14 files changed, 256 insertions, 93 deletions

diff --git a/crates/hir_def/src/attr.rs b/crates/hir_def/src/attr.rs
index a2479016e..aadd4e44a 100644
--- a/crates/hir_def/src/attr.rs
+++ b/crates/hir_def/src/attr.rs
@@ -9,7 +9,7 @@ use std::{
 use base_db::CrateId;
 use cfg::{CfgExpr, CfgOptions};
 use either::Either;
-use hir_expand::{hygiene::Hygiene, name::AsName, AstId, AttrId, InFile};
+use hir_expand::{hygiene::Hygiene, name::AsName, AstId, InFile};
 use itertools::Itertools;
 use la_arena::ArenaMap;
 use mbe::ast_to_token_tree;
@@ -101,17 +101,13 @@ impl RawAttrs {
         hygiene: &Hygiene,
     ) -> Self {
         let entries = collect_attrs(owner)
-            .enumerate()
-            .flat_map(|(i, attr)| {
-                let index = AttrId(i as u32);
-                match attr {
-                    Either::Left(attr) => Attr::from_src(db, 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))),
-                    }),
-                }
+            .flat_map(|(id, attr)| match attr {
+                Either::Left(attr) => Attr::from_src(db, attr, hygiene, id),
+                Either::Right(comment) => comment.doc_comment().map(|doc| Attr {
+                    id,
+                    input: Some(AttrInput::Literal(SmolStr::new(doc))),
+                    path: Interned::new(ModPath::from(hir_expand::name!(doc))),
+                }),
             })
             .collect::<Arc<_>>();
 
@@ -124,6 +120,7 @@ impl RawAttrs {
     }
 
     pub(crate) fn merge(&self, other: Self) -> Self {
+        // FIXME: This needs to fixup `AttrId`s
         match (&self.entries, &other.entries) {
             (None, None) => Self::EMPTY,
             (Some(entries), None) | (None, Some(entries)) => {
@@ -375,39 +372,26 @@ impl AttrsWithOwner {
 
                 let def_map = module.def_map(db);
                 let mod_data = &def_map[module.local_id];
-                let attrs = match mod_data.declaration_source(db) {
+                match mod_data.declaration_source(db) {
                     Some(it) => {
-                        let mut attrs: Vec<_> = collect_attrs(&it.value as &dyn ast::AttrsOwner)
-                            .map(|attr| InFile::new(it.file_id, attr))
-                            .collect();
+                        let mut map = AttrSourceMap::new(InFile::new(it.file_id, &it.value));
                         if let InFile { file_id, value: ModuleSource::SourceFile(file) } =
                             mod_data.definition_source(db)
                         {
-                            attrs.extend(
-                                collect_attrs(&file as &dyn ast::AttrsOwner)
-                                    .map(|attr| InFile::new(file_id, attr)),
-                            )
+                            map.merge(AttrSourceMap::new(InFile::new(file_id, &file)));
                         }
-                        attrs
+                        return map;
                     }
                     None => {
                         let InFile { file_id, value } = mod_data.definition_source(db);
-                        match &value {
-                            ModuleSource::SourceFile(file) => {
-                                collect_attrs(file as &dyn ast::AttrsOwner)
-                            }
-                            ModuleSource::Module(module) => {
-                                collect_attrs(module as &dyn ast::AttrsOwner)
-                            }
-                            ModuleSource::BlockExpr(block) => {
-                                collect_attrs(block as &dyn ast::AttrsOwner)
-                            }
-                        }
-                        .map(|attr| InFile::new(file_id, attr))
-                        .collect()
+                        let attrs_owner = match &value {
+                            ModuleSource::SourceFile(file) => file as &dyn ast::AttrsOwner,
+                            ModuleSource::Module(module) => module as &dyn ast::AttrsOwner,
+                            ModuleSource::BlockExpr(block) => block as &dyn ast::AttrsOwner,
+                        };
+                        return AttrSourceMap::new(InFile::new(file_id, attrs_owner));
                     }
-                };
-                return AttrSourceMap { attrs };
+                }
             }
             AttrDefId::FieldId(id) => {
                 let map = db.fields_attrs_source_map(id.parent);
@@ -462,11 +446,7 @@ impl AttrsWithOwner {
             },
         };
 
