Put the expression stuff in the expression store behind an Option<Box>

And leave only the type stuff without it.

This is because most expression stores don't have anything but types (e.g. generics, fields, signatures) so this saves a lot of memory.

This saves 58mb on `analysis-stats .`.

crates/hir-def/src/expr_store.rs

@@ -22,6 +22,7 @@ use rustc_hash::FxHashMap;
 use smallvec::SmallVec;
 use span::{Edition, SyntaxContext};
 use syntax::{AstPtr, SyntaxNodePtr, ast};
+use thin_vec::ThinVec;
 use triomphe::Arc;
 use tt::TextRange;
 
@@ -93,17 +94,17 @@ pub type TypeSource = InFile<TypePtr>;
 pub type LifetimePtr = AstPtr<ast::Lifetime>;
 pub type LifetimeSource = InFile<LifetimePtr>;
 
+// We split the store into types-only and expressions, because most stores (e.g. generics)
+// don't store any expressions and this saves memory. Same thing for the source map.
 #[derive(Debug, PartialEq, Eq)]
-pub struct ExpressionStore {
+struct ExpressionOnlyStore {
-    pub exprs: Arena<Expr>,
+    exprs: Arena<Expr>,
-    pub pats: Arena<Pat>,
+    pats: Arena<Pat>,
-    pub bindings: Arena<Binding>,
+    bindings: Arena<Binding>,
-    pub labels: Arena<Label>,
+    labels: Arena<Label>,
-    pub types: Arena<TypeRef>,
-    pub lifetimes: Arena<LifetimeRef>,
     /// Id of the closure/coroutine that owns the corresponding binding. If a binding is owned by the
     /// top level expression, it will not be listed in here.
-    pub binding_owners: FxHashMap<BindingId, ExprId>,
+    binding_owners: FxHashMap<BindingId, ExprId>,
     /// Block expressions in this store that may contain inner items.
     block_scopes: Box<[BlockId]>,
 
@@ -114,8 +115,118 @@ pub struct ExpressionStore {
     ident_hygiene: FxHashMap<ExprOrPatId, HygieneId>,
 }
 
+#[derive(Debug, PartialEq, Eq)]
+pub struct ExpressionStore {
+    expr_only: Option<Box<ExpressionOnlyStore>>,
+    pub types: Arena<TypeRef>,
+    pub lifetimes: Arena<LifetimeRef>,
+}
+
+#[derive(Debug, Eq, Default)]
+struct ExpressionOnlySourceMap {
+    // AST expressions can create patterns in destructuring assignments. Therefore, `ExprSource` can also map
+    // to `PatId`, and `PatId` can also map to `ExprSource` (the other way around is unaffected).
+    expr_map: FxHashMap<ExprSource, ExprOrPatId>,
+    expr_map_back: ArenaMap<ExprId, ExprOrPatSource>,
+
+    pat_map: FxHashMap<PatSource, ExprOrPatId>,
+    pat_map_back: ArenaMap<PatId, ExprOrPatSource>,
+
+    label_map: FxHashMap<LabelSource, LabelId>,
+    label_map_back: ArenaMap<LabelId, LabelSource>,
+
+    binding_definitions:
+        ArenaMap<BindingId, SmallVec<[PatId; 2 * size_of::<usize>() / size_of::<PatId>()]>>,
+
+    /// 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_back: FxHashMap<ExprId, FieldSource>,
+    pat_field_map_back: FxHashMap<PatId, PatFieldSource>,
+
+    template_map: Option<Box<FormatTemplate>>,
+
+    expansions: FxHashMap<InFile<MacroCallPtr>, MacroCallId>,
+
+    /// Diagnostics accumulated during lowering. These contain `AstPtr`s and so are stored in
+    /// the source map (since they're just as volatile).
+    //
+    // We store diagnostics on the `ExpressionOnlySourceMap` because diagnostics are rare (except
+    // maybe for cfgs, and they are also not common in type places).
+    diagnostics: ThinVec<ExpressionStoreDiagnostics>,
+}
+
+impl PartialEq for ExpressionOnlySourceMap {
+    fn eq(&self, other: &Self) -> bool {
+        // we only need to compare one of the two mappings
+        // as the other is a reverse mapping and thus will compare
+        // the same as normal mapping
+        let Self {
+            expr_map: _,
+            expr_map_back,
+            pat_map: _,
+            pat_map_back,
+            label_map: _,
+            label_map_back,
+            // If this changed, our pattern data must have changed
+            binding_definitions: _,
+            // If this changed, our expression data must have changed
+            field_map_back: _,
+            // If this changed, our pattern data must have changed
+            pat_field_map_back: _,
+            template_map,
+            expansions,
+            diagnostics,
+        } = self;
+        *expr_map_back == other.expr_map_back
+            && *pat_map_back == other.pat_map_back
+            && *label_map_back == other.label_map_back
+            && *template_map == other.template_map
+            && *expansions == other.expansions
+            && *diagnostics == other.diagnostics
+    }
+}
+
 #[derive(Debug, Eq, Default)]
 pub struct ExpressionStoreSourceMap {
+    expr_only: Option<Box<ExpressionOnlySourceMap>>,
+
+    types_map_back: ArenaMap<TypeRefId, TypeSource>,
+    types_map: FxHashMap<TypeSource, TypeRefId>,
+
+    lifetime_map_back: ArenaMap<LifetimeRefId, LifetimeSource>,
+    #[expect(
+        unused,
+        reason = "this is here for completeness, and maybe we'll need it in the future"
+    )]
+    lifetime_map: FxHashMap<LifetimeSource, LifetimeRefId>,
+}
+
+impl PartialEq for ExpressionStoreSourceMap {
+    fn eq(&self, other: &Self) -> bool {
+        // we only need to compare one of the two mappings
+        // as the other is a reverse mapping and thus will compare
+        // the same as normal mapping
+        let Self { expr_only, types_map_back, types_map: _, lifetime_map_back, lifetime_map: _ } =
+            self;
+        *expr_only == other.expr_only
+            && *types_map_back == other.types_map_back
+            && *lifetime_map_back == other.lifetime_map_back
+    }
+}
+
+/// The body of an item (function, const etc.).
+#[derive(Debug, Eq, PartialEq, Default)]
+pub struct ExpressionStoreBuilder {
+    pub exprs: Arena<Expr>,
+    pub pats: Arena<Pat>,
+    pub bindings: Arena<Binding>,
+    pub labels: Arena<Label>,
+    pub lifetimes: Arena<LifetimeRef>,
+    pub binding_owners: FxHashMap<BindingId, ExprId>,
+    pub types: Arena<TypeRef>,
+    block_scopes: Vec<BlockId>,
+    ident_hygiene: FxHashMap<ExprOrPatId, HygieneId>,
+
     // AST expressions can create patterns in destructuring assignments. Therefore, `ExprSource` can also map
     // to `PatId`, and `PatId` can also map to `ExprSource` (the other way around is unaffected).
     expr_map: FxHashMap<ExprSource, ExprOrPatId>,
@@ -143,62 +254,14 @@ pub struct ExpressionStoreSourceMap {
 
     template_map: Option<Box<FormatTemplate>>,
 
-    pub expansions: FxHashMap<InFile<MacroCallPtr>, MacroCallId>,
+    expansions: FxHashMap<InFile<MacroCallPtr>, MacroCallId>,
 
     /// Diagnostics accumulated during lowering. These contain `AstPtr`s and so are stored in
     /// the source map (since they're just as volatile).
-    pub diagnostics: Vec<ExpressionStoreDiagnostics>,
+    //
-}
+    // We store diagnostics on the `ExpressionOnlySourceMap` because diagnostics are rare (except
-
+    // maybe for cfgs, and they are also not common in type places).
-impl PartialEq for ExpressionStoreSourceMap {
+    pub(crate) diagnostics: Vec<ExpressionStoreDiagnostics>,
-    fn eq(&self, other: &Self) -> bool {
-        // we only need to compare one of the two mappings
-        // as the other is a reverse mapping and thus will compare
-        // the same as normal mapping
-        let Self {
-            expr_map: _,
-            expr_map_back,
-            pat_map: _,
-            pat_map_back,
-            label_map: _,
-            label_map_back,
-            types_map_back,
-            types_map: _,
-            lifetime_map_back,
-            lifetime_map: _,
-            // If this changed, our pattern data must have changed
-            binding_definitions: _,
-            // If this changed, our expression data must have changed
-            field_map_back: _,
-            // If this changed, our pattern data must have changed
-            pat_field_map_back: _,
-            template_map,
-            expansions,
-            diagnostics,
-        } = self;
-        *expr_map_back == other.expr_map_back
-            && *pat_map_back == other.pat_map_back
-            && *label_map_back == other.label_map_back
-            && *types_map_back == other.types_map_back
-            && *lifetime_map_back == other.lifetime_map_back
-            && *template_map == other.template_map
-            && *expansions == other.expansions
-            && *diagnostics == other.diagnostics
-    }
-}
-
-/// The body of an item (function, const etc.).
-#[derive(Debug, Eq, PartialEq, Default)]
-pub struct ExpressionStoreBuilder {
-    pub exprs: Arena<Expr>,
-    pub pats: Arena<Pat>,
-    pub bindings: Arena<Binding>,
-    pub labels: Arena<Label>,
-    pub lifetimes: Arena<LifetimeRef>,
-    pub binding_owners: FxHashMap<BindingId, ExprId>,
-    pub types: Arena<TypeRef>,
-    block_scopes: Vec<BlockId>,
-    ident_hygiene: FxHashMap<ExprOrPatId, HygieneId>,
 }
 
