-
Notifications
You must be signed in to change notification settings - Fork 1.6k
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
An implementation for the lint described in #11721
- Loading branch information
Showing
13 changed files
with
4,374 additions
and
12 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,221 @@ | ||
| //! This lint works by looking at the min_captures that `rustc` uses, | ||
| //! and checks that for the expression `capture_kind_expr_id`, it would | ||
| //! actually borrow normally, if it weren't for the move keyword. | ||
| //! | ||
| //! In such cases, the move keyword changes the semantics of the code (e.g. | ||
| //! without it that capture would be a normal by reference capture, but with | ||
| //! move it would get captured by value, and therefore we do not remove the `move` | ||
| //! keyword from the closure). | ||
| //! | ||
| //! A small caveat for the approach above: | ||
| //! There's both a borrow and a move of the same value into the closure, e.g.: | ||
| //! | ||
| //! ```no_run | ||
| //! let x = String::new(); | ||
| //! let closure = move || { | ||
| //! let s = x.as_str(); // L1 | ||
| //! println!("{s}"); | ||
| //! drop(x); // L2 | ||
| //! }; | ||
| //! ``` | ||
| //! | ||
| //! In this case, the `x` `String` gets moved into the closure (because of L2), but | ||
| //! it is also borrowed prior to that at L1. | ||
| //! | ||
| //! `rustc`, in the presence of the `move` keyword automatically assumes that if | ||
| //! it borrows a value, it's going to move it into the closure (in the example above at L1, | ||
| //! so capture_kind_expr_id would point to the use on L1), but here, in the case | ||
| //! of this lint, we should behave a little differently, namely we should first look | ||
| //! at all the locations where a place is captured, and if any of them actually moves it, | ||
| //! the closure would consume the value. | ||
| //! | ||
| //! The logic for this is handled in `MovedVariablesCtxt::get_required_kind`, where we | ||
| //! try to infer the actual min capture kind needed. | ||
| use clippy_utils::diagnostics::span_lint_and_then; | ||
| use clippy_utils::sugg::DiagnosticExt; | ||
| use rustc_errors::Applicability; | ||
| use rustc_hir::{CaptureBy, Closure, Expr, ExprKind, HirId}; | ||
| use rustc_hir_typeck::expr_use_visitor as euv; | ||
| use rustc_infer::infer::TyCtxtInferExt; | ||
| use rustc_lint::{LateContext, LateLintPass}; | ||
| use rustc_middle::mir::FakeReadCause; | ||
| use rustc_middle::ty; | ||
| use rustc_middle::ty::UpvarCapture; | ||
| use rustc_session::{declare_lint_pass, declare_tool_lint}; | ||
|
|
||
| declare_clippy_lint! { | ||
| /// ### What it does | ||
| /// Checks for closures and `async` blocks where the `move` is not necessary. | ||
| /// E.g. all the values are captured by value into the closure / `async` block. | ||
| /// | ||
| /// ### Why is this bad? | ||
| /// Pedantry | ||
| /// ### Example | ||
| /// ```no_run | ||
| /// let a = String::new(); | ||
| /// let closure = move || { | ||
| /// drop(a); | ||
| /// }; | ||
| /// ``` | ||
| /// Use instead: | ||
| /// ```no_run | ||
| /// let a = String::new(); | ||
| /// let closure = || { | ||
| /// drop(a); | ||
| /// }; | ||
| /// ``` | ||
| #[clippy::version = "1.76.0"] | ||
| pub NEEDLESS_MOVE, | ||
| pedantic, | ||
| "checks for needless `move`s on closures / `async` blocks" | ||
| } | ||
|
|
||
| declare_lint_pass!(NeedlessMove => [NEEDLESS_MOVE]); | ||
|
|
||
| impl NeedlessMove { | ||
| fn check_closure<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>, closure: &'tcx Closure<'tcx>) { | ||
| let CaptureBy::Value { move_kw } = closure.capture_clause else { | ||
| return; | ||
| }; | ||
|
|
||
| if move_kw.is_dummy() { | ||
| // async fn ...() {} convert the body to an `async move {}` block, | ||
| // with a DUMMY_SP for the move_kw | ||
| return; | ||
| } | ||
|
|
||
| // Collect moved & borrowed variables from the closure, which the closure *actually* needs. | ||
| let ctx = { | ||
| let mut ctx = MovedVariablesCtxt::default(); | ||
| let body = cx.tcx.hir().body(closure.body); | ||
| let infcx = cx.tcx.infer_ctxt().build(); | ||
| euv::ExprUseVisitor::new(&mut ctx, &infcx, closure.def_id, cx.param_env, cx.typeck_results()) | ||
| .consume_body(body); | ||
| ctx | ||
| }; | ||
