26 files changed, 1110 insertions, 555 deletions

diff --git a/crates/hir_def/src/attr.rs b/crates/hir_def/src/attr.rs
index 442c5fb5b..d9294d93a 100644
--- a/crates/hir_def/src/attr.rs
+++ b/crates/hir_def/src/attr.rs
@@ -1,18 +1,22 @@
 //! A higher level attributes based on TokenTree, with also some shortcuts.
 
-use std::{ops, sync::Arc};
+use std::{
+    convert::{TryFrom, TryInto},
+    ops,
+    sync::Arc,
+};
 
 use base_db::CrateId;
 use cfg::{CfgExpr, CfgOptions};
 use either::Either;
-use hir_expand::{hygiene::Hygiene, name::AsName, AstId, InFile};
+use hir_expand::{hygiene::Hygiene, name::AsName, AstId, AttrId, InFile};
 use itertools::Itertools;
 use la_arena::ArenaMap;
 use mbe::ast_to_token_tree;
 use smallvec::{smallvec, SmallVec};
 use syntax::{
     ast::{self, AstNode, AttrsOwner},
-    match_ast, AstToken, SmolStr, SyntaxNode,
+    match_ast, AstPtr, AstToken, SmolStr, SyntaxNode, TextRange, TextSize,
 };
 use tt::Subtree;
 
@@ -94,13 +98,16 @@ impl RawAttrs {
     pub(crate) fn new(owner: &dyn ast::AttrsOwner, hygiene: &Hygiene) -> Self {
         let entries = collect_attrs(owner)
             .enumerate()
-            .flat_map(|(i, attr)| match attr {
-                Either::Left(attr) => Attr::from_src(attr, hygiene, i as u32),
-                Either::Right(comment) => comment.doc_comment().map(|doc| Attr {
-                    index: i as u32,
-                    input: Some(AttrInput::Literal(SmolStr::new(doc))),
-                    path: Interned::new(ModPath::from(hir_expand::name!(doc))),
-                }),
+            .flat_map(|(i, attr)| {
+                let index = AttrId(i as u32);
+                match attr {
+                    Either::Left(attr) => Attr::from_src(attr, hygiene, index),
+                    Either::Right(comment) => comment.doc_comment().map(|doc| Attr {
+                        id: index,
+                        input: Some(AttrInput::Literal(SmolStr::new(doc))),
+                        path: Interned::new(ModPath::from(hir_expand::name!(doc))),
+                    }),
+                }
             })
             .collect::<Arc<_>>();
 
@@ -157,7 +164,7 @@ impl RawAttrs {
                 let cfg = parts.next().unwrap();
                 let cfg = Subtree { delimiter: subtree.delimiter, token_trees: cfg.to_vec() };
                 let cfg = CfgExpr::parse(&cfg);
-                let index = attr.index;
+                let index = attr.id;
                 let attrs = parts.filter(|a| !a.is_empty()).filter_map(|attr| {
                     let tree = Subtree { delimiter: None, token_trees: attr.to_vec() };
                     let attr = ast::Attr::parse(&format!("#[{}]", tree)).ok()?;
@@ -211,12 +218,11 @@ impl Attrs {
         let mut res = ArenaMap::default();
 
         for (id, fld) in src.value.iter() {
-            let attrs = match fld {
-                Either::Left(_tuple) => Attrs::default(),
-                Either::Right(record) => {
-                    RawAttrs::from_attrs_owner(db, src.with_value(record)).filter(db, krate)
-                }
+            let owner: &dyn AttrsOwner = match fld {
+                Either::Left(tuple) => tuple,
+                Either::Right(record) => record,
             };
+            let attrs = RawAttrs::from_attrs_owner(db, src.with_value(owner)).filter(db, krate);
 
             res.insert(id, attrs);
         }
@@ -400,10 +406,14 @@ impl AttrsWithOwner {
                 return AttrSourceMap { attrs };
             }
             AttrDefId::FieldId(id) => {
-                id.parent.child_source(db).map(|source| match &source[id.local_id] {
-                    Either::Left(field) => ast::AttrsOwnerNode::new(field.clone()),
-                    Either::Right(field) => ast::AttrsOwnerNode::new(field.clone()),
-                })
+                let map = db.fields_attrs_source_map(id.parent);
+                let file_id = id.parent.file_id(db);
+                let root = db.parse_or_expand(file_id).unwrap();
+                let owner = match &map[id.local_id] {
+                    Either::Left(it) => ast::AttrsOwnerNode::new(it.to_node(&root)),
+                    Either::Right(it) => ast::AttrsOwnerNode::new(it.to_node(&root)),
+                };
+                InFile::new(file_id, owner)
             }
             AttrDefId::AdtId(adt) => match adt {
                 AdtId::StructId(id) => id.lookup(db).source(db).map(ast::AttrsOwnerNode::new),
@@ -411,10 +421,12 @@ impl AttrsWithOwner {
                 AdtId::EnumId(id) => id.lookup(db).source(db).map(ast::AttrsOwnerNode::new),
             },
             AttrDefId::FunctionId(id) => id.lookup(db).source(db).map(ast::AttrsOwnerNode::new),
-            AttrDefId::EnumVariantId(id) => id
-                .parent
-                .child_source(db)
-                .map(|source| ast::AttrsOwnerNode::new(source[id.local_id].clone())),
+            AttrDefId::EnumVariantId(id) => {
+                let map = db.variants_attrs_source_map(id.parent);
+                let file_id = id.parent.lookup(db).id.file_id();
+                let root = db.parse_or_expand(file_id).unwrap();
+                InFile::new(file_id, ast::AttrsOwnerNode::new(map[id.local_id].to_node(&root)))
+            }
             AttrDefId::StaticId(id) => id.lookup(db).source(db).map(ast::AttrsOwnerNode::new),
             AttrDefId::ConstId(id) => id.lookup(db).source(db).map(ast::AttrsOwnerNode::new),
             AttrDefId::TraitId(id) => id.lookup(db).source(db).map(ast::AttrsOwnerNode::new),
@@ -452,6 +464,55 @@ impl AttrsWithOwner {
                 .collect(),
         }
     }
+
+    pub fn docs_with_rangemap(
+        &self,
+        db: &dyn DefDatabase,
+    ) -> Option<(Documentation, DocsRangeMap)> {
+        // FIXME: code duplication in `docs` above
+        let docs = self.by_key("doc").attrs().flat_map(|attr| match attr.input.as_ref()? {
+            AttrInput::Literal(s) => Some((s, attr.id)),
+            AttrInput::TokenTree(_) => None,
+        });
+        let indent = docs
+            .clone()
+            .flat_map(|(s, _)| s.lines())
+            .filter(|line| !line.chars().all(|c| c.is_whitespace()))
+            .map(|line| line.chars().take_while(|c| c.is_whitespace()).count())
+            .min()
+            .unwrap_or(0);
+        let mut buf = String::new();
+        let mut mapping = Vec::new();
+        for (doc, idx) in docs {
+            // str::lines doesn't yield anything for the empty string
+            if !doc.is_empty() {
+                for line in doc.split('\n') {
+                    let line = line.trim_end();
+                    let line_len = line.len();
+                    let (offset, line) = match line.char_indices().nth(indent) {
+                        Some((offset, _)) => (offset, &line[offset..]),
+                        None => (0, line),
+                    };
+                    let buf_offset = buf.len();
+                    buf.push_str(line);
+                    mapping.push((
+                        TextRange::new(buf_offset.try_into().ok()?, buf.len().try_into().ok()?),
+                        idx,
+                        TextRange::new(offset.try_into().ok()?, line_len.try_into().ok()?),
+                    ));
+                    buf.push('\n');
+                }
+            } else {
+                buf.push('\n');
+            }
+        }
+        buf.pop();
+        if buf.is_empty() {
+            None
+        } else {
+            Some((Documentation(buf), DocsRangeMap { mapping, source: self.source_map(db).attrs }))
+        }
+    }
 }
 
 fn inner_attributes(
@@ -484,7 +545,7 @@ fn inner_attributes(
             _ => return None,
         }
     };
-    let attrs = attrs.filter(|attr| attr.excl_token().is_some());
+    let attrs = attrs.filter(|attr| attr.kind().is_inner());
     let docs = docs.filter(|doc| doc.is_inner());
     Some((attrs, docs))
 }
@@ -502,15 +563,53 @@ impl AttrSourceMap {
     /// the attribute represented by `Attr`.
     pub fn source_of(&self, attr: &Attr) -> InFile<&Either<ast::Attr, ast::Comment>> {
         self.attrs
-            .get(attr.index as usize)
-            .unwrap_or_else(|| panic!("cannot find `Attr` at index {}", attr.index))
+            .get(attr.id.0 as usize)
+            .unwrap_or_else(|| panic!("cannot find `Attr` at index {:?}", attr.id))
             .as_ref()
     }
 }
 
+/// A struct to map text ranges from [`Documentation`] back to TextRanges in the syntax tree.
+pub struct DocsRangeMap {
+    source: Vec<InFile<Either<ast::Attr, ast::Comment>>>,
+    // (docstring-line-range, attr_index, attr-string-range)
+    // a mapping from the text range of a line of the [`Documentation`] to the attribute index and
+    // the original (untrimmed) syntax doc line
+    mapping: Vec<(TextRange, AttrId, TextRange)>,
+}
+
+impl DocsRangeMap {
+    pub fn map(&self, range: TextRange) -> Option<InFile<TextRange>> {
+        let found = self.mapping.binary_search_by(|(probe, ..)| probe.ordering(range)).ok()?;
+        let (line_docs_range, idx, original_line_src_range) = self.mapping[found].clone();
+        if !line_docs_range.contains_range(range) {
+            return None;
+        }
+
+        let relative_range = range - line_docs_range.start();
+
+        let &InFile { file_id, value: ref source } = &self.source[idx.0 as usize];
+        match source {
+            Either::Left(_) => None, // FIXME, figure out a nice way to handle doc attributes here
+            // as well as for whats done in syntax highlight doc injection
+            Either::Right(comment) => {
+                let text_range = comment.syntax().text_range();
+                let range = TextRange::at(
+                    text_range.start()
+                        + TextSize::try_from(comment.prefix().len()).ok()?
+                        + original_line_src_range.start()
+                        + relative_range.start(),
+                    text_range.len().min(range.len()),
+                );
+                Some(InFile { file_id, value: range })
+            }
+        }
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct Attr {
-    index: u32,
+    pub(crate) id: AttrId,
     pub(crate) path: Interned<ModPath>,
     pub(crate) input: Option<AttrInput>,
 }
@@ -524,7 +623,7 @@ pub enum AttrInput {
 }
 
 impl Attr {
-    fn from_src(ast: ast::Attr, hygiene: &Hygiene, index: u32) -> Option<Attr> {
+    fn from_src(ast: ast::Attr, hygiene: &Hygiene, id: AttrId) -> Option<Attr> {
         let path = Interned::new(ModPath::from_src(ast.path()?, hygiene)?);
         let input = if let Some(ast::Expr::Literal(lit)) = ast.expr() {
             let value = match lit.kind() {
@@ -537,7 +636,7 @@ impl Attr {
         } else {
             None
         };
-        Some(Attr { index, path, input })
+        Some(Attr { id, path, input })
     }
 
     /// Parses this attribute as a `#[derive]`, returns an iterator that yields all contained paths
@@ -641,7 +740,7 @@ fn collect_attrs(
     let (inner_attrs, inner_docs) = inner_attributes(owner.syntax())
         .map_or((None, None), |(attrs, docs)| (Some(attrs), Some(docs)));
 
-    let outer_attrs = owner.attrs().filter(|attr| attr.excl_token().is_none());
+    let outer_attrs = owner.attrs().filter(|attr| attr.kind().is_outer());
     let attrs = outer_attrs
         .chain(inner_attrs.into_iter().flatten())
         .map(|attr| (attr.syntax().text_range().start(), Either::Left(attr)));
@@ -652,7 +751,38 @@ fn collect_attrs(
         .chain(inner_docs.into_iter().flatten())
         .map(|docs_text| (docs_text.syntax().text_range().start(), Either::Right(docs_text)));
     // sort here by syntax node offset because the source can have doc attributes and doc strings be interleaved
-    let attrs: Vec<_> = docs.chain(attrs).sorted_by_key(|&(offset, _)| offset).collect();
+    docs.chain(attrs).sorted_by_key(|&(offset, _)| offset).map(|(_, attr)| attr)
+}
+
+pub(crate) fn variants_attrs_source_map(
+    db: &dyn DefDatabase,
+    def: EnumId,
+) -> Arc<ArenaMap<LocalEnumVariantId, AstPtr<ast::Variant>>> {
+    let mut res = ArenaMap::default();
+    let child_source = def.child_source(db);
+
+    for (idx, variant) in child_source.value.iter() {
+        res.insert(idx, AstPtr::new(variant));
+    }
+
+    Arc::new(res)
+}
+
+pub(crate) fn fields_attrs_source_map(
+    db: &dyn DefDatabase,
+    def: VariantId,
+) -> Arc<ArenaMap<LocalFieldId, Either<AstPtr<ast::TupleField>, AstPtr<ast::RecordField>>>> {
+    let mut res = ArenaMap::default();
+    let child_source = def.child_source(db);
+
+    for (idx, variant) in child_source.value.iter() {
+        res.insert(
+            idx,
+            variant
+                .as_ref()
+                .either(|l| Either::Left(AstPtr::new(l)), |r| Either::Right(AstPtr::new(r))),
+        );
+    }
 
-    attrs.into_iter().map(|(_, attr)| attr)
+    Arc::new(res)
 }
diff --git a/crates/hir_def/src/body.rs b/crates/hir_def/src/body.rs
index 96b959967..131f424cc 100644
--- a/crates/hir_def/src/body.rs
+++ b/crates/hir_def/src/body.rs
@@ -21,7 +21,7 @@ use profile::Count;
 use rustc_hash::FxHashMap;
 use syntax::{ast, AstNode, AstPtr};
 
-pub(crate) use lower::LowerCtx;
+pub use lower::LowerCtx;
 
 use crate::{
     attr::{Attrs, RawAttrs},
@@ -37,13 +37,15 @@ use crate::{
 
 /// A subset of Expander that only deals with cfg attributes. We only need it to
 /// avoid cyclic queries in crate def map during enum processing.
+#[derive(Debug)]
 pub(crate) struct CfgExpander {
     cfg_options: CfgOptions,
     hygiene: Hygiene,
     krate: CrateId,
 }
 
-pub(crate) struct Expander {
+#[derive(Debug)]
+pub struct Expander {
     cfg_expander: CfgExpander,
     def_map: Arc<DefMap>,
     current_file_id: HirFileId,
@@ -80,11 +82,7 @@ impl CfgExpander {
 }
 
 impl Expander {
-    pub(crate) fn new(
-        db: &dyn DefDatabase,
-        current_file_id: HirFileId,
-        module: ModuleId,
-    ) -> Expander {
+    pub fn new(db: &dyn DefDatabase, current_file_id: HirFileId, module: ModuleId) -> Expander {
         let cfg_expander = CfgExpander::new(db, current_file_id, module.krate);
         let def_map = module.def_map(db);
         let ast_id_map = db.ast_id_map(current_file_id);
@@ -98,7 +96,7 @@ impl Expander {
         }
     }
 
-    pub(crate) fn enter_expand<T: ast::AstNode>(
+    pub fn enter_expand<T: ast::AstNode>(
         &mut self,
         db: &dyn DefDatabase,
         macro_call: ast::MacroCall,
@@ -170,7 +168,7 @@ impl Expander {
         Ok(ExpandResult { value: Some((mark, node)), err })
     }
 
-    pub(crate) fn exit(&mut self, db: &dyn DefDatabase, mut mark: Mark) {
+    pub fn exit(&mut self, db: &dyn DefDatabase, mut mark: Mark) {
         self.cfg_expander.hygiene = Hygiene::new(db.upcast(), mark.file_id);
         self.current_file_id = mark.file_id;
         self.ast_id_map = mem::take(&mut mark.ast_id_map);
@@ -190,8 +188,13 @@ impl Expander {
         &self.cfg_expander.cfg_options
     }
 
+    pub fn current_file_id(&self) -> HirFileId {
+        self.current_file_id
+    }
+
     fn parse_path(&mut self, path: ast::Path) -> Option<Path> {
-        Path::from_src(path, &self.cfg_expander.hygiene)
+        let ctx = LowerCtx::with_hygiene(&self.cfg_expander.hygiene);
+        Path::from_src(path, &ctx)
     }
 
     fn resolve_path_as_macro(&self, db: &dyn DefDatabase, path: &ModPath) -> Option<MacroDefId> {
@@ -204,7 +207,8 @@ impl Expander {
     }
 }
 
-pub(crate) struct Mark {
+#[derive(Debug)]
+pub struct Mark {
     file_id: HirFileId,
     ast_id_map: Arc<AstIdMap>,
     bomb: DropBomb,
diff --git a/crates/hir_def/src/body/lower.rs b/crates/hir_def/src/body/lower.rs
index 63e89a1f4..c11da30d2 100644
--- a/crates/hir_def/src/body/lower.rs
+++ b/crates/hir_def/src/body/lower.rs
@@ -1,10 +1,11 @@
 //! Transforms `ast::Expr` into an equivalent `hir_def::expr::Expr`
 //! representation.
 