 #[derive(Default, Debug, Eq, PartialEq)]
@@ -226,7 +289,7 @@ pub enum ExpressionStoreDiagnostics {
 }
 
 impl ExpressionStoreBuilder {
-    pub fn finish(self) -> ExpressionStore {
+    pub fn finish(self) -> (ExpressionStore, ExpressionStoreSourceMap) {
         let Self {
             block_scopes,
             mut exprs,
@@ -237,6 +300,23 @@ impl ExpressionStoreBuilder {
             mut ident_hygiene,
             mut types,
             mut lifetimes,
+
+            mut expr_map,
+            mut expr_map_back,
+            mut pat_map,
+            mut pat_map_back,
+            mut label_map,
+            mut label_map_back,
+            mut types_map_back,
+            mut types_map,
+            mut lifetime_map_back,
+            mut lifetime_map,
+            mut binding_definitions,
+            mut field_map_back,
+            mut pat_field_map_back,
+            mut template_map,
+            mut expansions,
+            diagnostics,
         } = self;
         exprs.shrink_to_fit();
         labels.shrink_to_fit();
@@ -247,24 +327,90 @@ impl ExpressionStoreBuilder {
         types.shrink_to_fit();
         lifetimes.shrink_to_fit();
 
-        ExpressionStore {
+        expr_map.shrink_to_fit();
-            exprs,
+        expr_map_back.shrink_to_fit();
-            pats,
+        pat_map.shrink_to_fit();
-            bindings,
+        pat_map_back.shrink_to_fit();
-            labels,
+        label_map.shrink_to_fit();
-            binding_owners,
+        label_map_back.shrink_to_fit();
-            types,
+        types_map_back.shrink_to_fit();
-            lifetimes,
+        types_map.shrink_to_fit();
-            block_scopes: block_scopes.into_boxed_slice(),
+        lifetime_map_back.shrink_to_fit();
-            ident_hygiene,
+        lifetime_map.shrink_to_fit();
+        binding_definitions.shrink_to_fit();
+        field_map_back.shrink_to_fit();
+        pat_field_map_back.shrink_to_fit();
+        if let Some(template_map) = &mut template_map {
+            let FormatTemplate {
+                format_args_to_captures,
+                asm_to_captures,
+                implicit_capture_to_source,
+            } = &mut **template_map;
+            format_args_to_captures.shrink_to_fit();
+            asm_to_captures.shrink_to_fit();
+            implicit_capture_to_source.shrink_to_fit();
         }
+        expansions.shrink_to_fit();
+
+        let has_exprs =
+            !exprs.is_empty() || !labels.is_empty() || !pats.is_empty() || !bindings.is_empty();
+
+        let store = {
+            let expr_only = if has_exprs {
+                Some(Box::new(ExpressionOnlyStore {
+                    exprs,
+                    pats,
+                    bindings,
+                    labels,
+                    binding_owners,
+                    block_scopes: block_scopes.into_boxed_slice(),
+                    ident_hygiene,
+                }))
+            } else {
+                None
+            };
+            ExpressionStore { expr_only, types, lifetimes }
+        };
+
+        let source_map = {
+            let expr_only = if has_exprs || !expansions.is_empty() || !diagnostics.is_empty() {
+                Some(Box::new(ExpressionOnlySourceMap {
+                    expr_map,
+                    expr_map_back,
+                    pat_map,
+                    pat_map_back,
+                    label_map,
+                    label_map_back,
+                    binding_definitions,
+                    field_map_back,
+                    pat_field_map_back,
+                    template_map,
+                    expansions,
+                    diagnostics: ThinVec::from_iter(diagnostics),
+                }))
+            } else {
+                None
+            };
+            ExpressionStoreSourceMap {
+                expr_only,
+                types_map_back,
+                types_map,
+                lifetime_map_back,
+                lifetime_map,
+            }
+        };
+
+        (store, source_map)
     }
 }
 
 impl ExpressionStore {
-    pub fn empty_singleton() -> Arc<Self> {
+    pub fn empty_singleton() -> (Arc<ExpressionStore>, Arc<ExpressionStoreSourceMap>) {
-        static EMPTY: LazyLock<Arc<ExpressionStore>> =
+        static EMPTY: LazyLock<(Arc<ExpressionStore>, Arc<ExpressionStoreSourceMap>)> =
-            LazyLock::new(|| Arc::new(ExpressionStoreBuilder::default().finish()));
+            LazyLock::new(|| {
+                let (store, source_map) = ExpressionStoreBuilder::default().finish();
+                (Arc::new(store), Arc::new(source_map))
+            });
         EMPTY.clone()
     }
 
@@ -273,7 +419,12 @@ impl ExpressionStore {
         &'a self,
         db: &'a dyn DefDatabase,
     ) -> impl Iterator<Item = (BlockId, &'a DefMap)> + 'a {
-        self.block_scopes.iter().map(move |&block| (block, block_def_map(db, block)))
+        self.expr_only
+            .as_ref()
+            .map(|it| &*it.block_scopes)
+            .unwrap_or_default()
+            .iter()
+            .map(move |&block| (block, block_def_map(db, block)))
     }
 
     pub fn walk_bindings_in_pat(&self, pat_id: PatId, mut f: impl FnMut(BindingId)) {
@@ -320,7 +471,8 @@ impl ExpressionStore {
     }
 
     pub fn is_binding_upvar(&self, binding: BindingId, relative_to: ExprId) -> bool {
-        match self.binding_owners.get(&binding) {
+        let Some(expr_only) = &self.expr_only else { return false };
+        match expr_only.binding_owners.get(&binding) {
             Some(it) => {
                 // We assign expression ids in a way that outer closures will receive
                 // a lower id
@@ -330,6 +482,11 @@ impl ExpressionStore {
         }
     }
 
+    #[inline]
+    pub fn binding_owner(&self, id: BindingId) -> Option<ExprId> {
+        self.expr_only.as_ref()?.binding_owners.get(&id).copied()
+    }
+
     /// Walks the immediate children expressions and calls `f` for each child expression.
     ///
     /// Note that this does not walk const blocks.
@@ -601,16 +758,22 @@ impl ExpressionStore {
         });
     }
 
+    #[inline]
+    #[track_caller]
+    fn assert_expr_only(&self) -> &ExpressionOnlyStore {
+        self.expr_only.as_ref().expect("should have `ExpressionStore::expr_only`")
+    }
+
     fn binding_hygiene(&self, binding: BindingId) -> HygieneId {
-        self.bindings[binding].hygiene
+        self.assert_expr_only().bindings[binding].hygiene
     }
 
     pub fn expr_path_hygiene(&self, expr: ExprId) -> HygieneId {
-        self.ident_hygiene.get(&expr.into()).copied().unwrap_or(HygieneId::ROOT)
+        self.assert_expr_only().ident_hygiene.get(&expr.into()).copied().unwrap_or(HygieneId::ROOT)
     }
 
     pub fn pat_path_hygiene(&self, pat: PatId) -> HygieneId {
-        self.ident_hygiene.get(&pat.into()).copied().unwrap_or(HygieneId::ROOT)
+        self.assert_expr_only().ident_hygiene.get(&pat.into()).copied().unwrap_or(HygieneId::ROOT)
     }
 
     pub fn expr_or_pat_path_hygiene(&self, id: ExprOrPatId) -> HygieneId {
@@ -619,43 +782,72 @@ impl ExpressionStore {
             ExprOrPatId::PatId(id) => self.pat_path_hygiene(id),
         }
     }
+
+    #[inline]
+    pub fn exprs(&self) -> impl Iterator<Item = (ExprId, &Expr)> {
+        match &self.expr_only {
+            Some(it) => it.exprs.iter(),
+            None => const { &Arena::new() }.iter(),
+        }
+    }
+
+    #[inline]
+    pub fn pats(&self) -> impl Iterator<Item = (PatId, &Pat)> {
+        match &self.expr_only {
+            Some(it) => it.pats.iter(),
+            None => const { &Arena::new() }.iter(),
+        }
+    }
+
+    #[inline]
+    pub fn bindings(&self) -> impl Iterator<Item = (BindingId, &Binding)> {
+        match &self.expr_only {
+            Some(it) => it.bindings.iter(),
+            None => const { &Arena::new() }.iter(),
+        }
+    }
 }
 
 impl Index<ExprId> for ExpressionStore {
     type Output = Expr;
 
+    #[inline]
     fn index(&self, expr: ExprId) -> &Expr {
-        &self.exprs[expr]
+        &self.assert_expr_only().exprs[expr]
     }
 }
 
 impl Index<PatId> for ExpressionStore {
     type Output = Pat;
 
+    #[inline]
     fn index(&self, pat: PatId) -> &Pat {
-        &self.pats[pat]
+        &self.assert_expr_only().pats[pat]
     }
 }
 
 impl Index<LabelId> for ExpressionStore {
     type Output = Label;
 
