspace::Json { project, sysroot } => {
                 let mut debug_struct = f.debug_struct("Json");
@@ -200,7 +205,19 @@ impl ProjectWorkspace {
                 } else {
                     Sysroot::default()
                 };
-                ProjectWorkspace::Cargo { cargo, sysroot }
+
+                let rustc = if let Some(rustc_dir) = &cargo_config.rustc_source {
+                    Some(
+                        CargoWorkspace::from_cargo_metadata(&rustc_dir, cargo_config)
+                            .with_context(|| {
+                                format!("Failed to read Cargo metadata for Rust sources")
+                            })?,
+                    )
+                } else {
+                    None
+                };
+
+                ProjectWorkspace::Cargo { cargo, sysroot, rustc }
             }
         };
 
@@ -238,31 +255,43 @@ impl ProjectWorkspace {
                     })
                 }))
                 .collect::<Vec<_>>(),
-            ProjectWorkspace::Cargo { cargo, sysroot } => cargo
-                .packages()
-                .map(|pkg| {
-                    let is_member = cargo[pkg].is_member;
-                    let pkg_root = cargo[pkg].root().to_path_buf();
-
-                    let mut include = vec![pkg_root.clone()];
-                    include.extend(cargo[pkg].out_dir.clone());
-
-                    let mut exclude = vec![pkg_root.join(".git")];
-                    if is_member {
-                        exclude.push(pkg_root.join("target"));
-                    } else {
-                        exclude.push(pkg_root.join("tests"));
-                        exclude.push(pkg_root.join("examples"));
-                        exclude.push(pkg_root.join("benches"));
-                    }
-                    PackageRoot { is_member, include, exclude }
-                })
-                .chain(sysroot.crates().map(|krate| PackageRoot {
-                    is_member: false,
-                    include: vec![sysroot[krate].root_dir().to_path_buf()],
-                    exclude: Vec::new(),
-                }))
-                .collect(),
+            ProjectWorkspace::Cargo { cargo, sysroot, rustc } => {
+                let roots = cargo
+                    .packages()
+                    .map(|pkg| {
+                        let is_member = cargo[pkg].is_member;
+                        let pkg_root = cargo[pkg].root().to_path_buf();
+
+                        let mut include = vec![pkg_root.clone()];
+                        include.extend(cargo[pkg].out_dir.clone());
+
+                        let mut exclude = vec![pkg_root.join(".git")];
+                        if is_member {
+                            exclude.push(pkg_root.join("target"));
+                        } else {
+                            exclude.push(pkg_root.join("tests"));
+                            exclude.push(pkg_root.join("examples"));
+                            exclude.push(pkg_root.join("benches"));
+                        }
+                        PackageRoot { is_member, include, exclude }
+                    })
+                    .chain(sysroot.crates().map(|krate| PackageRoot {
+                        is_member: false,
+                        include: vec![sysroot[krate].root_dir().to_path_buf()],
+                        exclude: Vec::new(),
+                    }));
+                if let Some(rustc_packages) = rustc {
+                    roots
+                        .chain(rustc_packages.packages().map(|krate| PackageRoot {
+                            is_member: false,
+                            include: vec![rustc_packages[krate].root().to_path_buf()],
+                            exclude: Vec::new(),
+                        }))
+                        .collect()
+                } else {
+                    roots.collect()
+                }
+            }
         }
     }
 
@@ -273,7 +302,7 @@ impl ProjectWorkspace {
                 .filter_map(|(_, krate)| krate.proc_macro_dylib_path.as_ref())
                 .cloned()
                 .collect(),
-            ProjectWorkspace::Cargo { cargo, sysroot: _sysroot } => cargo
+            ProjectWorkspace::Cargo { cargo, sysroot: _sysroot, rustc: _rustc_crates } => cargo
                 .packages()
                 .filter_map(|pkg| cargo[pkg].proc_macro_dylib_path.as_ref())
                 .cloned()
@@ -284,8 +313,9 @@ impl ProjectWorkspace {
     pub fn n_packages(&self) -> usize {
         match self {
             ProjectWorkspace::Json { project, .. } => project.n_crates(),
-            ProjectWorkspace::Cargo { cargo, sysroot } => {
-                cargo.packages().len() + sysroot.crates().len()
+            ProjectWorkspace::Cargo { cargo, sysroot, rustc } => {
+                let rustc_package_len = rustc.as_ref().map_or(0, |rc| rc.packages().len());
+                cargo.packages().len() + sysroot.crates().len() + rustc_package_len
             }
         }
     }
@@ -365,7 +395,7 @@ impl ProjectWorkspace {
                     }
                 }
             }
-            ProjectWorkspace::Cargo { cargo, sysroot } => {
+            ProjectWorkspace::Cargo { cargo, sysroot, rustc } => {
                 let (public_deps, libproc_macro) =
                     sysroot_to_crate_graph(&mut crate_graph, sysroot, target, load);
 
