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

   1 use clippy_utils::diagnostics::span_lint_and_sugg;
   2 use clippy_utils::is_trait_method;
   3 use clippy_utils::ty::has_iter_method;
   4 use if_chain::if_chain;
   5 use rustc_errors::Applicability;
   6 use rustc_hir as hir;
   7 use rustc_lint::LateContext;
   8 use rustc_middle::ty::{self, Ty};
   9 use rustc_span::source_map::Span;
  10 use rustc_span::symbol::{sym, Symbol};
  11
  12 use super::INTO_ITER_ON_REF;
  13
  14 pub(super) fn check(
  15     cx: &LateContext<'_>,
  16     expr: &hir::Expr<'_>,
  17     method_span: Span,
  18     method_name: Symbol,
  19     receiver: &hir::Expr<'_>,
  20 ) {
  21     let self_ty = cx.typeck_results().expr_ty_adjusted(receiver);
  22     if_chain! {
  23         if let ty::Ref(..) = self_ty.kind();
  24         if method_name == sym::into_iter;
  25         if is_trait_method(cx, expr, sym::IntoIterator);
  26         if let Some((kind, method_name)) = ty_has_iter_method(cx, self_ty);
  27         then {
  28             span_lint_and_sugg(
  29                 cx,
  30                 INTO_ITER_ON_REF,
  31                 method_span,
  32                 &format!(
  33                     "this `.into_iter()` call is equivalent to `.{}()` and will not consume the `{}`",
  34                     method_name, kind,
  35                 ),
  36                 "call directly",
  37                 method_name.to_string(),
  38                 Applicability::MachineApplicable,
  39             );
  40         }
  41     }
  42 }
  43
  44 fn ty_has_iter_method(cx: &LateContext<'_>, self_ref_ty: Ty<'_>) -> Option<(Symbol, &'static str)> {
  45     has_iter_method(cx, self_ref_ty).map(|ty_name| {
  46         let mutbl = match self_ref_ty.kind() {
  47             ty::Ref(_, _, mutbl) => mutbl,
  48             _ => unreachable!(),
  49         };
  50         let method_name = match mutbl {
  51             hir::Mutability::Not => "iter",
  52             hir::Mutability::Mut => "iter_mut",
  53         };
  54         (ty_name, method_name)
  55     })
  56 }