-use std::mem;
+use std::{mem, sync::Arc};
 
 use either::Either;
 use hir_expand::{
+    ast_id_map::{AstIdMap, FileAstId},
     hygiene::Hygiene,
     name::{name, AsName, Name},
     ExpandError, HirFileId,
@@ -30,6 +31,7 @@ use crate::{
         LabelId, Literal, LogicOp, MatchArm, Ordering, Pat, PatId, RecordFieldPat, RecordLitField,
         Statement,
     },
+    intern::Interned,
     item_scope::BuiltinShadowMode,
     path::{GenericArgs, Path},
     type_ref::{Mutability, Rawness, TypeRef},
@@ -38,20 +40,39 @@ use crate::{
 
 use super::{diagnostics::BodyDiagnostic, ExprSource, PatSource};
 
-pub(crate) struct LowerCtx {
+pub struct LowerCtx {
     hygiene: Hygiene,
+    file_id: Option<HirFileId>,
+    source_ast_id_map: Option<Arc<AstIdMap>>,
 }
 
 impl LowerCtx {
-    pub(crate) fn new(db: &dyn DefDatabase, file_id: HirFileId) -> Self {
-        LowerCtx { hygiene: Hygiene::new(db.upcast(), file_id) }
+    pub fn new(db: &dyn DefDatabase, file_id: HirFileId) -> Self {
+        LowerCtx {
+            hygiene: Hygiene::new(db.upcast(), file_id),
+            file_id: Some(file_id),
+            source_ast_id_map: Some(db.ast_id_map(file_id)),
+        }
     }
-    pub(crate) fn with_hygiene(hygiene: &Hygiene) -> Self {
-        LowerCtx { hygiene: hygiene.clone() }
+
+    pub fn with_hygiene(hygiene: &Hygiene) -> Self {
+        LowerCtx { hygiene: hygiene.clone(), file_id: None, source_ast_id_map: None }
+    }
+
+    pub(crate) fn hygiene(&self) -> &Hygiene {
+        &self.hygiene
+    }
+
+    pub(crate) fn file_id(&self) -> HirFileId {
+        self.file_id.unwrap()
     }
 
     pub(crate) fn lower_path(&self, ast: ast::Path) -> Option<Path> {
-        Path::from_src(ast, &self.hygiene)
+        Path::from_src(ast, self)
+    }
+
+    pub(crate) fn ast_id<N: AstNode>(&self, item: &N) -> Option<FileAstId<N>> {
+        self.source_ast_id_map.as_ref().map(|ast_id_map| ast_id_map.ast_id(item))
     }
 }
 
@@ -322,8 +343,10 @@ impl ExprCollector<'_> {
                     Vec::new()
                 };
                 let method_name = e.name_ref().map(|nr| nr.as_name()).unwrap_or_else(Name::missing);
-                let generic_args =
-                    e.generic_arg_list().and_then(|it| GenericArgs::from_ast(&self.ctx(), it));
+                let generic_args = e
+                    .generic_arg_list()
+                    .and_then(|it| GenericArgs::from_ast(&self.ctx(), it))
+                    .map(Box::new);
                 self.alloc_expr(
                     Expr::MethodCall { receiver, method_name, args, generic_args },
                     syntax_ptr,
@@ -385,7 +408,7 @@ impl ExprCollector<'_> {
                 self.alloc_expr(Expr::Yield { expr }, syntax_ptr)
             }
             ast::Expr::RecordExpr(e) => {
-                let path = e.path().and_then(|path| self.expander.parse_path(path));
+                let path = e.path().and_then(|path| self.expander.parse_path(path)).map(Box::new);
                 let record_lit = if let Some(nfl) = e.record_expr_field_list() {
                     let fields = nfl
                         .fields()
@@ -430,7 +453,7 @@ impl ExprCollector<'_> {
             }
             ast::Expr::CastExpr(e) => {
                 let expr = self.collect_expr_opt(e.expr());
-                let type_ref = TypeRef::from_ast_opt(&self.ctx(), e.ty());
+                let type_ref = Interned::new(TypeRef::from_ast_opt(&self.ctx(), e.ty()));
                 self.alloc_expr(Expr::Cast { expr, type_ref }, syntax_ptr)
             }
             ast::Expr::RefExpr(e) => {
@@ -464,13 +487,16 @@ impl ExprCollector<'_> {
                 if let Some(pl) = e.param_list() {
                     for param in pl.params() {
                         let pat = self.collect_pat_opt(param.pat());
-                        let type_ref = param.ty().map(|it| TypeRef::from_ast(&self.ctx(), it));
+                        let type_ref =
+                            param.ty().map(|it| Interned::new(TypeRef::from_ast(&self.ctx(), it)));
                         args.push(pat);
                         arg_types.push(type_ref);
                     }
                 }
-                let ret_type =
-                    e.ret_type().and_then(|r| r.ty()).map(|it| TypeRef::from_ast(&self.ctx(), it));
+                let ret_type = e
+                    .ret_type()
+                    .and_then(|r| r.ty())
+                    .map(|it| Interned::new(TypeRef::from_ast(&self.ctx(), it)));
                 let body = self.collect_expr_opt(e.body());
                 self.alloc_expr(Expr::Lambda { args, arg_types, ret_type, body }, syntax_ptr)
             }
@@ -525,8 +551,9 @@ impl ExprCollector<'_> {
                 }
             }
             ast::Expr::MacroCall(e) => {
+                let macro_ptr = AstPtr::new(&e);
                 let mut ids = vec![];
-                self.collect_macro_call(e, syntax_ptr.clone(), true, |this, expansion| {
+                self.collect_macro_call(e, macro_ptr, true, |this, expansion| {
                     ids.push(match expansion {
                         Some(it) => this.collect_expr(it),
                         None => this.alloc_expr(Expr::Missing, syntax_ptr.clone()),
@@ -549,7 +576,7 @@ impl ExprCollector<'_> {
     fn collect_macro_call<F: FnMut(&mut Self, Option<T>), T: ast::AstNode>(
         &mut self,
         e: ast::MacroCall,
-        syntax_ptr: AstPtr<ast::Expr>,
+        syntax_ptr: AstPtr<ast::MacroCall>,
         is_error_recoverable: bool,
         mut collector: F,
     ) {
@@ -561,9 +588,13 @@ impl ExprCollector<'_> {
 
         let res = match res {
             Ok(res) => res,
-            Err(UnresolvedMacro) => {
+            Err(UnresolvedMacro { path }) => {
                 self.source_map.diagnostics.push(BodyDiagnostic::UnresolvedMacroCall(
-                    UnresolvedMacroCall { file: outer_file, node: syntax_ptr.cast().unwrap() },
+                    UnresolvedMacroCall {
+                        file: outer_file,
+                        node: syntax_ptr.cast().unwrap(),
+                        path,
+                    },
                 ));
                 collector(self, None);
                 return;
@@ -625,7 +656,8 @@ impl ExprCollector<'_> {
                     return;
                 }
                 let pat = self.collect_pat_opt(stmt.pat());
-                let type_ref = stmt.ty().map(|it| TypeRef::from_ast(&self.ctx(), it));
+                let type_ref =
+                    stmt.ty().map(|it| Interned::new(TypeRef::from_ast(&self.ctx(), it)));
                 let initializer = stmt.initializer().map(|e| self.collect_expr(e));
                 self.statements_in_scope.push(Statement::Let { pat, type_ref, initializer });
             }
@@ -636,10 +668,14 @@ impl ExprCollector<'_> {
 
                 // Note that macro could be expended to multiple statements
                 if let Some(ast::Expr::MacroCall(m)) = stmt.expr() {
+                    let macro_ptr = AstPtr::new(&m);
                     let syntax_ptr = AstPtr::new(&stmt.expr().unwrap());
 
-                    self.collect_macro_call(m, syntax_ptr.clone(), false, |this, expansion| {
-                        match expansion {
+                    self.collect_macro_call(
+                        m,
+                        macro_ptr,
+                        false,
+                        |this, expansion| match expansion {
                             Some(expansion) => {
                                 let statements: ast::MacroStmts = expansion;
 
@@ -653,8 +689,8 @@ impl ExprCollector<'_> {
                                 let expr = this.alloc_expr(Expr::Missing, syntax_ptr.clone());
                                 this.statements_in_scope.push(Statement::Expr(expr));
                             }
-                        }
-                    });
+                        },
+                    );
                 } else {
                     let expr = self.collect_expr_opt(stmt.expr());
                     self.statements_in_scope.push(Statement::Expr(expr));
@@ -755,7 +791,7 @@ impl ExprCollector<'_> {
                 }
             }
             ast::Pat::TupleStructPat(p) => {
-                let path = p.path().and_then(|path| self.expander.parse_path(path));
+                let path = p.path().and_then(|path| self.expander.parse_path(path)).map(Box::new);
                 let (args, ellipsis) = self.collect_tuple_pat(p.fields());
                 Pat::TupleStruct { path, args, ellipsis }
             }
@@ -765,7 +801,7 @@ impl ExprCollector<'_> {
                 Pat::Ref { pat, mutability }
             }
             ast::Pat::PathPat(p) => {
-                let path = p.path().and_then(|path| self.expander.parse_path(path));
+                let path = p.path().and_then(|path| self.expander.parse_path(path)).map(Box::new);
                 path.map(Pat::Path).unwrap_or(Pat::Missing)
             }
             ast::Pat::OrPat(p) => {
@@ -779,7 +815,7 @@ impl ExprCollector<'_> {
             }
             ast::Pat::WildcardPat(_) => Pat::Wild,
             ast::Pat::RecordPat(p) => {
-                let path = p.path().and_then(|path| self.expander.parse_path(path));
+                let path = p.path().and_then(|path| self.expander.parse_path(path)).map(Box::new);
                 let args: Vec<_> = p
                     .record_pat_field_list()
                     .expect("every struct should have a field list")
@@ -841,8 +877,23 @@ impl ExprCollector<'_> {
                     Pat::Missing
                 }
             }
+            ast::Pat::MacroPat(mac) => match mac.macro_call() {
+                Some(call) => {
+                    let macro_ptr = AstPtr::new(&call);
+                    let mut pat = None;
+                    self.collect_macro_call(call, macro_ptr, true, |this, expanded_pat| {
+                        pat = Some(this.collect_pat_opt(expanded_pat));
+                    });
+
+                    match pat {
+                        Some(pat) => return pat,
+                        None => Pat::Missing,
+                    }
+                }
+                None => Pat::Missing,
+            },
             // FIXME: implement
-            ast::Pat::RangePat(_) | ast::Pat::MacroPat(_) => Pat::Missing,
+            ast::Pat::RangePat(_) => Pat::Missing,
         };
         let ptr = AstPtr::new(&pat);
         self.alloc_pat(pattern, Either::Left(ptr))
diff --git a/crates/hir_def/src/body/tests.rs b/crates/hir_def/src/body/tests.rs
index faa133297..3e8f16306 100644
--- a/crates/hir_def/src/body/tests.rs
+++ b/crates/hir_def/src/body/tests.rs
@@ -40,6 +40,14 @@ fn block_def_map_at(ra_fixture: &str) -> String {
     module.def_map(&db).dump(&db)
 }
 
+fn check_block_scopes_at(ra_fixture: &str, expect: Expect) {
+    let (db, position) = crate::test_db::TestDB::with_position(ra_fixture);
+
+    let module = db.module_at_position(position);
+    let actual = module.def_map(&db).dump_block_scopes(&db);
+    expect.assert_eq(&actual);
+}
+
 fn check_at(ra_fixture: &str, expect: Expect) {
     let actual = block_def_map_at(ra_fixture);
     expect.assert_eq(&actual);
@@ -143,7 +151,7 @@ fn f() {
   //^^^^^^^^^^^^^ could not convert tokens
 
     env!("OUT_DIR");
-  //^^^^^^^^^^^^^^^ `OUT_DIR` not set, enable "load out dirs from check" to fix
+  //^^^^^^^^^^^^^^^ `OUT_DIR` not set, enable "run build scripts" to fix
 
     compile_error!("compile_error works");
   //^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ compile_error works
@@ -180,7 +188,7 @@ fn unresolved_macro_diag() {
         r#"
 fn f() {
     m!();
-  //^^^^ unresolved macro call
+  //^^^^ unresolved macro `m!`
 }
       "#,
     );
diff --git a/crates/hir_def/src/body/tests/block.rs b/crates/hir_def/src/body/tests/block.rs
index 3b6ba4cde..bc3d0f138 100644
--- a/crates/hir_def/src/body/tests/block.rs
+++ b/crates/hir_def/src/body/tests/block.rs
@@ -134,6 +134,30 @@ struct Struct {}
 }
 