+    #[inline]
     fn index(&self, label: LabelId) -> &Label {
-        &self.labels[label]
+        &self.assert_expr_only().labels[label]
     }
 }
 
 impl Index<BindingId> for ExpressionStore {
     type Output = Binding;
 
+    #[inline]
     fn index(&self, b: BindingId) -> &Binding {
-        &self.bindings[b]
+        &self.assert_expr_only().bindings[b]
     }
 }
 
 impl Index<TypeRefId> for ExpressionStore {
     type Output = TypeRef;
 
+    #[inline]
     fn index(&self, b: TypeRefId) -> &TypeRef {
         &self.types[b]
     }
@@ -664,6 +856,7 @@ impl Index<TypeRefId> for ExpressionStore {
 impl Index<LifetimeRefId> for ExpressionStore {
     type Output = LifetimeRef;
 
+    #[inline]
     fn index(&self, b: LifetimeRefId) -> &LifetimeRef {
         &self.lifetimes[b]
     }
@@ -684,12 +877,6 @@ impl Index<PathId> for ExpressionStore {
 // FIXME: Change `node_` prefix to something more reasonable.
 // Perhaps `expr_syntax` and `expr_id`?
 impl ExpressionStoreSourceMap {
-    pub fn empty_singleton() -> Arc<Self> {
-        static EMPTY: LazyLock<Arc<ExpressionStoreSourceMap>> =
-            LazyLock::new(|| Arc::new(ExpressionStoreSourceMap::default()));
-        EMPTY.clone()
-    }
-
     pub fn expr_or_pat_syntax(&self, id: ExprOrPatId) -> Result<ExprOrPatSource, SyntheticSyntax> {
         match id {
             ExprOrPatId::ExprId(id) => self.expr_syntax(id),
@@ -697,30 +884,46 @@ impl ExpressionStoreSourceMap {
         }
     }
 
+    #[inline]
+    fn expr_or_synthetic(&self) -> Result<&ExpressionOnlySourceMap, SyntheticSyntax> {
+        self.expr_only.as_deref().ok_or(SyntheticSyntax)
+    }
+
+    #[inline]
+    fn expr_only(&self) -> Option<&ExpressionOnlySourceMap> {
+        self.expr_only.as_deref()
+    }
+
+    #[inline]
+    #[track_caller]
+    fn assert_expr_only(&self) -> &ExpressionOnlySourceMap {
+        self.expr_only.as_ref().expect("should have `ExpressionStoreSourceMap::expr_only`")
+    }
+
     pub fn expr_syntax(&self, expr: ExprId) -> Result<ExprOrPatSource, SyntheticSyntax> {
-        self.expr_map_back.get(expr).cloned().ok_or(SyntheticSyntax)
+        self.expr_or_synthetic()?.expr_map_back.get(expr).cloned().ok_or(SyntheticSyntax)
     }
 
     pub fn node_expr(&self, node: InFile<&ast::Expr>) -> Option<ExprOrPatId> {
         let src = node.map(AstPtr::new);
-        self.expr_map.get(&src).cloned()
+        self.expr_only()?.expr_map.get(&src).cloned()
     }
 
     pub fn node_macro_file(&self, node: InFile<&ast::MacroCall>) -> Option<MacroCallId> {
         let src = node.map(AstPtr::new);
-        self.expansions.get(&src).cloned()
+        self.expr_only()?.expansions.get(&src).cloned()
     }
 
     pub fn macro_calls(&self) -> impl Iterator<Item = (InFile<MacroCallPtr>, MacroCallId)> + '_ {
-        self.expansions.iter().map(|(&a, &b)| (a, b))
+        self.expr_only().into_iter().flat_map(|it| it.expansions.iter().map(|(&a, &b)| (a, b)))
     }
 
     pub fn pat_syntax(&self, pat: PatId) -> Result<ExprOrPatSource, SyntheticSyntax> {
-        self.pat_map_back.get(pat).cloned().ok_or(SyntheticSyntax)
+        self.expr_or_synthetic()?.pat_map_back.get(pat).cloned().ok_or(SyntheticSyntax)
     }
 
     pub fn node_pat(&self, node: InFile<&ast::Pat>) -> Option<ExprOrPatId> {
-        self.pat_map.get(&node.map(AstPtr::new)).cloned()
+        self.expr_only()?.pat_map.get(&node.map(AstPtr::new)).cloned()
     }
 
     pub fn type_syntax(&self, id: TypeRefId) -> Result<TypeSource, SyntheticSyntax> {
@@ -732,49 +935,50 @@ impl ExpressionStoreSourceMap {
     }
 
     pub fn label_syntax(&self, label: LabelId) -> LabelSource {
-        self.label_map_back[label]
+        self.assert_expr_only().label_map_back[label]
     }
 
     pub fn patterns_for_binding(&self, binding: BindingId) -> &[PatId] {
-        self.binding_definitions.get(binding).map_or(&[], Deref::deref)
+        self.assert_expr_only().binding_definitions.get(binding).map_or(&[], Deref::deref)
     }
 
     pub fn node_label(&self, node: InFile<&ast::Label>) -> Option<LabelId> {
         let src = node.map(AstPtr::new);
-        self.label_map.get(&src).cloned()
+        self.expr_only()?.label_map.get(&src).cloned()
     }
 
     pub fn field_syntax(&self, expr: ExprId) -> FieldSource {
-        self.field_map_back[&expr]
+        self.assert_expr_only().field_map_back[&expr]
     }
 
     pub fn pat_field_syntax(&self, pat: PatId) -> PatFieldSource {
-        self.pat_field_map_back[&pat]
+        self.assert_expr_only().pat_field_map_back[&pat]
     }
 
     pub fn macro_expansion_expr(&self, node: InFile<&ast::MacroExpr>) -> Option<ExprOrPatId> {
         let src = node.map(AstPtr::new).map(AstPtr::upcast::<ast::MacroExpr>).map(AstPtr::upcast);
-        self.expr_map.get(&src).copied()
+        self.expr_only()?.expr_map.get(&src).copied()
     }
 
     pub fn expansions(&self) -> impl Iterator<Item = (&InFile<MacroCallPtr>, &MacroCallId)> {
-        self.expansions.iter()
+        self.expr_only().into_iter().flat_map(|it| it.expansions.iter())
     }
 
     pub fn expansion(&self, node: InFile<&ast::MacroCall>) -> Option<MacroCallId> {
-        self.expansions.get(&node.map(AstPtr::new)).copied()
+        self.expr_only()?.expansions.get(&node.map(AstPtr::new)).copied()
     }
 
     pub fn implicit_format_args(
         &self,
         node: InFile<&ast::FormatArgsExpr>,
     ) -> Option<(HygieneId, &[(syntax::TextRange, Name)])> {
+        let expr_only = self.expr_only()?;
         let src = node.map(AstPtr::new).map(AstPtr::upcast::<ast::Expr>);
-        let (hygiene, names) = self
+        let (hygiene, names) = expr_only
             .template_map
             .as_ref()?
             .format_args_to_captures
-            .get(&self.expr_map.get(&src)?.as_expr()?)?;
+            .get(&expr_only.expr_map.get(&src)?.as_expr()?)?;
         Some((*hygiene, &**names))
     }
 
@@ -782,67 +986,28 @@ impl ExpressionStoreSourceMap {
         &self,
         capture_expr: ExprId,
     ) -> Option<InFile<(ExprPtr, TextRange)>> {
-        self.template_map.as_ref()?.implicit_capture_to_source.get(&capture_expr).copied()
+        self.expr_only()?
+            .template_map
+            .as_ref()?
+            .implicit_capture_to_source
+            .get(&capture_expr)
+            .copied()
     }
 
     pub fn asm_template_args(
         &self,
         node: InFile<&ast::AsmExpr>,
     ) -> Option<(ExprId, &[Vec<(syntax::TextRange, usize)>])> {
+        let expr_only = self.expr_only()?;
         let src = node.map(AstPtr::new).map(AstPtr::upcast::<ast::Expr>);
-        let expr = self.expr_map.get(&src)?.as_expr()?;
+        let expr = expr_only.expr_map.get(&src)?.as_expr()?;
-        Some(expr)
+        Some(expr).zip(
-            .zip(self.template_map.as_ref()?.asm_to_captures.get(&expr).map(std::ops::Deref::deref))
+            expr_only.template_map.as_ref()?.asm_to_captures.get(&expr).map(std::ops::Deref::deref),
+        )
     }
 
