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

   1 use clippy_utils::diagnostics::span_lint;
   2 use clippy_utils::macros::{find_assert_eq_args, root_macro_call_first_node};
   3 use rustc_hir::{BinOpKind, Expr, ExprKind};
   4 use rustc_lint::LateContext;
   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(macro_call) = root_macro_call_first_node(cx, expr) {
  11             let macro_name = cx.tcx.item_name(macro_call.def_id);
  12             let result = match macro_name.as_str() {
  13                 "assert_eq" | "debug_assert_eq" => "succeed",
  14                 "assert_ne" | "debug_assert_ne" => "fail",
  15                 _ => return,
  16             };
  17             let Some ((left, _, _)) = find_assert_eq_args(cx, expr, macro_call.expn) else { return };
  18             if !cx.typeck_results().expr_ty(left).is_unit() {
  19                 return;
  20             }
  21             span_lint(
  22                 cx,
  23                 UNIT_CMP,
  24                 macro_call.span,
  25                 &format!("`{macro_name}` of unit values detected. This will always {result}"),
  26             );
  27         }
  28         return;
  29     }
  30
  31     if let ExprKind::Binary(ref cmp, left, _) = expr.kind {
  32         let op = cmp.node;
  33         if op.is_comparison() && cx.typeck_results().expr_ty(left).is_unit() {
  34             let result = match op {
  35                 BinOpKind::Eq | BinOpKind::Le | BinOpKind::Ge => "true",
  36                 _ => "false",
  37             };
  38             span_lint(
  39                 cx,
  40                 UNIT_CMP,
  41                 expr.span,
  42                 &format!(
  43                     "{}-comparison of unit values detected. This will always be {result}",
  44                     op.as_str()
  45                 ),
  46             );
  47         }
  48     }
  49 }