Drop unnecessary "parent context" state from TypeRefinementContextBuilder

This state is a holdover from when accessors we stored "alongside"
their variable declarations, rather than contained within them. That's
no longer the case, so we don't need to track this information any
more.

Author: DougGregor

lib/Sema/TypeCheckAvailability.cpp

@@ -388,20 +388,6 @@ class TypeRefinementContextBuilder : private ASTWalker {
   };
   std::vector<DeclBodyContextInfo> DeclBodyContextStack;
 
-  /// A mapping from abstract storage declarations with accessors to
-  /// to the type refinement contexts for those declarations. We refer to
-  /// this map to determine the appropriate parent TRC to use when
-  /// walking the accessor function.
-  llvm::DenseMap<AbstractStorageDecl *, TypeRefinementContext *>
-      StorageContexts;
-
-  /// A mapping from pattern binding storage declarations to the type refinement
-  /// contexts for those declarations. We refer to this map to determine the
-  /// appropriate parent TRC to use when walking a var decl that belongs to a
-  /// pattern containing multiple vars.
-  llvm::DenseMap<PatternBindingDecl *, TypeRefinementContext *>
-      PatternBindingContexts;
-
   TypeRefinementContext *getCurrentTRC() {
     return ContextStack.back().TRC;
   }
@@ -482,19 +468,9 @@ class TypeRefinementContextBuilder : private ASTWalker {
   PreWalkAction walkToDeclPre(Decl *D) override {
     PrettyStackTraceDecl trace(stackTraceAction(), D);
 
-    // Adds in a parent TRC for decls which are syntactically nested but are not
-    // represented that way in the AST. (Particularly, AbstractStorageDecl
-    // parents for AccessorDecl children.)
-    if (auto ParentTRC = getEffectiveParentContextForDecl(D)) {
-      pushContext(ParentTRC, D);
-    }
-
     // Adds in a TRC that covers the entire declaration.
     if (auto DeclTRC = getNewContextForSignatureOfDecl(D)) {
       pushContext(DeclTRC, D);
-
-      // Possibly use this as an effective parent context later.
-      recordEffectiveParentContext(D, DeclTRC);
     }
 
     // Create TRCs that cover only the body of the declaration.
@@ -515,49 +491,6 @@ class TypeRefinementContextBuilder : private ASTWalker {
     return Action::Continue();
   }
 
-  TypeRefinementContext *getEffectiveParentContextForDecl(Decl *D) {
-    // FIXME: Can we assert that we won't walk parent decls later that should
-    //        have been returned here?
-    if (auto *accessor = dyn_cast<AccessorDecl>(D)) {
-      // Use TRC of the storage rather the current TRC when walking this
-      // function.
-      auto it = StorageContexts.find(accessor->getStorage());
-      if (it != StorageContexts.end()) {
-        return it->second;
-      }
-    } else if (auto *VD = dyn_cast<VarDecl>(D)) {
-      // Use the TRC of the pattern binding decl as the parent for var decls.
-      if (auto *PBD = VD->getParentPatternBinding()) {
-        auto it = PatternBindingContexts.find(PBD);
-        if (it != PatternBindingContexts.end()) {
-          return it->second;
-        }
-      }
-    }
-
-    return nullptr;
-  }
-
-  /// If necessary, records a TRC so it can be returned by subsequent calls to
-  /// `getEffectiveParentContextForDecl()`.
-  void recordEffectiveParentContext(Decl *D, TypeRefinementContext *NewTRC) {
-    if (auto *StorageDecl = dyn_cast<AbstractStorageDecl>(D)) {
-      // Stash the TRC for the storage declaration to use as the parent of
-      // accessor decls later.
-      if (StorageDecl->hasParsedAccessors())
-        StorageContexts[StorageDecl] = NewTRC;
-    }
-
-    if (auto *VD = dyn_cast<VarDecl>(D)) {
-      // Stash the TRC for the var decl if its parent pattern binding decl has
-      // more than one entry so that the sibling var decls can reuse it.
-      if (auto *PBD = VD->getParentPatternBinding()) {
-        if (PBD->getNumPatternEntries() > 1)
-          PatternBindingContexts[PBD] = NewTRC;
-      }
-    }
-  }
-
   /// Returns a new context to be introduced for the declaration, or nullptr
   /// if no new context should be introduced.
   TypeRefinementContext *getNewContextForSignatureOfDecl(Decl *D) {