-use crate::utils::span_lint;
-use rustc::hir::*;
-use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
-use rustc::{declare_lint_pass, declare_tool_lint};
+use clippy_utils::diagnostics::span_lint;
+use rustc_ast::ast::{FloatTy, LitFloatType, LitKind};
+use rustc_hir::{Expr, ExprKind};
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::symbol;
use std::f64::consts as f64;
-use syntax::ast::{FloatTy, Lit, LitKind};
-use syntax::symbol;
declare_clippy_lint! {
/// **What it does:** Checks for floating point literals that approximate
/// **Example:**
/// ```rust
/// let x = 3.14;
+ /// let y = 1_f64 / x;
+ /// ```
+ /// Use predefined constants instead:
+ /// ```rust
+ /// let x = std::f32::consts::PI;
+ /// let y = std::f64::consts::FRAC_1_PI;
/// ```
pub APPROX_CONSTANT,
correctness,
}
// Tuples are of the form (constant, name, min_digits)
-const KNOWN_CONSTS: &[(f64, &str, usize)] = &[
+const KNOWN_CONSTS: [(f64, &str, usize); 18] = [
(f64::E, "E", 4),
(f64::FRAC_1_PI, "FRAC_1_PI", 4),
(f64::FRAC_1_SQRT_2, "FRAC_1_SQRT_2", 5),
(f64::LN_2, "LN_2", 5),
(f64::LOG10_E, "LOG10_E", 5),
(f64::LOG2_E, "LOG2_E", 5),
+ (f64::LOG2_10, "LOG2_10", 5),
+ (f64::LOG10_2, "LOG10_2", 5),
(f64::PI, "PI", 3),
(f64::SQRT_2, "SQRT_2", 5),
];
declare_lint_pass!(ApproxConstant => [APPROX_CONSTANT]);
-impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ApproxConstant {
- fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
- if let ExprKind::Lit(lit) = &e.node {
- check_lit(cx, lit, e);
+impl<'tcx> LateLintPass<'tcx> for ApproxConstant {
+ fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
+ if let ExprKind::Lit(lit) = &e.kind {
+ check_lit(cx, &lit.node, e);
}
}
}
-fn check_lit(cx: &LateContext<'_, '_>, lit: &Lit, e: &Expr) {
- match lit.node {
- LitKind::Float(s, FloatTy::F32) => check_known_consts(cx, e, s, "f32"),
- LitKind::Float(s, FloatTy::F64) => check_known_consts(cx, e, s, "f64"),
- LitKind::FloatUnsuffixed(s) => check_known_consts(cx, e, s, "f{32, 64}"),
+fn check_lit(cx: &LateContext<'_>, lit: &LitKind, e: &Expr<'_>) {
+ match *lit {
+ LitKind::Float(s, LitFloatType::Suffixed(fty)) => match fty {
+ FloatTy::F32 => check_known_consts(cx, e, s, "f32"),
+ FloatTy::F64 => check_known_consts(cx, e, s, "f64"),
+ },
+ LitKind::Float(s, LitFloatType::Unsuffixed) => check_known_consts(cx, e, s, "f{32, 64}"),
_ => (),
}
}
-fn check_known_consts(cx: &LateContext<'_, '_>, e: &Expr, s: symbol::Symbol, module: &str) {
+fn check_known_consts(cx: &LateContext<'_>, e: &Expr<'_>, s: symbol::Symbol, module: &str) {
let s = s.as_str();
if s.parse::<f64>().is_ok() {
- for &(constant, name, min_digits) in KNOWN_CONSTS {
+ for &(constant, name, min_digits) in &KNOWN_CONSTS {
if is_approx_const(constant, &s, min_digits) {
span_lint(
cx,
/// 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`.
+#[must_use]
fn is_approx_const(constant: f64, value: &str, min_digits: usize) -> bool {
if value.len() <= min_digits {
false
+ } else if constant.to_string().starts_with(value) {
+ // The value is a truncated constant
+ true
} else {
let round_const = format!("{:.*}", value.len() - 2, constant);
-
- let mut trunc_const = constant.to_string();
- if trunc_const.len() > value.len() {
- trunc_const.truncate(value.len());
- }
-
- (value == round_const) || (value == trunc_const)
+ value == round_const
}
}