 #[test]
+fn nested_module_scoping() {
+    check_block_scopes_at(
+        r#"
+fn f() {
+    mod module {
+        struct Struct {}
+        fn f() {
+            use self::Struct;
+            $0
+        }
+    }
+}
+    "#,
+        expect![[r#"
+            BlockId(1) in ModuleId { krate: CrateId(0), block: Some(BlockId(0)), local_id: Idx::<ModuleData>(0) }
+            BlockId(0) in ModuleId { krate: CrateId(0), block: None, local_id: Idx::<ModuleData>(0) }
+            crate scope
+        "#]],
+    );
+    // FIXME: The module nesting here is wrong!
+    // The first block map should be located in module #1 (`mod module`), not #0 (BlockId(0) root module)
+}
+
+#[test]
 fn legacy_macro_items() {
     // Checks that legacy-scoped `macro_rules!` from parent namespaces are resolved and expanded
     // correctly.
diff --git a/crates/hir_def/src/child_by_source.rs b/crates/hir_def/src/child_by_source.rs
index f40a7f80d..f2e809ca9 100644
--- a/crates/hir_def/src/child_by_source.rs
+++ b/crates/hir_def/src/child_by_source.rs
@@ -80,6 +80,10 @@ impl ChildBySource for ModuleId {
 impl ChildBySource for ItemScope {
     fn child_by_source_to(&self, db: &dyn DefDatabase, res: &mut DynMap) {
         self.declarations().for_each(|item| add_module_def(db, res, item));
+        self.unnamed_consts().for_each(|konst| {
+            let src = konst.lookup(db).source(db);
+            res[keys::CONST].insert(src, konst);
+        });
         self.impls().for_each(|imp| add_impl(db, res, imp));
 
         fn add_module_def(db: &dyn DefDatabase, map: &mut DynMap, item: ModuleDefId) {
diff --git a/crates/hir_def/src/db.rs b/crates/hir_def/src/db.rs
index 068b2ee38..7eadc8e0d 100644
--- a/crates/hir_def/src/db.rs
+++ b/crates/hir_def/src/db.rs
@@ -2,9 +2,10 @@
 use std::sync::Arc;
 
 use base_db::{salsa, CrateId, SourceDatabase, Upcast};
+use either::Either;
 use hir_expand::{db::AstDatabase, HirFileId};
 use la_arena::ArenaMap;
-use syntax::SmolStr;
+use syntax::{ast, AstPtr, SmolStr};
 
 use crate::{
     adt::{EnumData, StructData},
@@ -13,6 +14,7 @@ use crate::{
     data::{ConstData, FunctionData, ImplData, StaticData, TraitData, TypeAliasData},
     generics::GenericParams,
     import_map::ImportMap,
+    intern::Interned,
     item_tree::ItemTree,
     lang_item::{LangItemTarget, LangItems},
     nameres::DefMap,
@@ -113,7 +115,7 @@ pub trait DefDatabase: InternDatabase + AstDatabase + Upcast<dyn AstDatabase> {
     fn expr_scopes(&self, def: DefWithBodyId) -> Arc<ExprScopes>;
 
     #[salsa::invoke(GenericParams::generic_params_query)]
-    fn generic_params(&self, def: GenericDefId) -> Arc<GenericParams>;
+    fn generic_params(&self, def: GenericDefId) -> Interned<GenericParams>;
 
     #[salsa::invoke(Attrs::variants_attrs_query)]
     fn variants_attrs(&self, def: EnumId) -> Arc<ArenaMap<LocalEnumVariantId, Attrs>>;
@@ -121,6 +123,18 @@ pub trait DefDatabase: InternDatabase + AstDatabase + Upcast<dyn AstDatabase> {
     #[salsa::invoke(Attrs::fields_attrs_query)]
     fn fields_attrs(&self, def: VariantId) -> Arc<ArenaMap<LocalFieldId, Attrs>>;
 
+    #[salsa::invoke(crate::attr::variants_attrs_source_map)]
+    fn variants_attrs_source_map(
+        &self,
+        def: EnumId,
+    ) -> Arc<ArenaMap<LocalEnumVariantId, AstPtr<ast::Variant>>>;
+
+    #[salsa::invoke(crate::attr::fields_attrs_source_map)]
+    fn fields_attrs_source_map(
+        &self,
+        def: VariantId,
+    ) -> Arc<ArenaMap<LocalFieldId, Either<AstPtr<ast::TupleField>, AstPtr<ast::RecordField>>>>;
+
     #[salsa::invoke(AttrsWithOwner::attrs_query)]
     fn attrs(&self, def: AttrDefId) -> AttrsWithOwner;
 
diff --git a/crates/hir_def/src/diagnostics.rs b/crates/hir_def/src/diagnostics.rs
index 97abf8653..a71ae2668 100644
--- a/crates/hir_def/src/diagnostics.rs
+++ b/crates/hir_def/src/diagnostics.rs
@@ -8,7 +8,7 @@ use hir_expand::diagnostics::{Diagnostic, DiagnosticCode, DiagnosticSink};
 use hir_expand::{HirFileId, InFile};
 use syntax::{ast, AstPtr, SyntaxNodePtr, TextRange};
 
-use crate::{db::DefDatabase, DefWithBodyId};
+use crate::{db::DefDatabase, path::ModPath, DefWithBodyId};
 
 pub fn validate_body(db: &dyn DefDatabase, owner: DefWithBodyId, sink: &mut DiagnosticSink<'_>) {
     let source_map = db.body_with_source_map(owner).1;
@@ -103,6 +103,7 @@ impl Diagnostic for UnresolvedImport {
 pub struct UnresolvedMacroCall {
     pub file: HirFileId,
     pub node: AstPtr<ast::MacroCall>,
+    pub path: ModPath,
 }
 
 impl Diagnostic for UnresolvedMacroCall {
@@ -110,7 +111,7 @@ impl Diagnostic for UnresolvedMacroCall {
         DiagnosticCode("unresolved-macro-call")
     }
     fn message(&self) -> String {
-        "unresolved macro call".to_string()
+        format!("unresolved macro `{}!`", self.path)
     }
     fn display_source(&self) -> InFile<SyntaxNodePtr> {
         InFile::new(self.file, self.node.clone().into())
diff --git a/crates/hir_def/src/expr.rs b/crates/hir_def/src/expr.rs
index 6c7376fad..b4ad984bd 100644
--- a/crates/hir_def/src/expr.rs
+++ b/crates/hir_def/src/expr.rs
@@ -18,6 +18,7 @@ use syntax::ast::RangeOp;
 
 use crate::{
     builtin_type::{BuiltinFloat, BuiltinInt, BuiltinUint},
+    intern::Interned,
     path::{GenericArgs, Path},
     type_ref::{Mutability, Rawness, TypeRef},
     BlockId,
@@ -86,7 +87,7 @@ pub enum Expr {
         receiver: ExprId,
         method_name: Name,
         args: Vec<ExprId>,
-        generic_args: Option<GenericArgs>,
+        generic_args: Option<Box<GenericArgs>>,
     },
     Match {
         expr: ExprId,
@@ -106,7 +107,7 @@ pub enum Expr {
         expr: Option<ExprId>,
     },
     RecordLit {
-        path: Option<Path>,
+        path: Option<Box<Path>>,
         fields: Vec<RecordLitField>,
         spread: Option<ExprId>,
     },
@@ -131,7 +132,7 @@ pub enum Expr {
     },
     Cast {
         expr: ExprId,
-        type_ref: TypeRef,
+        type_ref: Interned<TypeRef>,
     },
     Ref {
         expr: ExprId,
@@ -161,8 +162,8 @@ pub enum Expr {
     },
     Lambda {
         args: Vec<PatId>,
-        arg_types: Vec<Option<TypeRef>>,
-        ret_type: Option<TypeRef>,
+        arg_types: Vec<Option<Interned<TypeRef>>>,
+        ret_type: Option<Interned<TypeRef>>,
         body: ExprId,
     },
     Tuple {
@@ -240,7 +241,7 @@ pub struct RecordLitField {
 
 #[derive(Debug, Clone, Eq, PartialEq)]
 pub enum Statement {
-    Let { pat: PatId, type_ref: Option<TypeRef>, initializer: Option<ExprId> },
+    Let { pat: PatId, type_ref: Option<Interned<TypeRef>>, initializer: Option<ExprId> },
     Expr(ExprId),
 }
 
@@ -412,13 +413,13 @@ pub enum Pat {
     Wild,
     Tuple { args: Vec<PatId>, ellipsis: Option<usize> },
     Or(Vec<PatId>),
-    Record { path: Option<Path>, args: Vec<RecordFieldPat>, ellipsis: bool },
+    Record { path: Option<Box<Path>>, args: Vec<RecordFieldPat>, ellipsis: bool },
     Range { start: ExprId, end: ExprId },
     Slice { prefix: Vec<PatId>, slice: Option<PatId>, suffix: Vec<PatId> },
-    Path(Path),
+    Path(Box<Path>),
     Lit(ExprId),
     Bind { mode: BindingAnnotation, name: Name, subpat: Option<PatId> },
-    TupleStruct { path: Option<Path>, args: Vec<PatId>, ellipsis: Option<usize> },
+    TupleStruct { path: Option<Box<Path>>, args: Vec<PatId>, ellipsis: Option<usize> },
     Ref { pat: PatId, mutability: Mutability },
     Box { inner: PatId },
     ConstBlock(ExprId),
diff --git a/crates/hir_def/src/find_path.rs b/crates/hir_def/src/find_path.rs
index 109d3552f..dc3f2908f 100644
--- a/crates/hir_def/src/find_path.rs
+++ b/crates/hir_def/src/find_path.rs
@@ -119,8 +119,7 @@ fn find_path_inner(
 
     // - if the item is the crate root, return `crate`
     let root = def_map.crate_root(db);
-    if item == ItemInNs::Types(ModuleDefId::ModuleId(root)) && def_map.block_id().is_none() {
-        // FIXME: the `block_id()` check should be unnecessary, but affects the result
+    if item == ItemInNs::Types(ModuleDefId::ModuleId(root)) {
         return Some(ModPath::from_segments(PathKind::Crate, Vec::new()));
     }
 
@@ -131,7 +130,7 @@ fn find_path_inner(
     }
 
     // - if the item is the crate root of a dependency crate, return the name from the extern prelude
-    for (name, def_id) in def_map.extern_prelude() {
+    for (name, def_id) in root.def_map(db).extern_prelude() {
         if item == ItemInNs::Types(*def_id) {
             let name = scope_name.unwrap_or_else(|| name.clone());
             return Some(ModPath::from_segments(PathKind::Plain, vec![name]));
@@ -298,6 +297,7 @@ fn find_local_import_locations(
     let data = &def_map[from.local_id];
     let mut worklist =
         data.children.values().map(|child| def_map.module_id(*child)).collect::<Vec<_>>();
+    // FIXME: do we need to traverse out of block expressions here?
     for ancestor in iter::successors(from.containing_module(db), |m| m.containing_module(db)) {
         worklist.push(ancestor);
     }
@@ -425,106 +425,142 @@ mod tests {
 
     #[test]
     fn same_module() {
-        let code = r#"
-            //- /main.rs
-            struct S;
-            $0
-        "#;
-        check_found_path(code, "S", "S", "crate::S", "self::S");
+        check_found_path(
+            r#"
+struct S;
+$0
+        "#,
+            "S",
+            "S",
+            "crate::S",
+            "self::S",
+        );
     }
 
     #[test]
     fn enum_variant() {
-        let code = r#"
-            //- /main.rs
-            enum E { A }
-            $0
-        "#;
-        check_found_path(code, "E::A", "E::A", "E::A", "E::A");
+        check_found_path(
+            r#"
+enum E { A }
+$0
+        "#,
+            "E::A",
+            "E::A",
+            "E::A",
+            "E::A",
+        );
     }
 
     #[test]
     fn sub_module() {
-        let code = r#"
-            //- /main.rs
-            mod foo {
-                pub struct S;
-            }
-            $0
-        "#;
-        check_found_path(code, "foo::S", "foo::S", "crate::foo::S", "self::foo::S");
+        check_found_path(
+            r#"
+mod foo {
+    pub struct S;
+}
+$0
+        "#,
+            "foo::S",
+            "foo::S",
+            "crate::foo::S",
+            "self::foo::S",
+        );
     }
 
     #[test]
     fn super_module() {
-        let code = r#"
-            //- /main.rs
-            mod foo;
-            //- /foo.rs
-            mod bar;
-            struct S;
-            //- /foo/bar.rs
-            $0
-        "#;
-        check_found_path(code, "super::S", "super::S", "crate::foo::S", "super::S");
+        check_found_path(
+            r#"
+//- /main.rs
+mod foo;
+//- /foo.rs
+mod bar;
+struct S;
+//- /foo/bar.rs
+$0
+        "#,
+            "super::S",
+            "super::S",
+            "crate::foo::S",
+            "super::S",
+        );
     }
 
     #[test]
     fn self_module() {
-        let code = r#"
-            //- /main.rs
-            mod foo;
-            //- /foo.rs
-            $0
-        "#;
-        check_found_path(code, "self", "self", "crate::foo", "self");
+        check_found_path(
+            r#"
+//- /main.rs
+mod foo;
+//- /foo.rs
+$0
+        "#,
+            "self",
+            "self",
+            "crate::foo",
+            "self",
+        );
     }
 
     #[test]
     fn crate_root() {
-        let code = r#"
-            //- /main.rs
-            mod foo;
-            //- /foo.rs
-            $0
-        "#;
-        check_found_path(code, "crate", "crate", "crate", "crate");
+        check_found_path(
+            r#"
+//- /main.rs
+mod foo;
+//- /foo.rs
+$0
+        "#,
+            "crate",
+            "crate",
+            "crate",
+            "crate",
+        );
     }
 
     #[test]
     fn same_crate() {
-        let code = r#"
-            //- /main.rs
-            mod foo;
-            struct S;
-            //- /foo.rs
-            $0
-        "#;
-        check_found_path(code, "crate::S", "crate::S", "crate::S", "crate::S");
+        check_found_path(
+            r#"
+//- /main.rs
+mod foo;
+struct S;
+//- /foo.rs
+$0
+        "#,
+            "crate::S",
+            "crate::S",
+            "crate::S",
+            "crate::S",
+        );
     }
 
     #[test]
     fn different_crate() {
-        let code = r#"
-            //- /main.rs crate:main deps:std
-            $0
-            //- /std.rs crate:std
-            pub struct S;
-        "#;
-        check_found_path(code, "std::S", "std::S", "std::S", "std::S");
+        check_found_path(
+            r#"
+//- /main.rs crate:main deps:std
+$0
+//- /std.rs crate:std
+pub struct S;
+        "#,
+            "std::S",
+            "std::S",
+            "std::S",
+            "std::S",
+        );
     }
 
     #[test]
     fn different_crate_renamed() {
-        let code = r#"
-            //- /main.rs crate:main deps:std
-            extern crate std as std_renamed;
-            $0
-            //- /std.rs crate:std
-            pub struct S;
-        "#;
         check_found_path(
-            code,
+            r#"
+//- /main.rs crate:main deps:std
+extern crate std as std_renamed;
+$0
+//- /std.rs crate:std
+pub struct S;
+        "#,
             "std_renamed::S",
             "std_renamed::S",
             "std_renamed::S",
@@ -537,41 +573,38 @@ mod tests {
         cov_mark::check!(partially_imported);
         // Tests that short paths are used even for external items, when parts of the path are
         // already in scope.
-        let code = r#"
-            //- /main.rs crate:main deps:syntax
+        check_found_path(
+            r#"
+//- /main.rs crate:main deps:syntax
 
