Sema: Build TypeRefinementContexts correctly for multi-element enum cases.

Nodes in the TypeRefinementContext tree should be introduced for enum cases,
rather than enum elements, since its the cases that carry availability
annotations. Previously, enum cases in source that contained more than one
element would result in a malformed TRC tree that had overlapping sibling nodes
for each of the elements in a case declaration.

Author: tshortli

lib/AST/TypeRefinementContext.cpp

@@ -381,6 +381,10 @@ void TypeRefinementContext::print(raw_ostream &OS, SourceManager &SrcMgr,
       if (auto VD = PBD->getAnchoringVarDecl(0)) {
         OS << VD->getName();
       }
+    } else if (auto ECD = dyn_cast<EnumCaseDecl>(D)) {
+      if (auto EED = ECD->getFirstElement()) {
+        OS << EED->getName();
+      }
     }
   }
 

lib/Sema/TypeCheckAvailability.cpp

@@ -640,6 +640,7 @@ class TypeRefinementContextBuilder : private ASTWalker {
   /// if no new context should be introduced.
   TypeRefinementContext *getNewContextForSignatureOfDecl(Decl *D) {
     if (!isa<ValueDecl>(D) &&
+        !isa<EnumCaseDecl>(D) &&
         !isa<ExtensionDecl>(D) &&
         !isa<MacroExpansionDecl>(D) &&
         !isa<PatternBindingDecl>(D))
@@ -658,6 +659,11 @@ class TypeRefinementContextBuilder : private ASTWalker {
         return nullptr;
     }
 
+    // Don't introduce for enum element declarations. All the relevant
+    // information is on the enum case declaration.
+    if (isa<EnumElementDecl>(D))
+      return nullptr;
+
     // Declarations with an explicit availability attribute always get a TRC.
     if (hasActiveAvailableAttribute(D, Context)) {
       AvailabilityRange DeclaredAvailability =

test/Sema/availability_refinement_contexts.swift

@@ -273,3 +273,16 @@ struct SomeStruct {
   @available(OSX 52, *)
   func someMethodAvailable52() -> Int { return 52 }
 }
+
+// CHECK-NEXT: {{^}}  (decl version=51 decl=SomeEnum
+// CHECK-NEXT: {{^}}    (decl version=52 decl=a
+// CHECK-NEXT: {{^}}    (decl version=53 decl=b
+
+@available(OSX 51, *)
+enum SomeEnum {
+  @available(OSX 52, *)
+  case a
+
+  @available(OSX 53, *)
+  case b, c
+}