[cxx-interop] Small fixes and cleanup based on review.

 * Check isAggregate instead of hasUserDeclaredConstructor.
 * Rename addEmptyArgNamesForCxxFunc ->  addEmptyArgNamesForClangFunction.
 * Other minor fixes and cleanups.

Author: zoecarver

lib/ClangImporter/ImportDecl.cpp

@@ -3452,10 +3452,8 @@ namespace {
         ctors.push_back(createDefaultConstructor(Impl, result));
       }
 
-      bool hasUserDeclaredConstructor =
-          cxxRecordDecl && cxxRecordDecl->hasUserDeclaredConstructor();
-      if (hasReferenceableFields && hasMemberwiseInitializer &&
-          !hasUserDeclaredConstructor) {
+      bool isAggregate = cxxRecordDecl && cxxRecordDecl->isAggregate();
+      if (hasReferenceableFields && hasMemberwiseInitializer && isAggregate) {
         // The default zero initializer suppresses the implicit value
         // constructor that would normally be formed, so we have to add that
         // explicitly as well.

lib/ClangImporter/ImportName.cpp

@@ -1367,11 +1367,10 @@ static bool suppressFactoryMethodAsInit(const clang::ObjCMethodDecl *method,
 }
 
 static void
-addEmptyArgNamesForCxxFunc(const clang::FunctionDecl *funcDecl,
-                           SmallVectorImpl<StringRef> &argumentNames) {
-  for (size_t i = 0; i < funcDecl->param_size(); ++i) {
+addEmptyArgNamesForClangFunction(const clang::FunctionDecl *funcDecl,
+                                 SmallVectorImpl<StringRef> &argumentNames) {
+  for (size_t i = 0; i < funcDecl->param_size(); ++i)
     argumentNames.push_back(StringRef());
-  }
   if (funcDecl->isVariadic())
     argumentNames.push_back(StringRef());
 }
@@ -1614,9 +1613,8 @@ ImportedName NameImporter::importNameImpl(const clang::NamedDecl *D,
     isFunction = true;
     result.info.initKind = CtorInitializerKind::Designated;
     baseName = "init";
-    if (auto ctor = dyn_cast<clang::CXXConstructorDecl>(D)) {
-      addEmptyArgNamesForCxxFunc(ctor, argumentNames);
-    }
+    addEmptyArgNamesForClangFunction(cast<clang::CXXConstructorDecl>(D),
+                                     argumentNames);
     break;
 
   case clang::DeclarationName::CXXConversionFunctionName:
@@ -1691,7 +1689,7 @@ ImportedName NameImporter::importNameImpl(const clang::NamedDecl *D,
 
     if (auto function = dyn_cast<clang::FunctionDecl>(D)) {
       isFunction = true;
-      addEmptyArgNamesForCxxFunc(function, argumentNames);
+      addEmptyArgNamesForClangFunction(function, argumentNames);
     }
     break;
 

test/Interop/Cxx/class/constructors-module-interface.swift

@@ -16,6 +16,7 @@
 // CHECK-NEXT: }
 // CHECK-NEXT: struct DefaultConstructorDeleted {
 // CHECK-NEXT:   var a: UnsafeMutablePointer<Int32>
+// CHECK-NEXT:   init(a: UnsafeMutablePointer<Int32>)
 // CHECK-NEXT: }
 // CHECK-NEXT: struct ConstructorWithParam {
 // CHECK-NEXT:   var x: Int32

test/Interop/Cxx/class/constructors-typechecker.swift

@@ -8,6 +8,6 @@ let implicit = ImplicitDefaultConstructor()
 
 let deletedImplicitly = ConstructorWithParam() // expected-error {{missing argument for parameter #1 in call}}
 
-let deletedExplicitly = DefaultConstructorDeleted() // expected-error {{cannot be constructed because it has no accessible initializers}}
+let deletedExplicitly = DefaultConstructorDeleted() // expected-error {{missing argument for parameter 'a' in call}}
 
 let withArg = ConstructorWithParam(42)

test/Interop/Cxx/class/synthesized-initializers-silgen.swift

@@ -1,6 +1,7 @@
 // RUN: %target-swift-frontend -I %S/Inputs -enable-cxx-interop -emit-silgen %s | %FileCheck %s
 
 import SynthesizedInitializers
+import Constructors
 
 // CHECK-LABEL: sil [ossa] @$s4main18emptyTypeNoArgInityyF : $@convention(thin) () -> ()
 // CHECK: [[AS:%.*]] = alloc_stack $EmptyStruct
@@ -32,3 +33,12 @@ public func singleMemberTypeNoArgInit() {
 public func singleMemberTypeValueInit() {
   let i = IntBox(x: 42)
 }
+
+// CHECK-LABEL: sil shared [transparent] [serializable] [ossa] @$sSo25DefaultConstructorDeletedV1aABSpys5Int32VG_tcfC : $@convention(method) (UnsafeMutablePointer<Int32>, @thin DefaultConstructorDeleted.Type) -> DefaultConstructorDeleted
+// CHECK: bb0([[A:%.*]] : $UnsafeMutablePointer<Int32>
+// CHECK-NEXT: [[OUT:%.*]] = struct $DefaultConstructorDeleted ([[A]] : $UnsafeMutablePointer<Int32>)
+// CHECK-NEXT: return [[OUT]] : $DefaultConstructorDeleted
+// CHECK-LABEL:  end sil function '$sSo25DefaultConstructorDeletedV1aABSpys5Int32VG_tcfC'
+public func deletedConstructor(a: UnsafeMutablePointer<Int32>) {
+  let deletedExplicitly = DefaultConstructorDeleted(a: a)
+}