Isn't that pretty standard for compiler error messages? The C# compiler uses CS\d{4} for example. MSVC, MSBuild, various other build tools (at least on the Microsoft side) all use similar patterns with different prefixes.
That being said, it seems like Clang or GCC don't do that at all, which perplexes me a bit. Perhaps it doesn't matter much when error messages are never localized.
