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
   6 use crate::consts::{constant, Constant};
   7 use crate::syntax::ast::LitKind;
   8 use crate::utils::{in_macro, is_direct_expn_of, span_help_and_lint};
   9
  10 declare_clippy_lint! {
  11     /// **What it does:** Checks for `assert!(true)` and `assert!(false)` calls.
  12     ///
  13     /// **Why is this bad?** Will be optimized out by the compiler or should probably be replaced by a
  14     /// panic!() or unreachable!()
  15     ///
  16     /// **Known problems:** None
  17     ///
  18     /// **Example:**
  19     /// ```rust,ignore
  20     /// assert!(false)
  21     /// // or
  22     /// assert!(true)
  23     /// // or
  24     /// const B: bool = false;
  25     /// assert!(B)
  26     /// ```
  27     pub ASSERTIONS_ON_CONSTANTS,
  28     style,
  29     "`assert!(true)` / `assert!(false)` will be optimized out by the compiler, and should probably be replaced by a `panic!()` or `unreachable!()`"
  30 }
  31
  32 declare_lint_pass!(AssertionsOnConstants => [ASSERTIONS_ON_CONSTANTS]);
  33
  34 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AssertionsOnConstants {
  35     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
  36         let mut is_debug_assert = false;
  37         if_chain! {
  38             if let Some(assert_span) = is_direct_expn_of(e.span, "assert");
  39             if !in_macro(assert_span)
  40                 || is_direct_expn_of(assert_span, "debug_assert").map_or(false, |span| {
  41                     is_debug_assert = true;
  42                     // Check that `debug_assert!` itself is not inside a macro
  43                     !in_macro(span)
  44                 });
  45             if let ExprKind::Unary(_, ref lit) = e.node;
  46             then {
  47                 if let ExprKind::Lit(ref inner) = lit.node {
  48                     match inner.node {
  49                         LitKind::Bool(true) => {
  50                             span_help_and_lint(
  51                                 cx,
  52                                 ASSERTIONS_ON_CONSTANTS,
  53                                 e.span,
  54                                 "`assert!(true)` will be optimized out by the compiler",
  55                                 "remove it"
  56                             );
  57                         },
  58                         LitKind::Bool(false) if !is_debug_assert => {
  59                             span_help_and_lint(
  60                                 cx,
  61                                 ASSERTIONS_ON_CONSTANTS,
  62                                 e.span,
  63                                 "`assert!(false)` should probably be replaced",
  64                                 "use `panic!()` or `unreachable!()`"
  65                             );
  66                         },
  67                         _ => (),
  68                     }
  69                 } else if let Some(bool_const) = constant(cx, cx.tables, lit) {
  70                     match bool_const.0 {
  71                         Constant::Bool(true) => {
  72                             span_help_and_lint(
  73                                 cx,
  74                                 ASSERTIONS_ON_CONSTANTS,
  75                                 e.span,
  76                                 "`assert!(const: true)` will be optimized out by the compiler",
  77                                 "remove it"
  78                             );
  79                         },
  80                         Constant::Bool(false) if !is_debug_assert => {
  81                             span_help_and_lint(
  82                                 cx,
  83                                 ASSERTIONS_ON_CONSTANTS,
  84                                 e.span,
  85                                 "`assert!(const: false)` should probably be replaced",
  86                                 "use `panic!()` or `unreachable!()`"
  87                             );
  88                         },
  89                         _ => (),
  90                     }
  91                 }
  92             }
  93         }
  94     }
  95 }