|
|
||
| enum LintResult { | ||
| /// do not remove the `move` keyword. | ||
| NeedMove, | ||
| Consumed, | ||
| NothingCaptured, | ||
| } | ||
|
|
||
| let mut lint_result = LintResult::NothingCaptured; | ||
|
|
||
| for captured_place in cx.typeck_results().closure_min_captures_flattened(closure.def_id) { | ||
| let place = &captured_place.place; | ||
| if let Some(ck_expr_id) = captured_place.info.capture_kind_expr_id { | ||
| let required_ck = ctx.get_required_kind(place, ck_expr_id); | ||
| match required_ck { | ||
| UpvarCapture::ByRef(_) => { | ||
| // no matter what the old `lint_result` is, we keep the move. | ||
| lint_result = LintResult::NeedMove; | ||
| }, | ||
| UpvarCapture::ByValue => { | ||
| lint_result = match lint_result { | ||
| LintResult::NothingCaptured | LintResult::Consumed => LintResult::Consumed, | ||
| LintResult::NeedMove => LintResult::NeedMove, | ||
| } | ||
| }, | ||
| } | ||
| } | ||
| } | ||
|
|
||
| let lint = |note_msg: &'static str| { | ||
| span_lint_and_then( | ||
| cx, | ||
| NEEDLESS_MOVE, | ||
| expr.span, | ||
| "you seem to use `move`, but the `move` is unnecessary", | ||
| |diag| { | ||
| diag.suggest_remove_item(cx, move_kw, "remove the `move`", Applicability::MachineApplicable); | ||
| diag.note(note_msg); | ||
| }, | ||
| ); | ||
| }; | ||
|
|
||
| match lint_result { | ||
| LintResult::NothingCaptured => { | ||
| lint("there were no captured variables, so the `move` is unnecessary"); | ||
| }, | ||
| LintResult::Consumed => { | ||
| lint("there were consumed variables, but no borrowed variables, so the `move` is unnecessary"); | ||
| }, | ||
| LintResult::NeedMove => { | ||
| // there was a value which would be borrowed if it weren't for the move keyword, | ||
| // so we should keep it, as removing it would change semantics. | ||
| }, | ||
| } | ||
| } | ||
| } | ||
|
|
||
| impl<'tcx> LateLintPass<'tcx> for NeedlessMove { | ||
| fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) { | ||
| if expr.span.from_expansion() { | ||
| return; | ||
| } | ||
|
|
||
| let ExprKind::Closure(closure) = &expr.kind else { | ||
| return; | ||
| }; | ||
|
|
||
| Self::check_closure(cx, expr, closure); | ||
| } | ||
| } | ||
|
|
||
| #[derive(Debug, Default)] | ||
| struct MovedVariablesCtxt<'tcx> { | ||
| // for each base variable, we remember: | ||
| /// The places where it was captured (and consumed, e.g. moved into the closure). | ||
| moved: Vec<(euv::Place<'tcx>, HirId)>, | ||
| /// The places where it was captured by reference (and not consumed). | ||
| captured: Vec<(euv::Place<'tcx>, HirId, ty::BorrowKind)>, | ||
| } | ||
|
|
||
| impl<'tcx> MovedVariablesCtxt<'tcx> { | ||
| fn move_common(&mut self, cmt: &euv::PlaceWithHirId<'tcx>, hir_id: HirId) { | ||
| if let euv::PlaceBase::Upvar(_) = cmt.place.base { | ||
| self.moved.push((cmt.place.clone(), hir_id)); | ||
| } | ||
| } | ||
|
|
||
| fn borrow_common(&mut self, cmt: &euv::PlaceWithHirId<'tcx>, borrow_hir_id: HirId, bk: ty::BorrowKind) { | ||
| if let euv::PlaceBase::Upvar(_) = cmt.place.base { | ||
| self.captured.push((cmt.place.clone(), borrow_hir_id, bk)); | ||
| } | ||
| } | ||
|
|
||
| fn get_required_kind(&self, place: &euv::Place<'tcx>, ref_hir_id: HirId) -> UpvarCapture { | ||
| match self | ||
| .moved | ||
| .iter() | ||
| .any(|upvar_ref| upvar_ref.0 == *place || upvar_ref.1 == ref_hir_id) | ||
| { | ||
| true => UpvarCapture::ByValue, | ||
| false => self | ||
| .captured | ||
| .iter() | ||
| .find(|upvar_ref| upvar_ref.1 == ref_hir_id) | ||
| .map(|it| UpvarCapture::ByRef(it.2)) | ||
| .unwrap(), | ||
| } | ||
| } | ||
| } | ||
|
|
||
| impl<'tcx> euv::Delegate<'tcx> for MovedVariablesCtxt<'tcx> { | ||
| fn consume(&mut self, cmt: &euv::PlaceWithHirId<'tcx>, hir_id: HirId) { | ||
| self.move_common(cmt, hir_id); | ||
| } | ||
|
|
||
| fn borrow(&mut self, cmt: &euv::PlaceWithHirId<'tcx>, hir_id: HirId, bk: ty::BorrowKind) { | ||
| self.borrow_common(cmt, hir_id, bk); | ||
| } | ||
|
|
||
| fn mutate(&mut self, cmt: &euv::PlaceWithHirId<'tcx>, hir_id: HirId) { | ||
| self.borrow(cmt, hir_id, ty::BorrowKind::MutBorrow); | ||
| } | ||
|
|
||
| fn fake_read(&mut self, _: &euv::PlaceWithHirId<'tcx>, _: FakeReadCause, _: HirId) {} | ||
| } |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Oops, something went wrong.