[Sema] Don't crash when friending an unqualified templated constructor

Unqualified templated constructors cannot be friended and our lack of a
diagnostic led to violated invariants.  Instead, raise a diagnostic when
processing the friend declaration.

This fixes PR20251.

llvm-svn: 248953

1 files changed, 23 insertions, 7 deletions

diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index 07bf8567194..7617c92e4e4 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -12689,15 +12689,31 @@ NamedDecl *Sema::ActOnFriendFunctionDecl(Scope *S, Declarator &D,
     DC = CurContext;
     assert(isa<CXXRecordDecl>(DC) && "friend declaration not in class?");
   }
-  
+
   if (!DC->isRecord()) {
+    int DiagArg = -1;
+    switch (D.getName().getKind()) {
+    case UnqualifiedId::IK_ConstructorTemplateId:
+    case UnqualifiedId::IK_ConstructorName:
+      DiagArg = 0;
+      break;
+    case UnqualifiedId::IK_DestructorName:
+      DiagArg = 1;
+      break;
+    case UnqualifiedId::IK_ConversionFunctionId:
+      DiagArg = 2;
+      break;
+    case UnqualifiedId::IK_Identifier:
+    case UnqualifiedId::IK_ImplicitSelfParam:
+    case UnqualifiedId::IK_LiteralOperatorId:
+    case UnqualifiedId::IK_OperatorFunctionId:
+    case UnqualifiedId::IK_TemplateId:
+      break;
+      llvm_unreachable("Didn't expect this kind of unqualified-id!");
+    }
     // This implies that it has to be an operator or function.
-    if (D.getName().getKind() == UnqualifiedId::IK_ConstructorName ||
-        D.getName().getKind() == UnqualifiedId::IK_DestructorName ||
-        D.getName().getKind() == UnqualifiedId::IK_ConversionFunctionId) {
-      Diag(Loc, diag::err_introducing_special_friend) <<
-        (D.getName().getKind() == UnqualifiedId::IK_ConstructorName ? 0 :
-         D.getName().getKind() == UnqualifiedId::IK_DestructorName ? 1 : 2);
+    if (DiagArg >= 0) {
+      Diag(Loc, diag::err_introducing_special_friend) << DiagArg;
       return nullptr;
     }
   }