     /// Get a reference to the source map's diagnostics.
     pub fn diagnostics(&self) -> &[ExpressionStoreDiagnostics] {
-        &self.diagnostics
+        self.expr_only().map(|it| &*it.diagnostics).unwrap_or_default()
-    }
-
-    fn shrink_to_fit(&mut self) {
-        let Self {
-            expr_map,
-            expr_map_back,
-            pat_map,
-            pat_map_back,
-            label_map,
-            label_map_back,
-            field_map_back,
-            pat_field_map_back,
-            expansions,
-            template_map,
-            diagnostics,
-            binding_definitions,
-            types_map,
-            types_map_back,
-            lifetime_map_back,
-            lifetime_map,
-        } = self;
-        if let Some(template_map) = template_map {
-            let FormatTemplate {
-                format_args_to_captures,
-                asm_to_captures,
-                implicit_capture_to_source,
-            } = &mut **template_map;
-            format_args_to_captures.shrink_to_fit();
-            asm_to_captures.shrink_to_fit();
-            implicit_capture_to_source.shrink_to_fit();
-        }
-        expr_map.shrink_to_fit();
-        expr_map_back.shrink_to_fit();
-        pat_map.shrink_to_fit();
-        pat_map_back.shrink_to_fit();
-        label_map.shrink_to_fit();
-        label_map_back.shrink_to_fit();
-        field_map_back.shrink_to_fit();
-        pat_field_map_back.shrink_to_fit();
-        expansions.shrink_to_fit();
-        diagnostics.shrink_to_fit();
-        binding_definitions.shrink_to_fit();
-        types_map.shrink_to_fit();
-        types_map_back.shrink_to_fit();
-        lifetime_map.shrink_to_fit();
-        lifetime_map_back.shrink_to_fit();
     }
 }

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

@@ -36,6 +36,7 @@ pub struct Body {
 impl ops::Deref for Body {
     type Target = ExpressionStore;
 
+    #[inline]
     fn deref(&self) -> &Self::Target {
         &self.store
     }
@@ -61,6 +62,7 @@ pub struct BodySourceMap {
 impl ops::Deref for BodySourceMap {
     type Target = ExpressionStoreSourceMap;
 
+    #[inline]
     fn deref(&self) -> &Self::Target {
         &self.store
     }
@@ -102,9 +104,7 @@ impl Body {
             }
         };
         let module = def.module(db);
-        let (body, mut source_map) =
+        let (body, source_map) = lower_body(db, def, file_id, module, params, body, is_async_fn);
-            lower_body(db, def, file_id, module, params, body, is_async_fn);
-        source_map.store.shrink_to_fit();
 
         (Arc::new(body), Arc::new(source_map))
     }

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

@@ -121,14 +121,10 @@ pub(super) fn lower_body(
             params = (0..count).map(|_| collector.missing_pat()).collect();
         };
         let body_expr = collector.missing_expr();
+        let (store, source_map) = collector.store.finish();
         return (
-            Body {
+            Body { store, params: params.into_boxed_slice(), self_param, body_expr },
-                store: collector.store.finish(),
+            BodySourceMap { self_param: source_map_self_param, store: source_map },
-                params: params.into_boxed_slice(),
-                self_param,
-                body_expr,
-            },
-            BodySourceMap { self_param: source_map_self_param, store: collector.source_map },
         );
     }
 
@@ -171,14 +167,10 @@ pub(super) fn lower_body(
         },
     );
 
+    let (store, source_map) = collector.store.finish();
     (
-        Body {
+        Body { store, params: params.into_boxed_slice(), self_param, body_expr },
-            store: collector.store.finish(),
+        BodySourceMap { self_param: source_map_self_param, store: source_map },
-            params: params.into_boxed_slice(),
-            self_param,
-            body_expr,
-        },
-        BodySourceMap { self_param: source_map_self_param, store: collector.source_map },
     )
 }
 
@@ -190,7 +182,8 @@ pub(crate) fn lower_type_ref(
     let mut expr_collector = ExprCollector::new(db, module, type_ref.file_id);
     let type_ref =
         expr_collector.lower_type_ref_opt(type_ref.value, &mut ExprCollector::impl_trait_allocator);
-    (expr_collector.store.finish(), expr_collector.source_map, type_ref)
+    let (store, source_map) = expr_collector.store.finish();
+    (store, source_map, type_ref)
 }
 
 pub(crate) fn lower_generic_params(
@@ -205,7 +198,8 @@ pub(crate) fn lower_generic_params(
     let mut collector = generics::GenericParamsCollector::new(def);
     collector.lower(&mut expr_collector, param_list, where_clause);
     let params = collector.finish();
-    (Arc::new(expr_collector.store.finish()), params, expr_collector.source_map)
+    let (store, source_map) = expr_collector.store.finish();
+    (Arc::new(store), params, source_map)
 }
 
 pub(crate) fn lower_impl(
@@ -232,7 +226,8 @@ pub(crate) fn lower_impl(
         impl_syntax.value.where_clause(),
     );
     let params = collector.finish();
-    (expr_collector.store.finish(), expr_collector.source_map, self_ty, trait_, params)
+    let (store, source_map) = expr_collector.store.finish();
+    (store, source_map, self_ty, trait_, params)
 }
 
 pub(crate) fn lower_trait(
@@ -253,7 +248,8 @@ pub(crate) fn lower_trait(
         trait_syntax.value.where_clause(),
     );
     let params = collector.finish();
-    (expr_collector.store.finish(), expr_collector.source_map, params)
+    let (store, source_map) = expr_collector.store.finish();
+    (store, source_map, params)
 }
 
 pub(crate) fn lower_trait_alias(
@@ -274,7 +270,8 @@ pub(crate) fn lower_trait_alias(
         trait_syntax.value.where_clause(),
     );
     let params = collector.finish();
-    (expr_collector.store.finish(), expr_collector.source_map, params)
+    let (store, source_map) = expr_collector.store.finish();
+    (store, source_map, params)
 }
 
 pub(crate) fn lower_type_alias(
@@ -313,7 +310,8 @@ pub(crate) fn lower_type_alias(
         .value
         .ty()
         .map(|ty| expr_collector.lower_type_ref(ty, &mut ExprCollector::impl_trait_allocator));
-    (expr_collector.store.finish(), expr_collector.source_map, params, bounds, type_ref)
+    let (store, source_map) = expr_collector.store.finish();
+    (store, source_map, params, bounds, type_ref)
 }
 
 pub(crate) fn lower_function(
@@ -421,9 +419,10 @@ pub(crate) fn lower_function(
     } else {
         return_type
     };
+    let (store, source_map) = expr_collector.store.finish();
     (
-        expr_collector.store.finish(),
+        store,
-        expr_collector.source_map,
+        source_map,
         generics,
         params.into_boxed_slice(),
         return_type,
@@ -440,7 +439,6 @@ pub struct ExprCollector<'db> {
     local_def_map: &'db LocalDefMap,
     module: ModuleId,
     pub store: ExpressionStoreBuilder,
-    pub(crate) source_map: ExpressionStoreSourceMap,
 
     // state stuff
     // Prevent nested impl traits like `impl Foo<impl Bar>`.
@@ -551,7 +549,6 @@ impl ExprCollector<'_> {
             module,
             def_map,
             local_def_map,
-            source_map: ExpressionStoreSourceMap::default(),
             store: ExpressionStoreBuilder::default(),
             expander,
             current_try_block_label: None,
@@ -698,7 +695,7 @@ impl ExprCollector<'_> {
                     let id = self.collect_macro_call(mcall, macro_ptr, true, |this, expansion| {
                         this.lower_type_ref_opt(expansion, impl_trait_lower_fn)
                     });
-                    self.source_map.types_map.insert(src, id);
+                    self.store.types_map.insert(src, id);
                     return id;
                 }
                 None => TypeRef::Error,
@@ -732,8 +729,8 @@ impl ExprCollector<'_> {
     fn alloc_type_ref(&mut self, type_ref: TypeRef, node: TypePtr) -> TypeRefId {
         let id = self.store.types.alloc(type_ref);
         let ptr = self.expander.in_file(node);
-        self.source_map.types_map_back.insert(id, ptr);
+        self.store.types_map_back.insert(id, ptr);
-        self.source_map.types_map.insert(ptr, id);
+        self.store.types_map.insert(ptr, id);
         id
     }
 
@@ -744,8 +741,8 @@ impl ExprCollector<'_> {
     ) -> LifetimeRefId {
         let id = self.store.lifetimes.alloc(lifetime_ref);
         let ptr = self.expander.in_file(node);
-        self.source_map.lifetime_map_back.insert(id, ptr);
+        self.store.lifetime_map_back.insert(id, ptr);
-        self.source_map.lifetime_map.insert(ptr, id);
+        self.store.lifetime_map.insert(ptr, id);
         id
     }
 
