When performing template argument deduction against a template-id,

only keep deduction results for successful deductions, so that they
can be compared against each other. Fixes PR8462, from Richard Smith!

llvm-svn: 117983

2 files changed, 31 insertions, 2 deletions

diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
index 855516cf10c..905e17e9c14 100644
--- a/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -721,6 +721,8 @@ DeduceTemplateArguments(Sema &S,
           llvm::SmallVector<const RecordType *, 8> ToVisit;
           ToVisit.push_back(RecordT);
           bool Successful = false;
+          llvm::SmallVectorImpl<DeducedTemplateArgument> DeducedOrig(0);
+          DeducedOrig = Deduced;
           while (!ToVisit.empty()) {
             // Retrieve the next class in the inheritance hierarchy.
             const RecordType *NextT = ToVisit.back();
@@ -738,9 +740,14 @@ DeduceTemplateArguments(Sema &S,
                                           QualType(NextT, 0), Info, Deduced);
 
               // If template argument deduction for this base was successful,
-              // note that we had some success.
-              if (BaseResult == Sema::TDK_Success)
+              // note that we had some success. Otherwise, ignore any deductions
+              // from this base class.
+              if (BaseResult == Sema::TDK_Success) {
                 Successful = true;
+                DeducedOrig = Deduced;
+              }
+              else
+                Deduced = DeducedOrig;
             }
 
             // Visit base classes
diff --git a/clang/test/CXX/temp/temp.fct.spec/temp.deduct/temp.deduct.call/p3.cpp b/clang/test/CXX/temp/temp.fct.spec/temp.deduct/temp.deduct.call/p3.cpp
index 19962c53490..3c22cf349c9 100644
--- a/clang/test/CXX/temp/temp.fct.spec/temp.deduct/temp.deduct.call/p3.cpp
+++ b/clang/test/CXX/temp/temp.fct.spec/temp.deduct/temp.deduct.call/p3.cpp
@@ -101,3 +101,25 @@ void test_f4(D d, E e, F f, G g) {
   C<int, 1> *ci3c = f4c(&g);
   int       *ip1 = f4c(&f);
 }
+
+// PR8462
+namespace N {
+  struct T0;
+  struct T1;
+
+  template<typename X, typename Y> struct B {};
+
+  struct J : B<T0,T0> {};
+  struct K : B<T1,T1> {};
+
+  struct D : J, K {};
+
+  template<typename X, typename Y> void F(B<Y,X>);
+
+  void test()
+  {
+    D d; 
+    N::F<T0>(d); // Fails
+    N::F<T1>(d); // OK
+  }
+}