-            use syntax::ast;
-            $0
+use syntax::ast;
+$0
 
-            //- /lib.rs crate:syntax
-            pub mod ast {
-                pub enum ModuleItem {
-                    A, B, C,
-                }
-            }
-        "#;
-        check_found_path(
-            code,
+//- /lib.rs crate:syntax
+pub mod ast {
+    pub enum ModuleItem {
+        A, B, C,
+    }
+}
+        "#,
             "ast::ModuleItem",
             "syntax::ast::ModuleItem",
             "syntax::ast::ModuleItem",
             "syntax::ast::ModuleItem",
         );
 
-        let code = r#"
-            //- /main.rs crate:main deps:syntax
-
-            $0
-
-            //- /lib.rs crate:syntax
-            pub mod ast {
-                pub enum ModuleItem {
-                    A, B, C,
-                }
-            }
-        "#;
         check_found_path(
-            code,
+            r#"
+//- /main.rs crate:main deps:syntax
+$0
+
+//- /lib.rs crate:syntax
+pub mod ast {
+    pub enum ModuleItem {
+        A, B, C,
+    }
+}
+        "#,
             "syntax::ast::ModuleItem",
             "syntax::ast::ModuleItem",
             "syntax::ast::ModuleItem",
@@ -581,68 +614,86 @@ mod tests {
 
     #[test]
     fn same_crate_reexport() {
-        let code = r#"
-            //- /main.rs
-            mod bar {
-                mod foo { pub(super) struct S; }
-                pub(crate) use foo::*;
-            }
-            $0
-        "#;
-        check_found_path(code, "bar::S", "bar::S", "crate::bar::S", "self::bar::S");
+        check_found_path(
+            r#"
+mod bar {
+    mod foo { pub(super) struct S; }
+    pub(crate) use foo::*;
+}
+$0
+        "#,
+            "bar::S",
+            "bar::S",
+            "crate::bar::S",
+            "self::bar::S",
+        );
     }
 
     #[test]
     fn same_crate_reexport_rename() {
-        let code = r#"
-            //- /main.rs
-            mod bar {
-                mod foo { pub(super) struct S; }
-                pub(crate) use foo::S as U;
-            }
-            $0
-        "#;
-        check_found_path(code, "bar::U", "bar::U", "crate::bar::U", "self::bar::U");
+        check_found_path(
+            r#"
+mod bar {
+    mod foo { pub(super) struct S; }
+    pub(crate) use foo::S as U;
+}
+$0
+        "#,
+            "bar::U",
+            "bar::U",
+            "crate::bar::U",
+            "self::bar::U",
+        );
     }
 
     #[test]
     fn different_crate_reexport() {
-        let code = r#"
-            //- /main.rs crate:main deps:std
-            $0
-            //- /std.rs crate:std deps:core
-            pub use core::S;
-            //- /core.rs crate:core
-            pub struct S;
-        "#;
-        check_found_path(code, "std::S", "std::S", "std::S", "std::S");
+        check_found_path(
+            r#"
+//- /main.rs crate:main deps:std
+$0
+//- /std.rs crate:std deps:core
+pub use core::S;
+//- /core.rs crate:core
+pub struct S;
+        "#,
+            "std::S",
+            "std::S",
+            "std::S",
+            "std::S",
+        );
     }
 
     #[test]
     fn prelude() {
-        let code = r#"
-            //- /main.rs crate:main deps:std
-            $0
-            //- /std.rs crate:std
-            pub mod prelude { pub struct S; }
-            #[prelude_import]
-            pub use prelude::*;
-        "#;
-        check_found_path(code, "S", "S", "S", "S");
+        check_found_path(
+            r#"
+//- /main.rs crate:main deps:std
+$0
+//- /std.rs crate:std
+pub mod prelude { pub struct S; }
+#[prelude_import]
+pub use prelude::*;
+        "#,
+            "S",
+            "S",
+            "S",
+            "S",
+        );
     }
 
     #[test]
     fn enum_variant_from_prelude() {
         let code = r#"
-            //- /main.rs crate:main deps:std
-            $0
-            //- /std.rs crate:std
-            pub mod prelude {
-                pub enum Option<T> { Some(T), None }
-                pub use Option::*;
-            }
-            #[prelude_import]
-            pub use prelude::*;
+//- /main.rs crate:main deps:std
+$0
+//- /std.rs crate:std
+pub mod prelude {
+    pub enum Option<T> { Some(T), None }
+    pub use Option::*;
+}
+#[prelude_import]
+pub use prelude::*;
         "#;
         check_found_path(code, "None", "None", "None", "None");
         check_found_path(code, "Some", "Some", "Some", "Some");
@@ -650,71 +701,85 @@ mod tests {
 
     #[test]
     fn shortest_path() {
-        let code = r#"
-            //- /main.rs
-            pub mod foo;
-            pub mod baz;
-            struct S;
-            $0
-            //- /foo.rs
-            pub mod bar { pub struct S; }
-            //- /baz.rs
-            pub use crate::foo::bar::S;
-        "#;
-        check_found_path(code, "baz::S", "baz::S", "crate::baz::S", "self::baz::S");
+        check_found_path(
+            r#"
+//- /main.rs
+pub mod foo;
+pub mod baz;
+struct S;
+$0
+//- /foo.rs
+pub mod bar { pub struct S; }
+//- /baz.rs
+pub use crate::foo::bar::S;
+        "#,
+            "baz::S",
+            "baz::S",
+            "crate::baz::S",
+            "self::baz::S",
+        );
     }
 
     #[test]
     fn discount_private_imports() {
-        let code = r#"
-            //- /main.rs
-            mod foo;
-            pub mod bar { pub struct S; }
-            use bar::S;
-            //- /foo.rs
-            $0
-        "#;
-        // crate::S would be shorter, but using private imports seems wrong
-        check_found_path(code, "crate::bar::S", "crate::bar::S", "crate::bar::S", "crate::bar::S");
+        check_found_path(
+            r#"
+//- /main.rs
+mod foo;
+pub mod bar { pub struct S; }
+use bar::S;
+//- /foo.rs
+$0
+        "#,
+            // crate::S would be shorter, but using private imports seems wrong
+            "crate::bar::S",
+            "crate::bar::S",
+            "crate::bar::S",
+            "crate::bar::S",
+        );
     }
 
     #[test]
     fn import_cycle() {
-        let code = r#"
-            //- /main.rs
-            pub mod foo;
-            pub mod bar;
-            pub mod baz;
-            //- /bar.rs
-            $0
-            //- /foo.rs
-            pub use super::baz;
-            pub struct S;
-            //- /baz.rs
-            pub use super::foo;
-        "#;
-        check_found_path(code, "crate::foo::S", "crate::foo::S", "crate::foo::S", "crate::foo::S");
+        check_found_path(
+            r#"
+//- /main.rs
+pub mod foo;
+pub mod bar;
+pub mod baz;
+//- /bar.rs
+$0
+//- /foo.rs
+pub use super::baz;
+pub struct S;
+//- /baz.rs
+pub use super::foo;
+        "#,
+            "crate::foo::S",
+            "crate::foo::S",
+            "crate::foo::S",
+            "crate::foo::S",
+        );
     }
 
     #[test]
     fn prefer_std_paths_over_alloc() {
         cov_mark::check!(prefer_std_paths);
-        let code = r#"
-        //- /main.rs crate:main deps:alloc,std
-        $0
+        check_found_path(
+            r#"
+//- /main.rs crate:main deps:alloc,std
+$0
 
-        //- /std.rs crate:std deps:alloc
-        pub mod sync {
-            pub use alloc::sync::Arc;
-        }
+//- /std.rs crate:std deps:alloc
+pub mod sync {
+    pub use alloc::sync::Arc;
+}
 
-        //- /zzz.rs crate:alloc
-        pub mod sync {
-            pub struct Arc;
-        }
-        "#;
-        check_found_path(
-            code,
+//- /zzz.rs crate:alloc
+pub mod sync {
+    pub struct Arc;
+}
+        "#,
             "std::sync::Arc",
             "std::sync::Arc",
             "std::sync::Arc",
@@ -725,26 +790,25 @@ mod tests {
     #[test]
     fn prefer_core_paths_over_std() {
         cov_mark::check!(prefer_no_std_paths);
-        let code = r#"
-        //- /main.rs crate:main deps:core,std
-        #![no_std]
+        check_found_path(
+            r#"
+//- /main.rs crate:main deps:core,std
+#![no_std]
 
-        $0
+$0
 
-        //- /std.rs crate:std deps:core
+//- /std.rs crate:std deps:core
 
-        pub mod fmt {
-            pub use core::fmt::Error;
-        }
+pub mod fmt {
+    pub use core::fmt::Error;
+}
 
-        //- /zzz.rs crate:core
+//- /zzz.rs crate:core
 
-        pub mod fmt {
-            pub struct Error;
-        }
-        "#;
-        check_found_path(
-            code,
+pub mod fmt {
+    pub struct Error;
+}
+        "#,
             "core::fmt::Error",
             "core::fmt::Error",
             "core::fmt::Error",
@@ -754,26 +818,25 @@ mod tests {
 
     #[test]
     fn prefer_alloc_paths_over_std() {
-        let code = r#"
-        //- /main.rs crate:main deps:alloc,std
-        #![no_std]
+        check_found_path(
+            r#"
+//- /main.rs crate:main deps:alloc,std
+#![no_std]
 
-        $0
+$0
 
-        //- /std.rs crate:std deps:alloc
+//- /std.rs crate:std deps:alloc
 
-        pub mod sync {
-            pub use alloc::sync::Arc;
-        }
+pub mod sync {
+    pub use alloc::sync::Arc;
+}
 
-        //- /zzz.rs crate:alloc
+//- /zzz.rs crate:alloc
 
-        pub mod sync {
-            pub struct Arc;
-        }
-        "#;
-        check_found_path(
-            code,
+pub mod sync {
+    pub struct Arc;
+}
+            "#,
             "alloc::sync::Arc",
             "alloc::sync::Arc",
             "alloc::sync::Arc",
@@ -783,20 +846,19 @@ mod tests {
 
     #[test]
     fn prefer_shorter_paths_if_not_alloc() {
-        let code = r#"
-        //- /main.rs crate:main deps:megaalloc,std
-        $0
+        check_found_path(
+            r#"
+//- /main.rs crate:main deps:megaalloc,std
+$0
 
-        //- /std.rs crate:std deps:megaalloc
-        pub mod sync {
-            pub use megaalloc::sync::Arc;
-        }
+//- /std.rs crate:std deps:megaalloc
+pub mod sync {
+    pub use megaalloc::sync::Arc;
+}
 
-        //- /zzz.rs crate:megaalloc
-        pub struct Arc;
-        "#;
-        check_found_path(
-            code,
+//- /zzz.rs crate:megaalloc
+pub struct Arc;
+            "#,
             "megaalloc::Arc",
             "megaalloc::Arc",
             "megaalloc::Arc",
@@ -807,12 +869,11 @@ mod tests {
     #[test]
     fn builtins_are_in_scope() {
         let code = r#"
-        //- /main.rs
-        $0
+$0
 
-        pub mod primitive {
-            pub use u8;
-        }
+pub mod primitive {
+    pub use u8;
+}
         "#;
         check_found_path(code, "u8", "u8", "u8", "u8");
         check_found_path(code, "u16", "u16", "u16", "u16");
@@ -822,10 +883,10 @@ mod tests {
     fn inner_items() {
         check_found_path(
             r#"
-            fn main() {
-                struct Inner {}
-                $0
-            }
+fn main() {
+    struct Inner {}
+    $0
+}
         "#,
             "Inner",
             "Inner",
@@ -838,12 +899,12 @@ mod tests {
     fn inner_items_from_outer_scope() {
         check_found_path(
             r#"
-            fn main() {
-                struct Struct {}
-                {
-                    $0
-                }
-            }
+fn main() {
+    struct Struct {}
+    {
+        $0
+    }
+}
         "#,
             "Struct",
             "Struct",
@@ -857,14 +918,14 @@ mod tests {
         cov_mark::check!(prefixed_in_block_expression);
         check_found_path(
             r#"
-            fn main() {
-                mod module {
-                    struct Struct {}
-                }
-                {
-                    $0
-                }
-            }
+fn main() {
+    mod module {
+        struct Struct {}
+    }
+    {
+        $0
+    }
+}
         "#,
             "module::Struct",
             "module::Struct",
@@ -877,19 +938,65 @@ mod tests {
     fn outer_items_with_inner_items_present() {
         check_found_path(
             r#"
-            mod module {
-                pub struct CompleteMe;
-            }
+mod module {
+    pub struct CompleteMe;
+}
 
-            fn main() {
-                fn inner() {}
-                $0
-            }
+fn main() {
+    fn inner() {}
+    $0
+}
             "#,
+            // FIXME: these could use fewer/better prefixes
             "module::CompleteMe",
-            "module::CompleteMe",
             "crate::module::CompleteMe",
-            "self::module::CompleteMe",
+            "crate::module::CompleteMe",
+            "crate::module::CompleteMe",
+        )
+    }
+
+    #[test]
+    fn from_inside_module() {
+        // This worked correctly, but the test suite logic was broken.
+        cov_mark::check!(submodule_in_testdb);
+        check_found_path(
+            r#"
+mod baz {
+    pub struct Foo {}
+}
+
+mod bar {
+    fn bar() {
+        $0
+    }
+}
+            "#,
+            "crate::baz::Foo",
+            "crate::baz::Foo",
+            "crate::baz::Foo",
+            "crate::baz::Foo",
+        )
+    }
+
+    #[test]
+    fn from_inside_module_with_inner_items() {
+        check_found_path(
+            r#"
+mod baz {
+    pub struct Foo {}
+}
+
+mod bar {
+    fn bar() {
+        fn inner() {}
+        $0
+    }
+}
+            "#,
+            "crate::baz::Foo",
+            "crate::baz::Foo",
+            "crate::baz::Foo",
+            "crate::baz::Foo",
         )
     }
 
@@ -920,4 +1027,34 @@ pub mod name {
             "self::name::AsName",
         );
     }
+
+    #[test]
+    fn extern_crate() {
+        check_found_path(
+            r#"
+//- /main.rs crate:main deps:dep
+$0
+//- /dep.rs crate:dep
+"#,
+            "dep",
+            "dep",
+            "dep",
+            "dep",
+        );
+
+        check_found_path(
+            r#"
+//- /main.rs crate:main deps:dep
+fn f() {
+    fn inner() {}
+    $0
+}
+//- /dep.rs crate:dep
+"#,
+            "dep",
+            "dep",
+            "dep",
+            "dep",
+        );
+    }
 }
diff --git a/crates/hir_def/src/generics.rs b/crates/hir_def/src/generics.rs
index 7c6cbff11..de5acced8 100644
--- a/crates/hir_def/src/generics.rs
+++ b/crates/hir_def/src/generics.rs
@@ -2,7 +2,6 @@
 //! structs, impls, traits, etc. This module provides a common HIR for these
 //! generic parameters. See also the `Generics` type and the `generics_of` query
 //! in rustc.
-use std::sync::Arc;
 
 use base_db::FileId;
 use either::Either;
@@ -18,6 +17,7 @@ use crate::{
     child_by_source::ChildBySource,
     db::DefDatabase,
     dyn_map::DynMap,
+    intern::Interned,
     keys,
     src::{HasChildSource, HasSource},
     type_ref::{LifetimeRef, TypeBound, TypeRef},
@@ -26,27 +26,27 @@ use crate::{
 };
 