@@ -1190,14 +1187,14 @@ impl ExprCollector<'_> {
             }
             ast::Expr::ContinueExpr(e) => {
                 let label = self.resolve_label(e.lifetime()).unwrap_or_else(|e| {
-                    self.source_map.diagnostics.push(e);
+                    self.store.diagnostics.push(e);
                     None
                 });
                 self.alloc_expr(Expr::Continue { label }, syntax_ptr)
             }
             ast::Expr::BreakExpr(e) => {
                 let label = self.resolve_label(e.lifetime()).unwrap_or_else(|e| {
-                    self.source_map.diagnostics.push(e);
+                    self.store.diagnostics.push(e);
                     None
                 });
                 let expr = e.expr().map(|e| self.collect_expr(e));
@@ -1207,7 +1204,7 @@ impl ExprCollector<'_> {
                 let inner = self.collect_expr_opt(e.expr());
                 // make the paren expr point to the inner expression as well for IDE resolution
                 let src = self.expander.in_file(syntax_ptr);
-                self.source_map.expr_map.insert(src, inner.into());
+                self.store.expr_map.insert(src, inner.into());
                 inner
             }
             ast::Expr::ReturnExpr(e) => {
@@ -1248,7 +1245,7 @@ impl ExprCollector<'_> {
                                 None => self.missing_expr(),
                             };
                             let src = self.expander.in_file(AstPtr::new(&field));
-                            self.source_map.field_map_back.insert(expr, src);
+                            self.store.field_map_back.insert(expr, src);
                             Some(RecordLitField { name, expr })
                         })
                         .collect();
@@ -1271,12 +1268,10 @@ impl ExprCollector<'_> {
             ast::Expr::AwaitExpr(e) => {
                 let expr = self.collect_expr_opt(e.expr());
                 if let Awaitable::No(location) = self.is_lowering_awaitable_block() {
-                    self.source_map.diagnostics.push(
+                    self.store.diagnostics.push(ExpressionStoreDiagnostics::AwaitOutsideOfAsync {
-                        ExpressionStoreDiagnostics::AwaitOutsideOfAsync {
+                        node: self.expander.in_file(AstPtr::new(&e)),
-                            node: self.expander.in_file(AstPtr::new(&e)),
+                        location: location.to_string(),
-                            location: location.to_string(),
+                    });
-                        },
-                    );
                 }
                 self.alloc_expr(Expr::Await { expr }, syntax_ptr)
             }
@@ -1442,7 +1437,7 @@ impl ExprCollector<'_> {
                         // Make the macro-call point to its expanded expression so we can query
                         // semantics on syntax pointers to the macro
                         let src = self.expander.in_file(syntax_ptr);
-                        self.source_map.expr_map.insert(src, id.into());
+                        self.store.expr_map.insert(src, id.into());
                         id
                     }
                     None => self.alloc_expr(Expr::Missing, syntax_ptr),
@@ -1486,7 +1481,7 @@ impl ExprCollector<'_> {
             let expr = self.collect_expr(expr);
             // Do not use `alloc_pat_from_expr()` here, it will override the entry in `expr_map`.
             let id = self.store.pats.alloc(Pat::Expr(expr));
-            self.source_map.pat_map_back.insert(id, src);
+            self.store.pat_map_back.insert(id, src);
             id
         })
     }
@@ -1555,7 +1550,7 @@ impl ExprCollector<'_> {
                 let id = self.collect_macro_call(e, macro_ptr, true, |this, expansion| {
                     this.collect_expr_as_pat_opt(expansion)
                 });
-                self.source_map.expr_map.insert(src, id.into());
+                self.store.expr_map.insert(src, id.into());
                 id
             }
             ast::Expr::RecordExpr(e) => {
@@ -1576,7 +1571,7 @@ impl ExprCollector<'_> {
                         let pat = self.collect_expr_as_pat(field_expr);
                         let name = f.field_name()?.as_name();
                         let src = self.expander.in_file(AstPtr::new(&f).wrap_left());
-                        self.source_map.pat_field_map_back.insert(pat, src);
+                        self.store.pat_field_map_back.insert(pat, src);
                         Some(RecordFieldPat { name, pat })
                     })
                     .collect();
@@ -1622,7 +1617,7 @@ impl ExprCollector<'_> {
                         );
                         if let Either::Left(pat) = pat {
                             let src = this.expander.in_file(AstPtr::new(&expr).wrap_left());
-                            this.source_map.pat_map_back.insert(pat, src);
+                            this.store.pat_map_back.insert(pat, src);
                         }
                         pat
                     }
@@ -1968,7 +1963,7 @@ impl ExprCollector<'_> {
                     self.module.krate(),
                     resolver,
                     &mut |ptr, call| {
-                        _ = self.source_map.expansions.insert(ptr.map(|(it, _)| it), call);
+                        _ = self.store.expansions.insert(ptr.map(|(it, _)| it), call);
                     },
                 )
             }
@@ -1978,19 +1973,17 @@ impl ExprCollector<'_> {
             Ok(res) => res,
             Err(UnresolvedMacro { path }) => {
                 if record_diagnostics {
-                    self.source_map.diagnostics.push(
+                    self.store.diagnostics.push(ExpressionStoreDiagnostics::UnresolvedMacroCall {
-                        ExpressionStoreDiagnostics::UnresolvedMacroCall {
+                        node: self.expander.in_file(syntax_ptr),
-                            node: self.expander.in_file(syntax_ptr),
+                        path,
-                            path,
+                    });
-                        },
-                    );
                 }
                 return collector(self, None);
             }
         };
         if record_diagnostics {
             if let Some(err) = res.err {
-                self.source_map
+                self.store
                     .diagnostics
                     .push(ExpressionStoreDiagnostics::MacroError { node: macro_call_ptr, err });
             }
@@ -2001,7 +1994,7 @@ impl ExprCollector<'_> {
                 // Keep collecting even with expansion errors so we can provide completions and
                 // other services in incomplete macro expressions.
                 if let Some(macro_file) = self.expander.current_file_id().macro_file() {
-                    self.source_map.expansions.insert(macro_call_ptr, macro_file);
+                    self.store.expansions.insert(macro_call_ptr, macro_file);
                 }
 
                 if record_diagnostics {
@@ -2050,7 +2043,7 @@ impl ExprCollector<'_> {
             // Make the macro-call point to its expanded expression so we can query
             // semantics on syntax pointers to the macro
             let src = self.expander.in_file(syntax_ptr);
-            self.source_map.expr_map.insert(src, tail.into());
+            self.store.expr_map.insert(src, tail.into());
         })
     }
 
@@ -2361,7 +2354,7 @@ impl ExprCollector<'_> {
                         let pat = self.collect_pat(ast_pat, binding_list);
                         let name = f.field_name()?.as_name();
                         let src = self.expander.in_file(AstPtr::new(&f).wrap_right());
-                        self.source_map.pat_field_map_back.insert(pat, src);
+                        self.store.pat_field_map_back.insert(pat, src);
                         Some(RecordFieldPat { name, pat })
                     })
                     .collect();
@@ -2424,7 +2417,7 @@ impl ExprCollector<'_> {
                         self.collect_macro_call(call, macro_ptr, true, |this, expanded_pat| {
                             this.collect_pat_opt(expanded_pat, binding_list)
                         });
-                    self.source_map.pat_map.insert(src, pat.into());
+                    self.store.pat_map.insert(src, pat.into());
                     return pat;
                 }
                 None => Pat::Missing,
@@ -2515,7 +2508,7 @@ impl ExprCollector<'_> {
                             }
                         });
                     if let Some(pat) = pat.left() {
-                        self.source_map.pat_map.insert(src, pat.into());
+                        self.store.pat_map.insert(src, pat.into());
                     }
                     pat
                 }
@@ -2537,7 +2530,7 @@ impl ExprCollector<'_> {
         match enabled {
             Ok(()) => true,
             Err(cfg) => {
-                self.source_map.diagnostics.push(ExpressionStoreDiagnostics::InactiveCode {
+                self.store.diagnostics.push(ExpressionStoreDiagnostics::InactiveCode {
                     node: self.expander.in_file(SyntaxNodePtr::new(owner.syntax())),
                     cfg,
                     opts: self.cfg_options.clone(),
@@ -2548,7 +2541,7 @@ impl ExprCollector<'_> {
     }
 
     fn add_definition_to_binding(&mut self, binding_id: BindingId, pat_id: PatId) {
-        self.source_map.binding_definitions.entry(binding_id).or_default().push(pat_id);
+        self.store.binding_definitions.entry(binding_id).or_default().push(pat_id);
     }
 
     // region: labels
@@ -2724,7 +2717,7 @@ impl ExprCollector<'_> {
                     |name, range| {
                         let expr_id = self.alloc_expr_desugared(Expr::Path(Path::from(name)));
                         if let Some(range) = range {
-                            self.source_map
+                            self.store
                                 .template_map
                                 .get_or_insert_with(Default::default)
                                 .implicit_capture_to_source
@@ -2836,7 +2829,7 @@ impl ExprCollector<'_> {
             )
         };
 
