66 lines
2.5 KiB
Rust
66 lines
2.5 KiB
Rust
use crate::consts::{constant_simple, Constant};
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use crate::utils::span_lint_and_help;
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use if_chain::if_chain;
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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, declare_tool_lint};
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declare_clippy_lint! {
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/// **What it does:** Checks for `0.0 / 0.0`.
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///
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/// **Why is this bad?** It's less readable than `f32::NAN` or `f64::NAN`.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust
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/// // Bad
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/// let nan = 0.0f32 / 0.0;
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///
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/// // Good
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/// let nan = f32::NAN;
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/// ```
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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_chain! {
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if let ExprKind::Binary(ref op, ref left, ref right) = expr.kind;
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if let BinOpKind::Div = op.node;
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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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if let Some(lhs_value) = constant_simple(cx, cx.typeck_results(), left);
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if let Some(rhs_value) = constant_simple(cx, cx.typeck_results(), right);
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if Constant::F32(0.0) == lhs_value || Constant::F64(0.0) == lhs_value;
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if Constant::F32(0.0) == rhs_value || Constant::F64(0.0) == rhs_value;
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then {
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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(_), _)
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| (_, 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!(
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"consider using `{}::NAN` if you would like a constant representing NaN",
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float_type,
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),
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);
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}
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}
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}
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}
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