[clang][bytecode] Diagnose negative array sizes differently (llvm#114380)

We have a special diagnostic ID for this.

Author: tbaederr

clang/lib/AST/ByteCode/Interp.h

@@ -273,8 +273,14 @@ bool CheckArraySize(InterpState &S, CodePtr OpPC, SizeT *NumElements,
       *NumElements > MaxElements) {
     if (!IsNoThrow) {
       const SourceInfo &Loc = S.Current->getSource(OpPC);
-      S.FFDiag(Loc, diag::note_constexpr_new_too_large)
-          << NumElements->toDiagnosticString(S.getASTContext());
+
+      if (NumElements->isSigned() && NumElements->isNegative()) {
+        S.FFDiag(Loc, diag::note_constexpr_new_negative)
+            << NumElements->toDiagnosticString(S.getASTContext());
+      } else {
+        S.FFDiag(Loc, diag::note_constexpr_new_too_large)
+            << NumElements->toDiagnosticString(S.getASTContext());
+      }
     }
     return false;
   }

clang/test/AST/ByteCode/new-delete.cpp

@@ -274,6 +274,15 @@ namespace NowThrowNew {
   static_assert(erroneous_array_bound_nothrow2(-1) == 0);// expected-error {{not an integral constant expression}}
   static_assert(!erroneous_array_bound_nothrow2(1LL << 62));// expected-error {{not an integral constant expression}}
 
+  constexpr bool erroneous_array_bound(long long n) {
+    delete[] new int[n]; // both-note {{array bound -1 is negative}} both-note {{array bound 4611686018427387904 is too large}}
+    return true;
+  }
+  static_assert(erroneous_array_bound(3));
+  static_assert(erroneous_array_bound(0));
+  static_assert(erroneous_array_bound(-1)); // both-error {{constant expression}} both-note {{in call}}
+  static_assert(erroneous_array_bound(1LL << 62)); // both-error {{constant expression}} both-note {{in call}}
+
   constexpr bool evaluate_nothrow_arg() {
     bool ok = false;
     delete new ((ok = true, std::nothrow)) int;