Fix for PR28523: unexpected compilation error.

Clang emits error message for the following code:
```
template <class F> void parallel_loop(F &&f) { f(0); }

int main() {
  int x;
  parallel_loop([&](auto y) {
    {
      x = y;
    };
  });
}
```

$ clang++ --std=gnu++14 clang_test.cc -o clang_test
clang_test.cc:9:7: error: reference to local variable 'x' declared in enclosing function 'main'
      x = y;
            ^
clang_test.cc:2:48: note: in instantiation of function template specialization 'main()::(anonymous class)::operator()<int>' requested here
            template <class F> void parallel_loop(F &&f) { f(0); }
                                                           ^
clang_test.cc:6:3: note: in instantiation of function template specialization 'parallel_loop<(lambda at clang_test.cc:6:17)>' requested here parallel_loop([&](auto y) {
           ^
clang_test.cc:5:7: note: 'x' declared here
      int x;
          ^
1 error generated.

Patch fixes this issue.

llvm-svn: 286584

1 files changed, 7 insertions, 4 deletions

diff --git a/clang/lib/Sema/SemaLambda.cpp b/clang/lib/Sema/SemaLambda.cpp
index da4ba8b2a26..fb3ac072f1e 100644
--- a/clang/lib/Sema/SemaLambda.cpp
+++ b/clang/lib/Sema/SemaLambda.cpp
@@ -66,17 +66,20 @@ getStackIndexOfNearestEnclosingCaptureReadyLambda(
   // Label failure to capture.
   const Optional<unsigned> NoLambdaIsCaptureReady;
 
+  // Ignore all inner captured regions.
+  unsigned CurScopeIndex = FunctionScopes.size() - 1;
+  while (CurScopeIndex > 0 && isa<clang::sema::CapturedRegionScopeInfo>(
+                                  FunctionScopes[CurScopeIndex]))
+    --CurScopeIndex;
   assert(
-      isa<clang::sema::LambdaScopeInfo>(
-          FunctionScopes[FunctionScopes.size() - 1]) &&
+      isa<clang::sema::LambdaScopeInfo>(FunctionScopes[CurScopeIndex]) &&
       "The function on the top of sema's function-info stack must be a lambda");
-  
+
   // If VarToCapture is null, we are attempting to capture 'this'.
   const bool IsCapturingThis = !VarToCapture;
   const bool IsCapturingVariable = !IsCapturingThis;
 
   // Start with the current lambda at the top of the stack (highest index).
-  unsigned CurScopeIndex = FunctionScopes.size() - 1;
   DeclContext *EnclosingDC =
       cast<sema::LambdaScopeInfo>(FunctionScopes[CurScopeIndex])->CallOperator;