-        AttrSourceMap {
-            attrs: collect_attrs(&owner.value)
-                .map(|attr| InFile::new(owner.file_id, attr))
-                .collect(),
-        }
+        AttrSourceMap::new(owner.as_ref().map(|node| node as &dyn AttrsOwner))
     }
 
     pub fn docs_with_rangemap(
@@ -518,7 +498,7 @@ impl AttrsWithOwner {
         if buf.is_empty() {
             None
         } else {
-            Some((Documentation(buf), DocsRangeMap { mapping, source: self.source_map(db).attrs }))
+            Some((Documentation(buf), DocsRangeMap { mapping, source_map: self.source_map(db) }))
         }
     }
 }
@@ -559,27 +539,59 @@ fn inner_attributes(
 }
 
 pub struct AttrSourceMap {
-    attrs: Vec<InFile<Either<ast::Attr, ast::Comment>>>,
+    attrs: Vec<InFile<ast::Attr>>,
+    doc_comments: Vec<InFile<ast::Comment>>,
 }
 
 impl AttrSourceMap {
+    fn new(owner: InFile<&dyn ast::AttrsOwner>) -> Self {
+        let mut attrs = Vec::new();
+        let mut doc_comments = Vec::new();
+        for (_, attr) in collect_attrs(owner.value) {
+            match attr {
+                Either::Left(attr) => attrs.push(owner.with_value(attr)),
+                Either::Right(comment) => doc_comments.push(owner.with_value(comment)),
+            }
+        }
+
+        Self { attrs, doc_comments }
+    }
+
+    fn merge(&mut self, other: Self) {
+        self.attrs.extend(other.attrs);
+        self.doc_comments.extend(other.doc_comments);
+    }
+
     /// Maps the lowered `Attr` back to its original syntax node.
     ///
     /// `attr` must come from the `owner` used for AttrSourceMap
     ///
     /// Note that the returned syntax node might be a `#[cfg_attr]`, or a doc comment, instead of
     /// the attribute represented by `Attr`.
-    pub fn source_of(&self, attr: &Attr) -> InFile<&Either<ast::Attr, ast::Comment>> {
-        self.attrs
-            .get(attr.id.0 as usize)
-            .unwrap_or_else(|| panic!("cannot find `Attr` at index {:?}", attr.id))
-            .as_ref()
+    pub fn source_of(&self, attr: &Attr) -> InFile<Either<ast::Attr, ast::Comment>> {
+        self.source_of_id(attr.id)
+    }
+
+    fn source_of_id(&self, id: AttrId) -> InFile<Either<ast::Attr, ast::Comment>> {
+        if id.is_doc_comment {
+            self.doc_comments
+                .get(id.ast_index as usize)
+                .unwrap_or_else(|| panic!("cannot find doc comment at index {:?}", id))
+                .clone()
+                .map(|attr| Either::Right(attr))
+        } else {
+            self.attrs
+                .get(id.ast_index as usize)
+                .unwrap_or_else(|| panic!("cannot find `Attr` at index {:?}", id))
+                .clone()
+                .map(|attr| Either::Left(attr))
+        }
     }
 }
 
 /// 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>>>,
+    source_map: AttrSourceMap,
     // (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
@@ -596,7 +608,7 @@ impl DocsRangeMap {
 
         let relative_range = range - line_docs_range.start();
 
-        let &InFile { file_id, value: ref source } = &self.source[idx.0 as usize];
+        let &InFile { file_id, value: ref source } = &self.source_map.source_of_id(idx);
         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
@@ -615,6 +627,12 @@ impl DocsRangeMap {
     }
 }
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub(crate) struct AttrId {
+    is_doc_comment: bool,
+    pub(crate) ast_index: u32,
+}
+
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct Attr {
     pub(crate) id: AttrId,
@@ -749,22 +767,32 @@ fn attrs_from_item_tree<N: ItemTreeNode>(id: ItemTreeId<N>, db: &dyn DefDatabase
 
 fn collect_attrs(
     owner: &dyn ast::AttrsOwner,
-) -> impl Iterator<Item = Either<ast::Attr, ast::Comment>> {
+) -> impl Iterator<Item = (AttrId, Either<ast::Attr, ast::Comment>)> {
     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.kind().is_outer());
-    let attrs = outer_attrs
-        .chain(inner_attrs.into_iter().flatten())
-        .map(|attr| (attr.syntax().text_range().start(), Either::Left(attr)));
+    let attrs =
+        outer_attrs.chain(inner_attrs.into_iter().flatten()).enumerate().map(|(idx, attr)| {
+            (
+                AttrId { ast_index: idx as u32, is_doc_comment: false },
+                attr.syntax().text_range().start(),
+                Either::Left(attr),
+            )
+        });
 
