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Auto merge of #5257 - mlegner:cast_hex_fp, r=flip1995
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Resolve false positives of unnecessary_cast for non-decimal integers

This PR resolves false positives of `unnecessary_cast` for hexadecimal integers to floats and adds a corresponding test case.

Fixes: #5220

changelog: none
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@bors
bors committed Mar 4, 2020
2 parents 8c7b3ad + 185fa0d commit 329923e
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Showing 9 changed files with 274 additions and 248 deletions.
7 changes: 3 additions & 4 deletions clippy_lints/src/float_literal.rs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,4 @@
use crate::utils::span_lint_and_sugg;
use crate::utils::sugg::format_numeric_literal;
use crate::utils::{numeric_literal, span_lint_and_sugg};
use if_chain::if_chain;
use rustc::ty;
use rustc_ast::ast::{FloatTy, LitFloatType, LitKind};
Expand Down Expand Up @@ -109,7 +108,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for FloatLiteral {
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(&float_str, type_suffix, true),
numeric_literal::format(&float_str, type_suffix, true),
Applicability::MachineApplicable,
);
}
Expand All @@ -120,7 +119,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for FloatLiteral {
expr.span,
"float has excessive precision",
"consider changing the type or truncating it to",
format_numeric_literal(&float_str, type_suffix, true),
numeric_literal::format(&float_str, type_suffix, true),
Applicability::MachineApplicable,
);
}
Expand Down
6 changes: 3 additions & 3 deletions clippy_lints/src/floating_point_arithmetic.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,7 @@ use crate::consts::{
constant, constant_simple, Constant,
Constant::{F32, F64},
};
use crate::utils::{higher, span_lint_and_sugg, sugg, SpanlessEq};
use crate::utils::{higher, numeric_literal, span_lint_and_sugg, sugg, SpanlessEq};
use if_chain::if_chain;
use rustc::ty;
use rustc_errors::Applicability;
Expand All @@ -14,7 +14,7 @@ use rustc_span::source_map::Spanned;
use rustc_ast::ast;
use std::f32::consts as f32_consts;
use std::f64::consts as f64_consts;
use sugg::{format_numeric_literal, Sugg};
use sugg::Sugg;

declare_clippy_lint! {
/// **What it does:** Looks for floating-point expressions that
Expand Down Expand Up @@ -276,7 +276,7 @@ fn check_powf(cx: &LateContext<'_, '_>, expr: &Expr<'_>, args: &[Expr<'_>]) {
format!(
"{}.powi({})",
Sugg::hir(cx, &args[0], ".."),
format_numeric_literal(&exponent.to_string(), None, false)
numeric_literal::format(&exponent.to_string(), None, false)
),
)
} else {
Expand Down
226 changes: 6 additions & 220 deletions clippy_lints/src/literal_representation.rs
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Original file line number Diff line number Diff line change
@@ -1,10 +1,14 @@
//! Lints concerned with the grouping of digits with underscores in integral or
//! floating-point literal expressions.
use crate::utils::{in_macro, snippet_opt, span_lint_and_sugg};
use crate::utils::{
in_macro,
numeric_literal::{NumericLiteral, Radix},
snippet_opt, span_lint_and_sugg,
};
use if_chain::if_chain;
use rustc::lint::in_external_macro;
use rustc_ast::ast::{Expr, ExprKind, Lit, LitFloatType, LitIntType, LitKind};
use rustc_ast::ast::{Expr, ExprKind, Lit, LitKind};
use rustc_errors::Applicability;
use rustc_lint::{EarlyContext, EarlyLintPass, LintContext};
use rustc_session::{declare_lint_pass, declare_tool_lint, impl_lint_pass};
Expand Down Expand Up @@ -103,224 +107,6 @@ declare_clippy_lint! {
"using decimal representation when hexadecimal would be better"
}

#[derive(Debug, PartialEq)]
pub(super) enum Radix {
Binary,
Octal,
Decimal,
Hexadecimal,
}

impl Radix {
/// Returns a reasonable digit group size for this radix.
#[must_use]
fn suggest_grouping(&self) -> usize {
match *self {
Self::Binary | Self::Hexadecimal => 4,
Self::Octal | Self::Decimal => 3,
}
}
}

