src/tools/clippy/clippy_lints/src/misc_early/unneeded_wildcard_pattern.rs

   1 use clippy_utils::diagnostics::span_lint_and_sugg;
   2 use rustc_ast::ast::{Pat, PatKind};
   3 use rustc_errors::Applicability;
   4 use rustc_lint::EarlyContext;
   5 use rustc_span::source_map::Span;
   6
   7 use super::UNNEEDED_WILDCARD_PATTERN;
   8
   9 pub(super) fn check(cx: &EarlyContext<'_>, pat: &Pat) {
  10     if let PatKind::TupleStruct(_, ref patterns) | PatKind::Tuple(ref patterns) = pat.kind {
  11         if let Some(rest_index) = patterns.iter().position(|pat| pat.is_rest()) {
  12             if let Some((left_index, left_pat)) = patterns[..rest_index]
  13                 .iter()
  14                 .rev()
  15                 .take_while(|pat| matches!(pat.kind, PatKind::Wild))
  16                 .enumerate()
  17                 .last()
  18             {
  19                 span_lint(cx, left_pat.span.until(patterns[rest_index].span), left_index == 0);
  20             }
  21
  22             if let Some((right_index, right_pat)) = patterns[rest_index + 1..]
  23                 .iter()
  24                 .take_while(|pat| matches!(pat.kind, PatKind::Wild))
  25                 .enumerate()
  26                 .last()
  27             {
  28                 span_lint(
  29                     cx,
  30                     patterns[rest_index].span.shrink_to_hi().to(right_pat.span),
  31                     right_index == 0,
  32                 );
  33             }
  34         }
  35     }
  36 }
  37
  38 fn span_lint(cx: &EarlyContext<'_>, span: Span, only_one: bool) {
  39     span_lint_and_sugg(
  40         cx,
  41         UNNEEDED_WILDCARD_PATTERN,
  42         span,
  43         if only_one {
  44             "this pattern is unneeded as the `..` pattern can match that element"
  45         } else {
  46             "these patterns are unneeded as the `..` pattern can match those elements"
  47         },
  48         if only_one { "remove it" } else { "remove them" },
  49         "".to_string(),
  50         Applicability::MachineApplicable,
  51     );
  52 }