     let outer_docs =
         ast::CommentIter::from_syntax_node(owner.syntax()).filter(ast::Comment::is_outer);
-    let docs = outer_docs
-        .chain(inner_docs.into_iter().flatten())
-        .map(|docs_text| (docs_text.syntax().text_range().start(), Either::Right(docs_text)));
+    let docs =
+        outer_docs.chain(inner_docs.into_iter().flatten()).enumerate().map(|(idx, docs_text)| {
+            (
+                AttrId { ast_index: idx as u32, is_doc_comment: true },
+                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
-    docs.chain(attrs).sorted_by_key(|&(offset, _)| offset).map(|(_, attr)| attr)
+    docs.chain(attrs).sorted_by_key(|&(_, offset, _)| offset).map(|(id, _, attr)| (id, attr))
 }
 
 pub(crate) fn variants_attrs_source_map(
diff --git a/crates/hir_def/src/body.rs b/crates/hir_def/src/body.rs
index 8360426f1..98b485b60 100644
--- a/crates/hir_def/src/body.rs
+++ b/crates/hir_def/src/body.rs
@@ -21,8 +21,6 @@ use profile::Count;
 use rustc_hash::FxHashMap;
 use syntax::{ast, AstNode, AstPtr};
 
-pub use lower::LowerCtx;
-
 use crate::{
     attr::{Attrs, RawAttrs},
     db::DefDatabase,
@@ -35,6 +33,8 @@ use crate::{
     UnresolvedMacro,
 };
 
+pub use lower::LowerCtx;
+
 /// 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)]
diff --git a/crates/hir_def/src/body/lower.rs b/crates/hir_def/src/body/lower.rs
index 75dc19c11..2a7e0205f 100644
--- a/crates/hir_def/src/body/lower.rs
+++ b/crates/hir_def/src/body/lower.rs
@@ -205,7 +205,7 @@ impl ExprCollector<'_> {
         self.maybe_collect_expr(expr).unwrap_or_else(|| self.missing_expr())
     }
 
-    /// Returns `None` if the expression is `#[cfg]`d out.
+    /// Returns `None` if and only if the expression is `#[cfg]`d out.
     fn maybe_collect_expr(&mut self, expr: ast::Expr) -> Option<ExprId> {
         let syntax_ptr = AstPtr::new(&expr);
         self.check_cfg(&expr)?;
@@ -668,7 +668,7 @@ impl ExprCollector<'_> {
                 if self.check_cfg(&stmt).is_none() {
                     return;
                 }
-
+                let has_semi = stmt.semicolon_token().is_some();
                 // Note that macro could be expended to multiple statements
                 if let Some(ast::Expr::MacroCall(m)) = stmt.expr() {
                     let macro_ptr = AstPtr::new(&m);
@@ -685,18 +685,19 @@ impl ExprCollector<'_> {
                                 statements.statements().for_each(|stmt| this.collect_stmt(stmt));
                                 if let Some(expr) = statements.expr() {
                                     let expr = this.collect_expr(expr);
-                                    this.statements_in_scope.push(Statement::Expr(expr));
+                                    this.statements_in_scope
+                                        .push(Statement::Expr { expr, has_semi });
                                 }
                             }
                             None => {
                                 let expr = this.alloc_expr(Expr::Missing, syntax_ptr.clone());
-                                this.statements_in_scope.push(Statement::Expr(expr));
+                                this.statements_in_scope.push(Statement::Expr { expr, has_semi });
                             }
                         },
                     );
                 } else {
                     let expr = self.collect_expr_opt(stmt.expr());
-                    self.statements_in_scope.push(Statement::Expr(expr));
+                    self.statements_in_scope.push(Statement::Expr { expr, has_semi });
                 }
             }
             ast::Stmt::Item(item) => {
@@ -725,8 +726,17 @@ impl ExprCollector<'_> {
         let prev_statements = std::mem::take(&mut self.statements_in_scope);
 
