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); 24] = [
  13     ("contains", 0),
  14     ("starts_with", 0),
  15     ("ends_with", 0),
  16     ("find", 0),
  17     ("rfind", 0),
  18     ("split", 0),
  19     ("split_inclusive", 0),
  20     ("rsplit", 0),
  21     ("split_terminator", 0),
  22     ("rsplit_terminator", 0),
  23     ("splitn", 1),
  24     ("rsplitn", 1),
  25     ("split_once", 0),
  26     ("rsplit_once", 0),
  27     ("matches", 0),
  28     ("rmatches", 0),
  29     ("match_indices", 0),
  30     ("rmatch_indices", 0),
  31     ("strip_prefix", 0),
  32     ("strip_suffix", 0),
  33     ("trim_start_matches", 0),
  34     ("trim_end_matches", 0),
  35     ("replace", 0),
  36     ("replacen", 0),
  37 ];
  38
  39 /// lint for length-1 `str`s for methods in `PATTERN_METHODS`
  40 pub(super) fn check(
  41     cx: &LateContext<'_>,
  42     _expr: &hir::Expr<'_>,
  43     method_name: Symbol,
  44     receiver: &hir::Expr<'_>,
  45     args: &[hir::Expr<'_>],
  46 ) {
  47     for &(method, pos) in &PATTERN_METHODS {
  48         if_chain! {
  49             if let ty::Ref(_, ty, _) = cx.typeck_results().expr_ty_adjusted(receiver).kind();
  50             if *ty.kind() == ty::Str;
  51             if method_name.as_str() == method && args.len() > pos;
  52             let arg = &args[pos];
  53             let mut applicability = Applicability::MachineApplicable;
  54             if let Some(hint) = get_hint_if_single_char_arg(cx, arg, &mut applicability);
  55             then {
  56                 span_lint_and_sugg(
  57                     cx,
  58                     SINGLE_CHAR_PATTERN,
  59                     arg.span,
  60                     "single-character string constant used as pattern",
  61                     "try using a `char` instead",
  62                     hint,
  63                     applicability,
  64                 );
  65             }
  66         }
  67     }
  68 }