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use crate::utils::span_lint_and_help;
use if_chain::if_chain;
use rustc_hir as hir;
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
declare_clippy_lint! {
/// **What it does:** Checks for division of integers
///
/// **Why is this bad?** When outside of some very specific algorithms,
/// integer division is very often a mistake because it discards the
/// remainder.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// fn main() {
/// let x = 3 / 2;
/// println!("{}", x);
/// }
/// ```
pub INTEGER_DIVISION,
restriction,
"integer division may cause loss of precision"
}
declare_lint_pass!(IntegerDivision => [INTEGER_DIVISION]);
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for IntegerDivision {
fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr<'_>) {
if is_integer_division(cx, expr) {
span_lint_and_help(
cx,
INTEGER_DIVISION,
expr.span,
"integer division",
"division of integers may cause loss of precision. consider using floats.",
);
}
}
}
fn is_integer_division<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr<'_>) -> bool {
if_chain! {
if let hir::ExprKind::Binary(binop, left, right) = &expr.kind;
if let hir::BinOpKind::Div = &binop.node;
then {
let (left_ty, right_ty) = (cx.tables.expr_ty(left), cx.tables.expr_ty(right));
return left_ty.is_integral() && right_ty.is_integral();
}
}
false
}
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