diff --git a/clippy_lints/src/excessive_precision.rs b/clippy_lints/src/excessive_precision.rs index 2b63d5e9088e..781d85a00e4f 100644 --- a/clippy_lints/src/excessive_precision.rs +++ b/clippy_lints/src/excessive_precision.rs @@ -6,17 +6,15 @@ use rustc_errors::Applicability; use rustc_hir as hir; use rustc_lint::{LateContext, LateLintPass}; use rustc_session::{declare_lint_pass, declare_tool_lint}; -use rustc_span::symbol::Symbol; -use std::f32; -use std::f64; -use std::fmt; +use std::{f32, f64, fmt}; use syntax::ast::*; declare_clippy_lint! { /// **What it does:** Checks for float literals with a precision greater - /// than that supported by the underlying type + /// than that supported by the underlying type. /// - /// **Why is this bad?** Rust will truncate the literal silently. + /// **Why is this bad?** Rust will silently lose precision during conversion + /// to a float. /// /// **Known problems:** None. /// @@ -24,15 +22,15 @@ declare_clippy_lint! { /// /// ```rust /// // Bad - /// let v: f32 = 0.123_456_789_9; - /// println!("{}", v); // 0.123_456_789 + /// let a: f32 = 0.123_456_789_9; // 0.123_456_789 + /// let b: f32 = 16_777_217.0; // 16_777_216.0 /// /// // Good - /// let v: f64 = 0.123_456_789_9; - /// println!("{}", v); // 0.123_456_789_9 + /// let a: f64 = 0.123_456_789_9; + /// let b: f64 = 16_777_216.0; /// ``` pub EXCESSIVE_PRECISION, - style, + correctness, "excessive precision for float literal" } @@ -44,71 +42,62 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ExcessivePrecision { let ty = cx.tables.expr_ty(expr); if let ty::Float(fty) = ty.kind; if let hir::ExprKind::Lit(ref lit) = expr.kind; - if let LitKind::Float(sym, _) = lit.node; - if let Some(sugg) = Self::check(sym, fty); + if let LitKind::Float(sym, lit_float_ty) = lit.node; then { - span_lint_and_sugg( - cx, - EXCESSIVE_PRECISION, - expr.span, - "float has excessive precision", - "consider changing the type or truncating it to", - sugg, - Applicability::MachineApplicable, - ); - } - } - } -} - -impl ExcessivePrecision { - // None if nothing to lint, Some(suggestion) if lint necessary - #[must_use] - fn check(sym: Symbol, fty: FloatTy) -> Option { - let max = max_digits(fty); - let sym_str = sym.as_str(); - if dot_zero_exclusion(&sym_str) { - return None; - } - // Try to bail out if the float is for sure fine. - // If its within the 2 decimal digits of being out of precision we - // check if the parsed representation is the same as the string - // since we'll need the truncated string anyway. - let digits = count_digits(&sym_str); - if digits > max as usize { - let formatter = FloatFormat::new(&sym_str); - let sr = match fty { - FloatTy::F32 => sym_str.parse::().map(|f| formatter.format(f)), - FloatTy::F64 => sym_str.parse::().map(|f| formatter.format(f)), - }; - // We know this will parse since we are in LatePass - let s = sr.unwrap(); + let sym_str = sym.as_str(); + let formatter = FloatFormat::new(&sym_str); + // Try to bail out if the float is for sure fine. + // If its within the 2 decimal digits of being out of precision we + // check if the parsed representation is the same as the string + // since we'll need the truncated string anyway. + let digits = count_digits(&sym_str); + let max = max_digits(fty); + let float_str = match fty { + FloatTy::F32 => sym_str.parse::().map(|f| formatter.format(f)), + FloatTy::F64 => sym_str.parse::().map(|f| formatter.format(f)), + }.unwrap(); + let type_suffix = match lit_float_ty { + LitFloatType::Suffixed(FloatTy::F32) => Some("f32"), + LitFloatType::Suffixed(FloatTy::F64) => Some("f64"), + _ => None + }; - if sym_str == s { - None - } else { - Some(format_numeric_literal(&s, None, true)) + if is_whole_number(&sym_str, fty) { + // Normalize the literal by stripping the fractional portion + if sym_str.split('.').next().unwrap() != float_str { + span_lint_and_sugg( + cx, + EXCESSIVE_PRECISION, + expr.span, + "literal cannot be represented as the underlying type without loss of precision", + "consider changing the type or replacing it with", + format_numeric_literal(format!