 /// Data about a generic type parameter (to a function, struct, impl, ...).
-#[derive(Clone, PartialEq, Eq, Debug)]
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
 pub struct TypeParamData {
     pub name: Option<Name>,
-    pub default: Option<TypeRef>,
+    pub default: Option<Interned<TypeRef>>,
     pub provenance: TypeParamProvenance,
 }
 
 /// Data about a generic lifetime parameter (to a function, struct, impl, ...).
-#[derive(Clone, PartialEq, Eq, Debug)]
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
 pub struct LifetimeParamData {
     pub name: Name,
 }
 
 /// Data about a generic const parameter (to a function, struct, impl, ...).
-#[derive(Clone, PartialEq, Eq, Debug)]
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
 pub struct ConstParamData {
     pub name: Name,
-    pub ty: TypeRef,
+    pub ty: Interned<TypeRef>,
 }
 
-#[derive(Copy, Clone, PartialEq, Eq, Debug)]
+#[derive(Copy, Clone, PartialEq, Eq, Debug, Hash)]
 pub enum TypeParamProvenance {
     TypeParamList,
     TraitSelf,
@@ -54,7 +54,7 @@ pub enum TypeParamProvenance {
 }
 
 /// Data about the generic parameters of a function, struct, impl, etc.
-#[derive(Clone, PartialEq, Eq, Debug, Default)]
+#[derive(Clone, PartialEq, Eq, Debug, Default, Hash)]
 pub struct GenericParams {
     pub types: Arena<TypeParamData>,
     pub lifetimes: Arena<LifetimeParamData>,
@@ -66,16 +66,16 @@ pub struct GenericParams {
 /// where clauses like `where T: Foo + Bar` are turned into multiple of these.
 /// It might still result in multiple actual predicates though, because of
 /// associated type bindings like `Iterator<Item = u32>`.
-#[derive(Clone, PartialEq, Eq, Debug)]
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
 pub enum WherePredicate {
     TypeBound { target: WherePredicateTypeTarget, bound: TypeBound },
     Lifetime { target: LifetimeRef, bound: LifetimeRef },
     ForLifetime { lifetimes: Box<[Name]>, target: WherePredicateTypeTarget, bound: TypeBound },
 }
 
-#[derive(Clone, PartialEq, Eq, Debug)]
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
 pub enum WherePredicateTypeTarget {
-    TypeRef(TypeRef),
+    TypeRef(Interned<TypeRef>),
     /// For desugared where predicates that can directly refer to a type param.
     TypeParam(LocalTypeParamId),
 }
@@ -91,7 +91,7 @@ impl GenericParams {
     pub(crate) fn generic_params_query(
         db: &dyn DefDatabase,
         def: GenericDefId,
-    ) -> Arc<GenericParams> {
+    ) -> Interned<GenericParams> {
         let _p = profile::span("generic_params_query");
 
         let generics = match def {
@@ -99,47 +99,49 @@ impl GenericParams {
                 let id = id.lookup(db).id;
                 let tree = id.item_tree(db);
                 let item = &tree[id.value];
-                tree[item.generic_params].clone()
+                item.generic_params.clone()
             }
             GenericDefId::AdtId(AdtId::StructId(id)) => {
                 let id = id.lookup(db).id;
                 let tree = id.item_tree(db);
                 let item = &tree[id.value];
-                tree[item.generic_params].clone()
+                item.generic_params.clone()
             }
             GenericDefId::AdtId(AdtId::EnumId(id)) => {
                 let id = id.lookup(db).id;
                 let tree = id.item_tree(db);
                 let item = &tree[id.value];
-                tree[item.generic_params].clone()
+                item.generic_params.clone()
             }
             GenericDefId::AdtId(AdtId::UnionId(id)) => {
                 let id = id.lookup(db).id;
                 let tree = id.item_tree(db);
                 let item = &tree[id.value];
-                tree[item.generic_params].clone()
+                item.generic_params.clone()
             }
             GenericDefId::TraitId(id) => {
                 let id = id.lookup(db).id;
                 let tree = id.item_tree(db);
                 let item = &tree[id.value];
-                tree[item.generic_params].clone()
+                item.generic_params.clone()
             }
             GenericDefId::TypeAliasId(id) => {
                 let id = id.lookup(db).id;
                 let tree = id.item_tree(db);
                 let item = &tree[id.value];
-                tree[item.generic_params].clone()
+                item.generic_params.clone()
             }
             GenericDefId::ImplId(id) => {
                 let id = id.lookup(db).id;
                 let tree = id.item_tree(db);
                 let item = &tree[id.value];
-                tree[item.generic_params].clone()
+                item.generic_params.clone()
+            }
+            GenericDefId::EnumVariantId(_) | GenericDefId::ConstId(_) => {
+                Interned::new(GenericParams::default())
             }
-            GenericDefId::EnumVariantId(_) | GenericDefId::ConstId(_) => GenericParams::default(),
         };
-        Arc::new(generics)
+        generics
     }
 
     fn new(db: &dyn DefDatabase, def: GenericDefId) -> (GenericParams, InFile<SourceMap>) {
@@ -217,6 +219,7 @@ impl GenericParams {
             GenericDefId::EnumVariantId(_) | GenericDefId::ConstId(_) => FileId(!0).into(),
         };
 
+        generics.shrink_to_fit();
         (generics, InFile::new(file_id, sm))
     }
 
@@ -256,7 +259,8 @@ impl GenericParams {
         for type_param in params.type_params() {
             let name = type_param.name().map_or_else(Name::missing, |it| it.as_name());
             // FIXME: Use `Path::from_src`
-            let default = type_param.default_type().map(|it| TypeRef::from_ast(lower_ctx, it));
+            let default =
+                type_param.default_type().map(|it| Interned::new(TypeRef::from_ast(lower_ctx, it)));
             let param = TypeParamData {
                 name: Some(name.clone()),
                 default,
@@ -280,7 +284,7 @@ impl GenericParams {
         for const_param in params.const_params() {
             let name = const_param.name().map_or_else(Name::missing, |it| it.as_name());
             let ty = const_param.ty().map_or(TypeRef::Error, |it| TypeRef::from_ast(lower_ctx, it));
-            let param = ConstParamData { name, ty };
+            let param = ConstParamData { name, ty: Interned::new(ty) };
             let param_id = self.consts.alloc(param);
             sm.const_params.insert(param_id, const_param.clone());
         }
@@ -334,11 +338,11 @@ impl GenericParams {
             (Either::Left(type_ref), bound) => match hrtb_lifetimes {
                 Some(hrtb_lifetimes) => WherePredicate::ForLifetime {
                     lifetimes: hrtb_lifetimes.clone(),
-                    target: WherePredicateTypeTarget::TypeRef(type_ref),
+                    target: WherePredicateTypeTarget::TypeRef(Interned::new(type_ref)),
                     bound,
                 },
                 None => WherePredicate::TypeBound {
-                    target: WherePredicateTypeTarget::TypeRef(type_ref),
+                    target: WherePredicateTypeTarget::TypeRef(Interned::new(type_ref)),
                     bound,
                 },
             },
@@ -369,6 +373,14 @@ impl GenericParams {
         });
     }
 
+    pub(crate) fn shrink_to_fit(&mut self) {
+        let Self { consts, lifetimes, types, where_predicates } = self;
+        consts.shrink_to_fit();
+        lifetimes.shrink_to_fit();
+        types.shrink_to_fit();
+        where_predicates.shrink_to_fit();
+    }
+
     pub fn find_type_by_name(&self, name: &Name) -> Option<LocalTypeParamId> {
         self.types
             .iter()
diff --git a/crates/hir_def/src/intern.rs b/crates/hir_def/src/intern.rs
index d163f633f..abc304ef0 100644
--- a/crates/hir_def/src/intern.rs
+++ b/crates/hir_def/src/intern.rs
@@ -5,7 +5,7 @@
 use std::{
     collections::HashMap,
     fmt::{self, Debug},
-    hash::{BuildHasherDefault, Hash},
+    hash::{BuildHasherDefault, Hash, Hasher},
     ops::Deref,
     sync::Arc,
 };
@@ -14,11 +14,12 @@ use dashmap::{lock::RwLockWriteGuard, DashMap, SharedValue};
 use once_cell::sync::OnceCell;
 use rustc_hash::FxHasher;
 
+use crate::generics::GenericParams;
+
 type InternMap<T> = DashMap<Arc<T>, (), BuildHasherDefault<FxHasher>>;
 type Guard<T> =
     RwLockWriteGuard<'static, HashMap<Arc<T>, SharedValue<()>, BuildHasherDefault<FxHasher>>>;
 
-#[derive(Hash)]
 pub struct Interned<T: Internable + ?Sized> {
     arc: Arc<T>,
 }
@@ -135,6 +136,13 @@ impl PartialEq for Interned<str> {
 
 impl Eq for Interned<str> {}
 
+impl<T: Internable + ?Sized> Hash for Interned<T> {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        // NOTE: Cast disposes vtable pointer / slice/str length.
+        state.write_usize(Arc::as_ptr(&self.arc) as *const () as usize)
+    }
+}
+
 impl<T: Internable + ?Sized> AsRef<T> for Interned<T> {
     #[inline]
     fn as_ref(&self) -> &T {
@@ -183,7 +191,10 @@ pub trait Internable: Hash + Eq + 'static {
     fn storage() -> &'static InternStorage<Self>;
 }
 
-macro_rules! impl_internable {
+/// Implements `Internable` for a given list of types, making them usable with `Interned`.
+#[macro_export]
+#[doc(hidden)]
+macro_rules! _impl_internable {
     ( $($t:path),+ $(,)? ) => { $(
         impl Internable for $t {
             fn storage() -> &'static InternStorage<Self> {
@@ -194,4 +205,12 @@ macro_rules! impl_internable {
     )+ };
 }
 
-impl_internable!(crate::type_ref::TypeRef, crate::type_ref::TraitRef, crate::path::ModPath, str);
+pub use crate::_impl_internable as impl_internable;
+
+impl_internable!(
+    crate::type_ref::TypeRef,
+    crate::type_ref::TraitRef,
+    crate::path::ModPath,
+    GenericParams,
+    str,
+);
diff --git a/crates/hir_def/src/item_scope.rs b/crates/hir_def/src/item_scope.rs
index a8ee5eeac..9014468ea 100644
--- a/crates/hir_def/src/item_scope.rs
+++ b/crates/hir_def/src/item_scope.rs
@@ -11,7 +11,7 @@ use rustc_hash::{FxHashMap, FxHashSet};
 use stdx::format_to;
 
 use crate::{
-    db::DefDatabase, per_ns::PerNs, visibility::Visibility, AdtId, BuiltinType, ImplId,
+    db::DefDatabase, per_ns::PerNs, visibility::Visibility, AdtId, BuiltinType, ConstId, ImplId,
     LocalModuleId, MacroDefId, ModuleDefId, ModuleId, TraitId,
 };
 
@@ -37,6 +37,7 @@ pub struct ItemScope {
 
     defs: Vec<ModuleDefId>,
     impls: Vec<ImplId>,
+    unnamed_consts: Vec<ConstId>,
     /// Traits imported via `use Trait as _;`.
     unnamed_trait_imports: FxHashMap<TraitId, Visibility>,
     /// Macros visible in current module in legacy textual scope
@@ -106,6 +107,10 @@ impl ItemScope {
             .map(|(_, v)| v)
     }
 
+    pub fn unnamed_consts(&self) -> impl Iterator<Item = ConstId> + '_ {
+        self.unnamed_consts.iter().copied()
+    }
+
     /// Iterate over all module scoped macros
     pub(crate) fn macros<'a>(&'a self) -> impl Iterator<Item = (&'a Name, MacroDefId)> + 'a {
         self.entries().filter_map(|(name, def)| def.take_macros().map(|macro_| (name, macro_)))
@@ -156,6 +161,10 @@ impl ItemScope {
         self.impls.push(imp)
     }
 
+    pub(crate) fn define_unnamed_const(&mut self, konst: ConstId) {
+        self.unnamed_consts.push(konst);
+    }
+
     pub(crate) fn define_legacy_macro(&mut self, name: Name, mac: MacroDefId) {
         self.legacy_macros.insert(name, mac);
     }
@@ -295,6 +304,7 @@ impl ItemScope {
             unresolved,
             defs,
             impls,
+            unnamed_consts,
             unnamed_trait_imports,
             legacy_macros,
         } = self;
@@ -304,6 +314,7 @@ impl ItemScope {
         unresolved.shrink_to_fit();
         defs.shrink_to_fit();
         impls.shrink_to_fit();
+        unnamed_consts.shrink_to_fit();
         unnamed_trait_imports.shrink_to_fit();
         legacy_macros.shrink_to_fit();
     }
diff --git a/crates/hir_def/src/item_tree.rs b/crates/hir_def/src/item_tree.rs
index 739906778..eaeca01bd 100644
--- a/crates/hir_def/src/item_tree.rs
+++ b/crates/hir_def/src/item_tree.rs
@@ -58,13 +58,6 @@ impl fmt::Debug for RawVisibilityId {
     }
 }
 
-#[derive(Debug, Copy, Clone, Eq, PartialEq)]
-pub struct GenericParamsId(u32);
-
-impl GenericParamsId {
-    pub const EMPTY: Self = GenericParamsId(u32::max_value());
-}
-
 /// The item tree of a source file.
 #[derive(Debug, Default, Eq, PartialEq)]
 pub struct ItemTree {
@@ -106,6 +99,16 @@ impl ItemTree {
                     // items.
                     ctx.lower_macro_stmts(stmts)
                 },
+                ast::Pat(_pat) => {
+                    // FIXME: This occurs because macros in pattern position are treated as inner
+                    // items and expanded during block DefMap computation
+                    return Default::default();
+                },
+                ast::Type(ty) => {
+                    // Types can contain inner items. We return an empty item tree in this case, but
+                    // still need to collect inner items.
+                    ctx.lower_inner_items(ty.syntax())
+                },
                 ast::Expr(e) => {
                     // Macros can expand to expressions. We return an empty item tree in this case, but
                     // still need to collect inner items.
@@ -146,7 +149,6 @@ impl ItemTree {
                 macro_rules,
                 macro_defs,
                 vis,
-                generics,
                 inner_items,
             } = &mut **data;
 