-        self.source_map
+        self.store
             .template_map
             .get_or_insert_with(Default::default)
             .format_args_to_captures
@@ -3386,8 +3379,8 @@ impl ExprCollector<'_> {
     fn alloc_expr(&mut self, expr: Expr, ptr: ExprPtr) -> ExprId {
         let src = self.expander.in_file(ptr);
         let id = self.store.exprs.alloc(expr);
-        self.source_map.expr_map_back.insert(id, src.map(AstPtr::wrap_left));
+        self.store.expr_map_back.insert(id, src.map(AstPtr::wrap_left));
-        self.source_map.expr_map.insert(src, id.into());
+        self.store.expr_map.insert(src, id.into());
         id
     }
     // FIXME: desugared exprs don't have ptr, that's wrong and should be fixed.
@@ -3398,9 +3391,9 @@ impl ExprCollector<'_> {
     fn alloc_expr_desugared_with_ptr(&mut self, expr: Expr, ptr: ExprPtr) -> ExprId {
         let src = self.expander.in_file(ptr);
         let id = self.store.exprs.alloc(expr);
-        self.source_map.expr_map_back.insert(id, src.map(AstPtr::wrap_left));
+        self.store.expr_map_back.insert(id, src.map(AstPtr::wrap_left));
         // We intentionally don't fill this as it could overwrite a non-desugared entry
-        // self.source_map.expr_map.insert(src, id);
+        // self.store.expr_map.insert(src, id);
         id
     }
     fn missing_expr(&mut self) -> ExprId {
@@ -3423,24 +3416,24 @@ impl ExprCollector<'_> {
     fn alloc_pat_from_expr(&mut self, pat: Pat, ptr: ExprPtr) -> PatId {
         let src = self.expander.in_file(ptr);
         let id = self.store.pats.alloc(pat);
-        self.source_map.expr_map.insert(src, id.into());
+        self.store.expr_map.insert(src, id.into());
-        self.source_map.pat_map_back.insert(id, src.map(AstPtr::wrap_left));
+        self.store.pat_map_back.insert(id, src.map(AstPtr::wrap_left));
         id
     }
 
     fn alloc_expr_from_pat(&mut self, expr: Expr, ptr: PatPtr) -> ExprId {
         let src = self.expander.in_file(ptr);
         let id = self.store.exprs.alloc(expr);
-        self.source_map.pat_map.insert(src, id.into());
+        self.store.pat_map.insert(src, id.into());
-        self.source_map.expr_map_back.insert(id, src.map(AstPtr::wrap_right));
+        self.store.expr_map_back.insert(id, src.map(AstPtr::wrap_right));
         id
     }
 
     fn alloc_pat(&mut self, pat: Pat, ptr: PatPtr) -> PatId {
         let src = self.expander.in_file(ptr);
         let id = self.store.pats.alloc(pat);
-        self.source_map.pat_map_back.insert(id, src.map(AstPtr::wrap_right));
+        self.store.pat_map_back.insert(id, src.map(AstPtr::wrap_right));
-        self.source_map.pat_map.insert(src, id.into());
+        self.store.pat_map.insert(src, id.into());
         id
     }
     // FIXME: desugared pats don't have ptr, that's wrong and should be fixed somehow.
@@ -3454,8 +3447,8 @@ impl ExprCollector<'_> {
     fn alloc_label(&mut self, label: Label, ptr: LabelPtr) -> LabelId {
         let src = self.expander.in_file(ptr);
         let id = self.store.labels.alloc(label);
-        self.source_map.label_map_back.insert(id, src);
+        self.store.label_map_back.insert(id, src);
-        self.source_map.label_map.insert(src, id);
+        self.store.label_map.insert(src, id);
         id
     }
     // FIXME: desugared labels don't have ptr, that's wrong and should be fixed somehow.

crates/hir-def/src/expr_store/lower/asm.rs

@@ -273,7 +273,7 @@ impl ExprCollector<'_> {
             Expr::InlineAsm(InlineAsm { operands: operands.into_boxed_slice(), options }),
             syntax_ptr,
         );
-        self.source_map
+        self.store
             .template_map
             .get_or_insert_with(Default::default)
             .asm_to_captures

crates/hir-def/src/expr_store/lower/path/tests.rs

@@ -23,7 +23,7 @@ fn lower_path(path: ast::Path) -> (TestDB, ExpressionStore, Option<Path>) {
     let mut ctx =
         ExprCollector::new(&db, crate_def_map(&db, krate).root_module_id(), file_id.into());
     let lowered_path = ctx.lower_path(path, &mut ExprCollector::impl_trait_allocator);
-    let store = ctx.store.finish();
+    let (store, _) = ctx.store.finish();
     (db, store, lowered_path)
 }
 

crates/hir-def/src/expr_store/pretty.rs

@@ -902,7 +902,7 @@ impl Printer<'_> {
                         let mut same_name = false;
                         if let Pat::Bind { id, subpat: None } = &self.store[arg.pat] {
                             if let Binding { name, mode: BindingAnnotation::Unannotated, .. } =
-                                &self.store.bindings[*id]
+                                &self.store.assert_expr_only().bindings[*id]
                             {
                                 if name.as_str() == field_name {
                                     same_name = true;
@@ -1063,7 +1063,7 @@ impl Printer<'_> {
     }
 
     fn print_binding(&mut self, id: BindingId) {
-        let Binding { name, mode, .. } = &self.store.bindings[id];
+        let Binding { name, mode, .. } = &self.store.assert_expr_only().bindings[id];
         let mode = match mode {
             BindingAnnotation::Unannotated => "",
             BindingAnnotation::Mutable => "mut ",

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

@@ -106,7 +106,9 @@ impl ExprScopes {
         let mut scopes = ExprScopes {
             scopes: Arena::default(),
             scope_entries: Arena::default(),
-            scope_by_expr: ArenaMap::with_capacity(body.exprs.len()),
+            scope_by_expr: ArenaMap::with_capacity(
+                body.expr_only.as_ref().map_or(0, |it| it.exprs.len()),
+            ),
         };
         let mut root = scopes.root_scope();
         if let Some(self_param) = body.self_param {
@@ -179,7 +181,7 @@ impl ExprScopes {
         binding: BindingId,
         hygiene: HygieneId,
     ) {
-        let Binding { name, .. } = &store.bindings[binding];
+        let Binding { name, .. } = &store[binding];
         let entry = self.scope_entries.alloc(ScopeEntry { name: name.clone(), binding, hygiene });
         self.scopes[scope].entries =
             IdxRange::new_inclusive(self.scopes[scope].entries.start()..=entry);
@@ -251,7 +253,7 @@ fn compute_expr_scopes(
     scope: &mut ScopeId,
 ) {
     let make_label =
-        |label: &Option<LabelId>| label.map(|label| (label, store.labels[label].name.clone()));
+        |label: &Option<LabelId>| label.map(|label| (label, store[label].name.clone()));
 
     let compute_expr_scopes = |scopes: &mut ExprScopes, expr: ExprId, scope: &mut ScopeId| {
         compute_expr_scopes(expr, store, scopes, scope)
@@ -534,9 +536,8 @@ fn foo() {
         };
 
         let resolved = scopes.resolve_name_in_scope(expr_scope, &name_ref.as_name()).unwrap();
-        let pat_src = source_map
+        let pat_src =
-            .pat_syntax(*source_map.binding_definitions[resolved.binding()].first().unwrap())
+            source_map.pat_syntax(source_map.patterns_for_binding(resolved.binding())[0]).unwrap();
-            .unwrap();
 
         let local_name = pat_src.value.syntax_node_ptr().to_node(file.syntax());
         assert_eq!(local_name.text_range(), expected_name.syntax().text_range());

crates/hir-def/src/expr_store/tests/body.rs

@@ -508,9 +508,9 @@ fn f() {
 }
     "#,
     );
-    assert_eq!(body.bindings.len(), 1, "should have a binding for `B`");
+    assert_eq!(body.assert_expr_only().bindings.len(), 1, "should have a binding for `B`");
     assert_eq!(
-        body.bindings[BindingId::from_raw(RawIdx::from_u32(0))].name.as_str(),
+        body[BindingId::from_raw(RawIdx::from_u32(0))].name.as_str(),
         "B",
         "should have a binding for `B`",
     );
@@ -566,6 +566,7 @@ const fn f(x: i32) -> i32 {
     );
 
     let mtch_arms = body
+        .assert_expr_only()
         .exprs
         .iter()
         .find_map(|(_, expr)| {
@@ -578,10 +579,10 @@ const fn f(x: i32) -> i32 {
         .unwrap();
 
     let MatchArm { pat, .. } = mtch_arms[1];
-    match body.pats[pat] {
+    match body[pat] {
         Pat::Range { start, end } => {
-            let hir_start = &body.exprs[start.unwrap()];
+            let hir_start = &body[start.unwrap()];
-            let hir_end = &body.exprs[end.unwrap()];
+            let hir_end = &body[end.unwrap()];
 
             assert!(matches!(hir_start, Expr::Path { .. }));
             assert!(matches!(hir_end, Expr::Path { .. }));

crates/hir-def/src/signatures.rs

@@ -779,14 +779,10 @@ impl VariantFields {
                 Arc::new(VariantFields { fields, store: Arc::new(store), shape }),
                 Arc::new(source_map),
             ),
-            None => (
+            None => {
-                Arc::new(VariantFields {
+                let (store, source_map) = ExpressionStore::empty_singleton();
-                    fields: Arena::default(),
+                (Arc::new(VariantFields { fields: Arena::default(), store, shape }), source_map)
-                    store: ExpressionStore::empty_singleton(),
+            }
-                    shape,
-                }),
-                ExpressionStoreSourceMap::empty_singleton(),
-            ),
         }
     }
 
@@ -878,7 +874,7 @@ fn lower_fields<Field: ast::HasAttrs + ast::HasVisibility>(
                 idx += 1;
             }
             Err(cfg) => {
-                col.source_map.diagnostics.push(
+                col.store.diagnostics.push(
                     crate::expr_store::ExpressionStoreDiagnostics::InactiveCode {
                         node: InFile::new(fields.file_id, SyntaxNodePtr::new(field.syntax())),
                         cfg,
@@ -891,9 +887,9 @@ fn lower_fields<Field: ast::HasAttrs + ast::HasVisibility>(
     if !has_fields {
         return None;
     }
-    let store = col.store.finish();
+    let (store, source_map) = col.store.finish();
     arena.shrink_to_fit();
-    Some((arena, store, col.source_map))
+    Some((arena, store, source_map))
 }
 
