63 lines
1.8 KiB
Rust
63 lines
1.8 KiB
Rust
use if_chain::if_chain;
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use rustc::hir::*;
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use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
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use rustc::{declare_lint_pass, declare_tool_lint};
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use syntax::source_map::{Span, Spanned};
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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<'a, 'tcx> LateLintPass<'a, 'tcx> for NegMultiply {
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fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
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if let ExprKind::Binary(
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Spanned {
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node: BinOpKind::Mul, ..
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},
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ref l,
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ref r,
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) = e.node
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{
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match (&l.node, &r.node) {
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(&ExprKind::Unary(..), &ExprKind::Unary(..)) => (),
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(&ExprKind::Unary(UnNeg, ref lit), _) => check_mul(cx, e.span, lit, r),
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(_, &ExprKind::Unary(UnNeg, ref lit)) => check_mul(cx, e.span, lit, l),
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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.node;
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if let Constant::Int(val) = consts::lit_to_constant(&l.node, cx.tables.expr_ty(lit));
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if val == 1;
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if cx.tables.expr_ty(exp).is_integral();
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then {
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span_lint(cx,
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NEG_MULTIPLY,
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span,
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"Negation by multiplying with -1");
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}
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}
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}
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