75 lines
2.8 KiB
Rust
75 lines
2.8 KiB
Rust
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use super::EXPLICIT_ITER_LOOP;
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use crate::utils::{match_trait_method, snippet_with_applicability, span_lint_and_sugg};
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use rustc_errors::Applicability;
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use rustc_hir::{Expr, Mutability};
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use rustc_lint::LateContext;
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use rustc_middle::ty::{self, Ty, TyS};
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use rustc_span::sym;
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use crate::utils::{is_type_diagnostic_item, match_type, paths};
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pub(super) fn check(cx: &LateContext<'_>, args: &[Expr<'_>], arg: &Expr<'_>, method_name: &str) {
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let should_lint = match method_name {
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"iter" | "iter_mut" => is_ref_iterable_type(cx, &args[0]),
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"into_iter" if match_trait_method(cx, arg, &paths::INTO_ITERATOR) => {
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let receiver_ty = cx.typeck_results().expr_ty(&args[0]);
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let receiver_ty_adjusted = cx.typeck_results().expr_ty_adjusted(&args[0]);
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let ref_receiver_ty = cx.tcx.mk_ref(
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cx.tcx.lifetimes.re_erased,
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ty::TypeAndMut {
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ty: receiver_ty,
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mutbl: Mutability::Not,
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},
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);
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TyS::same_type(receiver_ty_adjusted, ref_receiver_ty)
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},
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_ => false,
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};
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if !should_lint {
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return;
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}
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let mut applicability = Applicability::MachineApplicable;
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let object = snippet_with_applicability(cx, args[0].span, "_", &mut applicability);
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let muta = if method_name == "iter_mut" { "mut " } else { "" };
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span_lint_and_sugg(
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cx,
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EXPLICIT_ITER_LOOP,
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arg.span,
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"it is more concise to loop over references to containers instead of using explicit \
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iteration methods",
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"to write this more concisely, try",
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format!("&{}{}", muta, object),
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applicability,
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)
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}
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/// Returns `true` if the type of expr is one that provides `IntoIterator` impls
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/// for `&T` and `&mut T`, such as `Vec`.
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#[rustfmt::skip]
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fn is_ref_iterable_type(cx: &LateContext<'_>, e: &Expr<'_>) -> bool {
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// no walk_ptrs_ty: calling iter() on a reference can make sense because it
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// will allow further borrows afterwards
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let ty = cx.typeck_results().expr_ty(e);
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is_iterable_array(ty, cx) ||
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is_type_diagnostic_item(cx, ty, sym::vec_type) ||
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match_type(cx, ty, &paths::LINKED_LIST) ||
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is_type_diagnostic_item(cx, ty, sym::hashmap_type) ||
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is_type_diagnostic_item(cx, ty, sym::hashset_type) ||
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is_type_diagnostic_item(cx, ty, sym::vecdeque_type) ||
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match_type(cx, ty, &paths::BINARY_HEAP) ||
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match_type(cx, ty, &paths::BTREEMAP) ||
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match_type(cx, ty, &paths::BTREESET)
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}
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fn is_iterable_array<'tcx>(ty: Ty<'tcx>, cx: &LateContext<'tcx>) -> bool {
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// IntoIterator is currently only implemented for array sizes <= 32 in rustc
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match ty.kind() {
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ty::Array(_, n) => n
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.try_eval_usize(cx.tcx, cx.param_env)
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.map_or(false, |val| (0..=32).contains(&val)),
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_ => false,
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}
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}
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