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use rustc::hir::*;
use rustc::lint::*;
use syntax::codemap::{Span, Spanned};
use consts::{self, Constant};
use utils::span_lint;
declare_clippy_lint! {
pub NEG_MULTIPLY,
style,
"multiplying integers with -1"
}
#[derive(Copy, Clone)]
pub struct NegMultiply;
impl LintPass for NegMultiply {
fn get_lints(&self) -> LintArray {
lint_array!(NEG_MULTIPLY)
}
}
#[allow(match_same_arms)]
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NegMultiply {
fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
if let ExprBinary(Spanned { node: BiMul, .. }, ref l, ref r) = e.node {
match (&l.node, &r.node) {
(&ExprUnary(..), &ExprUnary(..)) => (),
(&ExprUnary(UnNeg, ref lit), _) => check_mul(cx, e.span, lit, r),
(_, &ExprUnary(UnNeg, ref lit)) => check_mul(cx, e.span, lit, l),
_ => (),
}
}
}
}
fn check_mul(cx: &LateContext, span: Span, lit: &Expr, exp: &Expr) {
if_chain! {
if let ExprLit(ref l) = lit.node;
if let Constant::Int(val) = consts::lit_to_constant(&l.node, cx.tables.expr_ty(lit));
if val == 1;
if cx.tables.expr_ty(exp).is_integral();
then {
span_lint(cx,
NEG_MULTIPLY,
span,
"Negation by multiplying with -1");
}
}
}