@@ -373,50 +403,25 @@ impl ProjectWorkspace {
                 cfg_options.extend(get_rustc_cfg_options(target));
 
                 let mut pkg_to_lib_crate = FxHashMap::default();
-                let mut pkg_crates = FxHashMap::default();
 
                 // Add test cfg for non-sysroot crates
                 cfg_options.insert_atom("test".into());
                 cfg_options.insert_atom("debug_assertions".into());
 
+                let mut pkg_crates = FxHashMap::default();
+
                 // Next, create crates for each package, target pair
                 for pkg in cargo.packages() {
                     let mut lib_tgt = None;
                     for &tgt in cargo[pkg].targets.iter() {
-                        let root = cargo[tgt].root.as_path();
-                        if let Some(file_id) = load(root) {
-                            let edition = cargo[pkg].edition;
-                            let cfg_options = {
-                                let mut opts = cfg_options.clone();
-                                for feature in cargo[pkg].features.iter() {
-                                    opts.insert_key_value("feature".into(), feature.into());
-                                }
-                                opts.extend(cargo[pkg].cfgs.iter().cloned());
-                                opts
-                            };
-                            let mut env = Env::default();
-                            if let Some(out_dir) = &cargo[pkg].out_dir {
-                                // NOTE: cargo and rustc seem to hide non-UTF-8 strings from env! and option_env!()
-                                if let Some(out_dir) = out_dir.to_str().map(|s| s.to_owned()) {
-                                    env.set("OUT_DIR", out_dir);
-                                }
-                            }
-                            let proc_macro = cargo[pkg]
-                                .proc_macro_dylib_path
-                                .as_ref()
-                                .map(|it| proc_macro_client.by_dylib_path(&it))
-                                .unwrap_or_default();
-
-                            let display_name =
-                                CrateDisplayName::from_canonical_name(cargo[pkg].name.clone());
-                            let crate_id = crate_graph.add_crate_root(
-                                file_id,
-                                edition,
-                                Some(display_name),
-                                cfg_options,
-                                env,
-                                proc_macro.clone(),
-                            );
+                        if let Some(crate_id) = add_target_crate_root(
+                            &mut crate_graph,
+                            &cargo[pkg],
+                            &cargo[tgt],
+                            &cfg_options,
+                            proc_macro_client,
+                            load,
+                        ) {
                             if cargo[tgt].kind == TargetKind::Lib {
                                 lib_tgt = Some((crate_id, cargo[tgt].name.clone()));
                                 pkg_to_lib_crate.insert(pkg, crate_id);
@@ -484,6 +489,92 @@ impl ProjectWorkspace {
                         }
                     }
                 }
+
+                let mut rustc_pkg_crates = FxHashMap::default();
+
+                // If the user provided a path to rustc sources, we add all the rustc_private crates
+                // and create dependencies on them for the crates in the current workspace
+                if let Some(rustc_workspace) = rustc {
+                    for pkg in rustc_workspace.packages() {
+                        for &tgt in rustc_workspace[pkg].targets.iter() {
+                            if rustc_workspace[tgt].kind != TargetKind::Lib {
+                                continue;
+                            }
+                            // Exclude alloc / core / std
+                            if rustc_workspace[tgt]
+                                .root
+                                .components()
+                                .any(|c| c == Component::Normal("library".as_ref()))
+                            {
+                                continue;
+                            }
+
+                            if let Some(crate_id) = add_target_crate_root(
+                                &mut crate_graph,
+                                &rustc_workspace[pkg],
+                                &rustc_workspace[tgt],
+                                &cfg_options,
+                                proc_macro_client,
+                                load,
+                            ) {
+                                pkg_to_lib_crate.insert(pkg, crate_id);
+                                // Add dependencies on the core / std / alloc for rustc
+                                for (name, krate) in public_deps.iter() {
+                                    if let Err(_) =
+                                        crate_graph.add_dep(crate_id, name.clone(), *krate)
+                                    {
+                                        log::error!(
+                                            "cyclic dependency on {} for {}",
+                                            name,
+                                            &cargo[pkg].name
+                                        )
+                                    }
+                                }
+                                rustc_pkg_crates.entry(pkg).or_insert_with(Vec::new).push(crate_id);
+                            }
+                        }
+                    }
+                    // Now add a dep edge from all targets of upstream to the lib
+                    // target of downstream.
+                    for pkg in rustc_workspace.packages() {
+                        for dep in rustc_workspace[pkg].dependencies.iter() {
+                            let name = CrateName::new(&dep.name).unwrap();
+                            if let Some(&to) = pkg_to_lib_crate.get(&dep.pkg) {
+                                for &from in rustc_pkg_crates.get(&pkg).into_iter().flatten() {
+                                    if let Err(_) = crate_graph.add_dep(from, name.clone(), to) {
+                                        log::error!(
+                                            "cyclic dependency {} -> {}",
+                                            &rustc_workspace[pkg].name,
+                                            &rustc_workspace[dep.pkg].name
+                                        )
+                                    }
+                                }
+                            }
+                        }
+                    }
+
+                    // Add dependencies for all the crates of the current workspace to rustc_private libraries
+                    for dep in rustc_workspace.packages() {
+                        let name = CrateName::normalize_dashes(&rustc_workspace[dep].name);
+
+                        if let Some(&to) = pkg_to_lib_crate.get(&dep) {
+                            for pkg in cargo.packages() {
+                                if !cargo[pkg].is_member {
+                                    continue;
+                                }
+                                for &from in pkg_crates.get(&pkg).into_iter().flatten() {
+                                    if let Err(_) = crate_graph.add_dep(from, name.clone(), to) {
+                                        log::error!(
+                                            "cyclic dependency {} -> {}",
+                                            &cargo[pkg].name,
+                                            &rustc_workspace[dep].name
+                                        )
+                                    }
+                                }
+                            }
+                        }
+                    }
+                }
             }
         }
         if crate_graph.patch_cfg_if() {
@@ -537,6 +628,52 @@ fn utf8_stdout(mut cmd: Command) -> Result<String> {
     Ok(stdout.trim().to_string())
 }
 
