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

   1 use clippy_utils::diagnostics::span_lint_and_then;
   2 use clippy_utils::source::snippet_opt;
   3 use clippy_utils::ty::{implements_trait, is_copy};
   4 use rustc_errors::Applicability;
   5 use rustc_hir::Expr;
   6 use rustc_lint::LateContext;
   7 use rustc_middle::ty;
   8 use rustc_span::sym;
   9
  10 use super::ITER_OVEREAGER_CLONED;
  11 use crate::redundant_clone::REDUNDANT_CLONE;
  12
  13 pub(super) fn check<'tcx>(
  14     cx: &LateContext<'tcx>,
  15     expr: &'tcx Expr<'_>,
  16     cloned_call: &'tcx Expr<'_>,
  17     cloned_recv: &'tcx Expr<'_>,
  18     is_count: bool,
  19     needs_into_iter: bool,
  20 ) {
  21     let typeck = cx.typeck_results();
  22     if let Some(iter_id) = cx.tcx.get_diagnostic_item(sym::Iterator)
  23         && let Some(method_id) = typeck.type_dependent_def_id(expr.hir_id)
  24         && cx.tcx.trait_of_item(method_id) == Some(iter_id)
  25         && let Some(method_id) = typeck.type_dependent_def_id(cloned_call.hir_id)
  26         && cx.tcx.trait_of_item(method_id) == Some(iter_id)
  27         && let cloned_recv_ty = typeck.expr_ty_adjusted(cloned_recv)
  28         && let Some(iter_assoc_ty) = cx.get_associated_type(cloned_recv_ty, iter_id, "Item")
  29         && matches!(*iter_assoc_ty.kind(), ty::Ref(_, ty, _) if !is_copy(cx, ty))
  30     {
  31         if needs_into_iter
  32             && let Some(into_iter_id) = cx.tcx.get_diagnostic_item(sym::IntoIterator)
  33             && !implements_trait(cx, iter_assoc_ty, into_iter_id, &[])
  34         {
  35             return;
  36         }
  37
  38         let (lint, msg, trailing_clone) = if is_count {
  39             (REDUNDANT_CLONE, "unneeded cloning of iterator items", "")
  40         } else {
  41             (ITER_OVEREAGER_CLONED, "unnecessarily eager cloning of iterator items", ".cloned()")
  42         };
  43
  44         span_lint_and_then(
  45             cx,
  46             lint,
  47             expr.span,
  48             msg,
  49             |diag| {
  50                 let method_span = expr.span.with_lo(cloned_call.span.hi());
  51                 if let Some(mut snip) = snippet_opt(cx, method_span) {
  52                     snip.push_str(trailing_clone);
  53                     let replace_span = expr.span.with_lo(cloned_recv.span.hi());
  54                     diag.span_suggestion(replace_span, "try this", snip, Applicability::MachineApplicable);
  55                 }
  56             }
  57         );
  58     }
  59 }