("{}.0", float_str).as_str(), type_suffix, true), + Applicability::MachineApplicable, + ); + } + } else if digits > max as usize && sym_str != float_str { + span_lint_and_sugg( + cx, + EXCESSIVE_PRECISION, + expr.span, + "float has excessive precision", + "consider changing the type or truncating it to", + format_numeric_literal(&float_str, type_suffix, true), + Applicability::MachineApplicable, + ); + } } - } else { - None } } } -/// Should we exclude the float because it has a `.0` or `.` suffix -/// Ex `1_000_000_000.0` -/// Ex `1_000_000_000.` +// Checks whether a float literal is a whole number #[must_use] -fn dot_zero_exclusion(s: &str) -> bool { - s.split('.').nth(1).map_or(false, |after_dec| { - let mut decpart = after_dec.chars().take_while(|c| *c != 'e' || *c != 'E'); - - match decpart.next() { - Some('0') => decpart.count() == 0, - Some(_) => false, - None => true, - } - }) +fn is_whole_number(sym_str: &str, fty: FloatTy) -> bool { + match fty { + FloatTy::F32 => sym_str.parse::().unwrap().fract() == 0.0, + FloatTy::F64 => sym_str.parse::().unwrap().fract() == 0.0, + } } #[must_use] diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs index 1cf01d2e02e5..8bd0d187061a 100644 --- a/clippy_lints/src/lib.rs +++ b/clippy_lints/src/lib.rs @@ -1386,7 +1386,6 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: LintId::of(&enum_variants::MODULE_INCEPTION), LintId::of(&eq_op::OP_REF), LintId::of(&eta_reduction::REDUNDANT_CLOSURE), - LintId::of(&excessive_precision::EXCESSIVE_PRECISION), LintId::of(&formatting::SUSPICIOUS_ASSIGNMENT_FORMATTING), LintId::of(&formatting::SUSPICIOUS_ELSE_FORMATTING), LintId::of(&formatting::SUSPICIOUS_UNARY_OP_FORMATTING), @@ -1567,6 +1566,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: LintId::of(&enum_clike::ENUM_CLIKE_UNPORTABLE_VARIANT), LintId::of(&eq_op::EQ_OP), LintId::of(&erasing_op::ERASING_OP), + LintId::of(&excessive_precision::EXCESSIVE_PRECISION), LintId::of(&formatting::POSSIBLE_MISSING_COMMA), LintId::of(&functions::NOT_UNSAFE_PTR_ARG_DEREF), LintId::of(&indexing_slicing::OUT_OF_BOUNDS_INDEXING), diff --git a/src/lintlist/mod.rs b/src/lintlist/mod.rs index 06a1fca4fdd8..8c04afce1d27 100644 --- a/src/lintlist/mod.rs +++ b/src/lintlist/mod.rs @@ -492,7 +492,7 @@ pub const ALL_LINTS: [Lint; 355] = [ }, Lint { name: "excessive_precision", - group: "style", + group: "correctness", desc: "excessive precision for float literal", deprecation: None, module: "excessive_precision", diff --git a/tests/ui/excessive_precision.fixed b/tests/ui/excessive_precision.fixed index 1646dff9064d..f32307ce9107 100644 --- a/tests/ui/excessive_precision.fixed +++ b/tests/ui/excessive_precision.fixed @@ -12,12 +12,12 @@ fn main() { const GOOD64_SM: f32 = 0.000_000_000_000_000_1; const GOOD64_DOT: f32 = 10_000_000_000_000_000.0; - const BAD32_1: f32 = 0.123_456_79; + const BAD32_1: f32 = 0.123_456_79_f32; const BAD32_2: f32 = 0.123_456_79; const BAD32_3: f32 = 0.1; const BAD32_EDGE: f32 = 1.000_001; - const BAD64_1: f64 = 0.123_456_789_012_345_66; + const BAD64_1: f64 = 0.123_456_789_012_345_66_f64; const BAD64_2: f64 = 0.123_456_789_012_345_66; const BAD64_3: f64 = 0.1; @@ -34,11 +34,11 @@ fn main() { let good64_inf = 0.123_456_789_012; let bad32: f32 = 1.123_456_8; - let bad32_suf: f32 = 1.123_456_8; - let bad32_inf = 1.123_456_8; + let bad32_suf: f32 = 1.123_456_8_f32; + let bad32_inf = 