 #[derive(Debug, PartialEq, Eq)]
@@ -980,7 +976,7 @@ impl EnumVariants {
             if !matches!(variant.shape, FieldsShape::Unit) {
                 let body = db.body(v.into());
                 // A variant with explicit discriminant
-                if body.exprs[body.body_expr] != crate::hir::Expr::Missing {
+                if !matches!(body[body.body_expr], crate::hir::Expr::Missing) {
                     return false;
                 }
             }

crates/hir-ty/src/consteval.rs

@@ -281,7 +281,7 @@ pub(crate) fn const_eval_discriminant_variant(
     let def = variant_id.into();
     let body = db.body(def);
     let loc = variant_id.lookup(db);
-    if body.exprs[body.body_expr] == Expr::Missing {
+    if matches!(body[body.body_expr], Expr::Missing) {
         let prev_idx = loc.index.checked_sub(1);
         let value = match prev_idx {
             Some(prev_idx) => {
@@ -334,7 +334,7 @@ pub(crate) fn eval_to_const(
         // Type checking clousres need an isolated body (See the above FIXME). Bail out early to prevent panic.
         return unknown_const(infer[expr].clone());
     }
-    if let Expr::Path(p) = &ctx.body.exprs[expr] {
+    if let Expr::Path(p) = &ctx.body[expr] {
         let resolver = &ctx.resolver;
         if let Some(c) =
             path_to_const(db, resolver, p, mode, || ctx.generics(), debruijn, infer[expr].clone())

crates/hir-ty/src/diagnostics/decl_check.rs

@@ -226,11 +226,10 @@ impl<'a> DeclValidator<'a> {
         let body = self.db.body(func.into());
         let edition = self.edition(func);
         let mut pats_replacements = body
-            .pats
+            .pats()
-            .iter()
             .filter_map(|(pat_id, pat)| match pat {
                 Pat::Bind { id, .. } => {
-                    let bind_name = &body.bindings[*id].name;
+                    let bind_name = &body[*id].name;
                     let mut suggested_text = to_lower_snake_case(bind_name.as_str())?;
                     if is_raw_identifier(&suggested_text, edition) {
                         suggested_text.insert_str(0, "r#");

crates/hir-ty/src/diagnostics/expr.rs

@@ -101,7 +101,7 @@ impl ExprValidator {
             self.check_for_trailing_return(body.body_expr, &body);
         }
 
-        for (id, expr) in body.exprs.iter() {
+        for (id, expr) in body.exprs() {
             if let Some((variant, missed_fields, true)) =
                 record_literal_missing_fields(db, &self.infer, id, expr)
             {
@@ -132,7 +132,7 @@ impl ExprValidator {
             }
         }
 
-        for (id, pat) in body.pats.iter() {
+        for (id, pat) in body.pats() {
             if let Some((variant, missed_fields, true)) =
                 record_pattern_missing_fields(db, &self.infer, id, pat)
             {
@@ -389,7 +389,7 @@ impl ExprValidator {
         if !self.validate_lints {
             return;
         }
-        match &body.exprs[body_expr] {
+        match &body[body_expr] {
             Expr::Block { statements, tail, .. } => {
                 let last_stmt = tail.or_else(|| match statements.last()? {
                     Statement::Expr { expr, .. } => Some(*expr),
@@ -428,7 +428,7 @@ impl ExprValidator {
             if else_branch.is_none() {
                 return;
             }
-            if let Expr::Block { statements, tail, .. } = &self.body.exprs[*then_branch] {
+            if let Expr::Block { statements, tail, .. } = &self.body[*then_branch] {
                 let last_then_expr = tail.or_else(|| match statements.last()? {
                     Statement::Expr { expr, .. } => Some(*expr),
                     _ => None,

crates/hir-ty/src/diagnostics/match_check.rs

@@ -151,7 +151,7 @@ impl<'a> PatCtxt<'a> {
             hir_def::hir::Pat::Bind { id, subpat, .. } => {
                 let bm = self.infer.binding_modes[pat];
                 ty = &self.infer[id];
-                let name = &self.body.bindings[id].name;
+                let name = &self.body[id].name;
                 match (bm, ty.kind(Interner)) {
                     (BindingMode::Ref(_), TyKind::Ref(.., rty)) => ty = rty,
                     (BindingMode::Ref(_), _) => {

crates/hir-ty/src/diagnostics/unsafe_check.rs

@@ -217,7 +217,7 @@ impl<'db> UnsafeVisitor<'db> {
     }
 
     fn walk_pat(&mut self, current: PatId) {
-        let pat = &self.body.pats[current];
+        let pat = &self.body[current];
 
         if self.inside_union_destructure {
             match pat {
@@ -264,7 +264,7 @@ impl<'db> UnsafeVisitor<'db> {
     }
 
     fn walk_expr(&mut self, current: ExprId) {
-        let expr = &self.body.exprs[current];
+        let expr = &self.body[current];
         let inside_assignment = mem::replace(&mut self.inside_assignment, false);
         match expr {
             &Expr::Call { callee, .. } => {
@@ -284,7 +284,7 @@ impl<'db> UnsafeVisitor<'db> {
                 self.resolver.reset_to_guard(guard);
             }
             Expr::Ref { expr, rawness: Rawness::RawPtr, mutability: _ } => {
-                match self.body.exprs[*expr] {
+                match self.body[*expr] {
                     // Do not report unsafe for `addr_of[_mut]!(EXTERN_OR_MUT_STATIC)`,
                     // see https://github.com/rust-lang/rust/pull/125834.
                     Expr::Path(_) => return,

crates/hir-ty/src/infer/mutability.rs

@@ -273,7 +273,7 @@ impl InferenceContext<'_> {
     fn pat_bound_mutability(&self, pat: PatId) -> Mutability {
         let mut r = Mutability::Not;
         self.body.walk_bindings_in_pat(pat, |b| {
-            if self.body.bindings[b].mode == BindingAnnotation::RefMut {
+            if self.body[b].mode == BindingAnnotation::RefMut {
                 r = Mutability::Mut;
             }
         });

crates/hir-ty/src/infer/pat.rs

@@ -459,7 +459,7 @@ impl InferenceContext<'_> {
         expected: &Ty,
         decl: Option<DeclContext>,
     ) -> Ty {
-        let Binding { mode, .. } = self.body.bindings[binding];
+        let Binding { mode, .. } = self.body[binding];
         let mode = if mode == BindingAnnotation::Unannotated {
             default_bm
         } else {
@@ -639,7 +639,7 @@ impl InferenceContext<'_> {
 pub(super) fn contains_explicit_ref_binding(body: &Body, pat_id: PatId) -> bool {
     let mut res = false;
     body.walk_pats(pat_id, &mut |pat| {
-        res |= matches!(body[pat], Pat::Bind { id, .. } if body.bindings[id].mode == BindingAnnotation::Ref);
+        res |= matches!(body[pat], Pat::Bind { id, .. } if body[id].mode == BindingAnnotation::Ref);
     });
     res
 }

crates/hir-ty/src/layout/tests.rs

@@ -119,8 +119,7 @@ fn eval_expr(
         .unwrap();
     let hir_body = db.body(function_id.into());
     let b = hir_body
-        .bindings
+        .bindings()
-        .iter()
         .find(|x| x.1.name.display_no_db(file_id.edition(&db)).to_smolstr() == "goal")
         .unwrap()
         .0;

crates/hir-ty/src/mir.rs

@@ -1212,10 +1212,9 @@ impl MirSpan {
         match *self {
             MirSpan::ExprId(expr) => matches!(body[expr], Expr::Ref { .. }),
             // FIXME: Figure out if this is correct wrt. match ergonomics.
-            MirSpan::BindingId(binding) => matches!(
+            MirSpan::BindingId(binding) => {
-                body.bindings[binding].mode,
+                matches!(body[binding].mode, BindingAnnotation::Ref | BindingAnnotation::RefMut)
-                BindingAnnotation::Ref | BindingAnnotation::RefMut
+            }
-            ),
             MirSpan::PatId(_) | MirSpan::SelfParam | MirSpan::Unknown => false,
         }
     }

crates/hir-ty/src/mir/lower.rs

@@ -321,7 +321,7 @@ impl<'ctx> MirLowerCtx<'ctx> {
         current: BasicBlockId,
     ) -> Result<Option<(Operand, BasicBlockId)>> {
         if !self.has_adjustments(expr_id) {
-            if let Expr::Literal(l) = &self.body.exprs[expr_id] {
+            if let Expr::Literal(l) = &self.body[expr_id] {
                 let ty = self.expr_ty_without_adjust(expr_id);
                 return Ok(Some((self.lower_literal_to_operand(ty, l)?, current)));
             }
@@ -411,7 +411,7 @@ impl<'ctx> MirLowerCtx<'ctx> {
         place: Place,
         mut current: BasicBlockId,
     ) -> Result<Option<BasicBlockId>> {
-        match &self.body.exprs[expr_id] {
+        match &self.body[expr_id] {
             Expr::OffsetOf(_) => {
                 not_supported!("builtin#offset_of")
             }
@@ -1374,7 +1374,7 @@ impl<'ctx> MirLowerCtx<'ctx> {
     }
 
