[ASTImporter] Import every Decl in lambda record

[gamesh411]

Summary

Previously only the fields were imported. Now every Decl is imported.
This way the destructor decl is not missing after import.

Patch by balazske (Balázs Kéri)

[balazske]

unittests/AST/ASTImporterTest.cpp

2432

Actually the ToTU is not needed, this line can be removed.

[gamesh411]

Remove unnecessary ToTU variable from test case.

[shafik]

LGTM although I wish we had more lambda tests.

Please remember to check the LLDB build bots when landing the patch.

lib/AST/ASTImporter.cpp

ExpectedStmt ASTNodeImporter::VisitLambdaExpr(LambdaExpr *E) {
   auto ToClassOrErr = import(FromClass);
   if (!ToClassOrErr)
     return ToClassOrErr.takeError();
   CXXRecordDecl *ToClass = *ToClassOrErr;
 
   // NOTE: lambda classes are created with BeingDefined flag set up.
   // It means that ImportDefinition doesn't work for them and we should fill it
   // manually.
-  if (ToClass->isBeingDefined()) {
-    for (auto FromField : FromClass->fields()) {
-      auto ToFieldOrErr = import(FromField);
-      if (!ToFieldOrErr)
-        return ToFieldOrErr.takeError();
-    }
-  }
+  if (ToClass->isBeingDefined())
+    if (Error Err = ImportDeclContext(FromClass, /*ForceImport = */ true))
+      return std::move(Err);
 
   auto ToCallOpOrErr = import(E->getCallOperator());
   if (!ToCallOpOrErr)
     return ToCallOpOrErr.takeError();
 
   ToClass->completeDefinition();
 
   SmallVector<LambdaCapture, 8> ToCaptures;

unittests/AST/ASTImporterTest.cpp

TEST_P(ImportFunctions,
   EXPECT_EQ(ToDFOutOfClass->getDeclContext(), ToD);
   EXPECT_EQ(ToDFOutOfClass->getLexicalDeclContext(), ToTU);
 
   // Check that the redecl chain is intact.
   EXPECT_EQ(ToBFOutOfClass->getPreviousDecl(), ToBFInClass);
   EXPECT_EQ(ToDFOutOfClass->getPreviousDecl(), ToDFInClass);
 }
 
+TEST_P(ImportFunctions, ImportImplicitFunctionsInLambda) {
+  Decl *FromTU = getTuDecl(
+      R"(
+      void foo() {
+        (void)[]() { ; };
+      }
+      )",
+      Lang_CXX11);
+  auto *FromD = FirstDeclMatcher<FunctionDecl>().match(
+      FromTU, functionDecl(hasName("foo")));
+  auto *ToD = Import(FromD, Lang_CXX);
+  EXPECT_TRUE(ToD);
+  Decl *ToTU = ToAST->getASTContext().getTranslationUnitDecl();
+  CXXRecordDecl *LambdaRec =
+      cast<LambdaExpr>(cast<CStyleCastExpr>(
+                           *cast<CompoundStmt>(ToD->getBody())->body_begin())
+                           ->getSubExpr())
+          ->getLambdaClass();
+  EXPECT_TRUE(LambdaRec->getDestructor());
+}
+
 struct ImportFriendFunctions : ImportFunctions {};
 
 TEST_P(ImportFriendFunctions, ImportFriendFunctionRedeclChainProto) {
   auto Pattern = functionDecl(hasName("f"));
 
   Decl *FromTU = getTuDecl("struct X { friend void f(); };"
                            "void f();",
                            Lang_CXX,