[Clang] prevent assertion failure in value-dependent initializer expressions

clang/docs/ReleaseNotes.rst

@@ -543,6 +543,7 @@ Bug Fixes to C++ Support
 - Clang incorrectly considered a class with an anonymous union member to not be
   const-default-constructible even if a union member has a default member initializer.
   (#GH95854).
+- Fixed an assertion failure when evaluating an invalid expression in an array initializer (#GH112140)
 
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^

clang/lib/AST/ExprConstant.cpp

@@ -11579,6 +11579,9 @@ bool ArrayExprEvaluator::VisitCXXParenListOrInitListExpr(
   LValue Subobject = This;
   Subobject.addArray(Info, ExprToVisit, CAT);
   auto Eval = [&](const Expr *Init, unsigned ArrayIndex) {
+    if (Init->isValueDependent())
+      return EvaluateDependentExpr(Init, Info);
+
     if (!EvaluateInPlace(Result.getArrayInitializedElt(ArrayIndex), Info,
                          Subobject, Init) ||
         !HandleLValueArrayAdjustment(Info, Init, Subobject,

clang/test/SemaCXX/constant-expression-cxx11.cpp

@@ -2564,3 +2564,13 @@ GH50055::E2 GlobalInitNotCE2 = GH50055::testDefaultArgForParam(); // ok, not a c
 constexpr GH50055::E2 GlobalInitCE = (GH50055::E2)-1;
 // expected-error@-1 {{constexpr variable 'GlobalInitCE' must be initialized by a constant expression}}
 // expected-note@-2 {{integer value -1 is outside the valid range of values [0, 7] for the enumeration type 'E2'}}
+
+namespace GH112140 {
+struct S {
+  constexpr S(const int &a = ) { } // expected-error {{expected expression}}
+};
+
+void foo() {
+  constexpr S s[2] = { }; // expected-error {{constexpr variable 's' must be initialized by a constant expression}}
+}
+}