104 lines
3.1 KiB
Rust
104 lines
3.1 KiB
Rust
use clippy_utils::diagnostics::span_lint_and_sugg;
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use clippy_utils::source::snippet;
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use clippy_utils::ty::{is_type_diagnostic_item, is_type_lang_item};
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use if_chain::if_chain;
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use rustc_errors::Applicability;
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use rustc_hir::{Expr, ExprKind, LangItem, MatchSource};
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use rustc_lint::{LateContext, LateLintPass, LintContext};
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use rustc_middle::lint::in_external_macro;
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use rustc_span::sym;
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declare_clippy_lint! {
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/// **What it does:** Checks for `match vec[idx]` or `match vec[n..m]`.
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///
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/// **Why is this bad?** This can panic at runtime.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust, no_run
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/// let arr = vec![0, 1, 2, 3];
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/// let idx = 1;
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///
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/// // Bad
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/// match arr[idx] {
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/// 0 => println!("{}", 0),
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/// 1 => println!("{}", 3),
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/// _ => {},
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/// }
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/// ```
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/// Use instead:
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/// ```rust, no_run
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/// let arr = vec![0, 1, 2, 3];
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/// let idx = 1;
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///
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/// // Good
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/// match arr.get(idx) {
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/// Some(0) => println!("{}", 0),
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/// Some(1) => println!("{}", 3),
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/// _ => {},
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/// }
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/// ```
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pub MATCH_ON_VEC_ITEMS,
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pedantic,
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"matching on vector elements can panic"
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}
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declare_lint_pass!(MatchOnVecItems => [MATCH_ON_VEC_ITEMS]);
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impl<'tcx> LateLintPass<'tcx> for MatchOnVecItems {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
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if_chain! {
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if !in_external_macro(cx.sess(), expr.span);
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if let ExprKind::Match(ref match_expr, _, MatchSource::Normal) = expr.kind;
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if let Some(idx_expr) = is_vec_indexing(cx, match_expr);
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if let ExprKind::Index(vec, idx) = idx_expr.kind;
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then {
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// FIXME: could be improved to suggest surrounding every pattern with Some(_),
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// but only when `or_patterns` are stabilized.
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span_lint_and_sugg(
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cx,
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MATCH_ON_VEC_ITEMS,
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match_expr.span,
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"indexing into a vector may panic",
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"try this",
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format!(
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"{}.get({})",
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snippet(cx, vec.span, ".."),
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snippet(cx, idx.span, "..")
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),
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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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}
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fn is_vec_indexing<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> Option<&'tcx Expr<'tcx>> {
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if_chain! {
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if let ExprKind::Index(ref array, ref index) = expr.kind;
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if is_vector(cx, array);
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if !is_full_range(cx, index);
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then {
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return Some(expr);
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}
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}
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None
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}
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fn is_vector(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
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let ty = cx.typeck_results().expr_ty(expr);
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let ty = ty.peel_refs();
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is_type_diagnostic_item(cx, ty, sym::vec_type)
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}
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fn is_full_range(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
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let ty = cx.typeck_results().expr_ty(expr);
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let ty = ty.peel_refs();
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is_type_lang_item(cx, ty, LangItem::RangeFull)
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}
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