Auto merge of rust-lang#13174 - Veykril:resolver, r=Veykril

Lift out the module scope into a field in the Resolver

A Resolver *always* has a module scope at the end of its scope stack,
instead of encoding this as an invariant we can just lift this scope
out into a field, allowing us to skip going through the scope vec
indirection entirely.

Author: bors

crates/hir-def/src/body.rs

@@ -250,6 +250,10 @@ pub type PatSource = InFile<PatPtr>;
 
 pub type LabelPtr = AstPtr<ast::Label>;
 pub type LabelSource = InFile<LabelPtr>;
+
+pub type FieldPtr = AstPtr<ast::RecordExprField>;
+pub type FieldSource = InFile<FieldPtr>;
+
 /// An item body together with the mapping from syntax nodes to HIR expression
 /// IDs. This is needed to go from e.g. a position in a file to the HIR
 /// expression containing it; but for type inference etc., we want to operate on
@@ -274,8 +278,8 @@ pub struct BodySourceMap {
 
     /// We don't create explicit nodes for record fields (`S { record_field: 92 }`).
     /// Instead, we use id of expression (`92`) to identify the field.
-    field_map: FxHashMap<InFile<AstPtr<ast::RecordExprField>>, ExprId>,
-    field_map_back: FxHashMap<ExprId, InFile<AstPtr<ast::RecordExprField>>>,
+    field_map: FxHashMap<FieldSource, ExprId>,
+    field_map_back: FxHashMap<ExprId, FieldSource>,
 
     expansions: FxHashMap<InFile<AstPtr<ast::MacroCall>>, HirFileId>,
 
@@ -456,9 +460,10 @@ impl BodySourceMap {
         self.label_map.get(&src).cloned()
     }
 
-    pub fn field_syntax(&self, expr: ExprId) -> InFile<AstPtr<ast::RecordExprField>> {
+    pub fn field_syntax(&self, expr: ExprId) -> FieldSource {
         self.field_map_back[&expr].clone()
     }
+
     pub fn node_field(&self, node: InFile<&ast::RecordExprField>) -> Option<ExprId> {
         let src = node.map(AstPtr::new);
         self.field_map.get(&src).cloned()

crates/hir-def/src/body/lower.rs

@@ -24,7 +24,7 @@ use syntax::{
 
 use crate::{
     adt::StructKind,
-    body::{Body, BodySourceMap, Expander, LabelSource, PatPtr},
+    body::{Body, BodySourceMap, Expander, ExprPtr, LabelPtr, LabelSource, PatPtr},
     body::{BodyDiagnostic, ExprSource, PatSource},
     builtin_type::{BuiltinFloat, BuiltinInt, BuiltinUint},
     db::DefDatabase,
@@ -150,7 +150,7 @@ impl ExprCollector<'_> {
         LowerCtx::new(self.db, self.expander.current_file_id)
     }
 
-    fn alloc_expr(&mut self, expr: Expr, ptr: AstPtr<ast::Expr>) -> ExprId {
+    fn alloc_expr(&mut self, expr: Expr, ptr: ExprPtr) -> ExprId {
         let src = self.expander.to_source(ptr);
         let id = self.make_expr(expr, src.clone());
         self.source_map.expr_map.insert(src, id);
@@ -185,7 +185,7 @@ impl ExprCollector<'_> {
         id
     }
 
-    fn alloc_label(&mut self, label: Label, ptr: AstPtr<ast::Label>) -> LabelId {
+    fn alloc_label(&mut self, label: Label, ptr: LabelPtr) -> LabelId {
         let src = self.expander.to_source(ptr);
         let id = self.make_label(label, src.clone());
         self.source_map.label_map.insert(src, id);

crates/hir-def/src/body/scope.rs

@@ -47,16 +47,9 @@ pub struct ScopeData {
 impl ExprScopes {
     pub(crate) fn expr_scopes_query(db: &dyn DefDatabase, def: DefWithBodyId) -> Arc<ExprScopes> {
         let body = db.body(def);
-        Arc::new(ExprScopes::new(&*body))
-    }
-
-    fn new(body: &Body) -> ExprScopes {
-        let mut scopes =
-            ExprScopes { scopes: Arena::default(), scope_by_expr: FxHashMap::default() };
-        let mut root = scopes.root_scope();
-        scopes.add_params_bindings(body, root, &body.params);
-        compute_expr_scopes(body.body_expr, body, &mut scopes, &mut root);
-        scopes
+        let mut scopes = ExprScopes::new(&*body);
+        scopes.shrink_to_fit();
+        Arc::new(scopes)
     }
 
     pub fn entries(&self, scope: ScopeId) -> &[ScopeEntry] {
@@ -89,6 +82,17 @@ impl ExprScopes {
     pub fn scope_by_expr(&self) -> &FxHashMap<ExprId, ScopeId> {
         &self.scope_by_expr
     }
+}
+
+impl ExprScopes {
+    fn new(body: &Body) -> ExprScopes {
+        let mut scopes =
+            ExprScopes { scopes: Arena::default(), scope_by_expr: FxHashMap::default() };
+        let mut root = scopes.root_scope();
+        scopes.add_params_bindings(body, root, &body.params);
+        compute_expr_scopes(body.body_expr, body, &mut scopes, &mut root);
+        scopes
+    }
 
     fn root_scope(&mut self) -> ScopeId {
         self.scopes.alloc(ScopeData { parent: None, block: None, label: None, entries: vec![] })
@@ -138,6 +142,13 @@ impl ExprScopes {
     fn set_scope(&mut self, node: ExprId, scope: ScopeId) {
         self.scope_by_expr.insert(node, scope);
     }
+
+    fn shrink_to_fit(&mut self) {
+        let ExprScopes { scopes, scope_by_expr } = self;
+        scopes.shrink_to_fit();
+        scopes.values_mut().for_each(|it| it.entries.shrink_to_fit());
+        scope_by_expr.shrink_to_fit();
+    }
 }
 
 fn compute_block_scopes(