The intent here is that changes to prelude.carbon shouldn't break every test that expects some error from prelude.carbon; that would be too fragile. As a consequence, this effectively ignores the line number in prelude.carbon.
This is a little complex because we don't know which line in the original source file is actually causing the error, just that there is an error. Also, the previous look-behind approach required a fixed-with prefix, whereas we want a little more than that in order to capture the filename for comparison.
This would be hard to do with extra_check_replacement because the path to bazel.runfiles is complex to calculate. As a consequence, this is basically all new code.
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
This switch is being done in order to make it easier to update tests when the parse tree structure changes. I've been spending a lot of time doing such updates as part of refactoring the parse tree, and I expect more, so that's really at the root of all the refactoring I've been doing to lit updates.
Jon Ross-PerkinsandRichard Smith