/// A helper method to format numeric literals with digit grouping.
/// `lit` must be a valid numeric literal without suffix.
pub fn format_numeric_literal(lit: &str, type_suffix: Option<&str>, float: bool) -> String {
NumericLiteral::new(lit, type_suffix, float).format()
}

#[derive(Debug)]
pub(super) struct NumericLiteral<'a> {
/// Which radix the literal was represented in.
radix: Radix,
/// The radix prefix, if present.
prefix: Option<&'a str>,

/// The integer part of the number.
integer: &'a str,
/// The fraction part of the number.
fraction: Option<&'a str>,
/// The character used as exponent seperator (b'e' or b'E') and the exponent part.
exponent: Option<(char, &'a str)>,

/// The type suffix, including preceding underscore if present.
suffix: Option<&'a str>,
}

impl<'a> NumericLiteral<'a> {
fn from_lit(src: &'a str, lit: &Lit) -> Option<NumericLiteral<'a>> {
if lit.kind.is_numeric() && src.chars().next().map_or(false, |c| c.is_digit(10)) {
let (unsuffixed, suffix) = split_suffix(&src, &lit.kind);
let float = if let LitKind::Float(..) = lit.kind { true } else { false };
Some(NumericLiteral::new(unsuffixed, suffix, float))
} else {
None
}
}

#[must_use]
fn new(lit: &'a str, suffix: Option<&'a str>, float: bool) -> Self {
// Determine delimiter for radix prefix, if present, and radix.
let radix = if lit.starts_with("0x") {
Radix::Hexadecimal
} else if lit.starts_with("0b") {
Radix::Binary
} else if lit.starts_with("0o") {
Radix::Octal
} else {
Radix::Decimal
};

// Grab part of the literal after prefix, if present.
let (prefix, mut sans_prefix) = if let Radix::Decimal = radix {
(None, lit)
} else {
let (p, s) = lit.split_at(2);
(Some(p), s)
};

if suffix.is_some() && sans_prefix.ends_with('_') {
// The '_' before the suffix isn't part of the digits
sans_prefix = &sans_prefix[..sans_prefix.len() - 1];
}

let (integer, fraction, exponent) = Self::split_digit_parts(sans_prefix, float);

Self {
radix,
prefix,
integer,
fraction,
exponent,
suffix,
}
}

fn split_digit_parts(digits: &str, float: bool) -> (&str, Option<&str>, Option<(char, &str)>) {
let mut integer = digits;
let mut fraction = None;
let mut exponent = None;

if float {
for (i, c) in digits.char_indices() {
match c {
'.' => {
integer = &digits[..i];
fraction = Some(&digits[i + 1..]);
},
'e' | 'E' => {
if integer.len() > i {
integer = &digits[..i];
} else {
fraction = Some(&digits[integer.len() + 1..i]);
};
exponent = Some((c, &digits[i + 1..]));
break;
},
_ => {},
}
}
}

(integer, fraction, exponent)
}

/// Returns literal formatted in a sensible way.
fn format(&self) -> String {
let mut output = String::new();

if let Some(prefix) = self.prefix {
output.push_str(prefix);
}

let group_size = self.radix.suggest_grouping();

Self::group_digits(
&mut output,
self.integer,
group_size,
true,
self.radix == Radix::Hexadecimal,
);

if let Some(fraction) = self.fraction {
output.push('.');
Self::group_digits(&mut output, fraction, group_size, false, false);
}

if let Some((separator, exponent)) = self.exponent {
output.push(separator);
Self::group_digits(&mut output, exponent, group_size, true, false);
}

if let Some(suffix) = self.suffix {
output.push('_');
output.push_str(suffix);
}

output
}

fn group_digits(output: &mut String, input: &str, group_size: usize, partial_group_first: bool, pad: bool) {
debug_assert!(group_size > 0);

let mut digits = input.chars().filter(|&c| c != '_');

let first_group_size;

if partial_group_first {
first_group_size = (digits.clone().count() - 1) % group_size + 1;
if pad {
for _ in 0..group_size - first_group_size {
output.push('0');
}
}
} else {
first_group_size = group_size;
}

for _ in 0..first_group_size {
if let Some(digit) = digits.next() {
output.push(digit);
}
}