@@ -170,7 +172,6 @@ impl ItemTree {
             macro_defs.shrink_to_fit();
 
             vis.arena.shrink_to_fit();
-            generics.arena.shrink_to_fit();
 
             inner_items.shrink_to_fit();
         }
@@ -195,13 +196,6 @@ impl ItemTree {
         self.raw_attrs(of).clone().filter(db, krate)
     }
 
-    pub fn all_inner_items(&self) -> impl Iterator<Item = ModItem> + '_ {
-        match &self.data {
-            Some(data) => Some(data.inner_items.values().flatten().copied()).into_iter().flatten(),
-            None => None.into_iter().flatten(),
-        }
-    }
-
     pub fn inner_items_of_block(&self, block: FileAstId<ast::BlockExpr>) -> &[ModItem] {
         match &self.data {
             Some(data) => data.inner_items.get(&block).map(|it| &**it).unwrap_or(&[]),
@@ -242,32 +236,6 @@ static VIS_PRIV: RawVisibility = RawVisibility::Module(ModPath::from_kind(PathKi
 static VIS_PUB_CRATE: RawVisibility = RawVisibility::Module(ModPath::from_kind(PathKind::Crate));
 
 #[derive(Default, Debug, Eq, PartialEq)]
-struct GenericParamsStorage {
-    arena: Arena<GenericParams>,
-}
-
-impl GenericParamsStorage {
-    fn alloc(&mut self, params: GenericParams) -> GenericParamsId {
-        if params.types.is_empty()
-            && params.lifetimes.is_empty()
-            && params.consts.is_empty()
-            && params.where_predicates.is_empty()
-        {
-            return GenericParamsId::EMPTY;
-        }
-
-        GenericParamsId(self.arena.alloc(params).into_raw().into())
-    }
-}
-
-static EMPTY_GENERICS: GenericParams = GenericParams {
-    types: Arena::new(),
-    lifetimes: Arena::new(),
-    consts: Arena::new(),
-    where_predicates: Vec::new(),
-};
-
-#[derive(Default, Debug, Eq, PartialEq)]
 struct ItemTreeData {
     imports: Arena<Import>,
     extern_crates: Arena<ExternCrate>,
@@ -289,7 +257,6 @@ struct ItemTreeData {
     macro_defs: Arena<MacroDef>,
 
     vis: ItemVisibilities,
-    generics: GenericParamsStorage,
 
     inner_items: FxHashMap<FileAstId<ast::BlockExpr>, SmallVec<[ModItem; 1]>>,
 }
@@ -508,17 +475,6 @@ impl Index<RawVisibilityId> for ItemTree {
     }
 }
 
-impl Index<GenericParamsId> for ItemTree {
-    type Output = GenericParams;
-
-    fn index(&self, index: GenericParamsId) -> &Self::Output {
-        match index {
-            GenericParamsId::EMPTY => &EMPTY_GENERICS,
-            _ => &self.data().generics.arena[Idx::from_raw(index.0.into())],
-        }
-    }
-}
-
 impl<N: ItemTreeNode> Index<FileItemTreeId<N>> for ItemTree {
     type Output = N;
     fn index(&self, id: FileItemTreeId<N>) -> &N {
@@ -555,7 +511,7 @@ pub struct ExternCrate {
 pub struct Function {
     pub name: Name,
     pub visibility: RawVisibilityId,
-    pub generic_params: GenericParamsId,
+    pub generic_params: Interned<GenericParams>,
     pub abi: Option<Interned<str>>,
     pub params: IdRange<Param>,
     pub ret_type: Interned<TypeRef>,
@@ -590,7 +546,7 @@ impl FnFlags {
 pub struct Struct {
     pub name: Name,
     pub visibility: RawVisibilityId,
-    pub generic_params: GenericParamsId,
+    pub generic_params: Interned<GenericParams>,
     pub fields: Fields,
     pub ast_id: FileAstId<ast::Struct>,
     pub kind: StructDefKind,
@@ -610,7 +566,7 @@ pub enum StructDefKind {
 pub struct Union {
     pub name: Name,
     pub visibility: RawVisibilityId,
-    pub generic_params: GenericParamsId,
+    pub generic_params: Interned<GenericParams>,
     pub fields: Fields,
     pub ast_id: FileAstId<ast::Union>,
 }
@@ -619,7 +575,7 @@ pub struct Union {
 pub struct Enum {
     pub name: Name,
     pub visibility: RawVisibilityId,
-    pub generic_params: GenericParamsId,
+    pub generic_params: Interned<GenericParams>,
     pub variants: IdRange<Variant>,
     pub ast_id: FileAstId<ast::Enum>,
 }
@@ -648,7 +604,7 @@ pub struct Static {
 pub struct Trait {
     pub name: Name,
     pub visibility: RawVisibilityId,
-    pub generic_params: GenericParamsId,
+    pub generic_params: Interned<GenericParams>,
     pub is_auto: bool,
     pub is_unsafe: bool,
     pub bounds: Box<[TypeBound]>,
@@ -658,7 +614,7 @@ pub struct Trait {
 
 #[derive(Debug, Clone, Eq, PartialEq)]
 pub struct Impl {
-    pub generic_params: GenericParamsId,
+    pub generic_params: Interned<GenericParams>,
     pub target_trait: Option<Interned<TraitRef>>,
     pub self_ty: Interned<TypeRef>,
     pub is_negative: bool,
@@ -672,7 +628,7 @@ pub struct TypeAlias {
     pub visibility: RawVisibilityId,
     /// Bounds on the type alias itself. Only valid in trait declarations, eg. `type Assoc: Copy;`.
     pub bounds: Box<[TypeBound]>,
-    pub generic_params: GenericParamsId,
+    pub generic_params: Interned<GenericParams>,
     pub type_ref: Option<Interned<TypeRef>>,
     pub is_extern: bool,
     pub ast_id: FileAstId<ast::TypeAlias>,
diff --git a/crates/hir_def/src/item_tree/lower.rs b/crates/hir_def/src/item_tree/lower.rs
index ab7ad8310..45b099cf3 100644
--- a/crates/hir_def/src/item_tree/lower.rs
+++ b/crates/hir_def/src/item_tree/lower.rs
@@ -189,7 +189,7 @@ impl Ctx {
                                 block_stack.push(self.source_ast_id_map.ast_id(&block));
                             },
                             ast::Item(item) => {
-                                // FIXME: This triggers for macro calls in expression position
+                                // FIXME: This triggers for macro calls in expression/pattern/type position
                                 let mod_items = self.lower_mod_item(&item, true);
                                 let current_block = block_stack.last();
                                 if let (Some(mod_items), Some(block)) = (mod_items, current_block) {
@@ -434,7 +434,7 @@ impl Ctx {
         let mut res = Function {
             name,
             visibility,
-            generic_params: GenericParamsId::EMPTY,
+            generic_params: Interned::new(GenericParams::default()),
             abi,
             params,
             ret_type: Interned::new(ret_type),
@@ -682,7 +682,7 @@ impl Ctx {
         &mut self,
         owner: GenericsOwner<'_>,
         node: &impl ast::GenericParamsOwner,
-    ) -> GenericParamsId {
+    ) -> Interned<GenericParams> {
         // Generics are part of item headers and may contain inner items we need to collect.
         if let Some(params) = node.generic_param_list() {
             self.collect_inner_items(params.syntax());
@@ -698,7 +698,7 @@ impl Ctx {
         &mut self,
         owner: GenericsOwner<'_>,
         node: &impl ast::GenericParamsOwner,
-    ) -> GenericParamsId {
+    ) -> Interned<GenericParams> {
         let mut sm = &mut Default::default();
         let mut generics = GenericParams::default();
         match owner {
@@ -739,7 +739,8 @@ impl Ctx {
             }
         }
 
-        self.data().generics.alloc(generics)
+        generics.shrink_to_fit();
+        Interned::new(generics)
     }
 
     fn lower_type_bounds(&mut self, node: &impl ast::TypeBoundsOwner) -> Vec<TypeBound> {
diff --git a/crates/hir_def/src/lib.rs b/crates/hir_def/src/lib.rs
index f408e510a..25694f037 100644
--- a/crates/hir_def/src/lib.rs
+++ b/crates/hir_def/src/lib.rs
@@ -27,6 +27,7 @@ pub mod dyn_map;
 pub mod keys;
 
 pub mod item_tree;
+pub mod intern;
 
 pub mod adt;
 pub mod data;
@@ -49,22 +50,23 @@ pub mod import_map;
 
 #[cfg(test)]
 mod test_db;
-mod intern;
 
 use std::{
     hash::{Hash, Hasher},
     sync::Arc,
 };
 
+use adt::VariantData;
 use base_db::{impl_intern_key, salsa, CrateId};
 use hir_expand::{
     ast_id_map::FileAstId,
     eager::{expand_eager_macro, ErrorEmitted, ErrorSink},
     hygiene::Hygiene,
-    AstId, HirFileId, InFile, MacroCallId, MacroCallKind, MacroDefId, MacroDefKind,
+    AstId, AttrId, HirFileId, InFile, MacroCallId, MacroCallKind, MacroDefId, MacroDefKind,
 };
 use la_arena::Idx;
 use nameres::DefMap;
+use path::ModPath;
 use syntax::ast;
 
 use crate::builtin_type::BuiltinType;
@@ -106,6 +108,18 @@ impl ModuleId {
     pub fn containing_module(&self, db: &dyn db::DefDatabase) -> Option<ModuleId> {
         self.def_map(db).containing_module(self.local_id)
     }
+
+    /// Returns `true` if this module represents a block expression.
+    ///
+    /// Returns `false` if this module is a submodule *inside* a block expression
+    /// (eg. `m` in `{ mod m {} }`).
+    pub fn is_block_root(&self, db: &dyn db::DefDatabase) -> bool {
+        if self.block.is_none() {
+            return false;
+        }
+
+        self.def_map(db)[self.local_id].parent.is_none()
+    }
 }
 
 /// An ID of a module, **local** to a specific crate
@@ -434,6 +448,16 @@ impl_from!(
     for AttrDefId
 );
 
+impl From<AssocContainerId> for AttrDefId {
+    fn from(acid: AssocContainerId) -> Self {
+        match acid {
+            AssocContainerId::ModuleId(mid) => AttrDefId::ModuleId(mid),
+            AssocContainerId::ImplId(iid) => AttrDefId::ImplId(iid),
+            AssocContainerId::TraitId(tid) => AttrDefId::TraitId(tid),
+        }
+    }
+}
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub enum VariantId {
     EnumVariantId(EnumVariantId),
@@ -442,6 +466,26 @@ pub enum VariantId {
 }
 impl_from!(EnumVariantId, StructId, UnionId for VariantId);
 
+impl VariantId {
+    pub fn variant_data(self, db: &dyn db::DefDatabase) -> Arc<VariantData> {
+        match self {
+            VariantId::StructId(it) => db.struct_data(it).variant_data.clone(),
+            VariantId::UnionId(it) => db.union_data(it).variant_data.clone(),
+            VariantId::EnumVariantId(it) => {
+                db.enum_data(it.parent).variants[it.local_id].variant_data.clone()
+            }
+        }
+    }
+
+    pub fn file_id(self, db: &dyn db::DefDatabase) -> HirFileId {
+        match self {
+            VariantId::EnumVariantId(it) => it.parent.lookup(db).id.file_id(),
+            VariantId::StructId(it) => it.lookup(db).id.file_id(),
+            VariantId::UnionId(it) => it.lookup(db).id.file_id(),
+        }
+    }
+}
+
 trait Intern {
     type ID;
     fn intern(self, db: &dyn db::DefDatabase) -> Self::ID;
@@ -644,7 +688,10 @@ impl<T: ast::AstNode> AstIdWithPath<T> {
     }
 }
 
-pub struct UnresolvedMacro;
+#[derive(Debug)]
+pub struct UnresolvedMacro {
+    pub path: ModPath,
+}
 
 fn macro_call_as_call_id(
     call: &AstIdWithPath<ast::MacroCall>,
@@ -653,7 +700,8 @@ fn macro_call_as_call_id(
     resolver: impl Fn(path::ModPath) -> Option<MacroDefId>,
     error_sink: &mut dyn FnMut(mbe::ExpandError),
 ) -> Result<Result<MacroCallId, ErrorEmitted>, UnresolvedMacro> {
-    let def: MacroDefId = resolver(call.path.clone()).ok_or(UnresolvedMacro)?;
+    let def: MacroDefId =
+        resolver(call.path.clone()).ok_or_else(|| UnresolvedMacro { path: call.path.clone() })?;
 
     let res = if let MacroDefKind::BuiltInEager(..) = def.kind {
         let macro_call = InFile::new(call.ast_id.file_id, call.ast_id.to_node(db.upcast()));
@@ -669,24 +717,36 @@ fn macro_call_as_call_id(
         )
         .map(MacroCallId::from)
     } else {
-        Ok(def.as_lazy_macro(db.upcast(), krate, MacroCallKind::FnLike(call.ast_id)).into())
+        Ok(def
+            .as_lazy_macro(db.upcast(), krate, MacroCallKind::FnLike { ast_id: call.ast_id })
+            .into())
     };
     Ok(res)
 }
 
 fn derive_macro_as_call_id(
     item_attr: &AstIdWithPath<ast::Item>,
+    derive_attr: AttrId,
     db: &dyn db::DefDatabase,
     krate: CrateId,
     resolver: impl Fn(path::ModPath) -> Option<MacroDefId>,
 ) -> Result<MacroCallId, UnresolvedMacro> {
-    let def: MacroDefId = resolver(item_attr.path.clone()).ok_or(UnresolvedMacro)?;
-    let last_segment = item_attr.path.segments().last().ok_or(UnresolvedMacro)?;
+    let def: MacroDefId = resolver(item_attr.path.clone())
+        .ok_or_else(|| UnresolvedMacro { path: item_attr.path.clone() })?;
+    let last_segment = item_attr
+        .path
+        .segments()
+        .last()
+        .ok_or_else(|| UnresolvedMacro { path: item_attr.path.clone() })?;
     let res = def
         .as_lazy_macro(
             db.upcast(),
             krate,
-            MacroCallKind::Derive(item_attr.ast_id, last_segment.to_string()),
+            MacroCallKind::Derive {
+                ast_id: item_attr.ast_id,
+                derive_name: last_segment.to_string(),
+                derive_attr,
+            },
         )
         .into();
     Ok(res)
diff --git a/crates/hir_def/src/nameres.rs b/crates/hir_def/src/nameres.rs
index 7dd68219f..ba027c44a 100644
--- a/crates/hir_def/src/nameres.rs
+++ b/crates/hir_def/src/nameres.rs
@@ -410,6 +410,20 @@ impl DefMap {
         }
     }
 
+    pub fn dump_block_scopes(&self, db: &dyn DefDatabase) -> String {
+        let mut buf = String::new();
+        let mut arc;
+        let mut current_map = self;
+        while let Some(block) = &current_map.block {
+            format_to!(buf, "{:?} in {:?}\n", block.block, block.parent);
+            arc = block.parent.def_map(db);
+            current_map = &*arc;
+        }
+
+        format_to!(buf, "crate scope\n");
+        buf
+    }
+
     fn shrink_to_fit(&mut self) {
         // Exhaustive match to require handling new fields.
         let Self {
@@ -481,7 +495,7 @@ mod diagnostics {
 
