[clang] fix linkage of nested lambda

[blastrock]

Summary

This is an attempt to fix https://bugs.llvm.org/show_bug.cgi?id=44368

This effectively reverts D1783. It doesn't break the current tests and fixes the test that this commit adds.

We now decide of a lambda linkage only depending on the visibility of its parent context.

[hliao]

+ rsmith

clang/lib/AST/Decl.cpp

1416–1417

The code is still inconsistent with the comment. Record is the lambda itself instead of the parent of the lambda.

[rsmith]

This is effectively reverting https://reviews.llvm.org/D1783. If we don't need that any more for whatever reason, can we also get rid of the check for whether the outermost lambda has a mangling number a few lines above? (Please also check if we can remove getOutermostEnclosingLambda, which was added for this purpose.)

clang/lib/AST/Decl.cpp

1416–1417

Record->getDeclContext() returns the parent of the lambda.

[blastrock]

Thank you for the answers.

I have removed all the outermost lambda code and tests still pass.

[hliao]

LGTM, but need @rsmith for the final review

[blastrock]

Thanks for the reviews! I do not have commit access, so please merge this whenever you can.

[hliao]

In D73701#1864136, @blastrock wrote:

Thanks for the reviews! I do not have commit access, so please merge this whenever you can.

done in 2926917f430. thanks for the patch!

clang/lib/AST/Decl.cpp

         // This lambda has its linkage/visibility determined:
         //  - either by the outermost lambda if that lambda has no mangling
         //    number.
-        //  - or by the parent of the outer most lambda
+        //  - or by the parent of the current lambda
         // This prevents infinite recursion in settings such as nested lambdas
         // used in NSDMI's, for e.g.
         //  struct L {

           return getInternalLinkageFor(D);
 
         return getLVForClosure(
-                  OuterMostLambda->getDeclContext()->getRedeclContext(),
-                  OuterMostLambda->getLambdaContextDecl(), computation);
+                  Record->getDeclContext()->getRedeclContext(),
+                  Record->getLambdaContextDecl(), computation);
       }
 
       break;

clang/test/CodeGenCXX/lambda-expressions-nested-linkage.cpp

-// RUN: %clang_cc1 -triple x86_64-apple-darwin10.0.0 -fblocks -emit-llvm -o - %s -fexceptions -std=c++11 | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-apple-darwin10.0.0 -fblocks -emit-llvm -o - %s -fexceptions -std=c++14 | FileCheck %s
 
 // CHECK-LABEL: define void @_ZN19non_inline_function3fooEv()
 // CHECK-LABEL: define internal void @"_ZZN19non_inline_function3fooEvENK3$_0clEi"(%class.anon

 }
 int use = foo();
 }
+
+// CHECK-LABEL: define internal void @"_ZZZN32lambda_capture_in_generic_lambda3fooIiEEDavENKUlT_E_clIZNS_L1fEvE3$_1EEDaS1_ENKUlvE_clEv"
+namespace lambda_capture_in_generic_lambda {
+template <typename T> auto foo() {
+  return [](auto func) {
+    [func] { func(); }();
+  };
+}
+static void f() {
+  foo<int>()([] { });
+}
+void f1() { f(); }
+}