src/tools/clippy/clippy_lints/src/mutable_debug_assertion.rs

   1 use clippy_utils::diagnostics::span_lint;
   2 use clippy_utils::{higher, is_direct_expn_of};
   3 use rustc_hir::intravisit::{walk_expr, NestedVisitorMap, Visitor};
   4 use rustc_hir::{BorrowKind, Expr, ExprKind, MatchSource, Mutability};
   5 use rustc_lint::{LateContext, LateLintPass};
   6 use rustc_middle::hir::map::Map;
   7 use rustc_middle::ty;
   8 use rustc_session::{declare_lint_pass, declare_tool_lint};
   9 use rustc_span::Span;
  10
  11 declare_clippy_lint! {
  12     /// **What it does:** Checks for function/method calls with a mutable
  13     /// parameter in `debug_assert!`, `debug_assert_eq!` and `debug_assert_ne!` macros.
  14     ///
  15     /// **Why is this bad?** In release builds `debug_assert!` macros are optimized out by the
  16     /// compiler.
  17     /// Therefore mutating something in a `debug_assert!` macro results in different behaviour
  18     /// between a release and debug build.
  19     ///
  20     /// **Known problems:** None
  21     ///
  22     /// **Example:**
  23     /// ```rust,ignore
  24     /// debug_assert_eq!(vec![3].pop(), Some(3));
  25     /// // or
  26     /// fn take_a_mut_parameter(_: &mut u32) -> bool { unimplemented!() }
  27     /// debug_assert!(take_a_mut_parameter(&mut 5));
  28     /// ```
  29     pub DEBUG_ASSERT_WITH_MUT_CALL,
  30     nursery,
  31     "mutable arguments in `debug_assert{,_ne,_eq}!`"
  32 }
  33
  34 declare_lint_pass!(DebugAssertWithMutCall => [DEBUG_ASSERT_WITH_MUT_CALL]);
  35
  36 const DEBUG_MACRO_NAMES: [&str; 3] = ["debug_assert", "debug_assert_eq", "debug_assert_ne"];
  37
  38 impl<'tcx> LateLintPass<'tcx> for DebugAssertWithMutCall {
  39     fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
  40         for dmn in &DEBUG_MACRO_NAMES {
  41             if is_direct_expn_of(e.span, dmn).is_some() {
  42                 if let Some(macro_args) = higher::extract_assert_macro_args(e) {
  43                     for arg in macro_args {
  44                         let mut visitor = MutArgVisitor::new(cx);
  45                         visitor.visit_expr(arg);
  46                         if let Some(span) = visitor.expr_span() {
  47                             span_lint(
  48                                 cx,
  49                                 DEBUG_ASSERT_WITH_MUT_CALL,
  50                                 span,
  51                                 &format!("do not call a function with mutable arguments inside of `{}!`", dmn),
  52                             );
  53                         }
  54                     }
  55                 }
  56             }
  57         }
  58     }
  59 }
  60
  61 struct MutArgVisitor<'a, 'tcx> {
  62     cx: &'a LateContext<'tcx>,
  63     expr_span: Option<Span>,
  64     found: bool,
  65 }
  66
  67 impl<'a, 'tcx> MutArgVisitor<'a, 'tcx> {
  68     fn new(cx: &'a LateContext<'tcx>) -> Self {
  69         Self {
  70             cx,
  71             expr_span: None,
  72             found: false,
  73         }
  74     }
  75
  76     fn expr_span(&self) -> Option<Span> {
  77         if self.found { self.expr_span } else { None }
  78     }
  79 }
  80
  81 impl<'a, 'tcx> Visitor<'tcx> for MutArgVisitor<'a, 'tcx> {
  82     type Map = Map<'tcx>;
  83
  84     fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
  85         match expr.kind {
  86             ExprKind::AddrOf(BorrowKind::Ref, Mutability::Mut, _) => {
  87                 self.found = true;
  88                 return;
  89             },
  90             ExprKind::If(..) => {
  91                 self.found = true;
  92                 return;
  93             },
  94             ExprKind::Path(_) => {
  95                 if let Some(adj) = self.cx.typeck_results().adjustments().get(expr.hir_id) {
  96                     if adj
  97                         .iter()
  98                         .any(|a| matches!(a.target.kind(), ty::Ref(_, _, Mutability::Mut)))
  99                     {
 100                         self.found = true;
 101                         return;
 102                     }
 103                 }
 104             },
 105             // Don't check await desugars
 106             ExprKind::Match(_, _, MatchSource::AwaitDesugar) => return,
 107             _ if !self.found => self.expr_span = Some(expr.span),
 108             _ => return,
 109         }
 110         walk_expr(self, expr);
 111     }
 112
 113     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
 114         NestedVisitorMap::OnlyBodies(self.cx.tcx.hir())
 115     }
 116 }