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

[via llvm-commits]

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@@ -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'">,
+      InGroup<ImplicitUnicodeConversion>;
+
+def warn_comparison_unicode_mixed_types
+    : Warning<"comparing values of different Unicode code unit types %0 and %1 "
+              "may compare different codepoints">,
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cor3ntin wrote:

Added the space - but "code point value" is a bit tautologic

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