[clang] fix expression classification for dependent binary operators (#159819)

This fixes a regression reported here:
#159463 (comment)

Since this regression was never released, there are no release notes.

Author: mizvekov

clang/lib/AST/ExprClassification.cpp

@@ -601,6 +601,13 @@ static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E) {
 static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E) {
   assert(Ctx.getLangOpts().CPlusPlus &&
          "This is only relevant for C++.");
+
+  // For binary operators which are unknown due to type dependence, the
+  // convention is to classify them as a prvalue. This does not matter much, but
+  // it needs to agree with how they are created.
+  if (E->getType() == Ctx.DependentTy)
+    return Cl::CL_PRValue;
+
   // C++ [expr.ass]p1: All [...] return an lvalue referring to the left operand.
   // Except we override this for writes to ObjC properties.
   if (E->isAssignmentOp())

clang/test/SemaTemplate/temp_arg_template.cpp

@@ -149,6 +149,12 @@ namespace CheckDependentNonTypeParamTypes {
   };
   // FIXME: This should be rejected, as there are no valid instantiations for E<char>::F
   template struct E<char>;
+
+#if __cplusplus >= 201703L
+  template<template<auto> class TT, class V> struct G {
+    using type = TT<((void)0, V::value)>;
+  };
+#endif
 }
 
 namespace PR32185 {