7 files changed, 53 insertions, 33 deletions

diff --git a/crates/hir_def/src/body/lower.rs b/crates/hir_def/src/body/lower.rs
index 63e89a1f4..1e743e5d5 100644
--- a/crates/hir_def/src/body/lower.rs
+++ b/crates/hir_def/src/body/lower.rs
@@ -322,8 +322,10 @@ impl ExprCollector<'_> {
                     Vec::new()
                 };
                 let method_name = e.name_ref().map(|nr| nr.as_name()).unwrap_or_else(Name::missing);
-                let generic_args =
-                    e.generic_arg_list().and_then(|it| GenericArgs::from_ast(&self.ctx(), it));
+                let generic_args = e
+                    .generic_arg_list()
+                    .and_then(|it| GenericArgs::from_ast(&self.ctx(), it))
+                    .map(Box::new);
                 self.alloc_expr(
                     Expr::MethodCall { receiver, method_name, args, generic_args },
                     syntax_ptr,
@@ -385,7 +387,7 @@ impl ExprCollector<'_> {
                 self.alloc_expr(Expr::Yield { expr }, syntax_ptr)
             }
             ast::Expr::RecordExpr(e) => {
-                let path = e.path().and_then(|path| self.expander.parse_path(path));
+                let path = e.path().and_then(|path| self.expander.parse_path(path)).map(Box::new);
                 let record_lit = if let Some(nfl) = e.record_expr_field_list() {
                     let fields = nfl
                         .fields()
@@ -430,7 +432,7 @@ impl ExprCollector<'_> {
             }
             ast::Expr::CastExpr(e) => {
                 let expr = self.collect_expr_opt(e.expr());
-                let type_ref = TypeRef::from_ast_opt(&self.ctx(), e.ty());
+                let type_ref = Box::new(TypeRef::from_ast_opt(&self.ctx(), e.ty()));
                 self.alloc_expr(Expr::Cast { expr, type_ref }, syntax_ptr)
             }
             ast::Expr::RefExpr(e) => {
@@ -469,8 +471,10 @@ impl ExprCollector<'_> {
                         arg_types.push(type_ref);
                     }
                 }
-                let ret_type =
-                    e.ret_type().and_then(|r| r.ty()).map(|it| TypeRef::from_ast(&self.ctx(), it));
+                let ret_type = e
+                    .ret_type()
+                    .and_then(|r| r.ty())
+                    .map(|it| Box::new(TypeRef::from_ast(&self.ctx(), it)));
                 let body = self.collect_expr_opt(e.body());
                 self.alloc_expr(Expr::Lambda { args, arg_types, ret_type, body }, syntax_ptr)
             }
@@ -755,7 +759,7 @@ impl ExprCollector<'_> {
                 }
             }
             ast::Pat::TupleStructPat(p) => {
-                let path = p.path().and_then(|path| self.expander.parse_path(path));
+                let path = p.path().and_then(|path| self.expander.parse_path(path)).map(Box::new);
                 let (args, ellipsis) = self.collect_tuple_pat(p.fields());
                 Pat::TupleStruct { path, args, ellipsis }
             }
@@ -765,7 +769,7 @@ impl ExprCollector<'_> {