for (c, i) in digits.zip((0..group_size).cycle()) {
if i == 0 {
output.push('_');
}
output.push(c);
}
}
}

fn split_suffix<'a>(src: &'a str, lit_kind: &LitKind) -> (&'a str, Option<&'a str>) {
debug_assert!(lit_kind.is_numeric());
if let Some(suffix_length) = lit_suffix_length(lit_kind) {
let (unsuffixed, suffix) = src.split_at(src.len() - suffix_length);
(unsuffixed, Some(suffix))
} else {
(src, None)
}
}

fn lit_suffix_length(lit_kind: &LitKind) -> Option<usize> {
debug_assert!(lit_kind.is_numeric());
let suffix = match lit_kind {
LitKind::Int(_, int_lit_kind) => match int_lit_kind {
LitIntType::Signed(int_ty) => Some(int_ty.name_str()),
LitIntType::Unsigned(uint_ty) => Some(uint_ty.name_str()),
LitIntType::Unsuffixed => None,
},
LitKind::Float(_, float_lit_kind) => match float_lit_kind {
LitFloatType::Suffixed(float_ty) => Some(float_ty.name_str()),
LitFloatType::Unsuffixed => None,
},
_ => None,
};

suffix.map(str::len)
}

enum WarningType {
UnreadableLiteral,
InconsistentDigitGrouping,
Expand Down
41 changes: 22 additions & 19 deletions clippy_lints/src/types.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -30,9 +30,9 @@ use crate::consts::{constant, Constant};
use crate::utils::paths;
use crate::utils::{
clip, comparisons, differing_macro_contexts, higher, in_constant, int_bits, last_path_segment, match_def_path,
match_path, method_chain_args, multispan_sugg, qpath_res, same_tys, sext, snippet, snippet_opt,
snippet_with_applicability, snippet_with_macro_callsite, span_lint, span_lint_and_help, span_lint_and_sugg,
span_lint_and_then, unsext,
match_path, method_chain_args, multispan_sugg, numeric_literal::NumericLiteral, qpath_res, same_tys, sext, snippet,
snippet_opt, snippet_with_applicability, snippet_with_macro_callsite, span_lint, span_lint_and_help,
span_lint_and_sugg, span_lint_and_then, unsext,
};

declare_clippy_lint! {
Expand Down Expand Up @@ -1210,22 +1210,25 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Casts {
let (cast_from, cast_to) = (cx.tables.expr_ty(ex), cx.tables.expr_ty(expr));
lint_fn_to_numeric_cast(cx, expr, ex, cast_from, cast_to);
if let ExprKind::Lit(ref lit) = ex.kind {
if let LitKind::Int(n, _) = lit.node {
if cast_to.is_floating_point() {
let from_nbits = 128 - n.leading_zeros();
let to_nbits = fp_ty_mantissa_nbits(cast_to);
if from_nbits != 0 && to_nbits != 0 && from_nbits <= to_nbits {
span_lint_and_sugg(
cx,
UNNECESSARY_CAST,
expr.span,
&format!("casting integer literal to `{}` is unnecessary", cast_to),
"try",
format!("{}_{}", n, cast_to),
Applicability::MachineApplicable,
);
return;
}
if_chain! {
if let LitKind::Int(n, _) = lit.node;
if let Some(src) = snippet_opt(cx, lit.span);
if cast_to.is_floating_point();
if let Some(num_lit) = NumericLiteral::from_lit_kind(&src, &lit.node);
let from_nbits = 128 - n.leading_zeros();
let to_nbits = fp_ty_mantissa_nbits(cast_to);
if from_nbits != 0 && to_nbits != 0 && from_nbits <= to_nbits && num_lit.is_decimal();
then {
span_lint_and_sugg(
cx,
UNNECESSARY_CAST,
expr.span,
&format!("casting integer literal to `{}` is unnecessary", cast_to),
"try",
format!("{}_{}", n, cast_to),
Applicability::MachineApplicable,
);
return;
}
}
match lit.node {
Expand Down
1 change: 1 addition & 0 deletions clippy_lints/src/utils/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@ pub mod higher;
mod hir_utils;
pub mod inspector;
pub mod internal_lints;
pub mod numeric_literal;
pub mod paths;
pub mod ptr;
pub mod sugg;
Expand Down
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