         block.statements().for_each(|s| self.collect_stmt(s));
-
-        let tail = block.tail_expr().map(|e| self.collect_expr(e));
+        block.tail_expr().and_then(|e| {
+            let expr = self.maybe_collect_expr(e)?;
+            Some(self.statements_in_scope.push(Statement::Expr { expr, has_semi: false }))
+        });
+
+        let mut tail = None;
+        if let Some(Statement::Expr { expr, has_semi: false }) = self.statements_in_scope.last() {
+            tail = Some(*expr);
+            self.statements_in_scope.pop();
+        }
+        let tail = tail;
         let statements = std::mem::replace(&mut self.statements_in_scope, prev_statements);
         let syntax_node_ptr = AstPtr::new(&block.into());
         let expr_id = self.alloc_expr(
@@ -996,23 +1006,27 @@ impl From<ast::BinOp> for BinaryOp {
 impl From<ast::LiteralKind> for Literal {
     fn from(ast_lit_kind: ast::LiteralKind) -> Self {
         match ast_lit_kind {
+            // FIXME: these should have actual values filled in, but unsure on perf impact
             LiteralKind::IntNumber(lit) => {
                 if let builtin @ Some(_) = lit.suffix().and_then(BuiltinFloat::from_suffix) {
                     return Literal::Float(Default::default(), builtin);
                 } else if let builtin @ Some(_) =
                     lit.suffix().and_then(|it| BuiltinInt::from_suffix(&it))
                 {
-                    Literal::Int(Default::default(), builtin)
+                    Literal::Int(lit.value().unwrap_or(0) as i128, builtin)
                 } else {
                     let builtin = lit.suffix().and_then(|it| BuiltinUint::from_suffix(&it));
-                    Literal::Uint(Default::default(), builtin)
+                    Literal::Uint(lit.value().unwrap_or(0), builtin)
                 }
             }
             LiteralKind::FloatNumber(lit) => {
                 let ty = lit.suffix().and_then(|it| BuiltinFloat::from_suffix(&it));
                 Literal::Float(Default::default(), ty)
             }
-            LiteralKind::ByteString(_) => Literal::ByteString(Default::default()),
+            LiteralKind::ByteString(bs) => {
+                let text = bs.value().map(Vec::from).unwrap_or_else(Default::default);
+                Literal::ByteString(text)
+            }
             LiteralKind::String(_) => Literal::String(Default::default()),
             LiteralKind::Byte => Literal::Uint(Default::default(), Some(BuiltinUint::U8)),
             LiteralKind::Bool(val) => Literal::Bool(val),
diff --git a/crates/hir_def/src/body/scope.rs b/crates/hir_def/src/body/scope.rs
index bd7005ca6..6764de3a7 100644
--- a/crates/hir_def/src/body/scope.rs
+++ b/crates/hir_def/src/body/scope.rs
@@ -157,7 +157,7 @@ fn compute_block_scopes(
                 scope = scopes.new_scope(scope);
                 scopes.add_bindings(body, scope, *pat);
             }
-            Statement::Expr(expr) => {
+            Statement::Expr { expr, .. } => {
                 scopes.set_scope(*expr, scope);
                 compute_expr_scopes(*expr, body, scopes, scope);
             }
diff --git a/crates/hir_def/src/expr.rs b/crates/hir_def/src/expr.rs
index b4ad984bd..2ba619d23 100644
--- a/crates/hir_def/src/expr.rs
+++ b/crates/hir_def/src/expr.rs
@@ -43,8 +43,8 @@ pub enum Literal {
     ByteString(Vec<u8>),
     Char(char),
     Bool(bool),
-    Int(u64, Option<BuiltinInt>),
-    Uint(u64, Option<BuiltinUint>),
+    Int(i128, Option<BuiltinInt>),
+    Uint(u128, Option<BuiltinUint>),
     Float(u64, Option<BuiltinFloat>), // FIXME: f64 is not Eq
 }
 
@@ -242,7 +242,7 @@ pub struct RecordLitField {
 #[derive(Debug, Clone, Eq, PartialEq)]
 pub enum Statement {
     Let { pat: PatId, type_ref: Option<Interned<TypeRef>>, initializer: Option<ExprId> },
-    Expr(ExprId),
+    Expr { expr: ExprId, has_semi: bool },
 }
 
 impl Expr {
@@ -265,7 +265,7 @@ impl Expr {
                                 f(*expr);
                             }
                         }
-                        Statement::Expr(e) => f(*e),
+                        Statement::Expr { expr: expression, .. } => f(*expression),
                     }
                 }
                 if let Some(expr) = tail {
diff --git a/crates/hir_def/src/find_path.rs b/crates/hir_def/src/find_path.rs
index 858e88038..ee52794aa 100644
--- a/crates/hir_def/src/find_path.rs
+++ b/crates/hir_def/src/find_path.rs
@@ -5,10 +5,10 @@ use std::iter;
 use hir_expand::name::{known, AsName, Name};
 use rustc_hash::FxHashSet;
 