+fn add_target_crate_root(
+    crate_graph: &mut CrateGraph,
+    pkg: &cargo_workspace::PackageData,
+    tgt: &cargo_workspace::TargetData,
+    cfg_options: &CfgOptions,
+    proc_macro_client: &ProcMacroClient,
+    load: &mut dyn FnMut(&AbsPath) -> Option<FileId>,
+) -> Option<CrateId> {
+    let root = tgt.root.as_path();
+    if let Some(file_id) = load(root) {
+        let edition = pkg.edition;
+        let cfg_options = {
+            let mut opts = cfg_options.clone();
+            for feature in pkg.features.iter() {
+                opts.insert_key_value("feature".into(), feature.into());
+            }
+            opts.extend(pkg.cfgs.iter().cloned());
+            opts
+        };
+        let mut env = Env::default();
+        if let Some(out_dir) = &pkg.out_dir {
+            // NOTE: cargo and rustc seem to hide non-UTF-8 strings from env! and option_env!()
+            if let Some(out_dir) = out_dir.to_str().map(|s| s.to_owned()) {
+                env.set("OUT_DIR", out_dir);
+            }
+        }
+        let proc_macro = pkg
+            .proc_macro_dylib_path
+            .as_ref()
+            .map(|it| proc_macro_client.by_dylib_path(&it))
+            .unwrap_or_default();
+
+        let display_name = CrateDisplayName::from_canonical_name(pkg.name.clone());
+        let crate_id = crate_graph.add_crate_root(
+            file_id,
+            edition,
+            Some(display_name),
+            cfg_options,
+            env,
+            proc_macro.clone(),
+        );
+
+        return Some(crate_id);
+    }
+    None
+}
 fn sysroot_to_crate_graph(
     crate_graph: &mut CrateGraph,
     sysroot: &Sysroot,
diff --git a/crates/rust-analyzer/src/config.rs b/crates/rust-analyzer/src/config.rs
index 9cc14fe82..372180ab5 100644
--- a/crates/rust-analyzer/src/config.rs
+++ b/crates/rust-analyzer/src/config.rs
@@ -7,7 +7,7 @@
 //! configure the server itself, feature flags are passed into analysis, and
 //! tweak things like automatic insertion of `()` in completions.
 
-use std::{ffi::OsString, path::PathBuf};
+use std::{convert::TryFrom, ffi::OsString, path::PathBuf};
 
 use flycheck::FlycheckConfig;
 use hir::PrefixKind;
@@ -227,12 +227,25 @@ impl Config {
         self.notifications =
             NotificationsConfig { cargo_toml_not_found: data.notifications_cargoTomlNotFound };
         self.cargo_autoreload = data.cargo_autoreload;
+
+        let rustc_source = if let Some(rustc_source) = data.rustcSource {
+            let rustpath: PathBuf = rustc_source.into();
+            AbsPathBuf::try_from(rustpath)
+                .map_err(|_| {
+                    log::error!("rustc source directory must be an absolute path");
+                })
+                .ok()
+        } else {
+            None
+        };
+
         self.cargo = CargoConfig {
             no_default_features: data.cargo_noDefaultFeatures,
             all_features: data.cargo_allFeatures,
             features: data.cargo_features.clone(),
             load_out_dirs_from_check: data.cargo_loadOutDirsFromCheck,
             target: data.cargo_target.clone(),
+            rustc_source: rustc_source,
         };
         self.runnables = RunnablesConfig {
             override_cargo: data.runnables_overrideCargo,
@@ -532,5 +545,6 @@ config_data! {
         rustfmt_overrideCommand: Option<Vec<String>> = None,
 
