diff options
| -rw-r--r-- | clippy_lints/src/approx_const.rs | 33 | ||||
| -rw-r--r-- | tests/ui/approx_const.rs | 15 | ||||
| -rw-r--r-- | tests/ui/approx_const.stderr | 34 |
3 files changed, 74 insertions, 8 deletions
diff --git a/clippy_lints/src/approx_const.rs b/clippy_lints/src/approx_const.rs index 852e48cbcae..c263d430bd8 100644 --- a/clippy_lints/src/approx_const.rs +++ b/clippy_lints/src/approx_const.rs @@ -92,9 +92,11 @@ impl LateLintPass<'_> for ApproxConstant { impl ApproxConstant { fn check_known_consts(&self, cx: &LateContext<'_>, span: Span, s: symbol::Symbol, module: &str) { let s = s.as_str(); - if s.parse::<f64>().is_ok() { + if let Ok(maybe_constant) = s.parse::<f64>() { for &(constant, name, min_digits, msrv) in &KNOWN_CONSTS { - if is_approx_const(constant, s, min_digits) && msrv.is_none_or(|msrv| self.msrv.meets(cx, msrv)) { + if is_approx_const(constant, s, maybe_constant, min_digits) + && msrv.is_none_or(|msrv| self.msrv.meets(cx, msrv)) + { span_lint_and_help( cx, APPROX_CONSTANT, @@ -112,18 +114,35 @@ impl ApproxConstant { impl_lint_pass!(ApproxConstant => [APPROX_CONSTANT]); +fn count_digits_after_dot(input: &str) -> usize { + input + .char_indices() + .find(|(_, ch)| *ch == '.') + .map_or(0, |(i, _)| input.len() - i - 1) +} + /// Returns `false` if the number of significant figures in `value` are /// less than `min_digits`; otherwise, returns true if `value` is equal -/// to `constant`, rounded to the number of digits present in `value`. +/// to `constant`, rounded to the number of significant digits present in `value`. #[must_use] -fn is_approx_const(constant: f64, value: &str, min_digits: usize) -> bool { +fn is_approx_const(constant: f64, value: &str, f_value: f64, min_digits: usize) -> bool { if value.len() <= min_digits { + // The value is not precise enough false - } else if constant.to_string().starts_with(value) { - // The value is a truncated constant + } else if f_value.to_string().len() > min_digits && constant.to_string().starts_with(&f_value.to_string()) { + // The value represents the same value true } else { - let round_const = format!("{constant:.*}", value.len() - 2); + // The value is a truncated constant + + // Print constant with numeric formatting (`0`), with the length of `value` as minimum width + // (`value_len$`), and with the same precision as `value` (`.value_prec$`). + // See https://doc.rust-lang.org/std/fmt/index.html. + let round_const = format!( + "{constant:0value_len$.value_prec$}", + value_len = value.len(), + value_prec = count_digits_after_dot(value) + ); value == round_const } } diff --git a/tests/ui/approx_const.rs b/tests/ui/approx_const.rs index 6461666be8f..fc493421a16 100644 --- a/tests/ui/approx_const.rs +++ b/tests/ui/approx_const.rs @@ -106,4 +106,19 @@ fn main() { //~^ approx_constant let no_tau = 6.3; + + // issue #15194 + #[allow(clippy::excessive_precision)] + let x: f64 = 3.1415926535897932384626433832; + //~^ approx_constant + + #[allow(clippy::excessive_precision)] + let _: f64 = 003.14159265358979311599796346854418516159057617187500; + //~^ approx_constant + + let almost_frac_1_sqrt_2 = 00.70711; + //~^ approx_constant + + let almost_frac_1_sqrt_2 = 00.707_11; + //~^ approx_constant } diff --git a/tests/ui/approx_const.stderr b/tests/ui/approx_const.stderr index f7bda0468cb..32a3517ff2e 100644 --- a/tests/ui/approx_const.stderr +++ b/tests/ui/approx_const.stderr @@ -184,5 +184,37 @@ LL | let almost_tau = 6.28; | = help: consider using the constant directly -error: aborting due to 23 previous errors +error: approximate value of `f{32, 64}::consts::PI` found + --> tests/ui/approx_const.rs:112:18 + | +LL | let x: f64 = 3.1415926535897932384626433832; + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = help: consider using the constant directly + +error: approximate value of `f{32, 64}::consts::PI` found + --> tests/ui/approx_const.rs:116:18 + | +LL | let _: f64 = 003.14159265358979311599796346854418516159057617187500; + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = help: consider using the constant directly + +error: approximate value of `f{32, 64}::consts::FRAC_1_SQRT_2` found + --> tests/ui/approx_const.rs:119:32 + | +LL | let almost_frac_1_sqrt_2 = 00.70711; + | ^^^^^^^^ + | + = help: consider using the constant directly + +error: approximate value of `f{32, 64}::consts::FRAC_1_SQRT_2` found + --> tests/ui/approx_const.rs:122:32 + | +LL | let almost_frac_1_sqrt_2 = 00.707_11; + | ^^^^^^^^^ + | + = help: consider using the constant directly + +error: aborting due to 27 previous errors |