[AST] TypeWrappers: Add request to retrieve type wrapper initializer

Author: xedin

include/swift/AST/Decl.h

@@ -3780,6 +3780,10 @@ class NominalTypeDecl : public GenericTypeDecl, public IterableDeclContext {
   /// by the wrapper.
   NominalTypeDecl *getTypeWrapperStorageDecl() const;
 
+  /// If this declaration is a type wrapper, retrieve
+  /// its required initializer - `init(storage:)`.
+  ConstructorDecl *getTypeWrapperInitializer() const;
+
   /// Get a memberwise initializer that could be used to instantiate a
   /// type wrapped type.
   ConstructorDecl *getTypeWrappedTypeMemberwiseInitializer() const;

include/swift/AST/TypeCheckRequests.h

@@ -3720,6 +3720,22 @@ class SynthesizeLocalVariableForTypeWrapperStorage
   bool isCached() const { return true; }
 };
 
+class GetTypeWrapperInitializer
+    : public SimpleRequest<GetTypeWrapperInitializer,
+                           ConstructorDecl *(NominalTypeDecl *),
+                           RequestFlags::Cached> {
+public:
+  using SimpleRequest::SimpleRequest;
+
+private:
+  friend SimpleRequest;
+
+  ConstructorDecl *evaluate(Evaluator &evaluator, NominalTypeDecl *) const;
+
+public:
+  bool isCached() const { return true; }
+};
+
 void simple_display(llvm::raw_ostream &out, ASTNode node);
 void simple_display(llvm::raw_ostream &out, Type value);
 void simple_display(llvm::raw_ostream &out, const TypeRepr *TyR);

include/swift/AST/TypeCheckerTypeIDZone.def

@@ -437,3 +437,6 @@ SWIFT_REQUEST(TypeChecker, SynthesizeTypeWrappedTypeMemberwiseInitializerBody,
 SWIFT_REQUEST(TypeChecker, SynthesizeLocalVariableForTypeWrapperStorage,
               VarDecl *(ConstructorDecl *),
               Cached, NoLocationInfo)
+SWIFT_REQUEST(TypeChecker, GetTypeWrapperInitializer,
+              ConstructorDecl *(NominalTypeDecl *),
+              Cached, NoLocationInfo)

lib/Sema/TypeCheckTypeWrapper.cpp

@@ -512,3 +512,24 @@ VarDecl *SynthesizeLocalVariableForTypeWrapperStorage::evaluate(
                      VarDecl::Introducer::Var);
   return PBD->getSingleVar();
 }
+
+ConstructorDecl *NominalTypeDecl::getTypeWrapperInitializer() const {
+  auto *mutableSelf = const_cast<NominalTypeDecl *>(this);
+  return evaluateOrDefault(getASTContext().evaluator,
+                           GetTypeWrapperInitializer{mutableSelf}, nullptr);
+}
+
+ConstructorDecl *
+GetTypeWrapperInitializer::evaluate(Evaluator &evaluator,
+                                    NominalTypeDecl *typeWrapper) const {
+  auto &ctx = typeWrapper->getASTContext();
+  assert(typeWrapper->getAttrs().hasAttribute<TypeWrapperAttr>());
+
+  auto ctors = typeWrapper->lookupDirect(
+      DeclName(ctx, DeclBaseName::createConstructor(), {ctx.Id_memberwise}));
+
+  if (ctors.size() != 1)
+    return nullptr;
+
+  return cast<ConstructorDecl>(ctors.front());
+}