[NFC] MemberTypeRepr: Tolerate zero member components in factory constructors

Author: AnthonyLatsis

include/swift/AST/TypeRepr.h

@@ -442,11 +442,11 @@ class MemberTypeRepr final : public DeclRefTypeRepr,
   }
 
 public:
-  static MemberTypeRepr *create(const ASTContext &Ctx, TypeRepr *Base,
-                                ArrayRef<IdentTypeRepr *> MemberComponents);
+  static TypeRepr *create(const ASTContext &Ctx, TypeRepr *Base,
+                          ArrayRef<IdentTypeRepr *> MemberComponents);
 
-  static MemberTypeRepr *create(const ASTContext &Ctx,
-                                ArrayRef<IdentTypeRepr *> Components);
+  static DeclRefTypeRepr *create(const ASTContext &Ctx,
+                                 ArrayRef<IdentTypeRepr *> Components);
 
   TypeRepr *getBaseComponent() const { return Base; }
 

lib/AST/TypeRepr.cpp

@@ -384,17 +384,20 @@ GenericIdentTypeRepr *GenericIdentTypeRepr::create(const ASTContext &C,
   return new (mem) GenericIdentTypeRepr(Loc, Id, GenericArgs, AngleBrackets);
 }
 
-MemberTypeRepr *
-MemberTypeRepr::create(const ASTContext &C, TypeRepr *Base,
-                       ArrayRef<IdentTypeRepr *> MemberComponents) {
+TypeRepr *MemberTypeRepr::create(const ASTContext &C, TypeRepr *Base,
+                                 ArrayRef<IdentTypeRepr *> MemberComponents) {
+  if (MemberComponents.empty())
+    return Base;
+
   auto size = totalSizeToAlloc<IdentTypeRepr *>(MemberComponents.size());
   auto mem = C.Allocate(size, alignof(MemberTypeRepr));
   return new (mem) MemberTypeRepr(Base, MemberComponents);
 }
 
-MemberTypeRepr *MemberTypeRepr::create(const ASTContext &Ctx,
-                                       ArrayRef<IdentTypeRepr *> Components) {
-  return create(Ctx, Components.front(), Components.drop_front());
+DeclRefTypeRepr *MemberTypeRepr::create(const ASTContext &Ctx,
+                                        ArrayRef<IdentTypeRepr *> Components) {
+  return cast<DeclRefTypeRepr>(
+      create(Ctx, Components.front(), Components.drop_front()));
 }
 
 PackTypeRepr::PackTypeRepr(SourceLoc keywordLoc, SourceRange braceLocs,

lib/Parse/ParseType.cpp

@@ -793,11 +793,7 @@ Parser::parseTypeIdentifier(bool isParsingQualifiedDeclBaseType) {
 
   DeclRefTypeRepr *DeclRefTR = nullptr;
   if (!ComponentsR.empty()) {
-    if (ComponentsR.size() == 1) {
-      DeclRefTR = ComponentsR.front();
-    } else {
-      DeclRefTR = MemberTypeRepr::create(Context, ComponentsR);
-    }
+    DeclRefTR = MemberTypeRepr::create(Context, ComponentsR);
   }
 
   if (Status.hasCodeCompletion()) {

lib/Sema/TypeCheckPattern.cpp

@@ -482,12 +482,7 @@ class ResolvePattern : public ASTVisitor<ResolvePattern,
     const auto options =
         TypeResolutionOptions(None) | TypeResolutionFlags::SilenceErrors;
 
-    DeclRefTypeRepr *repr = nullptr;
-    if (components.size() == 1) {
-      repr = components.front();
-    } else {
-      repr = MemberTypeRepr::create(Context, components);
-    }
+    DeclRefTypeRepr *repr = MemberTypeRepr::create(Context, components);
 
     // See if the repr resolves to a type.
     const auto ty = TypeResolution::resolveContextualType(
@@ -609,12 +604,7 @@ class ResolvePattern : public ASTVisitor<ResolvePattern,
 
       // Otherwise, see whether we had an enum type as the penultimate
       // component, and look up an element inside it.
-      DeclRefTypeRepr *prefixRepr = nullptr;
-      if (components.size() == 1) {
-        prefixRepr = components.front();
-      } else {
-        prefixRepr = MemberTypeRepr::create(Context, components);
-      }
+      DeclRefTypeRepr *prefixRepr = MemberTypeRepr::create(Context, components);
 
       // See first if the entire repr resolves to a type.
       const Type enumTy = TypeResolution::resolveContextualType(