Merging r309569:

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r309569 | alexfh | 2017-07-31 08:21:26 -0700 (Mon, 31 Jul 2017) | 39 lines

Fix -Wshadow false positives with function-local classes.

Summary:
Fixes http://llvm.org/PR33947.

https://godbolt.org/g/54XRMT

void f(int a) {
  struct A {
    void g(int a) {}
    A() { int a; }
  };
}

3 : <source>:3:16: warning: declaration shadows a local variable [-Wshadow]
    void g(int a) {}
               ^
1 : <source>:1:12: note: previous declaration is here
void f(int a) {
           ^
4 : <source>:4:15: warning: declaration shadows a local variable [-Wshadow]
    A() { int a; }
              ^
1 : <source>:1:12: note: previous declaration is here
void f(int a) {
           ^
2 warnings generated.

The local variable `a` of the function `f` can't be accessed from a method of
the function-local class A, thus no shadowing occurs and no diagnostic is
needed.

Reviewers: rnk, rsmith, arphaman, Quuxplusone

Reviewed By: rnk, Quuxplusone

Subscribers: Quuxplusone, cfe-commits

Differential Revision: https://reviews.llvm.org/D35941
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git-svn-id: https://llvm.org/svn/llvm-project/cfe/branches/release_50@310674 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 24 insertions, 0 deletions

diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 31b24f91c1..6bcb023174 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -6999,6 +6999,21 @@ void Sema::CheckShadow(NamedDecl *D, NamedDecl *ShadowedDecl,
           return;
         }
       }
+
+      if (cast<VarDecl>(ShadowedDecl)->hasLocalStorage()) {
+        // A variable can't shadow a local variable in an enclosing scope, if
+        // they are separated by a non-capturing declaration context.
+        for (DeclContext *ParentDC = NewDC;
+             ParentDC && !ParentDC->Equals(OldDC);
+             ParentDC = getLambdaAwareParentOfDeclContext(ParentDC)) {
+          // Only block literals, captured statements, and lambda expressions
+          // can capture; other scopes don't.
+          if (!isa<BlockDecl>(ParentDC) && !isa<CapturedDecl>(ParentDC) &&
+              !isLambdaCallOperator(ParentDC)) {
+            return;
+          }
+        }
+      }
     }
   }
 
diff --git a/test/SemaCXX/warn-shadow.cpp b/test/SemaCXX/warn-shadow.cpp
index d5f0623eb3..3d09c78628 100644
--- a/test/SemaCXX/warn-shadow.cpp
+++ b/test/SemaCXX/warn-shadow.cpp
@@ -213,3 +213,12 @@ typedef int externC; // expected-note {{previous declaration is here}}
 void handleLinkageSpec() {
   typedef void externC; // expected-warning {{declaration shadows a typedef in the global namespace}}
 }
+
+namespace PR33947 {
+void f(int a) {
+  struct A {
+    void g(int a) {}
+    A() { int a; }
+  };
+}
+}