Fix regex fixer to maintain string literal syntax

[stephentoub]

Fixes#78113

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Issue Details

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Fixes #78113

Author:	stephentoub
Assignees:	-
Labels:	area-System.Text.RegularExpressions
Milestone:	-

[Youssef1313]

LGTM

[joperezr]

Unless I'm missing something, this will generate code that won't compile sometimes. For example, the case of:

usingSystem.Text.RegularExpressions;partialclassProgram{staticvoidMain(string[]args){conststringpattern=@"a|b\s\n";conststringpattern2=$"{pattern}2";Regexregex=newRegex(pattern2);}}

If I'm following correctly, this will generate the new static method and pass in pattern2 as the argument to the GeneratedRegex attribute, which is not in scope so code won't compile. This is why today we instead have to evaluate the constant value and then use that as the argument to the attribute. If I'm correct with my assumption here, I'm not sure why we don't have a test that checks that, but we should add one if we don't.

[joperezr]

Just to confirm, I just tried out the sample I had above locally against your changes and it indeed produces a compile error:

[stephentoub]

if we don't

We don't :)

[joperezr]

Thanks for fixing this @stephentoub and thanks for the help @Youssef1313!