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Auto merge of #10363 - c410-f3r:lock-1, r=xFrednet
[significant_drop_tightening] Ignore inexpensive statements Not all statements that follow the last use of a lock guard are expensive and can therefore be ignored by the lint. ```rust pub fn foo() -> i32 { let mutex = Mutex::new(1); let lock = mutex.lock().unwrap(); let rslt = *lock; let another = rslt; another } ``` --- changelog: [`significant_drop_tightening`]: No longer lints for inexpensive statements after the lock guard [#10363](https://github.com/rust-lang/rust-clippy/pull/10363) <!-- changelog_checked -->
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commit
e1da00210a
4 changed files with 38 additions and 8 deletions
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@ -61,6 +61,18 @@ pub struct SignificantDropTightening<'tcx> {
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}
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impl<'tcx> SignificantDropTightening<'tcx> {
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/// Searches for at least one statement that could slow down the release of a significant drop.
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fn at_least_one_stmt_is_expensive(stmts: &[hir::Stmt<'_>]) -> bool {
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for stmt in stmts {
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match stmt.kind {
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hir::StmtKind::Local(local) if let Some(expr) = local.init
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&& let hir::ExprKind::Path(_) = expr.kind => {},
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_ => return true
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};
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}
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false
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}
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/// Verifies if the expression is of type `drop(some_lock_path)` to assert that the temporary
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/// is already being dropped before the end of its scope.
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fn has_drop(expr: &'tcx hir::Expr<'_>, init_bind_ident: Ident) -> bool {
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@ -198,13 +210,15 @@ impl<'tcx> LateLintPass<'tcx> for SignificantDropTightening<'tcx> {
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}
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self.modify_sdap_if_sig_drop_exists(cx, expr, idx, &mut sdap, stmt, |_| {});
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},
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_ => continue
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_ => {}
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};
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}
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if sdap.number_of_stmts > 1 && {
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let last_stmts_idx = block.stmts.len().wrapping_sub(1);
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sdap.last_use_stmt_idx != last_stmts_idx
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} {
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let stmts_after_last_use = sdap
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.last_use_stmt_idx
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.checked_add(1)
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.and_then(|idx| block.stmts.get(idx..))
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.unwrap_or_default();
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if sdap.number_of_stmts > 1 && Self::at_least_one_stmt_is_expensive(stmts_after_last_use) {
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span_lint_and_then(
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cx,
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SIGNIFICANT_DROP_TIGHTENING,
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@ -4,6 +4,14 @@
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use std::sync::Mutex;
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pub fn post_bindings_can_be_ignored() {
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let mutex = Mutex::new(1);
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let lock = mutex.lock().unwrap();
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let rslt = *lock;
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let another = rslt;
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let _ = another;
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}
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pub fn unnecessary_contention_with_multiple_owned_results() {
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{
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let mutex = Mutex::new(1i32);
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@ -4,6 +4,14 @@
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use std::sync::Mutex;
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pub fn post_bindings_can_be_ignored() {
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let mutex = Mutex::new(1);
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let lock = mutex.lock().unwrap();
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let rslt = *lock;
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let another = rslt;
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let _ = another;
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}
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pub fn unnecessary_contention_with_multiple_owned_results() {
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{
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let mutex = Mutex::new(1i32);
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@ -1,5 +1,5 @@
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error: temporary with significant `Drop` can be early dropped
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--> $DIR/significant_drop_tightening.rs:17:13
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--> $DIR/significant_drop_tightening.rs:25:13
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LL | / {
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LL | | let mutex = Mutex::new(1i32);
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@ -20,7 +20,7 @@ LL + drop(lock);
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error: temporary with significant `Drop` can be early dropped
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--> $DIR/significant_drop_tightening.rs:38:13
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--> $DIR/significant_drop_tightening.rs:46:13
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LL | / {
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LL | | let mutex = Mutex::new(1i32);
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@ -44,7 +44,7 @@ LL +
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error: temporary with significant `Drop` can be early dropped
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--> $DIR/significant_drop_tightening.rs:44:17
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--> $DIR/significant_drop_tightening.rs:52:17
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LL | / {
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LL | | let mutex = Mutex::new(vec![1i32]);
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