clippy_lints/src/mutable_debug_assertion.rs

   1 use crate::utils::{is_direct_expn_of, span_lint};
   2 use if_chain::if_chain;
   3 use matches::matches;
   4 use rustc::hir::intravisit::{walk_expr, NestedVisitorMap, Visitor};
   5 use rustc::hir::{Expr, ExprKind, Mutability, StmtKind, UnOp};
   6 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
   7 use rustc::{declare_lint_pass, declare_tool_lint, ty};
   8 use syntax_pos::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     correctness,
  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<'a, 'tcx> LateLintPass<'a, 'tcx> for DebugAssertWithMutCall {
  38     fn check_expr(&mut self, cx: &LateContext<'a, '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(span) = extract_call(cx, e) {
  42                     span_lint(
  43                         cx,
  44                         DEBUG_ASSERT_WITH_MUT_CALL,
  45                         span,
  46                         &format!("do not call a function with mutable arguments inside of `{}!`", dmn),
  47                     );
  48                 }
  49             }
  50         }
  51     }
  52 }
  53
  54 //HACK(hellow554): remove this when #4694 is implemented
  55 #[allow(clippy::cognitive_complexity)]
  56 fn extract_call<'a, 'tcx>(cx: &'a LateContext<'a, 'tcx>, e: &'tcx Expr) -> Option<Span> {
  57     if_chain! {
  58         if let ExprKind::Block(ref block, _) = e.kind;
  59         if block.stmts.len() == 1;
  60         if let StmtKind::Semi(ref matchexpr) = block.stmts[0].kind;
  61         then {
  62             if_chain! {
  63                 if let ExprKind::Match(ref ifclause, _, _) = matchexpr.kind;
  64                 if let ExprKind::DropTemps(ref droptmp) = ifclause.kind;
  65                 if let ExprKind::Unary(UnOp::UnNot, ref condition) = droptmp.kind;
  66                 then {
  67                     // debug_assert
  68                     let mut visitor = MutArgVisitor::new(cx);
  69                     visitor.visit_expr(condition);
  70                     return visitor.expr_span();
  71                 } else {
  72                     // debug_assert_{eq,ne}
  73                     if_chain! {
  74                         if let ExprKind::Block(ref matchblock, _) = matchexpr.kind;
  75                         if let Some(ref matchheader) = matchblock.expr;
  76                         if let ExprKind::Match(ref headerexpr, _, _) = matchheader.kind;
  77                         if let ExprKind::Tup(ref conditions) = headerexpr.kind;
  78                         if conditions.len() == 2;
  79                         then {
  80                             if let ExprKind::AddrOf(_, ref lhs) = conditions[0].kind {
  81                                 let mut visitor = MutArgVisitor::new(cx);
  82                                 visitor.visit_expr(lhs);
  83                                 if let Some(span) = visitor.expr_span() {
  84                                     return Some(span);
  85                                 }
  86                             }
  87                             if let ExprKind::AddrOf(_, ref rhs) = conditions[1].kind {
  88                                 let mut visitor = MutArgVisitor::new(cx);
  89                                 visitor.visit_expr(rhs);
  90                                 if let Some(span) = visitor.expr_span() {
  91                                     return Some(span);
  92                                 }
  93                             }
  94                         }
  95                     }
  96                 }
  97             }
  98         }
  99     }
 100
 101     None
 102 }
 103
 104 struct MutArgVisitor<'a, 'tcx> {
 105     cx: &'a LateContext<'a, 'tcx>,
 106     expr_span: Option<Span>,
 107     found: bool,
 108 }
 109
 110 impl<'a, 'tcx> MutArgVisitor<'a, 'tcx> {
 111     fn new(cx: &'a LateContext<'a, 'tcx>) -> Self {
 112         Self {
 113             cx,
 114             expr_span: None,
 115             found: false,
 116         }
 117     }
 118
 119     fn expr_span(&self) -> Option<Span> {
 120         if self.found {
 121             self.expr_span
 122         } else {
 123             None
 124         }
 125     }
 126 }
 127
 128 impl<'a, 'tcx> Visitor<'tcx> for MutArgVisitor<'a, 'tcx> {
 129     fn visit_expr(&mut self, expr: &'tcx Expr) {
 130         match expr.kind {
 131             ExprKind::AddrOf(Mutability::MutMutable, _) => {
 132                 self.found = true;
 133                 return;
 134             },
 135             ExprKind::Path(_) => {
 136                 if let Some(adj) = self.cx.tables.adjustments().get(expr.hir_id) {
 137                     if adj
 138                         .iter()
 139                         .any(|a| matches!(a.target.kind, ty::Ref(_, _, Mutability::MutMutable)))
 140                     {
 141                         self.found = true;
 142                         return;
 143                     }
 144                 }
 145             },
 146             _ if !self.found => self.expr_span = Some(expr.span),
 147             _ => return,
 148         }
 149         walk_expr(self, expr)
 150     }
 151
 152     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
 153         NestedVisitorMap::OnlyBodies(&self.cx.tcx.hir())
 154     }
 155 }