Use Box'es to reduce the size of hir_def::expr::Pat from 112 to 64 bytes on 64bit

Author: alexmaco

crates/hir_def/src/body/lower.rs

@@ -759,7 +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 }
             }
@@ -769,7 +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) => {
@@ -783,7 +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")

crates/hir_def/src/expr.rs

@@ -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),

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))

crates/hir_ty/src/infer/pat.rs

@@ -174,15 +174,15 @@ impl<'a> InferenceContext<'a> {
                 TyKind::Ref(mutability, 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,
                 pat,
                 *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