[libcxx-commits] [clang] [libcxx] [llvm] [Clang] Add warnings when mixing different charN_t types (PR #138708)

[Tom Honermann via libcxx-commits]

================
@@ -4357,6 +4357,29 @@ def warn_address_of_reference_bool_conversion : Warning<
   "code; pointer may be assumed to always convert to true">,
   InGroup<UndefinedBoolConversion>;
 
+def warn_impcast_unicode_char_type
+    : Warning<"implicit conversion from %0 to %1 may change the meaning of the "
+              "represented code unit">,
+      InGroup<ImplicitUnicodeConversion>;
+def warn_impcast_unicode_precision
+    : Warning<"implicit conversion from %0 to %1 may lose precision and change "
+              "the meaning of the represented code unit">,
+      InGroup<ImplicitUnicodeConversion>;
+def warn_impcast_unicode_char_type_constant
+    : Warning<"implicit conversion from %0 to %1 changes the meaning of the "
+              "%select{code unit|codepoint}2 '%3'">,
----------------
tahonermann wrote:

```suggestion
def warn_impcast_unicode_char_type_constant
    : Warning<"implicit conversion from %0 to %1 changes the meaning of the "
              "%select{code unit|code point}2 '%3'">,
```

https://github.com/llvm/llvm-project/pull/138708