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

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