68 lines
2.3 KiB
Rust
68 lines
2.3 KiB
Rust
use if_chain::if_chain;
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use rustc_errors::Applicability;
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use rustc_hir::{Expr, ExprKind, LangItem};
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use rustc_lint::{LateContext, LateLintPass, LintContext};
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use rustc_middle::{lint::in_external_macro, ty::TyS};
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use crate::utils::{is_type_lang_item, snippet_with_applicability, span_lint_and_sugg};
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declare_clippy_lint! {
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/// **What it does:** Checks for redundant slicing expressions which use the full range, and
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/// do not change the type.
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///
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/// **Why is this bad?** It unnecessarily adds complexity to the expression.
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///
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/// **Known problems:** If the type being sliced has an implementation of `Index<RangeFull>`
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/// that actually changes anything then it can't be removed. However, this would be surprising
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/// to people reading the code and should have a note with it.
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///
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/// **Example:**
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///
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/// ```ignore
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/// fn get_slice(x: &[u32]) -> &[u32] {
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/// &x[..]
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/// }
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/// ```
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/// Use instead:
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/// ```ignore
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/// fn get_slice(x: &[u32]) -> &[u32] {
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/// x
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/// }
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/// ```
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pub REDUNDANT_SLICING,
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complexity,
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"redundant slicing of the whole range of a type"
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}
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declare_lint_pass!(RedundantSlicing => [REDUNDANT_SLICING]);
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impl LateLintPass<'_> for RedundantSlicing {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
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if in_external_macro(cx.sess(), expr.span) {
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return;
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}
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if_chain! {
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if let ExprKind::AddrOf(_, _, addressee) = expr.kind;
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if let ExprKind::Index(indexed, range) = addressee.kind;
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if is_type_lang_item(cx, cx.typeck_results().expr_ty_adjusted(range), LangItem::RangeFull);
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if TyS::same_type(cx.typeck_results().expr_ty(expr), cx.typeck_results().expr_ty(indexed));
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then {
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let mut app = Applicability::MachineApplicable;
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let hint = snippet_with_applicability(cx, indexed.span, "..", &mut app).into_owned();
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span_lint_and_sugg(
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cx,
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REDUNDANT_SLICING,
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expr.span,
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"redundant slicing of the whole range",
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"use the original slice instead",
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hint,
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app,
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);
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}
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}
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}
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}
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