clippy_lints/src/assertions_on_constants.rs

   1 use crate::consts::{constant, Constant};
   2 use crate::rustc::hir::{Expr, ExprKind};
   3 use crate::rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
   4 use crate::rustc::{declare_tool_lint, lint_array};
   5 use crate::syntax::ast::LitKind;
   6 use crate::utils::{in_macro, is_direct_expn_of, span_help_and_lint};
   7 use if_chain::if_chain;
   8
   9 /// **What it does:** Check to call assert!(true/false)
  10 ///
  11 /// **Why is this bad?** Will be optimized out by the compiler or should probably be replaced by a
  12 /// panic!() or unreachable!()
  13 ///
  14 /// **Known problems:** None
  15 ///
  16 /// **Example:**
  17 /// ```rust
  18 /// assert!(false)
  19 /// // or
  20 /// assert!(true)
  21 /// // or
  22 /// const B: bool = false;
  23 /// assert!(B)
  24 /// ```
  25 declare_clippy_lint! {
  26     pub ASSERTIONS_ON_CONSTANTS,
  27     style,
  28     "assert!(true/false) will be optimized out by the compiler/should probably be replaced by a panic!() or unreachable!()"
  29 }
  30
  31 pub struct AssertionsOnConstants;
  32
  33 impl LintPass for AssertionsOnConstants {
  34     fn get_lints(&self) -> LintArray {
  35         lint_array![ASSERTIONS_ON_CONSTANTS]
  36     }
  37
  38     fn name(&self) -> &'static str {
  39         "AssertionsOnConstants"
  40     }
  41 }
  42
  43 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AssertionsOnConstants {
  44     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
  45         if_chain! {
  46             if let Some(assert_span) = is_direct_expn_of(e.span, "assert");
  47             if !in_macro(assert_span)
  48                 || is_direct_expn_of(assert_span, "debug_assert").map_or(false, |span| !in_macro(span));
  49             if let ExprKind::Unary(_, ref lit) = e.node;
  50             then {
  51                 if let ExprKind::Lit(ref inner) = lit.node {
  52                     match inner.node {
  53                         LitKind::Bool(true) => {
  54                             span_help_and_lint(cx, ASSERTIONS_ON_CONSTANTS, e.span,
  55                                 "assert!(true) will be optimized out by the compiler",
  56                                 "remove it");
  57                         },
  58                         LitKind::Bool(false) => {
  59                             span_help_and_lint(
  60                                 cx, ASSERTIONS_ON_CONSTANTS, e.span,
  61                                 "assert!(false) should probably be replaced",
  62                                 "use panic!() or unreachable!()");
  63                         },
  64                         _ => (),
  65                     }
  66                 } else if let Some(bool_const) = constant(cx, cx.tables, lit) {
  67                     match bool_const.0 {
  68                         Constant::Bool(true) => {
  69                             span_help_and_lint(cx, ASSERTIONS_ON_CONSTANTS, e.span,
  70                                 "assert!(const: true) will be optimized out by the compiler",
  71                                 "remove it");
  72                         },
  73                         Constant::Bool(false) => {
  74                             span_help_and_lint(cx, ASSERTIONS_ON_CONSTANTS, e.span,
  75                                 "assert!(const: false) should probably be replaced",
  76                                 "use panic!() or unreachable!()");
  77                         },
  78                         _ => (),
  79                     }
  80                 }
  81             }
  82         }
  83     }
  84 }