         UnresolvedProcMacro { ast: MacroCallKind },
 
-        UnresolvedMacroCall { ast: AstId<ast::MacroCall> },
+        UnresolvedMacroCall { ast: AstId<ast::MacroCall>, path: ModPath },
 
         MacroError { ast: MacroCallKind, message: String },
     }
@@ -546,8 +560,9 @@ mod diagnostics {
         pub(super) fn unresolved_macro_call(
             container: LocalModuleId,
             ast: AstId<ast::MacroCall>,
+            path: ModPath,
         ) -> Self {
-            Self { in_module: container, kind: DiagnosticKind::UnresolvedMacroCall { ast } }
+            Self { in_module: container, kind: DiagnosticKind::UnresolvedMacroCall { ast, path } }
         }
 
         pub(super) fn add_to(
@@ -613,12 +628,12 @@ mod diagnostics {
                 DiagnosticKind::UnresolvedProcMacro { ast } => {
                     let mut precise_location = None;
                     let (file, ast, name) = match ast {
-                        MacroCallKind::FnLike(ast) => {
-                            let node = ast.to_node(db.upcast());
-                            (ast.file_id, SyntaxNodePtr::from(AstPtr::new(&node)), None)
+                        MacroCallKind::FnLike { ast_id } => {
+                            let node = ast_id.to_node(db.upcast());
+                            (ast_id.file_id, SyntaxNodePtr::from(AstPtr::new(&node)), None)
                         }
-                        MacroCallKind::Derive(ast, name) => {
-                            let node = ast.to_node(db.upcast());
+                        MacroCallKind::Derive { ast_id, derive_name, .. } => {
+                            let node = ast_id.to_node(db.upcast());
 
                             // Compute the precise location of the macro name's token in the derive
                             // list.
@@ -639,7 +654,7 @@ mod diagnostics {
                                     });
                                 for token in tokens {
                                     if token.kind() == SyntaxKind::IDENT
-                                        && token.text() == name.as_str()
+                                        && token.text() == derive_name.as_str()
                                     {
                                         precise_location = Some(token.text_range());
                                         break 'outer;
@@ -648,9 +663,9 @@ mod diagnostics {
                             }
 
                             (
-                                ast.file_id,
+                                ast_id.file_id,
                                 SyntaxNodePtr::from(AstPtr::new(&node)),
-                                Some(name.clone()),
+                                Some(derive_name.clone()),
                             )
                         }
                     };
@@ -662,20 +677,24 @@ mod diagnostics {
                     });
                 }
 
-                DiagnosticKind::UnresolvedMacroCall { ast } => {
+                DiagnosticKind::UnresolvedMacroCall { ast, path } => {
                     let node = ast.to_node(db.upcast());
-                    sink.push(UnresolvedMacroCall { file: ast.file_id, node: AstPtr::new(&node) });
+                    sink.push(UnresolvedMacroCall {
+                        file: ast.file_id,
+                        node: AstPtr::new(&node),
+                        path: path.clone(),
+                    });
                 }
 
                 DiagnosticKind::MacroError { ast, message } => {
                     let (file, ast) = match ast {
-                        MacroCallKind::FnLike(ast) => {
-                            let node = ast.to_node(db.upcast());
-                            (ast.file_id, SyntaxNodePtr::from(AstPtr::new(&node)))
+                        MacroCallKind::FnLike { ast_id, .. } => {
+                            let node = ast_id.to_node(db.upcast());
+                            (ast_id.file_id, SyntaxNodePtr::from(AstPtr::new(&node)))
                         }
-                        MacroCallKind::Derive(ast, _) => {
-                            let node = ast.to_node(db.upcast());
-                            (ast.file_id, SyntaxNodePtr::from(AstPtr::new(&node)))
+                        MacroCallKind::Derive { ast_id, .. } => {
+                            let node = ast_id.to_node(db.upcast());
+                            (ast_id.file_id, SyntaxNodePtr::from(AstPtr::new(&node)))
                         }
                     };
                     sink.push(MacroError { file, node: ast, message: message.clone() });
diff --git a/crates/hir_def/src/nameres/collector.rs b/crates/hir_def/src/nameres/collector.rs
index 4ddc791ce..05ceb1efb 100644
--- a/crates/hir_def/src/nameres/collector.rs
+++ b/crates/hir_def/src/nameres/collector.rs
@@ -13,7 +13,7 @@ use hir_expand::{
     builtin_macro::find_builtin_macro,
     name::{AsName, Name},
     proc_macro::ProcMacroExpander,
-    HirFileId, MacroCallId, MacroCallKind, MacroDefId, MacroDefKind,
+    AttrId, HirFileId, MacroCallId, MacroCallKind, MacroDefId, MacroDefKind,
 };
 use hir_expand::{InFile, MacroCallLoc};
 use rustc_hash::{FxHashMap, FxHashSet};
@@ -215,8 +215,8 @@ struct MacroDirective {
 
 #[derive(Clone, Debug, Eq, PartialEq)]
 enum MacroDirectiveKind {
-    FnLike { ast_id: AstIdWithPath<ast::MacroCall>, legacy: Option<MacroCallId> },
-    Derive { ast_id: AstIdWithPath<ast::Item> },
+    FnLike { ast_id: AstIdWithPath<ast::MacroCall> },
+    Derive { ast_id: AstIdWithPath<ast::Item>, derive_attr: AttrId },
 }
 
 struct DefData<'a> {
@@ -478,7 +478,7 @@ impl DefCollector<'_> {
             self.def_map.edition,
         );
 
-        let res = self.def_map.resolve_name_in_extern_prelude(&extern_crate.name);
+        let res = self.def_map.resolve_name_in_extern_prelude(self.db, &extern_crate.name);
 
         if let Some(ModuleDefId::ModuleId(m)) = res.take_types() {
             cov_mark::hit!(macro_rules_from_other_crates_are_visible_with_macro_use);
@@ -534,6 +534,7 @@ impl DefCollector<'_> {
         log::debug!("resolving import: {:?} ({:?})", import, self.def_map.edition);
         if import.is_extern_crate {
             let res = self.def_map.resolve_name_in_extern_prelude(
+                self.db,
                 &import
                     .path
                     .as_ident()
@@ -806,13 +807,7 @@ impl DefCollector<'_> {
         let mut res = ReachedFixedPoint::Yes;
         macros.retain(|directive| {
             match &directive.kind {
-                MacroDirectiveKind::FnLike { ast_id, legacy } => {
-                    if let Some(call_id) = legacy {
-                        res = ReachedFixedPoint::No;
-                        resolved.push((directive.module_id, *call_id, directive.depth));
-                        return false;
-                    }
-
+                MacroDirectiveKind::FnLike { ast_id } => {
                     match macro_call_as_call_id(
                         ast_id,
                         self.db,
@@ -834,19 +829,23 @@ impl DefCollector<'_> {
                             res = ReachedFixedPoint::No;
                             return false;
                         }
-                        Err(UnresolvedMacro) | Ok(Err(_)) => {}
+                        Err(UnresolvedMacro { .. }) | Ok(Err(_)) => {}
                     }
                 }
-                MacroDirectiveKind::Derive { ast_id } => {
-                    match derive_macro_as_call_id(ast_id, self.db, self.def_map.krate, |path| {
-                        self.resolve_derive_macro(directive.module_id, &path)
-                    }) {
+                MacroDirectiveKind::Derive { ast_id, derive_attr } => {
+                    match derive_macro_as_call_id(
+                        ast_id,
+                        *derive_attr,
+                        self.db,
+                        self.def_map.krate,
+                        |path| self.resolve_derive_macro(directive.module_id, &path),
+                    ) {
                         Ok(call_id) => {
-                            resolved.push((directive.module_id, call_id, 0));
+                            resolved.push((directive.module_id, call_id, directive.depth));
                             res = ReachedFixedPoint::No;
                             return false;
                         }
-                        Err(UnresolvedMacro) => (),
+                        Err(UnresolvedMacro { .. }) => (),
                     }
                 }
             }
@@ -944,10 +943,11 @@ impl DefCollector<'_> {
                     &mut |_| (),
                 ) {
                     Ok(_) => (),
-                    Err(UnresolvedMacro) => {
+                    Err(UnresolvedMacro { path }) => {
                         self.def_map.diagnostics.push(DefDiagnostic::unresolved_macro_call(
                             directive.module_id,
                             ast_id.ast_id,
+                            path,
                         ));
                     }
                 },
@@ -1169,19 +1169,27 @@ impl ModCollector<'_, '_> {
                 }
                 ModItem::Const(id) => {
                     let it = &self.item_tree[id];
-
-                    if let Some(name) = &it.name {
-                        def = Some(DefData {
-                            id: ConstLoc {
-                                container: module.into(),
-                                id: ItemTreeId::new(self.file_id, id),
-                            }
-                            .intern(self.def_collector.db)
-                            .into(),
-                            name,
-                            visibility: &self.item_tree[it.visibility],
-                            has_constructor: false,
-                        });
+                    let const_id = ConstLoc {
+                        container: module.into(),
+                        id: ItemTreeId::new(self.file_id, id),
+                    }
+                    .intern(self.def_collector.db);
+
+                    match &it.name {
+                        Some(name) => {
+                            def = Some(DefData {
+                                id: const_id.into(),
+                                name,
+                                visibility: &self.item_tree[it.visibility],
+                                has_constructor: false,
+                            });
+                        }
+                        None => {
+                            // const _: T = ...;
+                            self.def_collector.def_map.modules[self.module_id]
+                                .scope
+                                .define_unnamed_const(const_id);
+                        }
                     }
                 }
                 ModItem::Static(id) => {
@@ -1366,7 +1374,7 @@ impl ModCollector<'_, '_> {
                         self.def_collector.unexpanded_macros.push(MacroDirective {
                             module_id: self.module_id,
                             depth: self.macro_depth + 1,
-                            kind: MacroDirectiveKind::Derive { ast_id },
+                            kind: MacroDirectiveKind::Derive { ast_id, derive_attr: derive.id },
                         });
                     }
                 }
@@ -1518,12 +1526,12 @@ impl ModCollector<'_, '_> {
                 // Built-in macro failed eager expansion.
                 self.def_collector.def_map.diagnostics.push(DefDiagnostic::macro_error(
                     self.module_id,
-                    MacroCallKind::FnLike(ast_id.ast_id),
+                    MacroCallKind::FnLike { ast_id: ast_id.ast_id },
                     error.unwrap().to_string(),
                 ));
                 return;
             }
-            Err(UnresolvedMacro) => (),
+            Err(UnresolvedMacro { .. }) => (),
         }
 
         // Case 2: resolve in module scope, expand during name resolution.
@@ -1535,7 +1543,7 @@ impl ModCollector<'_, '_> {
         self.def_collector.unexpanded_macros.push(MacroDirective {
             module_id: self.module_id,
             depth: self.macro_depth + 1,
-            kind: MacroDirectiveKind::FnLike { ast_id, legacy: None },
+            kind: MacroDirectiveKind::FnLike { ast_id },
         });
     }
 
diff --git a/crates/hir_def/src/nameres/path_resolution.rs b/crates/hir_def/src/nameres/path_resolution.rs
index 60471937c..c984148c3 100644
--- a/crates/hir_def/src/nameres/path_resolution.rs
+++ b/crates/hir_def/src/nameres/path_resolution.rs
@@ -60,12 +60,26 @@ impl ResolvePathResult {
 }
 
 impl DefMap {
-    pub(super) fn resolve_name_in_extern_prelude(&self, name: &Name) -> PerNs {
+    pub(super) fn resolve_name_in_extern_prelude(
+        &self,
+        db: &dyn DefDatabase,
+        name: &Name,
+    ) -> PerNs {
         if name == &name!(self) {
             cov_mark::hit!(extern_crate_self_as);
             return PerNs::types(self.module_id(self.root).into(), Visibility::Public);
         }
-        self.extern_prelude
+
+        let arc;
+        let root = match self.block {
+            Some(_) => {
+                arc = self.crate_root(db).def_map(db);
+                &*arc
+            }
+            None => self,
+        };
+
+        root.extern_prelude
             .get(name)
             .map_or(PerNs::none(), |&it| PerNs::types(it, Visibility::Public))
     }
@@ -191,7 +205,7 @@ impl DefMap {
                     None => return ResolvePathResult::empty(ReachedFixedPoint::Yes),
                 };
                 log::debug!("resolving {:?} in crate root (+ extern prelude)", segment);
-                self.resolve_name_in_crate_root_or_extern_prelude(&segment)
+                self.resolve_name_in_crate_root_or_extern_prelude(db, &segment)
             }
             PathKind::Plain => {
                 let (_, segment) = match segments.next() {
@@ -373,7 +387,13 @@ impl DefMap {
             .get_legacy_macro(name)
             .map_or_else(PerNs::none, |m| PerNs::macros(m, Visibility::Public));
         let from_scope = self[module].scope.get(name);
-        let from_builtin = BUILTIN_SCOPE.get(name).copied().unwrap_or_else(PerNs::none);
+        let from_builtin = match self.block {
+            Some(_) => {
+                // Only resolve to builtins in the root `DefMap`.
+                PerNs::none()
+            }
+            None => BUILTIN_SCOPE.get(name).copied().unwrap_or_else(PerNs::none),
+        };
         let from_scope_or_builtin = match shadow {
             BuiltinShadowMode::Module => from_scope.or(from_builtin),
             BuiltinShadowMode::Other => {
@@ -384,24 +404,31 @@ impl DefMap {
                 }
             }
         };
-        // Give precedence to names in outer `DefMap`s over the extern prelude; only check prelude
-        // from the crate DefMap.
-        let from_extern_prelude = match self.block {
-            Some(_) => PerNs::none(),
-            None => self
-                .extern_prelude
-                .get(name)
-                .map_or(PerNs::none(), |&it| PerNs::types(it, Visibility::Public)),
-        };
+        let from_extern_prelude = self
+            .extern_prelude
+            .get(name)
+            .map_or(PerNs::none(), |&it| PerNs::types(it, Visibility::Public));
 
         let from_prelude = self.resolve_in_prelude(db, name);
 
         from_legacy_macro.or(from_scope_or_builtin).or(from_extern_prelude).or(from_prelude)
     }
 
