61 lines
2.3 KiB
Rust
61 lines
2.3 KiB
Rust
use clippy_utils::consts::{constant_simple, Constant};
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use clippy_utils::diagnostics::span_lint_and_help;
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use rustc_hir::{BinOpKind, Expr, ExprKind};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_session::declare_lint_pass;
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for `0.0 / 0.0`.
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///
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/// ### Why is this bad?
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/// It's less readable than `f32::NAN` or `f64::NAN`.
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///
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/// ### Example
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/// ```no_run
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/// let nan = 0.0f32 / 0.0;
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/// ```
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///
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/// Use instead:
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/// ```no_run
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/// let nan = f32::NAN;
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/// ```
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#[clippy::version = "pre 1.29.0"]
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pub ZERO_DIVIDED_BY_ZERO,
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complexity,
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"usage of `0.0 / 0.0` to obtain NaN instead of `f32::NAN` or `f64::NAN`"
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}
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declare_lint_pass!(ZeroDiv => [ZERO_DIVIDED_BY_ZERO]);
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impl<'tcx> LateLintPass<'tcx> for ZeroDiv {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
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// check for instances of 0.0/0.0
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if let ExprKind::Binary(ref op, left, right) = expr.kind
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&& op.node == BinOpKind::Div
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// TODO - constant_simple does not fold many operations involving floats.
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// That's probably fine for this lint - it's pretty unlikely that someone would
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// do something like 0.0/(2.0 - 2.0), but it would be nice to warn on that case too.
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&& let Some(lhs_value) = constant_simple(cx, cx.typeck_results(), left)
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&& let Some(rhs_value) = constant_simple(cx, cx.typeck_results(), right)
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&& (Constant::F32(0.0) == lhs_value || Constant::F64(0.0) == lhs_value)
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&& (Constant::F32(0.0) == rhs_value || Constant::F64(0.0) == rhs_value)
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{
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// since we're about to suggest a use of f32::NAN or f64::NAN,
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// match the precision of the literals that are given.
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let float_type = match (lhs_value, rhs_value) {
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(Constant::F64(_), _) | (_, Constant::F64(_)) => "f64",
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_ => "f32",
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};
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span_lint_and_help(
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cx,
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ZERO_DIVIDED_BY_ZERO,
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expr.span,
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"constant division of `0.0` with `0.0` will always result in NaN",
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None,
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&format!("consider using `{float_type}::NAN` if you would like a constant representing NaN",),
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);
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}
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}
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}
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