[clang][Interp] Remove assertion to fix comma operators...

... involving function pointers on the RHS. The conversion to
an RValue _can_ be requested, but we just ignore it.

Author: tbaederr

clang/lib/AST/Interp/EvalEmitter.cpp

@@ -152,7 +152,6 @@ template <> bool EvalEmitter::emitRet<PT_FnPtr>(const SourceInfo &Info) {
   if (!isActive())
     return true;
   // Function pointers cannot be converted to rvalues.
-  assert(!ConvertResultToRValue);
   EvalResult.setFunctionPointer(S.Stk.pop<FunctionPointer>());
   return true;
 }

clang/test/AST/Interp/comma.cpp

@@ -0,0 +1,10 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+// RUN: %clang_cc1 -fsyntax-only -verify %s -fexperimental-new-constant-interpreter
+// expected-no-diagnostics
+
+// PR6076
+void f();
+void (&g)() = (void(), f);
+
+int a[1];
+int (&b)[1] = (void(), a);