compiletest should check for possible typos in annotated test directives

[klensy]

This should help with things like #83348 (comment)
Levenshtein distance with list of known directives will be enough?

[klensy]

@rustbot label: A-testsuite

[osa1]

Levenshtein distance with list of known directives will be enough?

Is this to distinguish an ordinary comment from a directive?

[klensy]

@osa1
Yes, this is the first idea that came into my mind.

[jieyouxu]

This is easier if/when we port over all current // directives in all test suites and modes over to use ui_test-style //@ directives, so that it is easier to detect between regular comments and directives.

Other bootstrap tools like tidy should also probably use something else to distinguish them from regular comments. Otherwise, trying to check between a valid directive vs comment is really cursed, and comments like

// testing testing one two three
// ignore-test is a very useful
// directive to have in compiletest

gets treated as // ignore-test, making it quite surprising.