Fix a crash in diagnostic printing when a template class type is diff'ed

against itself. PR14489.

llvm-svn: 170474

2 files changed, 18 insertions, 1 deletions

diff --git a/clang/lib/AST/ASTDiagnostic.cpp b/clang/lib/AST/ASTDiagnostic.cpp
index 31c1fbf1b78..a61abf7e34c 100644
--- a/clang/lib/AST/ASTDiagnostic.cpp
+++ b/clang/lib/AST/ASTDiagnostic.cpp
@@ -1125,7 +1125,12 @@ class TemplateDiff {
     TemplateDecl *FromTD, *ToTD;
     Tree.GetNode(FromTD, ToTD);
 
-    assert(Tree.HasChildren() && "Template difference not found in diff tree.");
+    if (!Tree.HasChildren()) {
+      // If we're dealing with a template specialization with zero
+      // arguments, there are no children; special-case this.
+      OS << FromTD->getNameAsString() << "<>";
+      return;
+    }
 
     Qualifiers FromQual, ToQual;
     Tree.GetNode(FromQual, ToQual);
diff --git a/clang/test/Misc/diag-template-diffing.cpp b/clang/test/Misc/diag-template-diffing.cpp
index 7d01f4695b0..e7a80488706 100644
--- a/clang/test/Misc/diag-template-diffing.cpp
+++ b/clang/test/Misc/diag-template-diffing.cpp
@@ -800,6 +800,18 @@ namespace PR14342 {
   // CHECK-ELIDE-NOTREE: error: no viable conversion from 'X<[...], 2>' to 'X<[...], 3UL>'
 }
 
+namespace PR14489 {
+  // The important thing here is that the diagnostic diffs a template specialization
+  // with no arguments against itself.  (We might need a different test if this
+  // diagnostic changes).
+  template<class ...V>
+  struct VariableList   {
+    void ConnectAllToAll(VariableList<>& params = VariableList<>())    {
+    }
+  };
+  // CHECK-ELIDE-NOTREE: non-const lvalue reference to type 'VariableList<>' cannot bind to a temporary of type 'VariableList<>'
+}
+
 // CHECK-ELIDE-NOTREE: {{[0-9]*}} errors generated.
 // CHECK-NOELIDE-NOTREE: {{[0-9]*}} errors generated.
 // CHECK-ELIDE-TREE: {{[0-9]*}} errors generated.