-use crate::nameres::DefMap;
 use crate::{
     db::DefDatabase,
     item_scope::ItemInNs,
+    nameres::DefMap,
     path::{ModPath, PathKind},
     visibility::Visibility,
     ModuleDefId, ModuleId,
@@ -134,7 +134,16 @@ fn find_path_inner(
     for (name, def_id) in root_def_map.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]));
+
+            let name_already_occupied_in_type_ns = def_map
+                .with_ancestor_maps(db, from.local_id, &mut |def_map, local_id| {
+                    def_map[local_id].scope.get(&name).take_types().filter(|&id| id != *def_id)
+                })
+                .is_some();
+            return Some(ModPath::from_segments(
+                if name_already_occupied_in_type_ns { PathKind::Abs } else { PathKind::Plain },
+                vec![name],
+            ));
         }
     }
 
diff --git a/crates/hir_def/src/item_tree.rs b/crates/hir_def/src/item_tree.rs
index 8d13c7e04..cad8a7479 100644
--- a/crates/hir_def/src/item_tree.rs
+++ b/crates/hir_def/src/item_tree.rs
@@ -18,7 +18,7 @@ use hir_expand::{
     ast_id_map::FileAstId,
     hygiene::Hygiene,
     name::{name, AsName, Name},
-    HirFileId, InFile,
+    FragmentKind, HirFileId, InFile,
 };
 use la_arena::{Arena, Idx, RawIdx};
 use profile::Count;
@@ -656,6 +656,7 @@ pub struct MacroCall {
     /// Path to the called macro.
     pub path: Interned<ModPath>,
     pub ast_id: FileAstId<ast::MacroCall>,
+    pub fragment: FragmentKind,
 }
 
 #[derive(Debug, Clone, Eq, PartialEq)]
diff --git a/crates/hir_def/src/item_tree/lower.rs b/crates/hir_def/src/item_tree/lower.rs
index 5743b3386..fe348091d 100644
--- a/crates/hir_def/src/item_tree/lower.rs
+++ b/crates/hir_def/src/item_tree/lower.rs
@@ -624,7 +624,8 @@ impl<'a> Ctx<'a> {
     fn lower_macro_call(&mut self, m: &ast::MacroCall) -> Option<FileItemTreeId<MacroCall>> {
         let path = Interned::new(ModPath::from_src(self.db, m.path()?, &self.hygiene)?);
         let ast_id = self.source_ast_id_map.ast_id(m);
-        let res = MacroCall { path, ast_id };
+        let fragment = hir_expand::to_fragment_kind(m);
+        let res = MacroCall { path, ast_id, fragment };
         Some(id(self.data().macro_calls.alloc(res)))
     }
 
diff --git a/crates/hir_def/src/lib.rs b/crates/hir_def/src/lib.rs
index da46f16f7..a82ea5957 100644
--- a/crates/hir_def/src/lib.rs
+++ b/crates/hir_def/src/lib.rs
@@ -62,13 +62,14 @@ use hir_expand::{
     ast_id_map::FileAstId,
     eager::{expand_eager_macro, ErrorEmitted, ErrorSink},
     hygiene::Hygiene,
-    AstId, AttrId, HirFileId, InFile, MacroCallId, MacroCallKind, MacroDefId, MacroDefKind,
+    AstId, FragmentKind, HirFileId, InFile, MacroCallId, MacroCallKind, MacroDefId, MacroDefKind,
 };
 use la_arena::Idx;
 use nameres::DefMap;
 use path::ModPath;
 use syntax::ast;
 
+use crate::attr::AttrId;
 use crate::builtin_type::BuiltinType;
 use item_tree::{
     Const, Enum, Function, Impl, ItemTreeId, ItemTreeNode, ModItem, Static, Struct, Trait,
@@ -652,6 +653,7 @@ impl AsMacroCall for InFile<&ast::MacroCall> {
         resolver: impl Fn(path::ModPath) -> Option<MacroDefId>,
         mut error_sink: &mut dyn FnMut(mbe::ExpandError),
     ) -> Result<Result<MacroCallId, ErrorEmitted>, UnresolvedMacro> {
+        let fragment = hir_expand::to_fragment_kind(self.value);
         let ast_id = AstId::new(self.file_id, db.ast_id_map(self.file_id).ast_id(self.value));
         let h = Hygiene::new(db.upcast(), self.file_id);
         let path = self.value.path().and_then(|path| path::ModPath::from_src(db, path, &h));
@@ -667,6 +669,7 @@ impl AsMacroCall for InFile<&ast::MacroCall> {
 
