69 lines
2.3 KiB
Rust
69 lines
2.3 KiB
Rust
use clippy_utils::diagnostics::span_lint_and_sugg;
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use clippy_utils::ty::is_type_diagnostic_item;
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use if_chain::if_chain;
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use rustc_errors::Applicability;
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use rustc_hir::{Expr, ExprKind, Mutability};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_middle::ty;
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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declare_clippy_lint! {
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/// **What it does:** Checks for `&mut Mutex::lock` calls
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///
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/// **Why is this bad?** `Mutex::lock` is less efficient than
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/// calling `Mutex::get_mut`. In addition you also have a statically
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/// guarantee that the mutex isn't locked, instead of just a runtime
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/// guarantee.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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///
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/// ```rust
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/// use std::sync::{Arc, Mutex};
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///
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/// let mut value_rc = Arc::new(Mutex::new(42_u8));
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/// let value_mutex = Arc::get_mut(&mut value_rc).unwrap();
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///
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/// let mut value = value_mutex.lock().unwrap();
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/// *value += 1;
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/// ```
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/// Use instead:
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/// ```rust
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/// use std::sync::{Arc, Mutex};
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///
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/// let mut value_rc = Arc::new(Mutex::new(42_u8));
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/// let value_mutex = Arc::get_mut(&mut value_rc).unwrap();
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///
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/// let value = value_mutex.get_mut().unwrap();
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/// *value += 1;
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/// ```
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pub MUT_MUTEX_LOCK,
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style,
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"`&mut Mutex::lock` does unnecessary locking"
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}
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declare_lint_pass!(MutMutexLock => [MUT_MUTEX_LOCK]);
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impl<'tcx> LateLintPass<'tcx> for MutMutexLock {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, ex: &'tcx Expr<'tcx>) {
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if_chain! {
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if let ExprKind::MethodCall(path, method_span, args, _) = &ex.kind;
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if path.ident.name == sym!(lock);
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let ty = cx.typeck_results().expr_ty(&args[0]);
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if let ty::Ref(_, inner_ty, Mutability::Mut) = ty.kind();
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if is_type_diagnostic_item(cx, inner_ty, sym!(mutex_type));
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then {
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span_lint_and_sugg(
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cx,
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MUT_MUTEX_LOCK,
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*method_span,
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"calling `&mut Mutex::lock` unnecessarily locks an exclusive (mutable) reference",
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"change this to",
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"get_mut".to_owned(),
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Applicability::MaybeIncorrect,
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);
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}
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}
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}
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}
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