         withSysroot: bool = true,
+        rustcSource : Option<String> = None,
     }
 }
diff --git a/crates/rust-analyzer/src/diagnostics/test_data/clippy_pass_by_ref.txt b/crates/rust-analyzer/src/diagnostics/test_data/clippy_pass_by_ref.txt
index 58d47d32a..5b2e5187a 100644
--- a/crates/rust-analyzer/src/diagnostics/test_data/clippy_pass_by_ref.txt
+++ b/crates/rust-analyzer/src/diagnostics/test_data/clippy_pass_by_ref.txt
@@ -1,6 +1,13 @@
 [
     MappedRustDiagnostic {
-        url: "file:///test/compiler/mir/tagset.rs",
+        url: Url {
+            scheme: "file",
+            host: None,
+            port: None,
+            path: "/test/compiler/mir/tagset.rs",
+            query: None,
+            fragment: None,
+        },
         diagnostic: Diagnostic {
             range: Range {
                 start: Position {
@@ -29,7 +36,14 @@
                 [
                     DiagnosticRelatedInformation {
                         location: Location {
-                            uri: "file:///test/compiler/lib.rs",
+                            uri: Url {
+                                scheme: "file",
+                                host: None,
+                                port: None,
+                                path: "/test/compiler/lib.rs",
+                                query: None,
+                                fragment: None,
+                            },
                             range: Range {
                                 start: Position {
                                     line: 0,
@@ -45,7 +59,14 @@
                     },
                     DiagnosticRelatedInformation {
                         location: Location {
-                            uri: "file:///test/compiler/mir/tagset.rs",
+                            uri: Url {
+                                scheme: "file",
+                                host: None,
+                                port: None,
+                                path: "/test/compiler/mir/tagset.rs",
+                                query: None,
+                                fragment: None,
+                            },
                             range: Range {
                                 start: Position {
                                     line: 41,
diff --git a/crates/rust-analyzer/src/diagnostics/test_data/handles_macro_location.txt b/crates/rust-analyzer/src/diagnostics/test_data/handles_macro_location.txt
index 6aa26bf63..116f0ff73 100644
--- a/crates/rust-analyzer/src/diagnostics/test_data/handles_macro_location.txt
+++ b/crates/rust-analyzer/src/diagnostics/test_data/handles_macro_location.txt
@@ -1,6 +1,13 @@
 [
     MappedRustDiagnostic {
-        url: "file:///test/src/main.rs",
+        url: Url {
+            scheme: "file",
+            host: None,
+            port: None,
+            path: "/test/src/main.rs",
+            query: None,
+            fragment: None,
+        },
         diagnostic: Diagnostic {
             range: Range {
                 start: Position {
diff --git a/crates/rust-analyzer/src/diagnostics/test_data/macro_compiler_error.txt b/crates/rust-analyzer/src/diagnostics/test_data/macro_compiler_error.txt
index 7aaffaba2..bbec6a796 100644
--- a/crates/rust-analyzer/src/diagnostics/test_data/macro_compiler_error.txt
+++ b/crates/rust-analyzer/src/diagnostics/test_data/macro_compiler_error.txt
@@ -1,6 +1,13 @@
 [
     MappedRustDiagnostic {
-        url: "file:///test/crates/hir_def/src/data.rs",
+        url: Url {
+            scheme: "file",
+            host: None,
+            port: None,
+            path: "/test/crates/hir_def/src/data.rs",
+            query: None,
+            fragment: None,
+        },
         diagnostic: Diagnostic {
             range: Range {
                 start: Position {
@@ -25,7 +32,14 @@
                 [
                     DiagnosticRelatedInformation {
                         location: Location {
-                            uri: "file:///test/crates/hir_def/src/path.rs",
+                            uri: Url {
+                                scheme: "file",
+                                host: None,
+                                port: None,
+                                path: "/test/crates/hir_def/src/path.rs",
+                                query: None,
+                                fragment: None,
+                            },
                             range: Range {
                                 start: Position {
                                     line: 264,
@@ -47,7 +61,14 @@
         fixes: [],
     },
     MappedRustDiagnostic {
-        url: "file:///test/crates/hir_def/src/path.rs",
+        url: Url {
+            scheme: "file",
+            host: None,
+            port: None,
+            path: "/test/crates/hir_def/src/path.rs",
+            query: None,
+            fragment: None,
+        },
         diagnostic: Diagnostic {
             range: Range {
                 start: Position {
@@ -72,7 +93,14 @@
                 [
                     DiagnosticRelatedInformation {
                         location: Location {
-                            uri: "file:///test/crates/hir_def/src/data.rs",
+                            uri: Url {
+                                scheme: "file",
+                                host: None,
+                                port: None,
+                                path: "/test/crates/hir_def/src/data.rs",
+                                query: None,
+                                fragment: None,
+                            },
                             range: Range {
                                 start: Position {