-    fn resolve_name_in_crate_root_or_extern_prelude(&self, name: &Name) -> PerNs {
-        let from_crate_root = self[self.root].scope.get(name);
-        let from_extern_prelude = self.resolve_name_in_extern_prelude(name);
+    fn resolve_name_in_crate_root_or_extern_prelude(
+        &self,
+        db: &dyn DefDatabase,
+        name: &Name,
+    ) -> PerNs {
+        let arc;
+        let crate_def_map = match self.block {
+            Some(_) => {
+                arc = self.crate_root(db).def_map(db);
+                &arc
+            }
+            None => self,
+        };
+        let from_crate_root = crate_def_map[crate_def_map.root].scope.get(name);
+        let from_extern_prelude = self.resolve_name_in_extern_prelude(db, name);
 
         from_crate_root.or(from_extern_prelude)
     }
diff --git a/crates/hir_def/src/nameres/tests/diagnostics.rs b/crates/hir_def/src/nameres/tests/diagnostics.rs
index fefdadb22..543975e07 100644
--- a/crates/hir_def/src/nameres/tests/diagnostics.rs
+++ b/crates/hir_def/src/nameres/tests/diagnostics.rs
@@ -170,7 +170,7 @@ fn unresolved_legacy_scope_macro() {
 
           m!();
           m2!();
-        //^^^^^^ unresolved macro call
+        //^^^^^^ unresolved macro `self::m2!`
         "#,
     );
 }
@@ -187,7 +187,7 @@ fn unresolved_module_scope_macro() {
 
           self::m!();
           self::m2!();
-        //^^^^^^^^^^^^ unresolved macro call
+        //^^^^^^^^^^^^ unresolved macro `self::m2!`
         "#,
     );
 }
@@ -233,7 +233,7 @@ fn good_out_dir_diagnostic() {
         macro_rules! concat { () => {} }
 
         include!(concat!(env!("OUT_DIR"), "/out.rs"));
-      //^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `OUT_DIR` not set, enable "load out dirs from check" to fix
+      //^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `OUT_DIR` not set, enable "run build scripts" to fix
         "#,
     );
 }
diff --git a/crates/hir_def/src/path.rs b/crates/hir_def/src/path.rs
index a3e83e2cf..509f77850 100644
--- a/crates/hir_def/src/path.rs
+++ b/crates/hir_def/src/path.rs
@@ -48,7 +48,8 @@ pub enum ImportAlias {
 
 impl ModPath {
     pub fn from_src(path: ast::Path, hygiene: &Hygiene) -> Option<ModPath> {
-        lower::lower_path(path, hygiene).map(|it| (*it.mod_path).clone())
+        let ctx = LowerCtx::with_hygiene(hygiene);
+        lower::lower_path(path, &ctx).map(|it| (*it.mod_path).clone())
     }
 
     pub fn from_segments(kind: PathKind, segments: impl IntoIterator<Item = Name>) -> ModPath {
@@ -122,7 +123,7 @@ impl ModPath {
 pub struct Path {
     /// Type based path like `<T>::foo`.
     /// Note that paths like `<Type as Trait>::foo` are desugard to `Trait::<Self=Type>::foo`.
-    type_anchor: Option<Box<TypeRef>>,
+    type_anchor: Option<Interned<TypeRef>>,
     mod_path: Interned<ModPath>,
     /// Invariant: the same len as `self.mod_path.segments`
     generic_args: Vec<Option<Arc<GenericArgs>>>,
@@ -167,8 +168,8 @@ pub enum GenericArg {
 impl Path {
     /// Converts an `ast::Path` to `Path`. Works with use trees.
     /// It correctly handles `$crate` based path from macro call.
-    pub fn from_src(path: ast::Path, hygiene: &Hygiene) -> Option<Path> {
-        lower::lower_path(path, hygiene)
+    pub fn from_src(path: ast::Path, ctx: &LowerCtx) -> Option<Path> {
+        lower::lower_path(path, ctx)
     }
 
     /// Converts a known mod path to `Path`.
@@ -289,6 +290,12 @@ impl From<Name> for Path {
     }
 }
 
+impl From<Name> for Box<Path> {
+    fn from(name: Name) -> Box<Path> {
+        Box::new(Path::from(name))
+    }
+}
+
 impl From<Name> for ModPath {
     fn from(name: Name) -> ModPath {
         ModPath::from_segments(PathKind::Plain, iter::once(name))
diff --git a/crates/hir_def/src/path/lower.rs b/crates/hir_def/src/path/lower.rs
index 28f6244da..1df6db525 100644
--- a/crates/hir_def/src/path/lower.rs
+++ b/crates/hir_def/src/path/lower.rs
@@ -6,10 +6,7 @@ use crate::intern::Interned;
 use std::sync::Arc;
 
 use either::Either;
-use hir_expand::{
-    hygiene::Hygiene,
-    name::{name, AsName},
-};
+use hir_expand::name::{name, AsName};
 use syntax::ast::{self, AstNode, TypeBoundsOwner};
 
 use super::AssociatedTypeBinding;
@@ -23,12 +20,12 @@ pub(super) use lower_use::lower_use_tree;
 
 /// Converts an `ast::Path` to `Path`. Works with use trees.
 /// It correctly handles `$crate` based path from macro call.
-pub(super) fn lower_path(mut path: ast::Path, hygiene: &Hygiene) -> Option<Path> {
+pub(super) fn lower_path(mut path: ast::Path, ctx: &LowerCtx) -> Option<Path> {
     let mut kind = PathKind::Plain;
     let mut type_anchor = None;
     let mut segments = Vec::new();
     let mut generic_args = Vec::new();
-    let ctx = LowerCtx::with_hygiene(hygiene);
+    let hygiene = ctx.hygiene();
     loop {
         let segment = path.segment()?;
 
@@ -43,10 +40,10 @@ pub(super) fn lower_path(mut path: ast::Path, hygiene: &Hygiene) -> Option<Path>
                     Either::Left(name) => {
                         let args = segment
                             .generic_arg_list()
-                            .and_then(|it| lower_generic_args(&ctx, it))
+                            .and_then(|it| lower_generic_args(ctx, it))
                             .or_else(|| {
                                 lower_generic_args_from_fn_path(
-                                    &ctx,
+                                    ctx,
                                     segment.param_list(),
                                     segment.ret_type(),
                                 )
@@ -64,17 +61,17 @@ pub(super) fn lower_path(mut path: ast::Path, hygiene: &Hygiene) -> Option<Path>
             ast::PathSegmentKind::Type { type_ref, trait_ref } => {
                 assert!(path.qualifier().is_none()); // this can only occur at the first segment
 
-                let self_type = TypeRef::from_ast(&ctx, type_ref?);
+                let self_type = TypeRef::from_ast(ctx, type_ref?);
 
                 match trait_ref {
                     // <T>::foo
                     None => {
-                        type_anchor = Some(Box::new(self_type));
+                        type_anchor = Some(Interned::new(self_type));
                         kind = PathKind::Plain;
                     }
                     // <T as Trait<A>>::Foo desugars to Trait<Self=T, A>::Foo
                     Some(trait_ref) => {
-                        let path = Path::from_src(trait_ref.path()?, hygiene)?;
+                        let path = Path::from_src(trait_ref.path()?, ctx)?;
                         let mod_path = (*path.mod_path).clone();
                         let num_segments = path.mod_path.segments.len();
                         kind = mod_path.kind;
diff --git a/crates/hir_def/src/resolver.rs b/crates/hir_def/src/resolver.rs
index a73585ee7..0391cc49b 100644
--- a/crates/hir_def/src/resolver.rs
+++ b/crates/hir_def/src/resolver.rs
@@ -14,6 +14,7 @@ use crate::{
     db::DefDatabase,
     expr::{ExprId, LabelId, PatId},
     generics::GenericParams,
+    intern::Interned,
     item_scope::{BuiltinShadowMode, BUILTIN_SCOPE},
     nameres::DefMap,
     path::{ModPath, PathKind},
@@ -50,7 +51,7 @@ enum Scope {
     /// All the items and imported names of a module
     ModuleScope(ModuleItemMap),
     /// Brings the generic parameters of an item into scope
-    GenericParams { def: GenericDefId, params: Arc<GenericParams> },
+    GenericParams { def: GenericDefId, params: Interned<GenericParams> },
     /// Brings `Self` in `impl` block into scope
     ImplDefScope(ImplId),
     /// Brings `Self` in enum, struct and union definitions into scope
diff --git a/crates/hir_def/src/test_db.rs b/crates/hir_def/src/test_db.rs
index dd36106f8..8fa703a57 100644
--- a/crates/hir_def/src/test_db.rs
+++ b/crates/hir_def/src/test_db.rs
@@ -15,7 +15,12 @@ use rustc_hash::FxHashSet;
 use syntax::{algo, ast, AstNode, TextRange, TextSize};
 use test_utils::extract_annotations;
 
-use crate::{db::DefDatabase, nameres::DefMap, src::HasSource, Lookup, ModuleDefId, ModuleId};
+use crate::{
+    db::DefDatabase,
+    nameres::{DefMap, ModuleSource},
+    src::HasSource,
+    LocalModuleId, Lookup, ModuleDefId, ModuleId,
+};
 
 #[salsa::database(
     base_db::SourceDatabaseExtStorage,
@@ -87,10 +92,11 @@ impl TestDB {
     pub(crate) fn module_at_position(&self, position: FilePosition) -> ModuleId {
         let file_module = self.module_for_file(position.file_id);
         let mut def_map = file_module.def_map(self);
+        let module = self.mod_at_position(&def_map, position);
 
         def_map = match self.block_at_position(&def_map, position) {
             Some(it) => it,
-            None => return file_module,
+            None => return def_map.module_id(module),
         };
         loop {
             let new_map = self.block_at_position(&def_map, position);
@@ -106,6 +112,47 @@ impl TestDB {
         }
     }
 
+    /// Finds the smallest/innermost module in `def_map` containing `position`.
+    fn mod_at_position(&self, def_map: &DefMap, position: FilePosition) -> LocalModuleId {
+        let mut size = None;
+        let mut res = def_map.root();
+        for (module, data) in def_map.modules() {
+            let src = data.definition_source(self);
+            if src.file_id != position.file_id.into() {
+                continue;
+            }
+
+            let range = match src.value {
+                ModuleSource::SourceFile(it) => it.syntax().text_range(),
+                ModuleSource::Module(it) => it.syntax().text_range(),
+                ModuleSource::BlockExpr(it) => it.syntax().text_range(),
+            };
+
+            if !range.contains(position.offset) {
+                continue;
+            }
+
+            let new_size = match size {
+                None => range.len(),
+                Some(size) => {
+                    if range.len() < size {
+                        range.len()
+                    } else {
+                        size
+                    }
+                }
+            };
+
+            if size != Some(new_size) {
+                cov_mark::hit!(submodule_in_testdb);
+                size = Some(new_size);
+                res = module;
+            }
+        }
+
+        res
+    }
+
     fn block_at_position(&self, def_map: &DefMap, position: FilePosition) -> Option<Arc<DefMap>> {
         // Find the smallest (innermost) function in `def_map` containing the cursor.
         let mut size = None;
diff --git a/crates/hir_def/src/type_ref.rs b/crates/hir_def/src/type_ref.rs
index 4c24aae94..ea29da5da 100644
--- a/crates/hir_def/src/type_ref.rs
+++ b/crates/hir_def/src/type_ref.rs
@@ -1,6 +1,7 @@
 //! HIR for references to types. Paths in these are not yet resolved. They can
 //! be directly created from an ast::TypeRef, without further queries.
-use hir_expand::name::Name;
+
+use hir_expand::{name::Name, AstId, InFile};
 use syntax::ast;
 
 use crate::{body::LowerCtx, path::Path};
@@ -68,6 +69,7 @@ impl TraitRef {
         }
     }
 }
+
 /// Compare ty::Ty
 #[derive(Clone, PartialEq, Eq, Hash, Debug)]
 pub enum TypeRef {
@@ -84,6 +86,7 @@ pub enum TypeRef {
     // For
     ImplTrait(Vec<TypeBound>),
     DynTrait(Vec<TypeBound>),
+    Macro(AstId<ast::MacroCall>),
     Error,
 }
 
@@ -116,7 +119,7 @@ pub enum TypeBound {
 
 impl TypeRef {
     /// Converts an `ast::TypeRef` to a `hir::TypeRef`.
-    pub(crate) fn from_ast(ctx: &LowerCtx, node: ast::Type) -> Self {
+    pub fn from_ast(ctx: &LowerCtx, node: ast::Type) -> Self {
         match node {
             ast::Type::ParenType(inner) => TypeRef::from_ast_opt(&ctx, inner.ty()),
             ast::Type::TupleType(inner) => {
@@ -176,8 +179,13 @@ impl TypeRef {
             ast::Type::DynTraitType(inner) => {
                 TypeRef::DynTrait(type_bounds_from_ast(ctx, inner.type_bound_list()))
             }
-            // FIXME: Macros in type position are not yet supported.
-            ast::Type::MacroType(_) => TypeRef::Error,
+            ast::Type::MacroType(mt) => match mt.macro_call() {
+                Some(mc) => ctx
+                    .ast_id(&mc)
+                    .map(|mc| TypeRef::Macro(InFile::new(ctx.file_id(), mc)))
+                    .unwrap_or(TypeRef::Error),
+                None => TypeRef::Error,
+            },
         }
     }
 
@@ -215,7 +223,7 @@ impl TypeRef {
                     }
                 }
                 TypeRef::Path(path) => go_path(path, f),
-                TypeRef::Never | TypeRef::Placeholder | TypeRef::Error => {}
+                TypeRef::Never | TypeRef::Placeholder | TypeRef::Macro(_) | TypeRef::Error => {}
             };
         }
 
diff --git a/crates/hir_def/src/visibility.rs b/crates/hir_def/src/visibility.rs
index 7d00a37c4..d4b7c9970 100644
--- a/crates/hir_def/src/visibility.rs
+++ b/crates/hir_def/src/visibility.rs
@@ -11,7 +11,7 @@ use crate::{
     nameres::DefMap,
     path::{ModPath, PathKind},
     resolver::HasResolver,
-    FunctionId, HasModule, LocalFieldId, ModuleDefId, ModuleId, VariantId,
+    FunctionId, HasModule, LocalFieldId, ModuleId, VariantId,
 };
 
 /// Visibility of an item, not yet resolved.
@@ -25,7 +25,7 @@ pub enum RawVisibility {
 }
 
 impl RawVisibility {
-    pub(crate) const fn private() -> RawVisibility {
+    pub(crate) fn private() -> RawVisibility {
         RawVisibility::Module(ModPath::from_kind(PathKind::Super(0)))
     }
 
@@ -123,11 +123,19 @@ impl Visibility {
         def_map: &DefMap,
         mut from_module: crate::LocalModuleId,
     ) -> bool {
-        let to_module = match self {
+        let mut to_module = match self {
             Visibility::Module(m) => m,
             Visibility::Public => return true,
         };
 
+        // `to_module` might be the root module of a block expression. Those have the same
+        // visibility as the containing module (even though no items are directly nameable from
+        // there, getting this right is important for method resolution).
+        // In that case, we adjust the visibility of `to_module` to point to the containing module.
+        if to_module.is_block_root(db) {
+            to_module = to_module.containing_module(db).unwrap();
+        }
+
         // from_module needs to be a descendant of to_module
         let mut def_map = def_map;
         let mut parent_arc;
@@ -217,6 +225,6 @@ pub(crate) fn field_visibilities_query(
 
 /// Resolve visibility of a function.
 pub(crate) fn function_visibility_query(db: &dyn DefDatabase, def: FunctionId) -> Visibility {
-    let resolver = ModuleDefId::from(def).module(db).unwrap().resolver(db);
+    let resolver = def.resolver(db);
     db.function_data(def).visibility.resolve(db, &resolver)
 }