[Sema] Don't diagnose an array type mismatch when the new or previous

declaration has a dependent type.

This fixes a bug where clang errors out on a valid code.

rdar://problem/28051467

Differential Revision: https://reviews.llvm.org/D24110

llvm-svn: 280330

2 files changed, 35 insertions, 2 deletions

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 9df9c63cfdf..8b148af8cce 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -3367,11 +3367,11 @@ void Sema::MergeVarDeclTypes(VarDecl *New, VarDecl *Old,
       // We are merging a variable declaration New into Old. If it has an array
       // bound, and that bound differs from Old's bound, we should diagnose the
       // mismatch.
-      if (!NewArray->isIncompleteArrayType()) {
+      if (!NewArray->isIncompleteArrayType() && !NewArray->isDependentType()) {
         for (VarDecl *PrevVD = Old->getMostRecentDecl(); PrevVD;
              PrevVD = PrevVD->getPreviousDecl()) {
           const ArrayType *PrevVDTy = Context.getAsArrayType(PrevVD->getType());
-          if (PrevVDTy->isIncompleteArrayType())
+          if (PrevVDTy->isIncompleteArrayType() || PrevVDTy->isDependentType())
             continue;
 
           if (!Context.hasSameType(NewArray, PrevVDTy))
diff --git a/clang/test/SemaTemplate/array-redeclaration.cpp b/clang/test/SemaTemplate/array-redeclaration.cpp
new file mode 100644
index 00000000000..4edee701cfc
--- /dev/null
+++ b/clang/test/SemaTemplate/array-redeclaration.cpp
@@ -0,0 +1,33 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+// expected-no-diagnostics
+
+extern int array[1];
+
+template <typename>
+class C {
+  enum { D };
+public:
+  template <typename A> void foo1() {
+    extern int array[((int)C<A>::k > (int)D) ? 1 : -1];
+  }
+};
+
+template<>
+class C<int> {
+public:
+  const static int k = 2;
+};
+
+void foo2() {
+  C<char> c;
+  c.foo1<int>();
+}
+
+template<int n>
+void foo3() {
+  extern int array[n ? 1 : -1];
+}
+
+void foo4() {
+  foo3<5>();
+}