X-Git-Url: https://git.lizzy.rs/?a=blobdiff_plain;f=clippy_lints%2Fsrc%2Fapprox_const.rs;h=3d04abe094d7811e25c34e0d42b9b8456776bb39;hb=b094bb1bd7f1cc702823c91ca509f338fedee24a;hp=fa586ad45c23c6bebde7edf3ac7dc062c4e59a93;hpb=6937d5581af14b71e23af0db81241a3fea11c70a;p=rust.git

diff --git a/clippy_lints/src/approx_const.rs b/clippy_lints/src/approx_const.rs
index fa586ad45c2..3d04abe094d 100644
--- a/clippy_lints/src/approx_const.rs
+++ b/clippy_lints/src/approx_const.rs
@@ -1,10 +1,10 @@
-use crate::utils::span_lint;
-use rustc::hir::*;
-use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
-use rustc::{declare_tool_lint, lint_array};
+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
@@ -19,14 +19,17 @@
     /// actually more precise, please [file a Rust
     /// issue](https://github.com/rust-lang/rust/issues).
     ///
-    /// **Known problems:** If you happen to have a value that is within 1/8192 of a
-    /// known constant, but is not *and should not* be the same, this lint will
-    /// report your value anyway. We have not yet noticed any false positives in
-    /// code we tested clippy with (this includes servo), but YMMV.
+    /// **Known problems:** None.
     ///
     /// **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,
@@ -34,7 +37,7 @@
 }
 
 // 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),
@@ -49,44 +52,37 @@
     (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),
 ];
 
-#[derive(Copy, Clone)]
-pub struct Pass;
-
-impl LintPass for Pass {
-    fn get_lints(&self) -> LintArray {
-        lint_array!(APPROX_CONSTANT)
-    }
-
-    fn name(&self) -> &'static str {
-        "ApproxConstant"
-    }
-}
+declare_lint_pass!(ApproxConstant => [APPROX_CONSTANT]);
 
-impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
-    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,
@@ -107,17 +103,15 @@ fn check_known_consts(cx: &LateContext<'_, '_>, e: &Expr, s: symbol::Symbol, mod
 /// 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
     }
 }