                                     line: 79,
diff --git a/crates/rust-analyzer/src/diagnostics/test_data/rustc_incompatible_type_for_trait.txt b/crates/rust-analyzer/src/diagnostics/test_data/rustc_incompatible_type_for_trait.txt
index 584213420..2cbf657e5 100644
--- a/crates/rust-analyzer/src/diagnostics/test_data/rustc_incompatible_type_for_trait.txt
+++ b/crates/rust-analyzer/src/diagnostics/test_data/rustc_incompatible_type_for_trait.txt
@@ -1,6 +1,13 @@
 [
     MappedRustDiagnostic {
-        url: "file:///test/compiler/ty/list_iter.rs",
+        url: Url {
+            scheme: "file",
+            host: None,
+            port: None,
+            path: "/test/compiler/ty/list_iter.rs",
+            query: None,
+            fragment: None,
+        },
         diagnostic: Diagnostic {
             range: Range {
                 start: Position {
diff --git a/crates/rust-analyzer/src/diagnostics/test_data/rustc_mismatched_type.txt b/crates/rust-analyzer/src/diagnostics/test_data/rustc_mismatched_type.txt
index 2610e4e20..1142dc2ac 100644
--- a/crates/rust-analyzer/src/diagnostics/test_data/rustc_mismatched_type.txt
+++ b/crates/rust-analyzer/src/diagnostics/test_data/rustc_mismatched_type.txt
@@ -1,6 +1,13 @@
 [
     MappedRustDiagnostic {
-        url: "file:///test/runtime/compiler_support.rs",
+        url: Url {
+            scheme: "file",
+            host: None,
+            port: None,
+            path: "/test/runtime/compiler_support.rs",
+            query: None,
+            fragment: None,
+        },
         diagnostic: Diagnostic {
             range: Range {
                 start: Position {
diff --git a/crates/rust-analyzer/src/diagnostics/test_data/rustc_unused_variable.txt b/crates/rust-analyzer/src/diagnostics/test_data/rustc_unused_variable.txt
index a8d85f008..c709de95f 100644
--- a/crates/rust-analyzer/src/diagnostics/test_data/rustc_unused_variable.txt
+++ b/crates/rust-analyzer/src/diagnostics/test_data/rustc_unused_variable.txt
@@ -1,6 +1,13 @@
 [
     MappedRustDiagnostic {
-        url: "file:///test/driver/subcommand/repl.rs",
+        url: Url {
+            scheme: "file",
+            host: None,
+            port: None,
+            path: "/test/driver/subcommand/repl.rs",
+            query: None,
+            fragment: None,
+        },
         diagnostic: Diagnostic {
             range: Range {
                 start: Position {
@@ -46,7 +53,14 @@
                     SnippetWorkspaceEdit {
                         changes: Some(
                             {
-                                "file:///test/driver/subcommand/repl.rs": [
+                                Url {
+                                    scheme: "file",
+                                    host: None,
+                                    port: None,
+                                    path: "/test/driver/subcommand/repl.rs",
+                                    query: None,
+                                    fragment: None,
+                                }: [
                                     TextEdit {
                                         range: Range {
                                             start: Position {
diff --git a/crates/rust-analyzer/src/diagnostics/test_data/rustc_unused_variable_as_hint.txt b/crates/rust-analyzer/src/diagnostics/test_data/rustc_unused_variable_as_hint.txt
index 0b8937376..632f438d7 100644
--- a/crates/rust-analyzer/src/diagnostics/test_data/rustc_unused_variable_as_hint.txt
+++ b/crates/rust-analyzer/src/diagnostics/test_data/rustc_unused_variable_as_hint.txt
@@ -1,6 +1,13 @@
 [
     MappedRustDiagnostic {
-        url: "file:///test/driver/subcommand/repl.rs",
+        url: Url {
+            scheme: "file",
+            host: None,
+            port: None,
+            path: "/test/driver/subcommand/repl.rs",
+            query: None,
+            fragment: None,
+        },
         diagnostic: Diagnostic {
             range: Range {
                 start: Position {
@@ -46,7 +53,14 @@
                     SnippetWorkspaceEdit {
                         changes: Some(
                             {
-                                "file:///test/driver/subcommand/repl.rs": [
+                                Url {
+                                    scheme: "file",
+                                    host: None,
+                                    port: None,
+                                    path: "/test/driver/subcommand/repl.rs",
+                                    query: None,
+                                    fragment: None,
+                                }: [
                                     TextEdit {
                                         range: Range {
                                             start: Position {
diff --git a/crates/rust-analyzer/src/diagnostics/test_data/rustc_unused_variable_as_info.txt b/crates/rust-analyzer/src/diagnostics/test_data/rustc_unused_variable_as_info.txt
index 7fa9dee62..c0b79428d 100644
--- a/crates/rust-analyzer/src/diagnostics/test_data/rustc_unused_variable_as_info.txt
+++ b/crates/rust-analyzer/src/diagnostics/test_data/rustc_unused_variable_as_info.txt
@@ -1,6 +1,13 @@
 [
     MappedRustDiagnostic {
-        url: "file:///test/driver/subcommand/repl.rs",
+        url: Url {
+            scheme: "file",
+            host: None,
+            port: None,
+            path: "/test/driver/subcommand/repl.rs",
+            query: None,
+            fragment: None,
+        },
         diagnostic: Diagnostic {
             range: Range {
                 start: Position {
@@ -46,7 +53,14 @@
                     SnippetWorkspaceEdit {
                         changes: Some(
