rustc: Harmonize DefKind and DefPathData

`DefPathData::(ClosureExpr,ImplTrait)` are renamed to match `DefKind::(Closure,OpaqueTy)`.

`DefPathData::ImplTraitAssocTy` is replaced with `DefPathData::TypeNS(kw::Empty)` because both correspond to `DefKind::AssocTy`.
It's possible that introducing `(DefKind,DefPathData)::AssocOpaqueTy` could be a better solution, but that would be a much more invasive change.

Const generic parameters introduced for effects are moved from `DefPathData::TypeNS` to `DefPathData::ValueNS`, because constants are values.

`DefPathData` is no longer passed to `create_def` functions to avoid redundancy.

compiler/rustc_middle/src/ty/context.rs

@@ -977,7 +977,7 @@ impl<'tcx> TyCtxtAt<'tcx> {
     pub fn create_def(
         self,
         parent: LocalDefId,
-        data: hir::definitions::DefPathData,
+        name: Symbol,
         def_kind: DefKind,
     ) -> TyCtxtFeed<'tcx, LocalDefId> {
         // This function modifies `self.definitions` using a side-effect.
@@ -1000,6 +1000,7 @@ impl<'tcx> TyCtxtAt<'tcx> {
         // This is fine because:
         // - those queries are `eval_always` so we won't miss their result changing;
         // - this write will have happened before these queries are called.
+        let data = def_kind.def_path_data(name);
         let key = self.untracked.definitions.write().create_def(parent, data);
 
         let feed = TyCtxtFeed { tcx: self.tcx, key };

compiler/rustc_middle/src/ty/instance.rs

@@ -215,7 +215,7 @@ impl<'tcx> InstanceDef<'tcx> {
         };
         matches!(
             tcx.def_key(def_id).disambiguated_data.data,
-            DefPathData::Ctor | DefPathData::ClosureExpr
+            DefPathData::Ctor | DefPathData::Closure
         )
     }
 

compiler/rustc_middle/src/ty/print/mod.rs

@@ -131,7 +131,7 @@ pub trait Printer<'tcx>: Sized {
 
                     match key.disambiguated_data.data {
                         // Closures' own generics are only captures, don't print them.
-                        DefPathData::ClosureExpr => {}
+                        DefPathData::Closure => {}
                         // This covers both `DefKind::AnonConst` and `DefKind::InlineConst`.
                         // Anon consts doesn't have their own generics, and inline consts' own
                         // generics are their inferred types, so don't print them.

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -1804,13 +1804,13 @@ impl<'a, 'tcx> FmtPrinter<'a, 'tcx> {
 // (but also some things just print a `DefId` generally so maybe we need this?)
 fn guess_def_namespace(tcx: TyCtxt<'_>, def_id: DefId) -> Namespace {
     match tcx.def_key(def_id).disambiguated_data.data {
-        DefPathData::TypeNs(..) | DefPathData::CrateRoot | DefPathData::ImplTrait => {
+        DefPathData::TypeNs(..) | DefPathData::CrateRoot | DefPathData::OpaqueTy => {
             Namespace::TypeNS
         }
 
         DefPathData::ValueNs(..)
         | DefPathData::AnonConst
-        | DefPathData::ClosureExpr
+        | DefPathData::Closure
         | DefPathData::Ctor => Namespace::ValueNS,
 
         DefPathData::MacroNs(..) => Namespace::MacroNS,