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