[clang] [Clang] Add '-Warray-compare' flag for C++ below version 20 (PR #118031)

[via cfe-commits]

================
@@ -11854,14 +11854,23 @@ static void diagnoseTautologicalComparison(Sema &S, SourceLocation Loc,
     AlwaysEqual, // std::strong_ordering::equal from operator<=>
   };
 
+  // C++1a [array.comp]:
+  //   Equality and relational comparisons ([expr.eq], [expr.rel]) between two
+  //   operands of array type.
   // C++2a [depr.array.comp]:
   //   Equality and relational comparisons ([expr.eq], [expr.rel]) between two
   //   operands of array type are deprecated.
-  if (S.getLangOpts().CPlusPlus20 && LHSStripped->getType()->isArrayType() &&
+  if (S.getLangOpts().CPlusPlus && LHSStripped->getType()->isArrayType() &&
       RHSStripped->getType()->isArrayType()) {
-    S.Diag(Loc, diag::warn_depr_array_comparison)
-        << LHS->getSourceRange() << RHS->getSourceRange()
-        << LHSStripped->getType() << RHSStripped->getType();
+    auto IsDeprArrayComparionIgnored =
+        S.getDiagnostics().isIgnored(diag::warn_depr_array_comparison, Loc);
+    auto IsDeprArrayComparion =
+        !S.getLangOpts().CPlusPlus20 || IsDeprArrayComparionIgnored;
+
+    auto DiagID = IsDeprArrayComparion ? diag::warn_array_comparison
----------------
cor3ntin wrote:

this looks inverted

https://github.com/llvm/llvm-project/pull/118031