clippy_lints/src/matches/infalliable_detructuring_match.rs

   1 use clippy_utils::diagnostics::span_lint_and_sugg;
   2 use clippy_utils::source::snippet_with_applicability;
   3 use clippy_utils::{path_to_local_id, peel_blocks, strip_pat_refs};
   4 use rustc_errors::Applicability;
   5 use rustc_hir::{ExprKind, Local, MatchSource, PatKind, QPath};
   6 use rustc_lint::LateContext;
   7
   8 use super::INFALLIBLE_DESTRUCTURING_MATCH;
   9
  10 pub(crate) fn check(cx: &LateContext<'_>, local: &Local<'_>) -> bool {
  11     if_chain! {
  12         if !local.span.from_expansion();
  13         if let Some(expr) = local.init;
  14         if let ExprKind::Match(target, arms, MatchSource::Normal) = expr.kind;
  15         if arms.len() == 1 && arms[0].guard.is_none();
  16         if let PatKind::TupleStruct(
  17             QPath::Resolved(None, variant_name), args, _) = arms[0].pat.kind;
  18         if args.len() == 1;
  19         if let PatKind::Binding(_, arg, ..) = strip_pat_refs(&args[0]).kind;
  20         let body = peel_blocks(arms[0].body);
  21         if path_to_local_id(body, arg);
  22
  23         then {
  24             let mut applicability = Applicability::MachineApplicable;
  25             span_lint_and_sugg(
  26                 cx,
  27                 INFALLIBLE_DESTRUCTURING_MATCH,
  28                 local.span,
  29                 "you seem to be trying to use `match` to destructure a single infallible pattern. \
  30                 Consider using `let`",
  31                 "try this",
  32                 format!(
  33                     "let {}({}) = {};",
  34                     snippet_with_applicability(cx, variant_name.span, "..", &mut applicability),
  35                     snippet_with_applicability(cx, local.pat.span, "..", &mut applicability),
  36                     snippet_with_applicability(cx, target.span, "..", &mut applicability),
  37                 ),
  38                 applicability,
  39             );
  40             return true;
  41         }
  42     }
  43     false
  44 }