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| 1 | +use crate::utils::{ |
| 2 | + match_type, method_calls, method_chain_args, paths, snippet, snippet_with_applicability, span_lint_and_sugg, |
| 3 | +}; |
| 4 | +use if_chain::if_chain; |
| 5 | +use rustc::ty; |
| 6 | +use rustc_errors::Applicability; |
| 7 | +use rustc_hir::{print, Expr, ExprKind, MatchSource, PatKind, QPath, StmtKind}; |
| 8 | +use rustc_lint::{LateContext, LateLintPass}; |
| 9 | +use rustc_session::{declare_lint_pass, declare_tool_lint}; |
| 10 | + |
| 11 | +declare_clippy_lint! { |
| 12 | + /// **What it does:** Checks for `Mutex::lock` calls in `if let` expression |
| 13 | + /// with lock calls in any of the else blocks. |
| 14 | + /// |
| 15 | + /// **Why is this bad?** The Mutex lock remains held for the whole |
| 16 | + /// `if let ... else` block and deadlocks. |
| 17 | + /// |
| 18 | + /// **Known problems:** None. |
| 19 | + /// |
| 20 | + /// **Example:** |
| 21 | + /// |
| 22 | + /// ```rust |
| 23 | + /// # use std::sync::Mutex; |
| 24 | + /// let mutex = Mutex::new(10); |
| 25 | + /// if let Ok(thing) = mutex.lock() { |
| 26 | + /// do_thing(); |
| 27 | + /// } else { |
| 28 | + /// mutex.lock(); |
| 29 | + /// } |
| 30 | + /// ``` |
| 31 | + pub IF_LET_MUTEX, |
| 32 | + correctness, |
| 33 | + "locking a `Mutex` in an `if let` block can cause deadlock" |
| 34 | +} |
| 35 | + |
| 36 | +declare_lint_pass!(IfLetMutex => [IF_LET_MUTEX]); |
| 37 | + |
| 38 | +impl LateLintPass<'_, '_> for IfLetMutex { |
| 39 | + fn check_expr(&mut self, cx: &LateContext<'_, '_>, ex: &'_ Expr<'_>) { |
| 40 | + if_chain! { |
| 41 | + if let ExprKind::Match(ref op, ref arms, MatchSource::IfLetDesugar { |
| 42 | + contains_else_clause: true, |
| 43 | + }) = ex.kind; // if let ... {} else {} |
| 44 | + if let ExprKind::MethodCall(_, _, ref args) = op.kind; |
| 45 | + let ty = cx.tables.expr_ty(&args[0]); |
| 46 | + if let ty::Adt(_, subst) = ty.kind; |
| 47 | + if match_type(cx, ty, &paths::MUTEX); // make sure receiver is Mutex |
| 48 | + if method_chain_names(op, 10).iter().any(|s| s == "lock"); // and lock is called |
| 49 | + |
| 50 | + let mut suggestion = String::from(&format!("if let _ = {} {{\n", snippet(cx, op.span, "_"))); |
| 51 | + |
| 52 | + if arms.iter().any(|arm| if_chain! { |
| 53 | + if let ExprKind::Block(ref block, _l) = arm.body.kind; |
| 54 | + if block.stmts.iter().any(|stmt| match stmt.kind { |
| 55 | + StmtKind::Local(l) => if_chain! { |
| 56 | + if let Some(ex) = l.init; |
| 57 | + if let ExprKind::MethodCall(_, _, ref args) = op.kind; |
| 58 | + if method_chain_names(ex, 10).iter().any(|s| s == "lock"); // and lock is called |
| 59 | + then { |
| 60 | + let ty = cx.tables.expr_ty(&args[0]); |
| 61 | + // // make sure receiver is Result<MutexGuard<...>> |
| 62 | + match_type(cx, ty, &paths::RESULT) |
| 63 | + } else { |
| 64 | + suggestion.push_str(&format!(" {}\n", snippet(cx, l.span, "_"))); |
| 65 | + false |
| 66 | + } |
| 67 | + }, |
| 68 | + StmtKind::Expr(e) => if_chain! { |
| 69 | + if let ExprKind::MethodCall(_, _, ref args) = e.kind; |
| 70 | + if method_chain_names(e, 10).iter().any(|s| s == "lock"); // and lock is called |
| 71 | + then { |
| 72 | + let ty = cx.tables.expr_ty(&args[0]); |
| 73 | + // // make sure receiver is Result<MutexGuard<...>> |
| 74 | + match_type(cx, ty, &paths::RESULT) |
| 75 | + } else { |
| 76 | + suggestion.push_str(&format!(" {}\n", snippet(cx, e.span, "_"))); |
| 77 | + false |
| 78 | + } |
| 79 | + }, |
| 80 | + StmtKind::Semi(e) => if_chain! { |
| 81 | + if let ExprKind::MethodCall(_, _, ref args) = e.kind; |
| 82 | + if method_chain_names(e, 10).iter().any(|s| s == "lock"); // and lock is called |
| 83 | + then { |
| 84 | + let ty = cx.tables.expr_ty(&args[0]); |
| 85 | + // // make sure receiver is Result<MutexGuard<...>> |
| 86 | + match_type(cx, ty, &paths::RESULT) |
| 87 | + } else { |
| 88 | + suggestion.push_str(&format!(" {}\n", snippet(cx, e.span, "_"))); |
| 89 | + false |
| 90 | + } |
| 91 | + }, |
| 92 | + _ => { suggestion.push_str(&format!(" {}\n", snippet(cx, stmt.span, "_"))); false }, |
| 93 | + }); |
| 94 | + then { |
| 95 | + true |
| 96 | + } else { |
| 97 | + suggestion.push_str(&format!("else {}\n", snippet(cx, arm.span, "_"))); |
| 98 | + false |
| 99 | + } |
| 100 | + }); |
| 101 | + then { |
| 102 | + println!("{}", suggestion); |
| 103 | + span_lint_and_sugg( |
| 104 | + cx, |
| 105 | + IF_LET_MUTEX, |
| 106 | + ex.span, |
| 107 | + "using a `Mutex` in inner scope of `.lock` call", |
| 108 | + "try", |
| 109 | + format!("{:?}", "hello"), |
| 110 | + Applicability::MachineApplicable, |
| 111 | + ); |
| 112 | + } |
| 113 | + } |
| 114 | + } |
| 115 | +} |
| 116 | + |
| 117 | +fn method_chain_names<'tcx>(expr: &'tcx Expr<'tcx>, max_depth: usize) -> Vec<String> { |
| 118 | + let mut method_names = Vec::with_capacity(max_depth); |
| 119 | + |
| 120 | + let mut current = expr; |
| 121 | + for _ in 0..max_depth { |
| 122 | + if let ExprKind::MethodCall(path, span, args) = ¤t.kind { |
| 123 | + if args.iter().any(|e| e.span.from_expansion()) { |
| 124 | + break; |
| 125 | + } |
| 126 | + method_names.push(path.ident.to_string()); |
| 127 | + println!("{:?}", method_names); |
| 128 | + current = &args[0]; |
| 129 | + } else { |
| 130 | + break; |
| 131 | + } |
| 132 | + } |
| 133 | + |
| 134 | + method_names |
| 135 | +} |
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