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 /// lint for length-1 `str`s for methods in `PATTERN_METHODS`
  13 pub(super) fn check(cx: &LateContext<'_>, _expr: &hir::Expr<'_>, method_name: Symbol, args: &[hir::Expr<'_>]) {
  14     for &(method, pos) in &crate::methods::PATTERN_METHODS {
  15         if_chain! {
  16             if let ty::Ref(_, ty, _) = cx.typeck_results().expr_ty_adjusted(&args[0]).kind();
  17             if *ty.kind() == ty::Str;
  18             if method_name.as_str() == method && args.len() > pos;
  19             let arg = &args[pos];
  20             let mut applicability = Applicability::MachineApplicable;
  21             if let Some(hint) = get_hint_if_single_char_arg(cx, arg, &mut applicability);
  22             then {
  23                 span_lint_and_sugg(
  24                     cx,
  25                     SINGLE_CHAR_PATTERN,
  26                     arg.span,
  27                     "single-character string constant used as pattern",
  28                     "try using a `char` instead",
  29                     hint,
  30                     applicability,
  31                 );
  32             }
  33         }
  34     }
  35 }