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

   1 use clippy_utils::diagnostics::span_lint_and_sugg;
   2 use clippy_utils::method_chain_args;
   3 use clippy_utils::source::snippet_with_applicability;
   4 use clippy_utils::ty::is_type_lang_item;
   5 use rustc_errors::Applicability;
   6 use rustc_hir as hir;
   7 use rustc_lint::LateContext;
   8 use rustc_middle::ty;
   9
  10 use super::STRING_EXTEND_CHARS;
  11
  12 pub(super) fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, recv: &hir::Expr<'_>, arg: &hir::Expr<'_>) {
  13     let obj_ty = cx.typeck_results().expr_ty(recv).peel_refs();
  14     if !is_type_lang_item(cx, obj_ty, hir::LangItem::String) {
  15         return;
  16     }
  17     if let Some(arglists) = method_chain_args(arg, &["chars"]) {
  18         let target = &arglists[0].0;
  19         let self_ty = cx.typeck_results().expr_ty(target).peel_refs();
  20         let ref_str = if *self_ty.kind() == ty::Str {
  21             if matches!(target.kind, hir::ExprKind::Index(..)) {
  22                 "&"
  23             } else {
  24                 ""
  25             }
  26         } else if is_type_lang_item(cx, self_ty, hir::LangItem::String) {
  27             "&"
  28         } else {
  29             return;
  30         };
  31
  32         let mut applicability = Applicability::MachineApplicable;
  33         span_lint_and_sugg(
  34             cx,
  35             STRING_EXTEND_CHARS,
  36             expr.span,
  37             "calling `.extend(_.chars())`",
  38             "try this",
  39             format!(
  40                 "{}.push_str({ref_str}{})",
  41                 snippet_with_applicability(cx, recv.span, "..", &mut applicability),
  42                 snippet_with_applicability(cx, target.span, "..", &mut applicability)
  43             ),
  44             applicability,
  45         );
  46     }
  47 }