clippy_lints/src/assertions_on_constants.rs

   1 use if_chain::if_chain;
   2 use rustc::hir::{Expr, ExprKind};
   3 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
   4 use rustc::{declare_lint_pass, declare_tool_lint};
   5 use syntax_pos::Span;
   6
   7 use crate::consts::{constant, Constant};
   8 use crate::utils::{in_macro_or_desugar, is_direct_expn_of, span_help_and_lint};
   9 use crate::utils::sym;
  10
  11 declare_clippy_lint! {
  12     /// **What it does:** Checks for `assert!(true)` and `assert!(false)` calls.
  13     ///
  14     /// **Why is this bad?** Will be optimized out by the compiler or should probably be replaced by a
  15     /// panic!() or unreachable!()
  16     ///
  17     /// **Known problems:** None
  18     ///
  19     /// **Example:**
  20     /// ```rust,ignore
  21     /// assert!(false)
  22     /// // or
  23     /// assert!(true)
  24     /// // or
  25     /// const B: bool = false;
  26     /// assert!(B)
  27     /// ```
  28     pub ASSERTIONS_ON_CONSTANTS,
  29     style,
  30     "`assert!(true)` / `assert!(false)` will be optimized out by the compiler, and should probably be replaced by a `panic!()` or `unreachable!()`"
  31 }
  32
  33 declare_lint_pass!(AssertionsOnConstants => [ASSERTIONS_ON_CONSTANTS]);
  34
  35 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AssertionsOnConstants {
  36     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
  37         let mut is_debug_assert = false;
  38         let debug_assert_not_in_macro_or_desugar = |span: Span| {
  39             is_debug_assert = true;
  40             // Check that `debug_assert!` itself is not inside a macro
  41             !in_macro_or_desugar(span)
  42         };
  43         if_chain! {
  44             if let Some(assert_span) = is_direct_expn_of(e.span, *sym::assert);
  45             if !in_macro_or_desugar(assert_span)
  46                 || is_direct_expn_of(assert_span, *sym::debug_assert)
  47                     .map_or(false, debug_assert_not_in_macro_or_desugar);
  48             if let ExprKind::Unary(_, ref lit) = e.node;
  49             if let Some(bool_const) = constant(cx, cx.tables, lit);
  50             then {
  51                 match bool_const.0 {
  52                     Constant::Bool(true) => {
  53                         span_help_and_lint(
  54                             cx,
  55                             ASSERTIONS_ON_CONSTANTS,
  56                             e.span,
  57                             "`assert!(true)` will be optimized out by the compiler",
  58                             "remove it"
  59                         );
  60                     },
  61                     Constant::Bool(false) if !is_debug_assert => {
  62                         span_help_and_lint(
  63                             cx,
  64                             ASSERTIONS_ON_CONSTANTS,
  65                             e.span,
  66                             "`assert!(false)` should probably be replaced",
  67                             "use `panic!()` or `unreachable!()`"
  68                         );
  69                     },
  70                     _ => (),
  71                 }
  72             }
  73         }
  74     }
  75 }