                             {
-                                "file:///test/driver/subcommand/repl.rs": [
+                                Url {
+                                    scheme: "file",
+                                    host: None,
+                                    port: None,
+                                    path: "/test/driver/subcommand/repl.rs",
+                                    query: None,
+                                    fragment: None,
+                                }: [
                                     TextEdit {
                                         range: Range {
                                             start: Position {
diff --git a/crates/rust-analyzer/src/diagnostics/test_data/rustc_wrong_number_of_parameters.txt b/crates/rust-analyzer/src/diagnostics/test_data/rustc_wrong_number_of_parameters.txt
index ba1b98b33..782c72dbd 100644
--- a/crates/rust-analyzer/src/diagnostics/test_data/rustc_wrong_number_of_parameters.txt
+++ b/crates/rust-analyzer/src/diagnostics/test_data/rustc_wrong_number_of_parameters.txt
@@ -1,6 +1,13 @@
 [
     MappedRustDiagnostic {
-        url: "file:///test/compiler/ty/select.rs",
+        url: Url {
+            scheme: "file",
+            host: None,
+            port: None,
+            path: "/test/compiler/ty/select.rs",
+            query: None,
+            fragment: None,
+        },
         diagnostic: Diagnostic {
             range: Range {
                 start: Position {
@@ -29,7 +36,14 @@
                 [
                     DiagnosticRelatedInformation {
                         location: Location {
-                            uri: "file:///test/compiler/ty/select.rs",
+                            uri: Url {
+                                scheme: "file",
+                                host: None,
+                                port: None,
+                                path: "/test/compiler/ty/select.rs",
+                                query: None,
+                                fragment: None,
+                            },
                             range: Range {
                                 start: Position {
                                     line: 218,
diff --git a/crates/rust-analyzer/src/diagnostics/test_data/snap_multi_line_fix.txt b/crates/rust-analyzer/src/diagnostics/test_data/snap_multi_line_fix.txt
index 3c97b2084..d3f27ab6a 100644
--- a/crates/rust-analyzer/src/diagnostics/test_data/snap_multi_line_fix.txt
+++ b/crates/rust-analyzer/src/diagnostics/test_data/snap_multi_line_fix.txt
@@ -1,6 +1,13 @@
 [
     MappedRustDiagnostic {
-        url: "file:///test/src/main.rs",
+        url: Url {
+            scheme: "file",
+            host: None,
+            port: None,
+            path: "/test/src/main.rs",
+            query: None,
+            fragment: None,
+        },
         diagnostic: Diagnostic {
             range: Range {
                 start: Position {
@@ -29,7 +36,14 @@
                 [
                     DiagnosticRelatedInformation {
                         location: Location {
-                            uri: "file:///test/src/main.rs",
+                            uri: Url {
+                                scheme: "file",
+                                host: None,
+                                port: None,
+                                path: "/test/src/main.rs",
+                                query: None,
+                                fragment: None,
+                            },
                             range: Range {
                                 start: Position {
                                     line: 2,
@@ -61,7 +75,14 @@
                     SnippetWorkspaceEdit {
                         changes: Some(
                             {
-                                "file:///test/src/main.rs": [
+                                Url {
+                                    scheme: "file",
+                                    host: None,
+                                    port: None,
+                                    path: "/test/src/main.rs",
+                                    query: None,
+                                    fragment: None,
+                                }: [
                                     TextEdit {
                                         range: Range {
                                             start: Position {
diff --git a/crates/rust-analyzer/src/reload.rs b/crates/rust-analyzer/src/reload.rs
index 0eabd51bd..11c8d0e5f 100644
--- a/crates/rust-analyzer/src/reload.rs
+++ b/crates/rust-analyzer/src/reload.rs
@@ -246,7 +246,9 @@ impl GlobalState {
             .iter()
             .enumerate()
             .filter_map(|(id, w)| match w {
-                ProjectWorkspace::Cargo { cargo, sysroot: _ } => Some((id, cargo.workspace_root())),
+                ProjectWorkspace::Cargo { cargo, sysroot: _, rustc: _ } => {
+                    Some((id, cargo.workspace_root()))
+                }
                 ProjectWorkspace::Json { project, .. } => {
                     // Enable flychecks for json projects if a custom flycheck command was supplied
                     // in the workspace configuration.
diff --git a/crates/syntax/Cargo.toml b/crates/syntax/Cargo.toml
index 61d2acb49..1fe907753 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 = "686.0.0", package = "rustc-ap-rustc_lexer" }
+rustc_lexer = { version = "688.0.0", 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.rs b/crates/syntax/src/ast.rs
index 8a0e3d27b..7844f9ed6 100644
--- a/crates/syntax/src/ast.rs
+++ b/crates/syntax/src/ast.rs
@@ -115,10 +115,10 @@ fn test_doc_comment_none() {
 }
 