         macro_call_as_call_id(
             &AstIdWithPath::new(ast_id.file_id, ast_id.value, path),
+            fragment,
             db,
             krate,
             resolver,
@@ -695,6 +698,7 @@ pub struct UnresolvedMacro {
 
 fn macro_call_as_call_id(
     call: &AstIdWithPath<ast::MacroCall>,
+    fragment: FragmentKind,
     db: &dyn db::DefDatabase,
     krate: CrateId,
     resolver: impl Fn(path::ModPath) -> Option<MacroDefId>,
@@ -718,7 +722,11 @@ fn macro_call_as_call_id(
         .map(MacroCallId::from)
     } else {
         Ok(def
-            .as_lazy_macro(db.upcast(), krate, MacroCallKind::FnLike { ast_id: call.ast_id })
+            .as_lazy_macro(
+                db.upcast(),
+                krate,
+                MacroCallKind::FnLike { ast_id: call.ast_id, fragment },
+            )
             .into())
     };
     Ok(res)
@@ -745,7 +753,7 @@ fn derive_macro_as_call_id(
             MacroCallKind::Derive {
                 ast_id: item_attr.ast_id,
                 derive_name: last_segment.to_string(),
-                derive_attr,
+                derive_attr_index: derive_attr.ast_index,
             },
         )
         .into();
diff --git a/crates/hir_def/src/nameres.rs b/crates/hir_def/src/nameres.rs
index 1bc72ec1f..249af6fc8 100644
--- a/crates/hir_def/src/nameres.rs
+++ b/crates/hir_def/src/nameres.rs
@@ -629,7 +629,7 @@ mod diagnostics {
                 DiagnosticKind::UnresolvedProcMacro { ast } => {
                     let mut precise_location = None;
                     let (file, ast, name) = match ast {
-                        MacroCallKind::FnLike { ast_id } => {
+                        MacroCallKind::FnLike { ast_id, .. } => {
                             let node = ast_id.to_node(db.upcast());
                             (ast_id.file_id, SyntaxNodePtr::from(AstPtr::new(&node)), None)
                         }
diff --git a/crates/hir_def/src/nameres/collector.rs b/crates/hir_def/src/nameres/collector.rs
index 05ceb1efb..19db6cc59 100644
--- a/crates/hir_def/src/nameres/collector.rs
+++ b/crates/hir_def/src/nameres/collector.rs
@@ -13,14 +13,14 @@ use hir_expand::{
     builtin_macro::find_builtin_macro,
     name::{AsName, Name},
     proc_macro::ProcMacroExpander,
-    AttrId, HirFileId, MacroCallId, MacroCallKind, MacroDefId, MacroDefKind,
+    FragmentKind, HirFileId, MacroCallId, MacroCallKind, MacroDefId, MacroDefKind,
 };
 use hir_expand::{InFile, MacroCallLoc};
 use rustc_hash::{FxHashMap, FxHashSet};
 use syntax::ast;
 
 use crate::{
-    attr::Attrs,
+    attr::{AttrId, Attrs},
     db::DefDatabase,
     derive_macro_as_call_id,
     intern::Interned,
@@ -215,7 +215,7 @@ struct MacroDirective {
 
 #[derive(Clone, Debug, Eq, PartialEq)]
 enum MacroDirectiveKind {
-    FnLike { ast_id: AstIdWithPath<ast::MacroCall> },
+    FnLike { ast_id: AstIdWithPath<ast::MacroCall>, fragment: FragmentKind },
     Derive { ast_id: AstIdWithPath<ast::Item>, derive_attr: AttrId },
 }
 
