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

   1 use super::utils::get_hint_if_single_char_arg;
   2 use clippy_utils::diagnostics::span_lint_and_sugg;
   3 use if_chain::if_chain;
   4 use rustc_errors::Applicability;
   5 use rustc_hir as hir;
   6 use rustc_lint::LateContext;
   7 use rustc_middle::ty;
   8 use rustc_span::symbol::Symbol;
   9
  10 use super::SINGLE_CHAR_PATTERN;
  11
  12 const PATTERN_METHODS: [(&str, usize); 19] = [
  13     ("contains", 1),
  14     ("starts_with", 1),
  15     ("ends_with", 1),
  16     ("find", 1),
  17     ("rfind", 1),
  18     ("split", 1),
  19     ("rsplit", 1),
  20     ("split_terminator", 1),
  21     ("rsplit_terminator", 1),
  22     ("splitn", 2),
  23     ("rsplitn", 2),
  24     ("matches", 1),
  25     ("rmatches", 1),
  26     ("match_indices", 1),
  27     ("rmatch_indices", 1),
  28     ("strip_prefix", 1),
  29     ("strip_suffix", 1),
  30     ("trim_start_matches", 1),
  31     ("trim_end_matches", 1),
  32 ];
  33
  34 /// lint for length-1 `str`s for methods in `PATTERN_METHODS`
  35 pub(super) fn check(cx: &LateContext<'_>, _expr: &hir::Expr<'_>, method_name: Symbol, args: &[hir::Expr<'_>]) {
  36     for &(method, pos) in &PATTERN_METHODS {
  37         if_chain! {
  38             if let ty::Ref(_, ty, _) = cx.typeck_results().expr_ty_adjusted(&args[0]).kind();
  39             if *ty.kind() == ty::Str;
  40             if method_name.as_str() == method && args.len() > pos;
  41             let arg = &args[pos];
  42             let mut applicability = Applicability::MachineApplicable;
  43             if let Some(hint) = get_hint_if_single_char_arg(cx, arg, &mut applicability);
  44             then {
  45                 span_lint_and_sugg(
  46                     cx,
  47                     SINGLE_CHAR_PATTERN,
  48                     arg.span,
  49                     "single-character string constant used as pattern",
  50                     "try using a `char` instead",
  51                     hint,
  52                     applicability,
  53                 );
  54             }
  55         }
  56     }
  57 }