67 lines
2.4 KiB
Rust
67 lines
2.4 KiB
Rust
use clippy_utils::diagnostics::span_lint_and_sugg;
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use clippy_utils::last_path_segment;
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use clippy_utils::source::snippet;
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use rustc_errors::Applicability;
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use rustc_hir::{GenericArg, GenericArgsParentheses, Mutability, Ty, TyKind};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use rustc_span::symbol::sym;
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for usage of `&Option<&T>`.
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///
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/// ### Why is this bad?
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/// Since `&` is Copy, it's useless to have a
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/// reference on `Option<&T>`.
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///
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/// ### Known problems
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/// It may be irrelevant to use this lint on
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/// public API code as it will make a breaking change to apply it.
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///
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/// ### Example
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/// ```rust,ignore
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/// let x: &Option<&u32> = &Some(&0u32);
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/// ```
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/// Use instead:
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/// ```rust,ignore
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/// let x: Option<&u32> = Some(&0u32);
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/// ```
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#[clippy::version = "1.49.0"]
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pub REF_OPTION_REF,
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pedantic,
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"use `Option<&T>` instead of `&Option<&T>`"
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}
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declare_lint_pass!(RefOptionRef => [REF_OPTION_REF]);
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impl<'tcx> LateLintPass<'tcx> for RefOptionRef {
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fn check_ty(&mut self, cx: &LateContext<'tcx>, ty: &'tcx Ty<'tcx>) {
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if let TyKind::Ref(_, ref mut_ty) = ty.kind
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&& mut_ty.mutbl == Mutability::Not
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&& let TyKind::Path(ref qpath) = &mut_ty.ty.kind
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&& let last = last_path_segment(qpath)
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&& let Some(def_id) = last.res.opt_def_id()
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&& cx.tcx.is_diagnostic_item(sym::Option, def_id)
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&& let Some(params) = last_path_segment(qpath).args
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&& params.parenthesized == GenericArgsParentheses::No
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&& let Some(inner_ty) = params.args.iter().find_map(|arg| match arg {
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GenericArg::Type(inner_ty) => Some(inner_ty),
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_ => None,
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})
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&& let TyKind::Ref(_, ref inner_mut_ty) = inner_ty.kind
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&& inner_mut_ty.mutbl == Mutability::Not
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{
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span_lint_and_sugg(
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cx,
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REF_OPTION_REF,
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ty.span,
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"since `&` implements the `Copy` trait, `&Option<&T>` can be simplified to `Option<&T>`",
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"try",
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format!("Option<{}>", &snippet(cx, inner_ty.span, "..")),
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Applicability::MaybeIncorrect,
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);
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}
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}
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}
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