[clang][Sema] Resolving Inconsistent Arguments Panic in Variadic Template Variables

clang/docs/ReleaseNotes.rst

@@ -674,6 +674,7 @@ Bug Fixes to C++ Support
   whose type is `decltype(auto)`. Fixes (#GH68885).
 - Clang now correctly treats the noexcept-specifier of a friend function to be a complete-class context.
 - Fix an assertion failure when parsing an invalid members of an anonymous class. (#GH85447)
+- Fixed crash when parsing inconsistent arguments in variadic template variables. Fixes (#GH70191)
 
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^

clang/lib/Sema/SemaOverload.cpp

@@ -11370,6 +11370,14 @@ static void DiagnoseBadConversion(Sema &S, OverloadCandidate *Cand,
       I--;
   }
 
+  bool isVariadic = false;
+  for (unsigned N = 0; N < Fn->getNumParams(); N++) {
+    if (Fn->getParamDecl(N)->isParameterPack()) {
+      isVariadic = true;
+      break;
+    }
+  }
+
   std::string FnDesc;
   std::pair<OverloadCandidateKind, OverloadCandidateSelect> FnKindPair =
       ClassifyOverloadCandidate(S, Cand->FoundDecl, Fn, Cand->getRewriteKind(),
@@ -11378,8 +11386,9 @@ static void DiagnoseBadConversion(Sema &S, OverloadCandidate *Cand,
   Expr *FromExpr = Conv.Bad.FromExpr;
   QualType FromTy = Conv.Bad.getFromType();
   QualType ToTy = Conv.Bad.getToType();
-  SourceRange ToParamRange =
-      !isObjectArgument ? Fn->getParamDecl(I)->getSourceRange() : SourceRange();
+  SourceRange ToParamRange = !isObjectArgument && !isVariadic
+                                 ? Fn->getParamDecl(I)->getSourceRange()
+                                 : SourceRange();
 
   if (FromTy == S.Context.OverloadTy) {
     assert(FromExpr && "overload set argument came from implicit argument?");

clang/test/SemaCXX/GH70280.cpp

@@ -0,0 +1,9 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+namespace PR70280 {
+  typedef a; // expected-error {{a type specifier is required for all declarations}}
+  using b = char*;
+  template <typename... c> void d(c...) = d<b, a>(0, ""); // expected-error {{no matching function for call to 'd'}}
+  // expected-error@-1 {{illegal initializer (only variables can be initialized)}}
+  // expected-note@-2 {{candidate function template not viable: no known conversion from 'const char[1]' to 'a' (aka 'int') for 2nd argument}}
+}