2018-10-06 16:18:06 +00:00
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// Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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2018-05-30 08:15:50 +00:00
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use crate::consts::{constant_simple, Constant};
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use crate::utils::span_help_and_lint;
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2018-11-27 20:14:15 +00:00
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use if_chain::if_chain;
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2018-12-29 15:04:45 +00:00
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use rustc::hir::*;
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use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
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use rustc::{declare_tool_lint, lint_array};
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2015-10-12 02:22:13 +00:00
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2016-08-06 07:55:04 +00:00
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/// **What it does:** Checks for `0.0 / 0.0`.
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2015-12-11 00:22:27 +00:00
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///
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2017-08-09 07:30:56 +00:00
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/// **Why is this bad?** It's less readable than `std::f32::NAN` or
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/// `std::f64::NAN`.
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2015-12-11 00:22:27 +00:00
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///
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2016-08-06 07:55:04 +00:00
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/// **Known problems:** None.
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2015-12-11 00:22:27 +00:00
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///
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2016-08-06 07:55:04 +00:00
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/// **Example:**
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2016-07-15 22:25:44 +00:00
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/// ```rust
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/// 0.0f32 / 0.0
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/// ```
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2018-03-28 13:24:26 +00:00
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declare_clippy_lint! {
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2016-02-05 23:13:29 +00:00
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pub ZERO_DIVIDED_BY_ZERO,
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2018-03-28 13:24:26 +00:00
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complexity,
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2016-02-05 23:13:29 +00:00
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"usage of `0.0 / 0.0` to obtain NaN instead of std::f32::NaN or std::f64::NaN"
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}
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2015-10-12 02:22:13 +00:00
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2016-08-06 07:55:04 +00:00
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pub struct Pass;
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2016-06-10 14:17:20 +00:00
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impl LintPass for Pass {
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2015-10-12 02:22:13 +00:00
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fn get_lints(&self) -> LintArray {
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lint_array!(ZERO_DIVIDED_BY_ZERO)
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}
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}
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2016-12-07 12:13:40 +00:00
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
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fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
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2015-10-12 02:22:13 +00:00
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// check for instances of 0.0/0.0
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2017-10-23 19:18:02 +00:00
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if_chain! {
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2018-07-12 07:30:57 +00:00
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if let ExprKind::Binary(ref op, ref left, ref right) = expr.node;
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2018-07-12 07:50:09 +00:00
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if let BinOpKind::Div = op.node;
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2016-06-06 00:09:19 +00:00
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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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2018-05-13 11:16:31 +00:00
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if let Some(lhs_value) = constant_simple(cx, cx.tables, left);
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if let Some(rhs_value) = constant_simple(cx, cx.tables, right);
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2018-03-13 10:38:11 +00:00
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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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2017-10-23 19:18:02 +00:00
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then {
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// since we're about to suggest a use of std::f32::NaN or std::f64::NaN,
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// match the precision of the literals that are given.
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2018-03-13 10:38:11 +00:00
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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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2017-10-23 19:18:02 +00:00
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_ => "f32"
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};
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2017-11-04 19:56:05 +00:00
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span_help_and_lint(
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cx,
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ZERO_DIVIDED_BY_ZERO,
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expr.span,
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2017-10-23 19:18:02 +00:00
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"constant division of 0.0 with 0.0 will always result in NaN",
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2017-11-04 19:56:05 +00:00
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&format!(
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"Consider using `std::{}::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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2017-10-23 19:18:02 +00:00
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}
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}
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2015-10-12 02:22:13 +00:00
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}
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}
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