src/tools/clippy/clippy_lints/src/methods/unit_hash.rs

   1 use clippy_utils::diagnostics::span_lint_and_then;
   2 use clippy_utils::is_trait_method;
   3 use clippy_utils::source::snippet;
   4 use rustc_errors::Applicability;
   5 use rustc_hir::Expr;
   6 use rustc_lint::LateContext;
   7 use rustc_span::sym;
   8
   9 use super::UNIT_HASH;
  10
  11 pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, recv: &'tcx Expr<'_>, arg: &'tcx Expr<'_>) {
  12     if is_trait_method(cx, expr, sym::Hash) && cx.typeck_results().expr_ty(recv).is_unit() {
  13         span_lint_and_then(
  14             cx,
  15             UNIT_HASH,
  16             expr.span,
  17             "this call to `hash` on the unit type will do nothing",
  18             |diag| {
  19                 diag.span_suggestion(
  20                     expr.span,
  21                     "remove the call to `hash` or consider using",
  22                     format!("0_u8.hash({})", snippet(cx, arg.span, ".."),),
  23                     Applicability::MaybeIncorrect,
  24                 );
  25                 diag.note("the implementation of `Hash` for `()` is a no-op");
  26             },
  27         );
  28     }
  29 }