[ConstraintSystem] Adjust isArgumentOfImportedDecl to handle synthesized declarations

lib/ClangImporter/SwiftDeclSynthesizer.cpp

@@ -522,6 +522,8 @@ SwiftDeclSynthesizer::createDefaultConstructor(NominalTypeDecl *structDecl) {
   // Mark the constructor transparent so that we inline it away completely.
   constructor->getAttrs().add(new (context) TransparentAttr(/*implicit*/ true));
 
+  constructor->setSynthesized();
+
   constructor->setBodySynthesizer(synthesizeStructDefaultConstructorBody,
                                   structDecl);
 
@@ -652,6 +654,8 @@ ConstructorDecl *SwiftDeclSynthesizer::createValueConstructor(
   // Make the constructor transparent so we inline it away completely.
   constructor->getAttrs().add(new (context) TransparentAttr(/*implicit*/ true));
 
+  constructor->setSynthesized();
+
   if (wantBody) {
     auto memberMemory =
         context.AllocateUninitialized<uintptr_t>(members.size() + 1);
@@ -1294,6 +1298,7 @@ SwiftDeclSynthesizer::makeEnumRawValueConstructor(EnumDecl *enumDecl) {
                               /*ThrownType=*/TypeLoc(), paramPL,
                               /*GenericParams=*/nullptr, enumDecl);
   ctorDecl->setImplicit();
+  ctorDecl->setSynthesized();
   ctorDecl->copyFormalAccessFrom(enumDecl);
   ctorDecl->setBodySynthesizer(synthesizeEnumRawValueConstructorBody, enumDecl);
   return ctorDecl;

lib/Sema/ConstraintSystem.cpp

@@ -4437,7 +4437,22 @@ bool ConstraintSystem::isArgumentOfImportedDecl(
     return false;
 
   auto *choice = overload->choice.getDecl();
-  return choice->hasClangNode();
+
+  // Imported declaration.
+  if (choice->hasClangNode())
+    return true;
+
+  // Implicit declaration synthesized by the compiler.
+  // Such declarations don't have clang nodes backing
+  // them but for the purposes of this check we consider
+  // them imported if the parent is.
+  if (choice->isSynthesized()) {
+    auto *dc = choice->getDeclContext();
+    if (auto *parent = dc->getAsDecl())
+      return parent->hasClangNode();
+  }
+
+  return false;
 }
 
 ConversionEphemeralness

test/Constraints/swift_to_c_pointer_conversions_in_synthesized.swift

@@ -0,0 +1,21 @@
+// RUN: %empty-directory(%t/src)
+// RUN: %empty-directory(%t/sdk)
+// RUN: split-file %s %t/src
+
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -typecheck %t/src/main.swift \
+// RUN:   -import-objc-header %t/src/Test.h \
+// RUN:   -module-name main -I %t -verify
+
+// REQUIRES: objc_interop
+
+//--- Test.h
+#include <stdint.h>
+
+typedef struct {
+    uint8_t* buffer;
+} frame_t __attribute__((swift_name("Frame")));
+
+//--- main.swift
+func test(rawPointer: UnsafeMutableRawPointer) {
+  _ = Frame(buffer: rawPointer) // Ok (even though init is synthesized the type is imported)
+}