[clang] [ObjC] Emit number, array, and dictionary literals as constants (PR #185130)

[Oliver Hunt via cfe-commits]

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@@ -12861,6 +12862,52 @@ bool Sema::CheckForConstantInitializer(Expr *Init, unsigned DiagID) {
   const Expr *Culprit;
   if (Init->isConstantInitializer(Context, false, &Culprit))
     return false;
+
+  // Emit ObjC-specific diagnostics for non-constant literals at file scope.
+  if (getLangOpts().ObjCConstantLiterals && isa<ObjCObjectLiteral>(Culprit)) {
+
+    // For collection literals iterate the elements to highlight which one is
+    // the offender.
+    if (auto ALE = dyn_cast<ObjCArrayLiteral>(Init)) {
+      for (size_t I = 0, N = ALE->getNumElements(); I != N; ++I) {
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ojhunt wrote:

Can we add an `elements()` iterator to `ObjCArrayLiteral`? I guess it doesn't need to be in this PR though

https://github.com/llvm/llvm-project/pull/185130