AST: Sink SubstFlags::DesugarMemberTypes hack down into ProtocolConformance::getTypeWitness()

Author: slavapestov

lib/AST/ProtocolConformance.cpp

@@ -147,7 +147,27 @@ ProtocolConformance::getTypeWitnessAndDecl(AssociatedTypeDecl *assocType,
 
 Type ProtocolConformance::getTypeWitness(AssociatedTypeDecl *assocType,
                                          SubstOptions options) const {
-  return getTypeWitnessAndDecl(assocType, options).getWitnessType();
+  auto witness = getTypeWitnessAndDecl(assocType, options);
+  auto witnessTy = witness.getWitnessType();
+  if (!witnessTy)
+    return witnessTy;
+
+  // This is a hacky feature allowing code completion to migrate to
+  // using Type::subst() without changing output.
+  //
+  // FIXME: Remove this hack and do whatever we need to do in the
+  // ASTPrinter instead.
+  if (options & SubstFlags::DesugarMemberTypes) {
+    if (auto *aliasType = dyn_cast<TypeAliasType>(witnessTy.getPointer()))
+      witnessTy = aliasType->getSinglyDesugaredType();
+
+    // Another hack. If the type witness is a opaque result type. They can
+    // only be referred using the name of the associated type.
+    if (witnessTy->is<OpaqueTypeArchetypeType>())
+      witnessTy = witness.getWitnessDecl()->getDeclaredInterfaceType();
+  }
+
+  return witnessTy;
 }
 
 ConcreteDeclRef

lib/AST/TypeSubstitution.cpp

@@ -579,25 +579,8 @@ Type TypeSubstituter::transformDependentMemberType(DependentMemberType *dependen
     witnessTy = conformance.getPack()->getTypeWitness(assocType,
                                                       IFS.getOptions());
   } else if (conformance.isConcrete()) {
-    auto witness =
-        conformance.getConcrete()->getTypeWitnessAndDecl(assocType,
-                                                         IFS.getOptions());
-
-    witnessTy = witness.getWitnessType();
-    if (!witnessTy || witnessTy->hasError())
-      return failed();
-
-    // This is a hacky feature allowing code completion to migrate to
-    // using Type::subst() without changing output.
-    if (IFS.getOptions() & SubstFlags::DesugarMemberTypes) {
-      if (auto *aliasType = dyn_cast<TypeAliasType>(witnessTy.getPointer()))
-        witnessTy = aliasType->getSinglyDesugaredType();
-
-      // Another hack. If the type witness is a opaque result type. They can
-      // only be referred using the name of the associated type.
-      if (witnessTy->is<OpaqueTypeArchetypeType>())
-        witnessTy = witness.getWitnessDecl()->getDeclaredInterfaceType();
-    }
+    witnessTy = conformance.getConcrete()->getTypeWitness(assocType,
+                                                          IFS.getOptions());
   }
 
   if (!witnessTy || witnessTy->is<ErrorType>())