                 Pat::Ref { pat, mutability }
             }
             ast::Pat::PathPat(p) => {
-                let path = p.path().and_then(|path| self.expander.parse_path(path));
+                let path = p.path().and_then(|path| self.expander.parse_path(path)).map(Box::new);
                 path.map(Pat::Path).unwrap_or(Pat::Missing)
             }
             ast::Pat::OrPat(p) => {
@@ -779,7 +783,7 @@ impl ExprCollector<'_> {
             }
             ast::Pat::WildcardPat(_) => Pat::Wild,
             ast::Pat::RecordPat(p) => {
-                let path = p.path().and_then(|path| self.expander.parse_path(path));
+                let path = p.path().and_then(|path| self.expander.parse_path(path)).map(Box::new);
                 let args: Vec<_> = p
                     .record_pat_field_list()
                     .expect("every struct should have a field list")
diff --git a/crates/hir_def/src/expr.rs b/crates/hir_def/src/expr.rs
index 6c7376fad..62a28bdba 100644
--- a/crates/hir_def/src/expr.rs
+++ b/crates/hir_def/src/expr.rs
@@ -86,7 +86,7 @@ pub enum Expr {
         receiver: ExprId,
         method_name: Name,
         args: Vec<ExprId>,
-        generic_args: Option<GenericArgs>,
+        generic_args: Option<Box<GenericArgs>>,
     },
     Match {
         expr: ExprId,
@@ -106,7 +106,7 @@ pub enum Expr {
         expr: Option<ExprId>,
     },
     RecordLit {
-        path: Option<Path>,
+        path: Option<Box<Path>>,
         fields: Vec<RecordLitField>,
         spread: Option<ExprId>,
     },
@@ -131,7 +131,7 @@ pub enum Expr {
     },
     Cast {
         expr: ExprId,
-        type_ref: TypeRef,
+        type_ref: Box<TypeRef>,
     },
     Ref {
         expr: ExprId,
@@ -162,7 +162,7 @@ pub enum Expr {
     Lambda {
         args: Vec<PatId>,
         arg_types: Vec<Option<TypeRef>>,
-        ret_type: Option<TypeRef>,
+        ret_type: Option<Box<TypeRef>>,
         body: ExprId,
     },
     Tuple {
@@ -412,13 +412,13 @@ pub enum Pat {
     Wild,
     Tuple { args: Vec<PatId>, ellipsis: Option<usize> },
     Or(Vec<PatId>),
-    Record { path: Option<Path>, args: Vec<RecordFieldPat>, ellipsis: bool },
+    Record { path: Option<Box<Path>>, args: Vec<RecordFieldPat>, ellipsis: bool },
     Range { start: ExprId, end: ExprId },
     Slice { prefix: Vec<PatId>, slice: Option<PatId>, suffix: Vec<PatId> },
-    Path(Path),
+    Path(Box<Path>),
     Lit(ExprId),
     Bind { mode: BindingAnnotation, name: Name, subpat: Option<PatId> },
-    TupleStruct { path: Option<Path>, args: Vec<PatId>, ellipsis: Option<usize> },
+    TupleStruct { path: Option<Box<Path>>, args: Vec<PatId>, ellipsis: Option<usize> },
     Ref { pat: PatId, mutability: Mutability },
     Box { inner: PatId },
     ConstBlock(ExprId),
diff --git a/crates/hir_def/src/path.rs b/crates/hir_def/src/path.rs
index f9c8328f0..b528ff8ba 100644
--- a/crates/hir_def/src/path.rs
+++ b/crates/hir_def/src/path.rs
@@ -289,6 +289,12 @@ impl From<Name> for Path {
     }
 }
 
