fix(resolve): Warn on Self-Type Lifetime Elision for Non-Self Types#153692
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TKanX wants to merge 4 commits intorust-lang:mainfrom
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fix(resolve): Warn on Self-Type Lifetime Elision for Non-Self Types#153692TKanX wants to merge 4 commits intorust-lang:mainfrom
Self Types#153692TKanX wants to merge 4 commits intorust-lang:mainfrom
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Some changes occurred in compiler/rustc_hir/src/attrs |
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before discussing this in a lang meeting, can you extend the PR description a bit to summarize the reasoning and discussion behind this? |
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Co-authored-by: lcnr <rust@lcnr.de> Co-authored-by: Michael Goulet <michael@errs.io>
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…deny for crater run (WILL BE REVERTED) Co-authored-by: Travis Cross <tc@traviscross.com>
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@TKanX: 🔑 Insufficient privileges: not in try users |
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@bors try |
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…e-match, r=<try> fix(resolve): Warn on Self-Type Lifetime Elision for Non-`Self` Types
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👌 Experiment ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more |
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☔ The latest upstream changes (presumably #154123) made this pull request unmergeable. Please resolve the merge conflicts. |
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GitHub repos: 778 entries (756 unique authors)Crates.io: 312 entriesSome important ones:
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my crate |
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See case f4. Logs |
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@lcnr what should we do next? |
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We chatted a bunch in the lang meeting today about the errors like this one: [INFO] [stdout] error: `self` parameter type does not contain `Self`
[INFO] [stdout] --> src/lowtagged.rs:176:31
[INFO] [stdout] |
[INFO] [stdout] 176 | pub fn extract_data(self: &TaggedMutRefLow<'a, T>) -> usize {
[INFO] [stdout] | ^^^^^^^^^^^^^^^^^^^^^^^Notably, that case just has So there's two reasons that it seems like that shouldn't actually be FCWing:
Thus it feels like there's no reason we'd need to change this case, at least in the context of a PR titled involving "lifetime elision". (There was as aside about maybe linting "that's not your self type?" anyway as a stylistic thing, but that didn't reach team consensus and probably isn't this issue anyway.) We were thinking thus that
Does that make sense? @lcnr, would that impact the original goal of doing this? It seemed to us like if there are only input |
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Summary
FCW lint
self_lifetime_elision_not_applicable: fires when aselfparameter contains&but does not syntactically containSelf.Tracking: #140611
Context
Self-type lifetime elision in
rustc_resolverelies on a name-matching hack (is_self_ty) that shallow-comparesResvalues between the self parameter type and the impl self type. As @compiler-errors identified in #140611, this hack cannot see through type aliases (differentRes) and only fires forStruct|Union|Enum|PrimTyimpls (excludesTyAlias). When it misses,find_lifetime_for_selfreturnsEmpty, self-elision silently fails, and a later parameter's lifetime may leak into the return type.@lcnr proposed restricting self-elision to genuine
Selfand FCW'ing everything else. This PR implements that.Behavior
impl Alias { fn f(self: &W) -> &() }'_impl Alias { fn f(self: &Alias) -> &() }'_impl Alias { fn f(&self) -> &() }impl W { fn f(self: &W) -> &() }impl W { fn f(self: &Alias) -> &() }'_impl W { fn f(&self) -> &() }A follow-up PR will remove the hack after a warning period.
r? @lcnr
cc @compiler-errors @traviscross