1.123_456_8_f32; let bad64: f64 = 0.123_456_789_012_345_66; - let bad64_suf: f64 = 0.123_456_789_012_345_66; + let bad64_suf: f64 = 0.123_456_789_012_345_66_f64; let bad64_inf = 0.123_456_789_012_345_66; // Vectors @@ -60,4 +60,26 @@ fn main() { // issue #2840 let num = 0.000_000_000_01e-10f64; + + // Lossy whole-number float literals + let _: f32 = 16_777_216.0; + let _: f32 = 16_777_220.0; + let _: f32 = 16_777_220.0; + let _: f32 = 16_777_220.0; + let _ = 16_777_220.0_f32; + let _: f32 = -16_777_220.0; + let _: f64 = 9_007_199_254_740_992.0; + let _: f64 = 9_007_199_254_740_992.0; + let _: f64 = 9_007_199_254_740_992.0; + let _ = 9_007_199_254_740_992.0_f64; + let _: f64 = -9_007_199_254_740_992.0; + + // Lossless whole number float literals + let _: f32 = 16_777_216.0; + let _: f32 = 16_777_218.0; + let _: f32 = 16_777_220.0; + let _: f32 = -16_777_216.0; + let _: f32 = -16_777_220.0; + let _: f64 = 9_007_199_254_740_992.0; + let _: f64 = -9_007_199_254_740_992.0; } diff --git a/tests/ui/excessive_precision.rs b/tests/ui/excessive_precision.rs index ce4722a90f90..a3d317400278 100644 --- a/tests/ui/excessive_precision.rs +++ b/tests/ui/excessive_precision.rs @@ -60,4 +60,26 @@ fn main() { // issue #2840 let num = 0.000_000_000_01e-10f64; + + // Lossy whole-number float literals + let _: f32 = 16_777_217.0; + let _: f32 = 16_777_219.0; + let _: f32 = 16_777_219.; + let _: f32 = 16_777_219.000; + let _ = 16_777_219f32; + let _: f32 = -16_777_219.0; + let _: f64 = 9_007_199_254_740_993.0; + let _: f64 = 9_007_199_254_740_993.; + let _: f64 = 9_007_199_254_740_993.000; + let _ = 9_007_199_254_740_993f64; + let _: f64 = -9_007_199_254_740_993.0; + + // Lossless whole number float literals + let _: f32 = 16_777_216.0; + let _: f32 = 16_777_218.0; + let _: f32 = 16_777_220.0; + let _: f32 = -16_777_216.0; + let _: f32 = -16_777_220.0; + let _: f64 = 9_007_199_254_740_992.0; + let _: f64 = -9_007_199_254_740_992.0; } diff --git a/tests/ui/excessive_precision.stderr b/tests/ui/excessive_precision.stderr index 12f8a61b75c5..8941bcfd86d8 100644 --- a/tests/ui/excessive_precision.stderr +++ b/tests/ui/excessive_precision.stderr @@ -2,7 +2,7 @@ error: float has excessive precision --> $DIR/excessive_precision.rs:15:26 | LL | const BAD32_1: f32 = 0.123_456_789_f32; - | ^^^^^^^^^^^^^^^^^ help: consider changing the type or truncating it to: `0.123_456_79` + | ^^^^^^^^^^^^^^^^^ help: consider changing the type or truncating it to: `0.123_456_79_f32` | = note: `-D clippy::excessive-precision` implied by `-D warnings` @@ -28,7 +28,7 @@ error: float has excessive precision --> $DIR/excessive_precision.rs:20:26 | LL | const BAD64_1: f64 = 0.123_456_789_012_345_67f64; - | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider changing the type or truncating it to: `0.123_456_789_012_345_66` + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider changing the type or truncating it to: `0.123_456_789_012_345_66_f64` error: float has excessive precision --> $DIR/excessive_precision.rs:21:26 @@ -58,13 +58,13 @@ error: float has excessive precision --> $DIR/excessive_precision.rs:37:26 | LL | let bad32_suf: f32 = 1.123_456_789_f32; - | ^^^^^^^^^^^^^^^^^ help: consider changing the type or truncating it to: `1.123_456_8` + | ^^^^^^^^^^^^^^^^^ help: consider changing the type or truncating it to: `1.123_456_8_f32` error: float has excessive precision --> $DIR/excessive_precision.rs:38:21 | LL | let bad32_inf = 1.123_456_789_f32; - | ^^^^^^^^^^^^^^^^^ help: consider changing the type or truncating it to: `1.123_456_8` + | ^^^^^^^^^^^^^^^^^ help: consider changing the type or truncating it to: `1.123_456_8_f32` error: float has excessive precision --> $DIR/excessive_precision.rs:40:22 @@ -76,7 +76,7 @@ error: float has excessive precision --> $DIR/excessive_precision.rs:41:26 | LL | let bad64_suf: f64 = 0.123_456_789_012_345_67f64; - | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider changing the type or truncating it to: `0.123_456_789_012_345_66` + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider changing the type or truncating it to: `0.123_456_789_012_345_66_f64` error: float has excessive precision --> $DIR/excessive_precision.rs:42:21 @@ -108,5 +108,71 @@ error: float has excessive precision LL | let bad_bige32: f32 = 1.123_456_788_888E-10; | ^^^^^^^^^^^^^^^^^^^^^ help: consider changing the type or truncating it to: `1.123_456_8E-10` -error: aborting due to 18 previous errors +error: literal cannot be represented as the underlying type without loss of precision + --> $DIR/excessive_precision.rs:65:18 + | +LL | let _: f32 = 16_777_217.0; + | ^^^^^^^^^^^^ help: consider changing the type or replacing it with: `16_777_216.0` + +error: literal cannot be represented as the underlying type without loss of precision + --> $DIR/excessive_precision.rs:66:18 + | +LL | let _: f32 = 16_777_219.0; + | ^^^^^^^^^^^^ help: consider changing the type or replacing it with: `16_777_220.0` + +error: literal cannot be represented as the underlying type without loss of precision + --> $DIR/excessive_precision.rs:67:18 + | +LL | let _: f32 = 16_777_219.; + | ^^^^^^^^^^^ help: consider changing the type or replacing it with: `16_777_220.0` + +error: literal cannot be represented as the underlying type without loss of precision + --> $DIR/excessive_precision.rs:68:18 + | +LL | let _: f32 = 16_777_219.000; + | ^^^^^^^^^^^^^^ help: consider changing the type or replacing it with: `16_777_220.0` + +error: literal cannot be represented as the underlying type without loss of precision + --> $DIR/excessive_precision.rs:69:13 + | +LL | let _ = 16_777_219f32; + | ^^^^^^^^^^^^^ help: consider changing the type or replacing it with: `16_777_220.0_f32` + +error: literal cannot be represented as the underlying type without loss of precision + --> $DIR/excessive_precision.rs:70:19 + | +LL | let _: f32 = -16_777_219.0; + | ^^^^^^^^^^^^ help: consider changing the type or replacing it with: `16_777_220.0` + +error: literal cannot be represented as the underlying type without loss of precision + --> $DIR/excessive_precision.rs:71:18 + | +LL | let _: f64 = 9_007_199_254_740_993.0; + | ^^^^^^^^^^^^^^^^^^^^^^^ help: consider changing the type or replacing it with: `9_007_199_254_740_992.0` + +error: literal cannot be represented as the underlying type without loss of precision + --> $DIR/excessive_precision.rs:72:18 + | +LL | let _: f64 = 9_007_199_254_740_993.; + | ^^^^^^^^^^^^^^^^^^^^^^ help: consider changing the type or replacing it with: `9_007_199_254_740_992.0` + +error: literal cannot be represented as the underlying type without loss of precision + --> $DIR/excessive_precision.rs:73:18 + | +LL | let _: f64 = 9_007_199_254_740_993.000; + | ^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider changing the type or replacing it with: `9_007_199_254_740_992.0` + +error: literal cannot be represented as the underlying type without loss of precision + --> $DIR/excessive_precision.rs:74:13 + | +LL | let _ = 9_007_199_254_740_993f64; + | ^^^^^^^^^^^^^^^^^^^^^^^^ help: consider changing the type or replacing it with: `9_007_199_254_740_992.0_f64` + +error: literal cannot be represented as the underlying type without loss of precision + --> $DIR/excessive_precision.rs:75:19 + | +LL | let _: f64 = -9_007_199_254_740_993.0; + | ^^^^^^^^^^^^^^^^^^^^^^^ help: consider changing the type or replacing it with: `9_007_199_254_740_992.0` + +error: aborting due to 29 previous errors