clippy_lints/src/methods/string_extend_chars.rs

   1 use crate::utils::{is_type_diagnostic_item, method_chain_args, snippet_with_applicability, span_lint_and_sugg};
   2 use rustc_errors::Applicability;
   3 use rustc_hir as hir;
   4 use rustc_lint::LateContext;
   5 use rustc_middle::ty;
   6 use rustc_span::symbol::sym;
   7
   8 use super::STRING_EXTEND_CHARS;
   9
  10 pub(super) fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
  11     let obj_ty = cx.typeck_results().expr_ty(&args[0]).peel_refs();
  12     if is_type_diagnostic_item(cx, obj_ty, sym::string_type) {
  13         let arg = &args[1];
  14         if let Some(arglists) = method_chain_args(arg, &["chars"]) {
  15             let target = &arglists[0][0];
  16             let self_ty = cx.typeck_results().expr_ty(target).peel_refs();
  17             let ref_str = if *self_ty.kind() == ty::Str {
  18                 ""
  19             } else if is_type_diagnostic_item(cx, self_ty, sym::string_type) {
  20                 "&"
  21             } else {
  22                 return;
  23             };
  24
  25             let mut applicability = Applicability::MachineApplicable;
  26             span_lint_and_sugg(
  27                 cx,
  28                 STRING_EXTEND_CHARS,
  29                 expr.span,
  30                 "calling `.extend(_.chars())`",
  31                 "try this",
  32                 format!(
  33                     "{}.push_str({}{})",
  34                     snippet_with_applicability(cx, args[0].span, "..", &mut applicability),
  35                     ref_str,
  36                     snippet_with_applicability(cx, target.span, "..", &mut applicability)
  37                 ),
  38                 applicability,
  39             );
  40         }
  41     }
  42 }