2020-03-03 16:58:37 +00:00
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use rustc_ast::ast::{Lit, LitFloatType, LitIntType, LitKind};
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#[derive(Debug, PartialEq)]
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2020-03-23 16:06:15 +00:00
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pub enum Radix {
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2020-03-03 16:58:37 +00:00
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Binary,
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Octal,
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Decimal,
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Hexadecimal,
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}
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impl Radix {
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/// Returns a reasonable digit group size for this radix.
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#[must_use]
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fn suggest_grouping(&self) -> usize {
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match *self {
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Self::Binary | Self::Hexadecimal => 4,
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Self::Octal | Self::Decimal => 3,
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}
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}
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}
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/// A helper method to format numeric literals with digit grouping.
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/// `lit` must be a valid numeric literal without suffix.
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pub fn format(lit: &str, type_suffix: Option<&str>, float: bool) -> String {
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NumericLiteral::new(lit, type_suffix, float).format()
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}
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#[derive(Debug)]
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2020-03-23 16:06:15 +00:00
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pub struct NumericLiteral<'a> {
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2020-03-03 16:58:37 +00:00
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/// Which radix the literal was represented in.
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pub radix: Radix,
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/// The radix prefix, if present.
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pub prefix: Option<&'a str>,
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/// The integer part of the number.
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pub integer: &'a str,
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/// The fraction part of the number.
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pub fraction: Option<&'a str>,
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/// The character used as exponent seperator (b'e' or b'E') and the exponent part.
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pub exponent: Option<(char, &'a str)>,
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/// The type suffix, including preceding underscore if present.
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pub suffix: Option<&'a str>,
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}
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impl<'a> NumericLiteral<'a> {
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pub fn from_lit(src: &'a str, lit: &Lit) -> Option<NumericLiteral<'a>> {
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NumericLiteral::from_lit_kind(src, &lit.kind)
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}
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pub fn from_lit_kind(src: &'a str, lit_kind: &LitKind) -> Option<NumericLiteral<'a>> {
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if lit_kind.is_numeric() && src.chars().next().map_or(false, |c| c.is_digit(10)) {
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let (unsuffixed, suffix) = split_suffix(&src, lit_kind);
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2020-07-14 12:59:59 +00:00
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let float = matches!(lit_kind, LitKind::Float(..));
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2020-03-03 16:58:37 +00:00
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Some(NumericLiteral::new(unsuffixed, suffix, float))
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} else {
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None
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}
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}
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#[must_use]
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pub fn new(lit: &'a str, suffix: Option<&'a str>, float: bool) -> Self {
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// Determine delimiter for radix prefix, if present, and radix.
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let radix = if lit.starts_with("0x") {
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Radix::Hexadecimal
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} else if lit.starts_with("0b") {
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Radix::Binary
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} else if lit.starts_with("0o") {
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Radix::Octal
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} else {
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Radix::Decimal
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};
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// Grab part of the literal after prefix, if present.
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let (prefix, mut sans_prefix) = if let Radix::Decimal = radix {
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(None, lit)
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} else {
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let (p, s) = lit.split_at(2);
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(Some(p), s)
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};
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if suffix.is_some() && sans_prefix.ends_with('_') {
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// The '_' before the suffix isn't part of the digits
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sans_prefix = &sans_prefix[..sans_prefix.len() - 1];
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}
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let (integer, fraction, exponent) = Self::split_digit_parts(sans_prefix, float);
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Self {
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radix,
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prefix,
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integer,
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fraction,
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exponent,
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suffix,
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}
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}
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pub fn is_decimal(&self) -> bool {
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self.radix == Radix::Decimal
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}
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pub fn split_digit_parts(digits: &str, float: bool) -> (&str, Option<&str>, Option<(char, &str)>) {
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let mut integer = digits;
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let mut fraction = None;
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let mut exponent = None;
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if float {
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for (i, c) in digits.char_indices() {
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match c {
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'.' => {
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integer = &digits[..i];
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fraction = Some(&digits[i + 1..]);
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},
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'e' | 'E' => {
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if integer.len() > i {
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integer = &digits[..i];
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} else {
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fraction = Some(&digits[integer.len() + 1..i]);
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};
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exponent = Some((c, &digits[i + 1..]));
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break;
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},
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_ => {},
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}
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}
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}
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(integer, fraction, exponent)
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}
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/// Returns literal formatted in a sensible way.
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pub fn format(&self) -> String {
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let mut output = String::new();
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if let Some(prefix) = self.prefix {
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output.push_str(prefix);
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}
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let group_size = self.radix.suggest_grouping();
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Self::group_digits(
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&mut output,
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self.integer,
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group_size,
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true,
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self.radix == Radix::Hexadecimal,
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);
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if let Some(fraction) = self.fraction {
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output.push('.');
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Self::group_digits(&mut output, fraction, group_size, false, false);
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}
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if let Some((separator, exponent)) = self.exponent {
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output.push(separator);
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Self::group_digits(&mut output, exponent, group_size, true, false);
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}
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if let Some(suffix) = self.suffix {
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output.push('_');
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output.push_str(suffix);
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}
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output
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}
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pub fn group_digits(output: &mut String, input: &str, group_size: usize, partial_group_first: bool, pad: bool) {
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debug_assert!(group_size > 0);
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let mut digits = input.chars().filter(|&c| c != '_');
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let first_group_size;
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if partial_group_first {
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first_group_size = (digits.clone().count() - 1) % group_size + 1;
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if pad {
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for _ in 0..group_size - first_group_size {
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output.push('0');
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}
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}
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} else {
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first_group_size = group_size;
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}
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for _ in 0..first_group_size {
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if let Some(digit) = digits.next() {
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output.push(digit);
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}
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}
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for (c, i) in digits.zip((0..group_size).cycle()) {
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if i == 0 {
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output.push('_');
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}
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output.push(c);
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}
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}
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}
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fn split_suffix<'a>(src: &'a str, lit_kind: &LitKind) -> (&'a str, Option<&'a str>) {
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debug_assert!(lit_kind.is_numeric());
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2020-07-14 12:59:59 +00:00
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lit_suffix_length(lit_kind).map_or((src, None), |suffix_length| {
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2020-03-03 16:58:37 +00:00
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let (unsuffixed, suffix) = src.split_at(src.len() - suffix_length);
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(unsuffixed, Some(suffix))
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2020-07-14 12:59:59 +00:00
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})
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2020-03-03 16:58:37 +00:00
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}
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fn lit_suffix_length(lit_kind: &LitKind) -> Option<usize> {
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debug_assert!(lit_kind.is_numeric());
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let suffix = match lit_kind {
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LitKind::Int(_, int_lit_kind) => match int_lit_kind {
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LitIntType::Signed(int_ty) => Some(int_ty.name_str()),
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LitIntType::Unsigned(uint_ty) => Some(uint_ty.name_str()),
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LitIntType::Unsuffixed => None,
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},
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LitKind::Float(_, float_lit_kind) => match float_lit_kind {
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LitFloatType::Suffixed(float_ty) => Some(float_ty.name_str()),
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LitFloatType::Unsuffixed => None,
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},
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_ => None,
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};
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suffix.map(str::len)
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}
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