@@ -481,6 +481,11 @@ impl DefCollector<'_> {
         let res = self.def_map.resolve_name_in_extern_prelude(self.db, &extern_crate.name);
 
         if let Some(ModuleDefId::ModuleId(m)) = res.take_types() {
+            if m == self.def_map.module_id(current_module_id) {
+                cov_mark::hit!(ignore_macro_use_extern_crate_self);
+                return;
+            }
+
             cov_mark::hit!(macro_rules_from_other_crates_are_visible_with_macro_use);
             self.import_all_macros_exported(current_module_id, m.krate);
         }
@@ -807,9 +812,10 @@ impl DefCollector<'_> {
         let mut res = ReachedFixedPoint::Yes;
         macros.retain(|directive| {
             match &directive.kind {
-                MacroDirectiveKind::FnLike { ast_id } => {
+                MacroDirectiveKind::FnLike { ast_id, fragment } => {
                     match macro_call_as_call_id(
                         ast_id,
+                        *fragment,
                         self.db,
                         self.def_map.krate,
                         |path| {
@@ -926,8 +932,9 @@ impl DefCollector<'_> {
 
         for directive in &self.unexpanded_macros {
             match &directive.kind {
-                MacroDirectiveKind::FnLike { ast_id, .. } => match macro_call_as_call_id(
+                MacroDirectiveKind::FnLike { ast_id, fragment } => match macro_call_as_call_id(
                     ast_id,
+                    *fragment,
                     self.db,
                     self.def_map.krate,
                     |path| {
@@ -1496,6 +1503,7 @@ impl ModCollector<'_, '_> {
         let mut error = None;
         match macro_call_as_call_id(
             &ast_id,
+            mac.fragment,
             self.def_collector.db,
             self.def_collector.def_map.krate,
             |path| {
@@ -1524,9 +1532,14 @@ impl ModCollector<'_, '_> {
             }
             Ok(Err(_)) => {
                 // Built-in macro failed eager expansion.
+
+                // FIXME: don't parse the file here
+                let fragment = hir_expand::to_fragment_kind(
+                    &ast_id.ast_id.to_node(self.def_collector.db.upcast()),
+                );
                 self.def_collector.def_map.diagnostics.push(DefDiagnostic::macro_error(
                     self.module_id,
-                    MacroCallKind::FnLike { ast_id: ast_id.ast_id },
+                    MacroCallKind::FnLike { ast_id: ast_id.ast_id, fragment },
                     error.unwrap().to_string(),
                 ));
                 return;
@@ -1543,7 +1556,7 @@ impl ModCollector<'_, '_> {
         self.def_collector.unexpanded_macros.push(MacroDirective {
             module_id: self.module_id,
             depth: self.macro_depth + 1,
-            kind: MacroDirectiveKind::FnLike { ast_id },
+            kind: MacroDirectiveKind::FnLike { ast_id, fragment: mac.fragment },
         });
     }
 
diff --git a/crates/hir_def/src/nameres/tests.rs b/crates/hir_def/src/nameres/tests.rs
index 4f2e7a2f9..9f652731d 100644
--- a/crates/hir_def/src/nameres/tests.rs
+++ b/crates/hir_def/src/nameres/tests.rs
@@ -411,6 +411,22 @@ struct Arc;
 }
 
 #[test]
+fn macro_use_extern_crate_self() {
+    cov_mark::check!(ignore_macro_use_extern_crate_self);
+    check(
+        r#"
+//- /main.rs crate:main
+#[macro_use]
+extern crate self as bla;
+"#,
+        expect![[r#"
+            crate
+            bla: t
+        "#]],
+    );
+}
+
+#[test]
 fn reexport_across_crates() {
     check(
         r#"
diff --git a/crates/hir_def/src/nameres/tests/incremental.rs b/crates/hir_def/src/nameres/tests/incremental.rs
index 227ecd162..d884a6eb4 100644
--- a/crates/hir_def/src/nameres/tests/incremental.rs
+++ b/crates/hir_def/src/nameres/tests/incremental.rs
@@ -137,6 +137,9 @@ m!(Z);
         });
         let n_recalculated_item_trees = events.iter().filter(|it| it.contains("item_tree")).count();
         assert_eq!(n_recalculated_item_trees, 6);
+        let n_reparsed_macros =
+            events.iter().filter(|it| it.contains("parse_macro_expansion")).count();
+        assert_eq!(n_reparsed_macros, 3);
     }
 
     let new_text = r#"
@@ -155,5 +158,8 @@ m!(Z);
         });
         let n_recalculated_item_trees = events.iter().filter(|it| it.contains("item_tree")).count();
         assert_eq!(n_recalculated_item_trees, 1);
+        let n_reparsed_macros =
+            events.iter().filter(|it| it.contains("parse_macro_expansion")).count();
+        assert_eq!(n_reparsed_macros, 0);
     }
 }
diff --git a/crates/hir_def/src/type_ref.rs b/crates/hir_def/src/type_ref.rs
index ea29da5da..9e44547cb 100644
--- a/crates/hir_def/src/type_ref.rs
+++ b/crates/hir_def/src/type_ref.rs
@@ -2,6 +2,7 @@
 //! be directly created from an ast::TypeRef, without further queries.
 
