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Change implementation of approx_const lint

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- Replace epsilon with lower and upper bounds for each constant.
- Warn on use of "3.14", and update tests accordingly.
This commit is contained in:
Kevin Yap 2015-10-22 15:19:03 -07:00
parent a927bc0b70
commit 546eb14b7e
2 changed files with 30 additions and 23 deletions
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50
src/approx_const.rs
View file

@ -1,6 +1,5 @@
use rustc::lint::*;
use rustc_front::hir::*;
use std::f64::consts as f64;
use utils::span_lint;
use syntax::ast::Lit_::*;
use syntax::ast::Lit;
@ -13,14 +12,26 @@ declare_lint! {
is found; suggests to use the constant"
}
const KNOWN_CONSTS : &'static [(f64, &'static str)] = &[(f64::E, "E"), (f64::FRAC_1_PI, "FRAC_1_PI"),
(f64::FRAC_1_SQRT_2, "FRAC_1_SQRT_2"), (f64::FRAC_2_PI, "FRAC_2_PI"),
(f64::FRAC_2_SQRT_PI, "FRAC_2_SQRT_PI"), (f64::FRAC_PI_2, "FRAC_PI_2"), (f64::FRAC_PI_3, "FRAC_PI_3"),
(f64::FRAC_PI_4, "FRAC_PI_4"), (f64::FRAC_PI_6, "FRAC_PI_6"), (f64::FRAC_PI_8, "FRAC_PI_8"),
(f64::LN_10, "LN_10"), (f64::LN_2, "LN_2"), (f64::LOG10_E, "LOG10_E"), (f64::LOG2_E, "LOG2_E"),
(f64::PI, "PI"), (f64::SQRT_2, "SQRT_2")];
const EPSILON_DIVISOR : f64 = 8192f64; //TODO: test to find a good value
// Tuples are of the form (name, lower_bound, upper_bound)
#[allow(approx_constant)]
const KNOWN_CONSTS : &'static [(&'static str, f64, f64)] = &[
("E", 2.7101, 2.7200),
("FRAC_1_PI", 0.31829, 0.31840),
("FRAC_1_SQRT_2", 0.7071, 0.7072),
("FRAC_2_PI", 0.6366, 0.6370),
("FRAC_2_SQRT_PI", 1.1283, 1.1284),
("FRAC_PI_2", 1.5707, 1.5708),
("FRAC_PI_3", 1.0471, 1.0472),
("FRAC_PI_4", 0.7853, 0.7854),
("FRAC_PI_6", 0.5235, 0.5236),
("FRAC_PI_8", 0.3926, 0.3927),
("LN_10", 2.302, 2.303),
("LN_2", 0.6931, 0.6932),
("LOG10_E", 0.4342, 0.4343),
("LOG2_E", 1.4426, 1.4427),
("PI", 3.140, 3.142),
("SQRT_2", 1.4142, 1.4143),
];
#[derive(Copy,Clone)]
pub struct ApproxConstant;
@ -49,19 +60,14 @@ fn check_lit(cx: &LateContext, lit: &Lit, e: &Expr) {
}
}
fn check_known_consts(cx: &LateContext, e: &Expr, str: &str, module: &str) {
if let Ok(value) = str.parse::<f64>() {
for &(constant, name) in KNOWN_CONSTS {
if !within_epsilon(constant, value) { continue; }
span_lint(cx, APPROX_CONSTANT, e.span, &format!(
"approximate value of `{}::{}` found. \
Consider using it directly", module, &name));
fn check_known_consts(cx: &LateContext, e: &Expr, s: &str, module: &str) {
if let Ok(value) = s.parse::<f64>() {
for &(name, lower_bound, upper_bound) in KNOWN_CONSTS {
if (value >= lower_bound) && (value < upper_bound) {
span_lint(cx, APPROX_CONSTANT, e.span, &format!(
"approximate value of `{}::{}` found. \
Consider using it directly", module, &name));
}
}
}
}
fn within_epsilon(target: f64, value: f64) -> bool {
f64::abs(value - target) < f64::abs(if target > value {
target
} else { value }) / EPSILON_DIVISOR
}

3
tests/compile-fail/approx_const.rs
View file

@ -49,7 +49,8 @@ fn main() {
let no_log2_e = 1.442;
let my_pi = 3.1415; //~ERROR approximate value of `f{32, 64}::PI` found
let almost_pi = 3.141;
let almost_pi = 3.14; //~ERROR approximate value of `f{32, 64}::PI` found
let no_pi = 3.15;
let my_sq2 = 1.4142; //~ERROR approximate value of `f{32, 64}::SQRT_2` found
let no_sq2 = 1.414;