Shrink `hir::def::Res`.

`Res::SelfTy` currently has two `Option`s. When the second one is `Some`
the first one is never consulted. So we can split it into two variants,
`Res::SelfTyParam` and `Res::SelfTyAlias`, reducing the size of `Res`
from 24 bytes to 12. This then shrinks `hir::Path` and
`hir::PathSegment`, which are the HIR types that take up the most space.

3 files changed, 6 insertions, 4 deletions

diff --git a/compiler/rustc_save_analysis/src/dump_visitor.rs b/compiler/rustc_save_analysis/src/dump_visitor.rs
index adbc119387d..ecb09f0c4b7 100644
--- a/compiler/rustc_save_analysis/src/dump_visitor.rs
+++ b/compiler/rustc_save_analysis/src/dump_visitor.rs
@@ -913,7 +913,8 @@ impl<'tcx> DumpVisitor<'tcx> {
                     | HirDefKind::AssocTy,
                     _,
                 )
-                | Res::SelfTy { .. } => {
+                | Res::SelfTyParam { .. }
+                | Res::SelfTyAlias { .. } => {
                     self.dump_path_segment_ref(
                         id,
                         &hir::PathSegment::new(ident, hir::HirId::INVALID, Res::Err),
diff --git a/compiler/rustc_save_analysis/src/lib.rs b/compiler/rustc_save_analysis/src/lib.rs
index ad7aca3cb94..aa000b7067b 100644
--- a/compiler/rustc_save_analysis/src/lib.rs
+++ b/compiler/rustc_save_analysis/src/lib.rs
@@ -740,7 +740,8 @@ impl<'tcx> SaveContext<'tcx> {
                 _,
             )
             | Res::PrimTy(..)
-            | Res::SelfTy { .. }
+            | Res::SelfTyParam { .. }
+            | Res::SelfTyAlias { .. }
             | Res::ToolMod
             | Res::NonMacroAttr(..)
             | Res::SelfCtor(..)
@@ -805,7 +806,7 @@ impl<'tcx> SaveContext<'tcx> {
 
     fn lookup_def_id(&self, ref_id: hir::HirId) -> Option<DefId> {
         match self.get_path_res(ref_id) {
-            Res::PrimTy(_) | Res::SelfTy { .. } | Res::Err => None,
+            Res::PrimTy(_) | Res::SelfTyParam { .. } | Res::SelfTyAlias { .. } | Res::Err => None,
             def => def.opt_def_id(),
         }
     }
diff --git a/compiler/rustc_save_analysis/src/sig.rs b/compiler/rustc_save_analysis/src/sig.rs
index bae1828cd18..62e9f6520fb 100644
--- a/compiler/rustc_save_analysis/src/sig.rs
+++ b/compiler/rustc_save_analysis/src/sig.rs
@@ -579,7 +579,7 @@ impl<'hir> Sig for hir::Path<'hir> {
         let res = scx.get_path_res(id.ok_or("Missing id for Path")?);
 
         let (name, start, end) = match res {
-            Res::PrimTy(..) | Res::SelfTy { .. } | Res::Err => {
+            Res::PrimTy(..) | Res::SelfTyParam { .. } | Res::SelfTyAlias { .. } | Res::Err => {
                 return Ok(Signature { text: path_to_string(self), defs: vec![], refs: vec![] });
             }
             Res::Def(DefKind::AssocConst | DefKind::Variant | DefKind::Ctor(..), _) => {