 #[test]
-fn test_doc_comment_of_items() {
+fn test_outer_doc_comment_of_items() {
     let file = SourceFile::parse(
         r#"
-        //! doc
+        /// doc
         // non-doc
         mod foo {}
         "#,
@@ -130,6 +130,21 @@ fn test_doc_comment_of_items() {
 }
 
 #[test]
+fn test_inner_doc_comment_of_items() {
+    let file = SourceFile::parse(
+        r#"
+        //! doc
+        // non-doc
+        mod foo {}
+        "#,
+    )
+    .ok()
+    .unwrap();
+    let module = file.syntax().descendants().find_map(Module::cast).unwrap();
+    assert!(module.doc_comment_text().is_none());
+}
+
+#[test]
 fn test_doc_comment_of_statics() {
     let file = SourceFile::parse(
         r#"
diff --git a/crates/syntax/src/ast/token_ext.rs b/crates/syntax/src/ast/token_ext.rs
index e4e512f2e..2661c753e 100644
--- a/crates/syntax/src/ast/token_ext.rs
+++ b/crates/syntax/src/ast/token_ext.rs
@@ -14,16 +14,15 @@ use crate::{
 
 impl ast::Comment {
     pub fn kind(&self) -> CommentKind {
-        kind_by_prefix(self.text())
+        CommentKind::from_text(self.text())
     }
 
     pub fn prefix(&self) -> &'static str {
-        for (prefix, k) in COMMENT_PREFIX_TO_KIND.iter() {
-            if *k == self.kind() && self.text().starts_with(prefix) {
-                return prefix;
-            }
-        }
-        unreachable!()
+        let &(prefix, _kind) = CommentKind::BY_PREFIX
+            .iter()
+            .find(|&(prefix, kind)| self.kind() == *kind && self.text().starts_with(prefix))
+            .unwrap();
+        prefix
     }
 }
 
@@ -55,29 +54,25 @@ pub enum CommentPlacement {
     Outer,
 }
 
-const COMMENT_PREFIX_TO_KIND: &[(&str, CommentKind)] = {
-    use {CommentPlacement::*, CommentShape::*};
-    &[
-        ("////", CommentKind { shape: Line, doc: None }),
-        ("///", CommentKind { shape: Line, doc: Some(Outer) }),
-        ("//!", CommentKind { shape: Line, doc: Some(Inner) }),
-        ("/**", CommentKind { shape: Block, doc: Some(Outer) }),
-        ("/*!", CommentKind { shape: Block, doc: Some(Inner) }),
-        ("//", CommentKind { shape: Line, doc: None }),
-        ("/*", CommentKind { shape: Block, doc: None }),
-    ]
-};
+impl CommentKind {
+    const BY_PREFIX: [(&'static str, CommentKind); 8] = [
+        ("/**/", CommentKind { shape: CommentShape::Block, doc: None }),
+        ("////", CommentKind { shape: CommentShape::Line, doc: None }),
+        ("///", CommentKind { shape: CommentShape::Line, doc: Some(CommentPlacement::Outer) }),
+        ("//!", CommentKind { shape: CommentShape::Line, doc: Some(CommentPlacement::Inner) }),
+        ("/**", CommentKind { shape: CommentShape::Block, doc: Some(CommentPlacement::Outer) }),
+        ("/*!", CommentKind { shape: CommentShape::Block, doc: Some(CommentPlacement::Inner) }),
+        ("//", CommentKind { shape: CommentShape::Line, doc: None }),
+        ("/*", CommentKind { shape: CommentShape::Block, doc: None }),
+    ];
 
