<regex>: Goofy message for error_badbrace

[Alcaro]

Describe the bug

The error_badbrace string is significantly goofy looking

Command-line test case

#include <regex>

int main()
{
    try {
        std::regex r("a{4,3}");
        puts("it's legal");
    } catch (std::exception& e) {
        puts(e.what());
    }
}

https://godbolt.org/z/Y14Exavx7

Expected behavior

The expression contained an invalid range in a {} expression.

Actual behavior

The expression contained an invalid range in a { expression }.

Why was the closing brace moved one word to the right? That's neither consistent with the C++ spec, nor with my understanding of English grammar.

STL version

Don't know, ask Godbolt

Additional context

Probably a good first issue Good for newcomers

[fsb4000]

Yes, I agree.
Code:

STL/stl/inc/regex

Lines 500 to 502 in faccf00

	case regex_constants::error_badbrace:
	return "regex_error(error_badbrace): The expression "
	"contained an invalid range in a { expression }.";

Why was the closing brace moved one word to the right?

Probably a copy-paste error. Look at the messages above:

STL/stl/inc/regex

Lines 491 to 499 in faccf00

	case regex_constants::error_brack:
	return "regex_error(error_brack): The expression "
	"contained mismatched [ and ].";
	case regex_constants::error_paren:
	return "regex_error(error_paren): The expression "
	"contained mismatched ( and ).";
	case regex_constants::error_brace:
	return "regex_error(error_brace): The expression "
	"contained mismatched { and }.";

https://godbolt.org/z/rKrbha61c
https://godbolt.org/z/bMdzrEhnv
https://godbolt.org/z/c8x4oTGEx

Click to expand unrelated discussion of other regex behavior:

By the way, we found a bug in the GCC standard library. I will check if that bug has been reported by someone; if not, I will create an issue.
An example with the bug: https://godbolt.org/z/c8x4oTGEx

[StephanTLavavej]

We talked about this at the weekly maintainer meeting and we agree that the error message can be easily improved.

@fsb4000 As this issue is about the error_badbrace message, discussion of other potential bugs should be done in a separate issue to avoid confusion. This is a good general principle to follow, but especially in things marked good first issue Good for newcomers which should be easy for new contributors to read and understand. Accordingly I'm going to collapse the unrelated comments.

[FranciscoThiesen]

Will take a look into fixing this!