 use hir_expand::{name::Name, AstId, InFile};
+use std::convert::TryInto;
 use syntax::ast;
 
 use crate::{body::LowerCtx, path::Path};
@@ -79,7 +80,9 @@ pub enum TypeRef {
     Path(Path),
     RawPtr(Box<TypeRef>, Mutability),
     Reference(Box<TypeRef>, Option<LifetimeRef>, Mutability),
-    Array(Box<TypeRef> /*, Expr*/),
+    // FIXME: for full const generics, the latter element (length) here is going to have to be an
+    // expression that is further lowered later in hir_ty.
+    Array(Box<TypeRef>, ConstScalar),
     Slice(Box<TypeRef>),
     /// A fn pointer. Last element of the vector is the return type.
     Fn(Vec<TypeRef>, bool /*varargs*/),
@@ -140,7 +143,16 @@ impl TypeRef {
                 TypeRef::RawPtr(Box::new(inner_ty), mutability)
             }
             ast::Type::ArrayType(inner) => {
-                TypeRef::Array(Box::new(TypeRef::from_ast_opt(&ctx, inner.ty())))
+                // FIXME: This is a hack. We should probably reuse the machinery of
+                // `hir_def::body::lower` to lower this into an `Expr` and then evaluate it at the
+                // `hir_ty` level, which would allow knowing the type of:
+                // let v: [u8; 2 + 2] = [0u8; 4];
+                let len = inner
+                    .expr()
+                    .map(ConstScalar::usize_from_literal_expr)
+                    .unwrap_or(ConstScalar::Unknown);
+
+                TypeRef::Array(Box::new(TypeRef::from_ast_opt(&ctx, inner.ty())), len)
             }
             ast::Type::SliceType(inner) => {
                 TypeRef::Slice(Box::new(TypeRef::from_ast_opt(&ctx, inner.ty())))
@@ -212,7 +224,7 @@ impl TypeRef {
                 }
                 TypeRef::RawPtr(type_ref, _)
                 | TypeRef::Reference(type_ref, ..)
-                | TypeRef::Array(type_ref)
+                | TypeRef::Array(type_ref, _)
                 | TypeRef::Slice(type_ref) => go(&type_ref, f),
                 TypeRef::ImplTrait(bounds) | TypeRef::DynTrait(bounds) => {
                     for bound in bounds {
@@ -298,3 +310,58 @@ impl TypeBound {
         }
     }
 }
+
+/// A concrete constant value
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum ConstScalar {
+    // for now, we only support the trivial case of constant evaluating the length of an array
+    // Note that this is u64 because the target usize may be bigger than our usize
+    Usize(u64),
+
+    /// Case of an unknown value that rustc might know but we don't
+    // FIXME: this is a hack to get around chalk not being able to represent unevaluatable
+    // constants
+    // https://github.com/rust-analyzer/rust-analyzer/pull/8813#issuecomment-840679177
+    // https://rust-lang.zulipchat.com/#narrow/stream/144729-wg-traits/topic/Handling.20non.20evaluatable.20constants'.20equality/near/238386348
+    Unknown,
+}
+
+impl std::fmt::Display for ConstScalar {
+    fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
+        match self {
+            ConstScalar::Usize(us) => write!(fmt, "{}", us),
+            ConstScalar::Unknown => write!(fmt, "_"),
+        }
+    }
+}
+
+impl ConstScalar {
+    /// Gets a target usize out of the ConstScalar
+    pub fn as_usize(&self) -> Option<u64> {
+        match self {
+            &ConstScalar::Usize(us) => Some(us),
+            _ => None,
+        }
+    }
+
+    // FIXME: as per the comments on `TypeRef::Array`, this evaluation should not happen at this
+    // parse stage.
+    fn usize_from_literal_expr(expr: ast::Expr) -> ConstScalar {
+        match expr {
+            ast::Expr::Literal(lit) => {
+                let lkind = lit.kind();
+                match lkind {
+                    ast::LiteralKind::IntNumber(num)
+                        if num.suffix() == None || num.suffix() == Some("usize") =>
+                    {
+                        num.value().and_then(|v| v.try_into().ok())
+                    }
+                    _ => None,
+                }
+            }
+            _ => None,
+        }
+        .map(ConstScalar::Usize)
+        .unwrap_or(ConstScalar::Unknown)
+    }
+}