-fn kind_by_prefix(text: &str) -> CommentKind {
-    if text == "/**/" {
-        return CommentKind { shape: CommentShape::Block, doc: None };
-    }
-    for (prefix, kind) in COMMENT_PREFIX_TO_KIND.iter() {
-        if text.starts_with(prefix) {
-            return *kind;
-        }
+    pub(crate) fn from_text(text: &str) -> CommentKind {
+        let &(_prefix, kind) = CommentKind::BY_PREFIX
+            .iter()
+            .find(|&(prefix, _kind)| text.starts_with(prefix))
+            .unwrap();
+        kind
     }
-    panic!("bad comment text: {:?}", text)
 }
 
 impl ast::Whitespace {
diff --git a/crates/syntax/src/parsing/text_tree_sink.rs b/crates/syntax/src/parsing/text_tree_sink.rs
index c1b5f246d..997bc5d28 100644
--- a/crates/syntax/src/parsing/text_tree_sink.rs
+++ b/crates/syntax/src/parsing/text_tree_sink.rs
@@ -5,6 +5,7 @@ use std::mem;
 use parser::{ParseError, TreeSink};
 
 use crate::{
+    ast,
     parsing::Token,
     syntax_node::GreenNode,
     SmolStr, SyntaxError,
@@ -153,24 +154,22 @@ fn n_attached_trivias<'a>(
 
             while let Some((i, (kind, text))) = trivias.next() {
                 match kind {
-                    WHITESPACE => {
-                        if text.contains("\n\n") {
-                            // we check whether the next token is a doc-comment
-                            // and skip the whitespace in this case
-                            if let Some((peek_kind, peek_text)) =
-                                trivias.peek().map(|(_, pair)| pair)
-                            {
-                                if *peek_kind == COMMENT
-                                    && peek_text.starts_with("///")
-                                    && !peek_text.starts_with("////")
-                                {
-                                    continue;
-                                }
+                    WHITESPACE if text.contains("\n\n") => {
+                        // we check whether the next token is a doc-comment
+                        // and skip the whitespace in this case
+                        if let Some((COMMENT, peek_text)) = trivias.peek().map(|(_, pair)| pair) {
+                            let comment_kind = ast::CommentKind::from_text(peek_text);
+                            if comment_kind.doc == Some(ast::CommentPlacement::Outer) {
+                                continue;
                             }
-                            break;
                         }
+                        break;
                     }
                     COMMENT => {
+                        let comment_kind = ast::CommentKind::from_text(text);
+                        if comment_kind.doc == Some(ast::CommentPlacement::Inner) {
+                            break;
+                        }
                         res = i + 1;
                     }
                     _ => (),
diff --git a/crates/syntax/test_data/parser/ok/0037_mod.rast b/crates/syntax/test_data/parser/ok/0037_mod.rast
index 1d5d94bde..35577272e 100644
--- a/crates/syntax/test_data/parser/ok/0037_mod.rast
+++ b/crates/syntax/test_data/parser/ok/0037_mod.rast
@@ -1,9 +1,9 @@
 [email protected]
   [email protected] "// https://github.com ..."
   [email protected] "\n\n"
-  MODULE@62..93
-    COMMENT@62..70 "//! docs"
-    WHITESPACE@70..71 "\n"
+  COMMENT@62..70 "//! docs"
+  WHITESPACE@70..71 "\n"
+  MODULE@71..93
     [email protected] "// non-docs"
     [email protected] "\n"
     [email protected] "mod"
diff --git a/editors/code/package.json b/editors/code/package.json
index b02c80773..3768679fe 100644
--- a/editors/code/package.json
+++ b/editors/code/package.json
@@ -692,6 +692,14 @@
                     },
                     "default": [],
                     "description": "Additional arguments to be passed to cargo for runnables such as tests or binaries.\nFor example, it may be '--release'"
+                },
+                "rust-analyzer.rustcSource": {
+                    "type": [
+                        "null",
+                        "string"
+                    ],
+                    "default": null,
+                    "description": "Path to the rust compiler sources, for usage in rustc_private projects."
                 }
             }
         },