     fn lower_literal_or_const_to_operand(&mut self, ty: Ty, loc: &ExprId) -> Result<Operand> {
-        match &self.body.exprs[*loc] {
+        match &self.body[*loc] {
             Expr::Literal(l) => self.lower_literal_to_operand(ty, l),
             Expr::Path(c) => {
                 let owner = self.owner;
@@ -1850,7 +1850,7 @@ impl<'ctx> MirLowerCtx<'ctx> {
             self.drop_scopes.last_mut().unwrap().locals.push(local_id);
             if let Pat::Bind { id, subpat: None } = self.body[it] {
                 if matches!(
-                    self.body.bindings[id].mode,
+                    self.body[id].mode,
                     BindingAnnotation::Unannotated | BindingAnnotation::Mutable
                 ) {
                     self.result.binding_locals.insert(id, local_id);
@@ -1859,7 +1859,7 @@ impl<'ctx> MirLowerCtx<'ctx> {
             local_id
         }));
         // and then rest of bindings
-        for (id, _) in self.body.bindings.iter() {
+        for (id, _) in self.body.bindings() {
             if !pick_binding(id) {
                 continue;
             }
@@ -2126,7 +2126,7 @@ pub fn mir_body_for_closure_query(
         .result
         .binding_locals
         .into_iter()
-        .filter(|it| ctx.body.binding_owners.get(&it.0).copied() == Some(expr))
+        .filter(|it| ctx.body.binding_owner(it.0) == Some(expr))
         .collect();
     if let Some(err) = err {
         return Err(MirLowerError::UnresolvedUpvar(err));
@@ -2191,7 +2191,7 @@ pub fn lower_to_mir(
     // 0 is return local
     ctx.result.locals.alloc(Local { ty: ctx.expr_ty_after_adjustments(root_expr) });
     let binding_picker = |b: BindingId| {
-        let owner = ctx.body.binding_owners.get(&b).copied();
+        let owner = ctx.body.binding_owner(b);
         if root_expr == body.body_expr { owner.is_none() } else { owner == Some(root_expr) }
     };
     // 1 to param_len is for params

crates/hir-ty/src/mir/lower/as_place.rs

@@ -133,7 +133,7 @@ impl MirLowerCtx<'_> {
             }
             this.lower_expr_to_some_place_without_adjust(expr_id, current)
         };
-        match &self.body.exprs[expr_id] {
+        match &self.body[expr_id] {
             Expr::Path(p) => {
                 let resolver_guard =
                     self.resolver.update_to_inner_scope(self.db, self.owner, expr_id);

crates/hir-ty/src/mir/lower/pattern_matching.rs

@@ -130,7 +130,7 @@ impl MirLowerCtx<'_> {
                 .collect::<Vec<_>>()
                 .into(),
         );
-        Ok(match &self.body.pats[pattern] {
+        Ok(match &self.body[pattern] {
             Pat::Missing => return Err(MirLowerError::IncompletePattern),
             Pat::Wild => (current, current_else),
             Pat::Tuple { args, ellipsis } => {
@@ -436,7 +436,7 @@ impl MirLowerCtx<'_> {
                     (next, Some(else_target))
                 }
             },
-            Pat::Lit(l) => match &self.body.exprs[*l] {
+            Pat::Lit(l) => match &self.body[*l] {
                 Expr::Literal(l) => {
                     if mode == MatchingMode::Check {
                         let c = self.lower_literal_to_operand(self.infer[pattern].clone(), l)?;

crates/hir-ty/src/mir/pretty.rs

@@ -219,7 +219,7 @@ impl<'a> MirPrettyCtx<'a> {
 
     fn local_name(&self, local: LocalId) -> LocalName {
         match self.local_to_binding.get(local) {
-            Some(b) => LocalName::Binding(self.hir_body.bindings[*b].name.clone(), local),
+            Some(b) => LocalName::Binding(self.hir_body[*b].name.clone(), local),
             None => LocalName::Unknown(local),
         }
     }

crates/hir-ty/src/tests.rs

@@ -168,7 +168,7 @@ fn check_impl(
         let inference_result = db.infer(def);
 
         for (pat, mut ty) in inference_result.type_of_pat.iter() {
-            if let Pat::Bind { id, .. } = body.pats[pat] {
+            if let Pat::Bind { id, .. } = body[pat] {
                 ty = &inference_result.type_of_binding[id];
             }
             let node = match pat_node(&body_source_map, pat, &db) {
@@ -316,7 +316,7 @@ fn infer_with_mismatches(content: &str, include_mismatches: bool) -> String {
         }
 
         for (pat, mut ty) in inference_result.type_of_pat.iter() {
-            if let Pat::Bind { id, .. } = body.pats[pat] {
+            if let Pat::Bind { id, .. } = body[pat] {
                 ty = &inference_result.type_of_binding[id];
             }
             let node = match body_source_map.pat_syntax(pat) {

crates/hir/src/lib.rs

@@ -2034,7 +2034,7 @@ impl DefWithBody {
                     )
                 }
                 let mol = &borrowck_result.mutability_of_locals;
-                for (binding_id, binding_data) in body.bindings.iter() {
+                for (binding_id, binding_data) in body.bindings() {
                     if binding_data.problems.is_some() {
                         // We should report specific diagnostics for these problems, not `need-mut` and `unused-mut`.
                         continue;

crates/hir/src/semantics.rs

@@ -677,8 +677,7 @@ impl<'db> SemanticsImpl<'db> {
     pub fn rename_conflicts(&self, to_be_renamed: &Local, new_name: &Name) -> Vec<Local> {
         let body = self.db.body(to_be_renamed.parent);
         let resolver = to_be_renamed.parent.resolver(self.db);
-        let starting_expr =
+        let starting_expr = body.binding_owner(to_be_renamed.binding_id).unwrap_or(body.body_expr);
-            body.binding_owners.get(&to_be_renamed.binding_id).copied().unwrap_or(body.body_expr);
         let mut visitor = RenameConflictsVisitor {
             body: &body,
             conflicts: FxHashSet::default(),

crates/hir/src/source_analyzer.rs

@@ -242,11 +242,7 @@ impl<'db> SourceAnalyzer<'db> {
 
     fn binding_id_of_pat(&self, pat: &ast::IdentPat) -> Option<BindingId> {
         let pat_id = self.pat_id(&pat.clone().into())?;
-        if let Pat::Bind { id, .. } = self.store()?.pats[pat_id.as_pat()?] {
+        if let Pat::Bind { id, .. } = self.store()?[pat_id.as_pat()?] { Some(id) } else { None }
-            Some(id)
-        } else {
-            None
-        }
     }
 
     pub(crate) fn expr_adjustments(&self, expr: &ast::Expr) -> Option<&[Adjustment]> {
@@ -997,7 +993,7 @@ impl<'db> SourceAnalyzer<'db> {
         let parent_hir_path = path
             .parent_path()
             .and_then(|p| collector.lower_path(p, &mut ExprCollector::impl_trait_error_allocator));
-        let store = collector.store.finish();
+        let (store, _) = collector.store.finish();
 
         // Case where path is a qualifier of a use tree, e.g. foo::bar::{Baz, Qux} where we are
         // trying to resolve foo::bar.
@@ -1206,7 +1202,7 @@ impl<'db> SourceAnalyzer<'db> {
         let mut collector = ExprCollector::new(db, self.resolver.module(), self.file_id);
         let hir_path =
             collector.lower_path(path.clone(), &mut ExprCollector::impl_trait_error_allocator)?;
-        let store = collector.store.finish();
+        let (store, _) = collector.store.finish();
         Some(resolve_hir_path_(
             db,
             &self.resolver,

crates/ide/src/inlay_hints/implicit_drop.rs

@@ -92,7 +92,7 @@ pub(super) fn hints(
                 },
                 MirSpan::Unknown => continue,
             };
-            let binding = &hir.bindings[binding_idx];
+            let binding = &hir[binding_idx];
             let name = binding.name.display_no_db(display_target.edition).to_smolstr();
             if name.starts_with("<ra@") {
                 continue; // Ignore desugared variables

crates/rust-analyzer/src/cli/analysis_stats.rs

@@ -796,7 +796,7 @@ impl flags::AnalysisStats {
             // region:expressions
             let (previous_exprs, previous_unknown, previous_partially_unknown) =
                 (num_exprs, num_exprs_unknown, num_exprs_partially_unknown);
-            for (expr_id, _) in body.exprs.iter() {
+            for (expr_id, _) in body.exprs() {
                 let ty = &inference_result[expr_id];
                 num_exprs += 1;
                 let unknown_or_partial = if ty.is_unknown() {
@@ -901,7 +901,7 @@ impl flags::AnalysisStats {
             // region:patterns
             let (previous_pats, previous_unknown, previous_partially_unknown) =
                 (num_pats, num_pats_unknown, num_pats_partially_unknown);
-            for (pat_id, _) in body.pats.iter() {
+            for (pat_id, _) in body.pats() {
                 let ty = &inference_result[pat_id];
                 num_pats += 1;
                 let unknown_or_partial = if ty.is_unknown() {