Fix unused_variables typo suggestions for const patterns#156904
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Some changes occurred to MIR optimizations cc @rust-lang/wg-mir-opt |
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r? @mejrs rustbot has assigned @mejrs. Use Why was this reviewer chosen?The reviewer was selected based on:
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mejrs
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May 26, 2026
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Thanks!
- Please add a regression test for not suggesting
path::_, like reported in the issue. - Please add explicit
HELPannotations in the new tests.
It looks good otherwise but I'm not familiar enough here to tell whether or not corner cases are being missed, so
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Reminder, once the PR becomes ready for a review, use |
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Thanks @mejrs for your comments, resolved. |
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@rustbot ready |
cjgillot
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| fn pattern_item_path(tcx: TyCtxt<'_>, body_def_id: DefId, item_def_id: DefId) -> String { | ||
| if is_nested_in(tcx, item_def_id, body_def_id) { | ||
| return relative_item_path(tcx, body_def_id, item_def_id); | ||
| } | ||
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| let body_mod = nearest_parent_module(tcx, body_def_id); | ||
| if body_mod == nearest_parent_module(tcx, item_def_id) { | ||
| relative_item_path(tcx, body_mod, item_def_id) | ||
| } else if item_def_id.is_local() && !body_mod.is_top_level_module() { | ||
| format!("{}::{}", kw::Crate, with_no_trimmed_paths!(tcx.def_path_str(item_def_id))) | ||
| } else { | ||
| with_no_trimmed_paths!(tcx.def_path_str(item_def_id)) | ||
| } | ||
| } | ||
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| fn is_nested_in(tcx: TyCtxt<'_>, mut def_id: DefId, parent_def_id: DefId) -> bool { | ||
| while let Some(parent) = tcx.opt_parent(def_id) { | ||
| if parent == parent_def_id { | ||
| return true; | ||
| } | ||
| def_id = parent; | ||
| } | ||
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| false | ||
| } | ||
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| fn relative_item_path(tcx: TyCtxt<'_>, parent_def_id: DefId, item_def_id: DefId) -> String { | ||
| let mut def_id = item_def_id; | ||
| let mut path = Vec::new(); | ||
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| loop { | ||
| if def_id == parent_def_id { | ||
| break; | ||
| } | ||
| if let Some(name) = tcx.opt_item_name(def_id) { | ||
| path.push(name.to_string()); | ||
| } | ||
| let Some(parent) = tcx.opt_parent(def_id) else { | ||
| return with_no_trimmed_paths!(tcx.def_path_str(item_def_id)); | ||
| }; | ||
| def_id = parent; | ||
| } | ||
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| path.reverse(); | ||
| path.join("::") | ||
| } | ||
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| fn nearest_parent_module(tcx: TyCtxt<'_>, mut def_id: DefId) -> DefId { | ||
| while let Some(parent) = tcx.opt_parent(def_id) { | ||
| def_id = parent; | ||
| if matches!(tcx.def_kind(def_id), DefKind::Mod) { | ||
| return def_id; | ||
| } | ||
| } | ||
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| def_id | ||
| } | ||
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Please use an existing printing mode from rustc_middle::ty::print. No need to create our own here.
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Closes #147595
This fixes
unused_variablestypo suggestions that could print replacementpatterns which are not valid from the binding site.
The fix keeps the existing
def_path_stroutput when it is already valid, butadjusts two local-item cases:
crate::...;It also suppresses const typo suggestions for bare
let x = ...bindings,because replacing the binding with a const path creates a refutable pattern.
Unit ADT typo suggestions are left unchanged.
The regression test covers 2015 and 2021 editions, cross-module consts,
same-module consts, function-local consts, cross-module variants, and bare
letconst initializers.