src/tools/clippy/clippy_lints/src/unit_types/unit_cmp.rs

   1 use clippy_utils::diagnostics::span_lint;
   2 use rustc_hir::{BinOpKind, Expr, ExprKind};
   3 use rustc_lint::LateContext;
   4 use rustc_span::hygiene::{ExpnKind, MacroKind};
   5
   6 use super::UNIT_CMP;
   7
   8 pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>) {
   9     if expr.span.from_expansion() {
  10         if let Some(callee) = expr.span.source_callee() {
  11             if let ExpnKind::Macro {
  12                 kind: MacroKind::Bang,
  13                 name: symbol,
  14                 proc_macro: _,
  15             } = callee.kind
  16             {
  17                 if let ExprKind::Binary(ref cmp, left, _) = expr.kind {
  18                     let op = cmp.node;
  19                     if op.is_comparison() && cx.typeck_results().expr_ty(left).is_unit() {
  20                         let result = match &*symbol.as_str() {
  21                             "assert_eq" | "debug_assert_eq" => "succeed",
  22                             "assert_ne" | "debug_assert_ne" => "fail",
  23                             _ => return,
  24                         };
  25                         span_lint(
  26                             cx,
  27                             UNIT_CMP,
  28                             expr.span,
  29                             &format!(
  30                                 "`{}` of unit values detected. This will always {}",
  31                                 symbol.as_str(),
  32                                 result
  33                             ),
  34                         );
  35                     }
  36                 }
  37             }
  38         }
  39         return;
  40     }
  41
  42     if let ExprKind::Binary(ref cmp, left, _) = expr.kind {
  43         let op = cmp.node;
  44         if op.is_comparison() && cx.typeck_results().expr_ty(left).is_unit() {
  45             let result = match op {
  46                 BinOpKind::Eq | BinOpKind::Le | BinOpKind::Ge => "true",
  47                 _ => "false",
  48             };
  49             span_lint(
  50                 cx,
  51                 UNIT_CMP,
  52                 expr.span,
  53                 &format!(
  54                     "{}-comparison of unit values detected. This will always be {}",
  55                     op.as_str(),
  56                     result
  57                 ),
  58             );
  59         }
  60     }
  61 }