61 lines
1.7 KiB
Rust
61 lines
1.7 KiB
Rust
use clippy_utils::diagnostics::span_lint_and_help;
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use if_chain::if_chain;
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use rustc_hir as hir;
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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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declare_clippy_lint! {
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/// ### What it does
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/// Checks for division of integers
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///
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/// ### Why is this bad?
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/// When outside of some very specific algorithms,
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/// integer division is very often a mistake because it discards the
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/// remainder.
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///
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/// ### Example
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/// ```rust
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/// // Bad
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/// let x = 3 / 2;
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/// println!("{}", x);
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///
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/// // Good
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/// let x = 3f32 / 2f32;
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/// println!("{}", x);
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/// ```
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#[clippy::version = "1.37.0"]
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pub INTEGER_DIVISION,
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restriction,
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"integer division may cause loss of precision"
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}
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declare_lint_pass!(IntegerDivision => [INTEGER_DIVISION]);
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impl<'tcx> LateLintPass<'tcx> for IntegerDivision {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
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if is_integer_division(cx, expr) {
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span_lint_and_help(
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cx,
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INTEGER_DIVISION,
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expr.span,
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"integer division",
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None,
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"division of integers may cause loss of precision. consider using floats",
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);
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}
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}
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}
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fn is_integer_division<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) -> bool {
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if_chain! {
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if let hir::ExprKind::Binary(binop, left, right) = &expr.kind;
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if binop.node == hir::BinOpKind::Div;
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then {
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let (left_ty, right_ty) = (cx.typeck_results().expr_ty(left), cx.typeck_results().expr_ty(right));
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return left_ty.is_integral() && right_ty.is_integral();
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}
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}
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false
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}
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