[AST] Make it possible to check if var decl is for _storage

Author: xedin

include/swift/AST/Decl.h

@@ -5714,6 +5714,11 @@ class VarDecl : public AbstractStorageDecl {
   /// backing property will be treated as the member-initialized property.
   bool isMemberwiseInitialized(bool preferDeclaredProperties) const;
 
+  /// Check whether this variable presents a local storage synthesized
+  /// by the compiler in a user-defined designated initializer to
+  /// support initialization of type wrapper managed properties.
+  bool isTypeWrapperLocalStorageForInitializer() const;
+
   /// Return the range of semantics attributes attached to this VarDecl.
   auto getSemanticsAttrs() const
       -> decltype(getAttrs().getAttributes<SemanticsAttr>()) {

lib/AST/Decl.cpp

@@ -6504,6 +6504,14 @@ bool VarDecl::isMemberwiseInitialized(bool preferDeclaredProperties) const {
   return true;
 }
 
+bool VarDecl::isTypeWrapperLocalStorageForInitializer() const {
+  if (auto *ctor =
+          dyn_cast_or_null<ConstructorDecl>(getDeclContext()->getAsDecl())) {
+    return this == ctor->getLocalTypeWrapperStorageVar();
+  }
+  return false;
+}
+
 bool VarDecl::isLet() const {
   // An awful hack that stabilizes the value of 'isLet' for ParamDecl instances.
   //
@@ -9527,4 +9535,4 @@ bool ActorIsolation::isDistributedActor() const {
 BuiltinTupleDecl::BuiltinTupleDecl(Identifier Name,
                                    DeclContext *Parent)
   : NominalTypeDecl(DeclKind::BuiltinTuple, Parent, Name, SourceLoc(),
-                    ArrayRef<InheritedEntry>(), nullptr) {}
+                    ArrayRef<InheritedEntry>(), nullptr) {}