mirror of
https://github.com/rust-lang/rust-clippy
synced 2024-12-22 11:03:16 +00:00
34b373d309
This renames the variants in HIR UnOp from
enum UnOp {
UnDeref,
UnNot,
UnNeg,
}
to
enum UnOp {
Deref,
Not,
Neg,
}
Motivations:
- This is more consistent with the rest of the code base where most enum
variants don't have a prefix.
- These variants are never used without the `UnOp` prefix so the extra
`Un` prefix doesn't help with readability. E.g. we don't have any
`UnDeref`s in the code, we only have `UnOp::UnDeref`.
- MIR `UnOp` type variants don't have a prefix so this is more
consistent with MIR types.
- "un" prefix reads like "inverse" or "reverse", so as a beginner in
rustc code base when I see "UnDeref" what comes to my mind is
something like "&*" instead of just "*".
53 lines
1.8 KiB
Rust
53 lines
1.8 KiB
Rust
use if_chain::if_chain;
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use rustc_hir::{BinOpKind, Expr, ExprKind, UnOp};
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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::source_map::Span;
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use crate::consts::{self, Constant};
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use crate::utils::span_lint;
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declare_clippy_lint! {
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/// **What it does:** Checks for multiplication by -1 as a form of negation.
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///
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/// **Why is this bad?** It's more readable to just negate.
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///
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/// **Known problems:** This only catches integers (for now).
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///
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/// **Example:**
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/// ```ignore
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/// x * -1
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/// ```
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pub NEG_MULTIPLY,
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style,
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"multiplying integers with `-1`"
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}
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declare_lint_pass!(NegMultiply => [NEG_MULTIPLY]);
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#[allow(clippy::match_same_arms)]
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impl<'tcx> LateLintPass<'tcx> for NegMultiply {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
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if let ExprKind::Binary(ref op, ref left, ref right) = e.kind {
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if BinOpKind::Mul == op.node {
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match (&left.kind, &right.kind) {
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(&ExprKind::Unary(..), &ExprKind::Unary(..)) => {},
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(&ExprKind::Unary(UnOp::Neg, ref lit), _) => check_mul(cx, e.span, lit, right),
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(_, &ExprKind::Unary(UnOp::Neg, ref lit)) => check_mul(cx, e.span, lit, left),
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_ => {},
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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 check_mul(cx: &LateContext<'_>, span: Span, lit: &Expr<'_>, exp: &Expr<'_>) {
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if_chain! {
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if let ExprKind::Lit(ref l) = lit.kind;
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if let Constant::Int(1) = consts::lit_to_constant(&l.node, cx.typeck_results().expr_ty_opt(lit));
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if cx.typeck_results().expr_ty(exp).is_integral();
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then {
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span_lint(cx, NEG_MULTIPLY, span, "negation by multiplying with `-1`");
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}
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}
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}
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