[`useless_conversion`]: only lint on paths to fn items and fix FP in macro #11070

y21 · 2023-07-02T23:31:01Z

Fixes #11065 (which is actually two issues: an ICE and a false positive)

It now makes sure that the function call path points to a function-like item (and not e.g. a const like in the linked issue), so that calling TyCtxt::fn_sig later in the lint does not ICE (fixes #11065 (comment)).
It also makes sure that the expression is not part of a macro call (fixes #11065 (comment)). ~~I'm not sure if there's a better way to check this other than to walk the parent expr chain and see if any of them are expansions.~~ (edit: it doesn't do this anymore)

changelog: [useless_conversion]: fix ICE when call receiver is a non-fn item
changelog: [useless_conversion]: don't lint if argument is a macro argument (fixes a FP)

r? @llogiq (reviewed #10814, which introduced these issues)

llogiq

Looks good in general. I only have one question regarding simplicity, otherwise I consider this merge-worthy.

llogiq · 2023-07-05T20:20:49Z

clippy_lints/src/useless_conversion.rs

+/// Checks if the given `expr` is an argument of a macro invocation.
+/// This is a slow-ish operation, so consider calling this late
+/// to avoid slowing down the lint in the happy path when not emitting a warning
+fn is_macro_argument(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {


Could we avoid that by keeping an Option<Span> in our lint to be set when we encounter an expression from a macro? That way this check would become a simple .is_some().

I'm not sure. How/When does it get reset to None? If we just set it to Some(span) once we see an expression from an expansion, it would forever think we are in a macro, no? Or do you mean we should also then check if the span in the lint struct fully encloses the span currently being looked at, or something like that?

Yeah, we can have check_expr set the span to Some(span) and then remove it if it matches in check_expr_post.

Hmm, but wouldn't this at least also need a stack of spans, to handle nested macro expansions? Alternatively, could we just use a u32 that we increment/decrement for entering or leaving a span from an expansion and check if == 0 when about to lint?

bors · 2023-08-11T15:48:55Z

☔ The latest upstream changes (presumably #11239) made this pull request unmergeable. Please resolve the merge conflicts.

flip1995

This LGTM. @llogiq can I ask you to give this another review, please? The issue for this was nominated to be backported, which will happen on Thursday.

y21 · 2023-08-14T15:18:28Z

(I didn't change anything with this rebase, just fixed the conflicts)

flip1995 · 2023-08-17T14:41:40Z

Thanks! I'm going ahead and approve this, so I can include it in the backports.

@bors r+

bors · 2023-08-17T14:41:42Z

📌 Commit f47165c has been approved by flip1995

It is now in the queue for this repository.

bors · 2023-08-17T14:41:50Z

⌛ Testing commit f47165c with merge 701e77c...

bors · 2023-08-17T14:55:52Z

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: flip1995
Pushing 701e77c to master...

flip1995 · 2023-08-17T16:10:43Z

rust-lang/rust#114937 for beta

and rust-lang/rust#114938 for master

…k-Simulacrum [beta] Clippy backports for ICE fixes This backports PRs to beta, that fix ICEs, some lint grouping and FP fixes. Namely: - rust-lang/rust-clippy#11191 - rust-lang/rust-clippy#11172 - rust-lang/rust-clippy#11130 - rust-lang/rust-clippy#11106 - rust-lang/rust-clippy#11104 - rust-lang/rust-clippy#11077 - rust-lang/rust-clippy#11070 (This PR is not synced to the Rust repo yet, but I will open a separate PR to get it into `master`, before beta is branched: rust-lang#114938) - rust-lang/rust-clippy#11069 Kind of a big backport, but most of it is tests. r? `@Mark-Simulacrum` cc `@Manishearth`

[`useless_conversion`]: only lint on paths to fn items and fix FP in macro Fixes rust-lang#11065 (which is actually two issues: an ICE and a false positive) It now makes sure that the function call path points to a function-like item (and not e.g. a `const` like in the linked issue), so that calling `TyCtxt::fn_sig` later in the lint does not ICE (fixes rust-lang#11065 (comment)). It *also* makes sure that the expression is not part of a macro call (fixes rust-lang#11065 (comment)). ~~I'm not sure if there's a better way to check this other than to walk the parent expr chain and see if any of them are expansions.~~ (edit: it doesn't do this anymore) changelog: [`useless_conversion`]: fix ICE when call receiver is a non-fn item changelog: [`useless_conversion`]: don't lint if argument is a macro argument (fixes a FP) r? `@llogiq` (reviewed rust-lang#10814, which introduced these issues)

rustbot assigned llogiq Jul 2, 2023

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties label Jul 2, 2023

y21 force-pushed the issue11065 branch from 3c67feb to 0165aa1 Compare July 2, 2023 23:44

llogiq reviewed Jul 5, 2023

View reviewed changes

flip1995 approved these changes Aug 14, 2023

View reviewed changes

flip1995 added the beta-nominated Nominated for backporting to the compiler in the beta channel. label Aug 14, 2023

y21 added 3 commits August 14, 2023 16:28

[useless_conversion]: make sure path points to fn-like item

34348f7

[useless_conversion]: fix FP in macro and add test

2820d98

find expansions more efficiently

f47165c

y21 force-pushed the issue11065 branch from 10d29eb to f47165c Compare August 14, 2023 15:09

bors merged commit 701e77c into rust-lang:master Aug 17, 2023
5 checks passed

flip1995 added beta-accepted Accepted for backporting to the compiler in the beta channel. and removed beta-nominated Nominated for backporting to the compiler in the beta channel. labels Aug 17, 2023

flip1995 mentioned this pull request Aug 17, 2023

[beta] Clippy backports for ICE fixes rust-lang/rust#114937

Merged

xFrednet removed the beta-accepted Accepted for backporting to the compiler in the beta channel. label Aug 18, 2023

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[`useless_conversion`]: only lint on paths to fn items and fix FP in macro #11070

[`useless_conversion`]: only lint on paths to fn items and fix FP in macro #11070

y21 commented Jul 2, 2023 •

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[useless_conversion]: only lint on paths to fn items and fix FP in macro #11070

[useless_conversion]: only lint on paths to fn items and fix FP in macro #11070

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flip1995 commented Aug 17, 2023 • edited Loading

[`useless_conversion`]: only lint on paths to fn items and fix FP in macro #11070

[`useless_conversion`]: only lint on paths to fn items and fix FP in macro #11070

y21 commented Jul 2, 2023 •

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flip1995 commented Aug 17, 2023 •

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