+impl From<Name> for Box<Path> {
+    fn from(name: Name) -> Box<Path> {
+        Box::new(Path::from(name))
+    }
+}
+
 impl From<Name> for ModPath {
     fn from(name: Name) -> ModPath {
         ModPath::from_segments(PathKind::Plain, iter::once(name))
diff --git a/crates/hir_ty/src/infer/expr.rs b/crates/hir_ty/src/infer/expr.rs
index dab137ae1..5b3cdab4e 100644
--- a/crates/hir_ty/src/infer/expr.rs
+++ b/crates/hir_ty/src/infer/expr.rs
@@ -318,7 +318,13 @@ impl<'a> InferenceContext<'a> {
                 self.normalize_associated_types_in(ret_ty)
             }
             Expr::MethodCall { receiver, args, method_name, generic_args } => self
-                .infer_method_call(tgt_expr, *receiver, &args, &method_name, generic_args.as_ref()),
+                .infer_method_call(
+                    tgt_expr,
+                    *receiver,
+                    &args,
+                    &method_name,
+                    generic_args.as_deref(),
+                ),
             Expr::Match { expr, arms } => {
                 let input_ty = self.infer_expr(*expr, &Expectation::none());
 
@@ -399,7 +405,7 @@ impl<'a> InferenceContext<'a> {
                 TyKind::Never.intern(&Interner)
             }
             Expr::RecordLit { path, fields, spread } => {
-                let (ty, def_id) = self.resolve_variant(path.as_ref());
+                let (ty, def_id) = self.resolve_variant(path.as_deref());
                 if let Some(variant) = def_id {
                     self.write_variant_resolution(tgt_expr.into(), variant);
                 }
diff --git a/crates/hir_ty/src/infer/pat.rs b/crates/hir_ty/src/infer/pat.rs
index fc2bc3ef8..12431ae07 100644
--- a/crates/hir_ty/src/infer/pat.rs
+++ b/crates/hir_ty/src/infer/pat.rs
@@ -174,7 +174,7 @@ impl<'a> InferenceContext<'a> {
                 TyKind::Ref(mutability, static_lifetime(), subty).intern(&Interner)
             }
             Pat::TupleStruct { path: p, args: subpats, ellipsis } => self.infer_tuple_struct_pat(
-                p.as_ref(),
+                p.as_deref(),
                 subpats,
                 expected,
                 default_bm,
@@ -182,7 +182,7 @@ impl<'a> InferenceContext<'a> {
                 *ellipsis,
             ),
             Pat::Record { path: p, args: fields, ellipsis: _ } => {
-                self.infer_record_pat(p.as_ref(), fields, expected, default_bm, pat)
+                self.infer_record_pat(p.as_deref(), fields, expected, default_bm, pat)
             }
             Pat::Path(path) => {
                 // FIXME use correct resolver for the surrounding expression
diff --git a/crates/vfs/Cargo.toml b/crates/vfs/Cargo.toml
index c318a68f7..894944b18 100644
--- a/crates/vfs/Cargo.toml
+++ b/crates/vfs/Cargo.toml
@@ -14,3 +14,4 @@ rustc-hash = "1.0"
 fst = "0.4"
 
 paths = { path = "../paths", version = "0.0.0" }
+indexmap = "1.6.2"
diff --git a/crates/vfs/src/path_interner.rs b/crates/vfs/src/path_interner.rs
index 2189e5e25..6e049f0d4 100644
--- a/crates/vfs/src/path_interner.rs
+++ b/crates/vfs/src/path_interner.rs
@@ -1,15 +1,22 @@
 //! Maps paths to compact integer ids. We don't care about clearings paths which
 //! no longer exist -- the assumption is total size of paths we ever look at is
 //! not too big.
-use rustc_hash::FxHashMap;
+use std::hash::BuildHasherDefault;
+
+use indexmap::IndexSet;
+use rustc_hash::FxHasher;
 
 use crate::{FileId, VfsPath};
 
 /// Structure to map between [`VfsPath`] and [`FileId`].
-#[derive(Default)]
 pub(crate) struct PathInterner {
-    map: FxHashMap<VfsPath, FileId>,
-    vec: Vec<VfsPath>,
+    map: IndexSet<VfsPath, BuildHasherDefault<FxHasher>>,
+}
+
+impl Default for PathInterner {
+    fn default() -> Self {
+        Self { map: IndexSet::default() }
+    }
 }
 
 impl PathInterner {
@@ -17,7 +24,7 @@ impl PathInterner {
     ///
     /// If `path` does not exists in `self`, returns [`None`].
     pub(crate) fn get(&self, path: &VfsPath) -> Option<FileId> {
-        self.map.get(path).copied()
+        self.map.get_index_of(path).map(|i| FileId(i as u32))
     }
 
     /// Insert `path` in `self`.
@@ -25,13 +32,9 @@ impl PathInterner {
     /// - If `path` already exists in `self`, returns its associated id;
     /// - Else, returns a newly allocated id.
     pub(crate) fn intern(&mut self, path: VfsPath) -> FileId {
-        if let Some(id) = self.get(&path) {
-            return id;
-        }
-        let id = FileId(self.vec.len() as u32);
-        self.map.insert(path.clone(), id);
-        self.vec.push(path);
-        id
+        let (id, _added) = self.map.insert_full(path);
+        assert!(id < u32::MAX as usize);
+        FileId(id as u32)
     }
 
     /// Returns the path corresponding to `id`.
@@ -40,6 +43,6 @@ impl PathInterner {
     ///
     /// Panics if `id` does not exists in `self`.
     pub(crate) fn lookup(&self, id: FileId) -> &VfsPath {
-        &self.vec[id.0 as usize]
+        self.map.get_index(id.0 as usize).unwrap()
     }
 }