Auto merge of #5257 - mlegner:cast_hex_fp, r=flip1995

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

Author: bors

clippy_lints/src/float_literal.rs

@@ -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};
@@ -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,
                         );
                     }
@@ -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,
                     );
                 }

clippy_lints/src/floating_point_arithmetic.rs

@@ -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;
@@ -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
@@ -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 {

clippy_lints/src/literal_representation.rs

@@ -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};
@@ -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,

clippy_lints/src/types.rs

@@ -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! {
@@ -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 {

clippy_lints/src/utils/mod.rs

@@ -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;