inconsistent lint flag args between normal and post-rustfix compiles in UI tests #50926
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A-testsuite
Area: The testsuite used to check the correctness of rustc
C-enhancement
Category: An issue proposing an enhancement or a PR with one.
T-compiler
Relevant to the compiler team, which will review and decide on the PR/issue.
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zackmdavis
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May 20, 2018
Consider this a down payment on rust-lang#50723. To recap, an `Applicability` enum was recently (rust-lang#50204) added, to convey to Rustfix and other tools whether we think it's OK for them to blindly apply the suggestion, or whether to prompt a human for guidance (because the suggestion might contain placeholders that we can't infer, or because we think it has a sufficiently high probability of being wrong even though it's— presumably—right often enough to be worth emitting in the first place). When a suggestion is marked as `MaybeIncorrect`, we try to use comments to indicate precisely why (although there are a few places where we just say `// speculative` because the present author's subjective judgement balked at the idea that the suggestion has no false positives). The `run-rustfix` directive is opporunistically set on some relevant UI tests (and a couple tests that were in the `test/ui/suggestions` directory, even if the suggestions didn't originate in librustc or libsyntax). This is less trivial than it sounds, because a surprising number of test files aren't equipped to be tested as fixed even when they contain successfully fixable errors, because, e.g., there are more, not-directly-related errors after fixing. Some test files need an attribute or underscore to avoid unused warnings tripping up the "fixed code is still producing diagnostics" check despite the fixes being correct; this is an interesting contrast-to/inconsistency-with the behavior of UI tests (which secretly pass `-A unused`), a behavior which we probably ought to resolve one way or the other (filed issue rust-lang#50926). A few suggestion labels are reworded (e.g., to avoid phrasing it as a question, which which is discouraged by the style guidelines listed in `.span_suggestion`'s doc-comment).
zackmdavis
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XAMPPRocky
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It does seem like passing -A unused to rustfix would be a good change to make here, and at a cursory look at the code it seems like we do that today? But if I'm wrong then we can, of course, reopen. |
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UI tests run with
-A unused, but UI tests with therun-rustfixdirective go on to apply suggestions and then check that there are no warnings, without passing any lint flags. The inconsistency is a papercut–footgun for UI test authors. We should do exactly one of—-A unusedfor the rustfix-succeeded check, too; or-A unusedfor UI tests.-A unusedfor UI tests? #43896, but the reception seemed unfavorable (one 👎 react and one negatively-disposed comment). If it turned out that there was support for this after all, we would want someone to edit existing tests to not produce spuriousunusedwarnings, which would be a very large PR.The text was updated successfully, but these errors were encountered: