core/num/
error.rs

1//! Error types for conversion to integral types.
2
3use crate::convert::Infallible;
4use crate::error::Error;
5use crate::fmt;
6
7/// The error type returned when a checked integral type conversion fails.
8#[stable(feature = "try_from", since = "1.34.0")]
9#[derive(Debug, Copy, Clone, PartialEq, Eq)]
10pub struct TryFromIntError(pub(crate) ());
11
12#[stable(feature = "try_from", since = "1.34.0")]
13impl fmt::Display for TryFromIntError {
14    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
15        #[allow(deprecated)]
16        self.description().fmt(fmt)
17    }
18}
19
20#[stable(feature = "try_from", since = "1.34.0")]
21impl Error for TryFromIntError {
22    #[allow(deprecated)]
23    fn description(&self) -> &str {
24        "out of range integral type conversion attempted"
25    }
26}
27
28#[stable(feature = "try_from", since = "1.34.0")]
29#[rustc_const_unstable(feature = "const_try", issue = "74935")]
30impl const From<Infallible> for TryFromIntError {
31    fn from(x: Infallible) -> TryFromIntError {
32        match x {}
33    }
34}
35
36#[unstable(feature = "never_type", issue = "35121")]
37#[rustc_const_unstable(feature = "const_try", issue = "74935")]
38impl const From<!> for TryFromIntError {
39    #[inline]
40    fn from(never: !) -> TryFromIntError {
41        // Match rather than coerce to make sure that code like
42        // `From<Infallible> for TryFromIntError` above will keep working
43        // when `Infallible` becomes an alias to `!`.
44        match never {}
45    }
46}
47
48/// An error which can be returned when parsing an integer.
49///
50/// For example, this error is returned by the `from_str_radix()` functions
51/// on the primitive integer types (such as [`i8::from_str_radix`])
52/// and is used as the error type in their [`FromStr`] implementations.
53///
54/// [`FromStr`]: crate::str::FromStr
55///
56/// # Potential causes
57///
58/// Among other causes, `ParseIntError` can be thrown because of leading or trailing whitespace
59/// in the string e.g., when it is obtained from the standard input.
60/// Using the [`str::trim()`] method ensures that no whitespace remains before parsing.
61///
62/// # Example
63///
64/// ```
65/// if let Err(e) = i32::from_str_radix("a12", 10) {
66///     println!("Failed conversion to i32: {e}");
67/// }
68/// ```
69#[derive(Debug, Clone, PartialEq, Eq)]
70#[stable(feature = "rust1", since = "1.0.0")]
71pub struct ParseIntError {
72    pub(super) kind: IntErrorKind,
73}
74
75/// Enum to store the various types of errors that can cause parsing an integer to fail.
76///
77/// # Example
78///
79/// ```
80/// # fn main() {
81/// if let Err(e) = i32::from_str_radix("a12", 10) {
82///     println!("Failed conversion to i32: {:?}", e.kind());
83/// }
84/// # }
85/// ```
86#[stable(feature = "int_error_matching", since = "1.55.0")]
87#[derive(Debug, Clone, PartialEq, Eq, Copy, Hash)]
88#[non_exhaustive]
89pub enum IntErrorKind {
90    /// Value being parsed is empty.
91    ///
92    /// This variant will be constructed when parsing an empty string.
93    #[stable(feature = "int_error_matching", since = "1.55.0")]
94    Empty,
95    /// Contains an invalid digit in its context.
96    ///
97    /// Among other causes, this variant will be constructed when parsing a string that
98    /// contains a non-ASCII char.
99    ///
100    /// This variant is also constructed when a `+` or `-` is misplaced within a string
101    /// either on its own or in the middle of a number.
102    #[stable(feature = "int_error_matching", since = "1.55.0")]
103    InvalidDigit,
104    /// Integer is too large to store in target integer type.
105    #[stable(feature = "int_error_matching", since = "1.55.0")]
106    PosOverflow,
107    /// Integer is too small to store in target integer type.
108    #[stable(feature = "int_error_matching", since = "1.55.0")]
109    NegOverflow,
110    /// Value was Zero
111    ///
112    /// This variant will be emitted when the parsing string has a value of zero, which
113    /// would be illegal for non-zero types.
114    #[stable(feature = "int_error_matching", since = "1.55.0")]
115    Zero,
116}
117
118impl ParseIntError {
119    /// Outputs the detailed cause of parsing an integer failing.
120    #[must_use]
121    #[rustc_const_stable(feature = "const_int_from_str", since = "1.82.0")]
122    #[stable(feature = "int_error_matching", since = "1.55.0")]
123    pub const fn kind(&self) -> &IntErrorKind {
124        &self.kind
125    }
126}
127
128#[stable(feature = "rust1", since = "1.0.0")]
129impl fmt::Display for ParseIntError {
130    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
131        #[allow(deprecated)]
132        self.description().fmt(f)
133    }
134}
135
136#[stable(feature = "rust1", since = "1.0.0")]
137impl Error for ParseIntError {
138    #[allow(deprecated)]
139    fn description(&self) -> &str {
140        match self.kind {
141            IntErrorKind::Empty => "cannot parse integer from empty string",
142            IntErrorKind::InvalidDigit => "invalid digit found in string",
143            IntErrorKind::PosOverflow => "number too large to fit in target type",
144            IntErrorKind::NegOverflow => "number too small to fit in target type",
145            IntErrorKind::Zero => "number would be zero for non-zero type",
146        }
147    }
148}
core/num/error.rs

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core/num/
error.rs
