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(#93493) Add items from code review

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George Bateman 2022-01-31 23:49:16 +00:00
parent 4d4ec97e0a
commit 5357ec1473
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2 changed files with 74 additions and 34 deletions
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52
library/core/src/primitive_docs.rs
View File

@ -289,32 +289,52 @@ mod prim_never {}
///
/// A `char` is a '[Unicode scalar value]', which is any '[Unicode code point]'
/// other than a [surrogate code point]. This has a fixed numerical definition:
/// code points are in the range `'\0'` to `char::MAX` (`'\u{10FFFF}'`), inclusive.
/// Surrogate code points, used by UTF-16, are in the range U+D800 to U+DFFF.
/// code points are in the range 0 to 0x10FFFF, inclusive.
/// Surrogate code points, used by UTF-16, are in the range 0xD800 to 0xDFFF.
///
/// No `char` may be constructed, whether as a literal or at runtime, that is not a
/// Unicode scalar value:
///
/// ```text
/// let forbidden_chars = [
/// // Each of these is a compiler error
/// '\u{D800}', '\u{DFFF}', '\u{110000}',
///
/// // Panics; from_u32 returns None.
/// char::from_u32(0xDE01).unwrap(),
///
/// // Undefined behaviour
/// unsafe { char::from_u32_unchecked(0x110000) },
/// ];
/// ['\u{D800}', '\u{DFFF}', '\u{110000}'];
/// ```
///
/// Unicode is regularly updated. Many USVs are not currently assigned to a
/// character, but may be in the future ("reserved"); some will never be a character
/// ("noncharacters"); and some may be given different meanings by different users
/// ("private use").
/// ```should_panic
/// // Panics; from_u32 returns None.
/// char::from_u32(0xDE01).unwrap();
/// ```
///
/// ```
/// // Undefined behaviour
/// unsafe { char::from_u32_unchecked(0x110000) };
/// ```
///
/// USVs are also the exact set of values that may be encoded in UTF-8. Because
/// `char` values are USVs and `str` values are valid UTF-8, it is safe to store
/// any `char` in a `str` or read any character from a `str` as a `char`.
///
/// The gap in valid `char` values is understood by the compiler, so in the
/// below example the two ranges are understood to cover the whole range of
/// possible `char` values and there is no error for a [non-exhaustive match].
///
/// ```
/// let c: char = 'a';
/// match c {
/// '\0' ..= '\u{D7FF}' => false,
/// '\u{E000}' ..= '\u{10FFFF}' => true,
/// };
/// ```
///
/// All USVs are valid `char` values, but not all of them represent a real
/// character. Many USVs are not currently assigned to a character, but may be
/// in the future ("reserved"); some will never be a character
/// ("noncharacters"); and some may be given different meanings by different
/// users ("private use").
///
/// [Unicode scalar value]: https://www.unicode.org/glossary/#unicode_scalar_value
/// [Unicode code point]: https://www.unicode.org/glossary/#code_point
/// [Unicode scalar value]: https://www.unicode.org/glossary/#unicode_scalar_value
/// [non-exhaustive match]: ../book/ch06-02-match.html#matches-are-exhaustive
/// [surrogate code point]: https://www.unicode.org/glossary/#surrogate_code_point
///
/// # Representation

52
library/std/src/primitive_docs.rs
View File

@ -289,32 +289,52 @@ mod prim_never {}
///
/// A `char` is a '[Unicode scalar value]', which is any '[Unicode code point]'
/// other than a [surrogate code point]. This has a fixed numerical definition:
/// code points are in the range `'\0'` to `char::MAX` (`'\u{10FFFF}'`), inclusive.
/// Surrogate code points, used by UTF-16, are in the range U+D800 to U+DFFF.
/// code points are in the range 0 to 0x10FFFF, inclusive.
/// Surrogate code points, used by UTF-16, are in the range 0xD800 to 0xDFFF.
///
/// No `char` may be constructed, whether as a literal or at runtime, that is not a
/// Unicode scalar value:
///
/// ```text
/// let forbidden_chars = [
/// // Each of these is a compiler error
/// '\u{D800}', '\u{DFFF}', '\u{110000}',
///
/// // Panics; from_u32 returns None.
/// char::from_u32(0xDE01).unwrap(),
///
/// // Undefined behaviour
/// unsafe { char::from_u32_unchecked(0x110000) },
/// ];
/// ['\u{D800}', '\u{DFFF}', '\u{110000}'];
/// ```
///
/// Unicode is regularly updated. Many USVs are not currently assigned to a
/// character, but may be in the future ("reserved"); some will never be a character
/// ("noncharacters"); and some may be given different meanings by different users
/// ("private use").
/// ```should_panic
/// // Panics; from_u32 returns None.
/// char::from_u32(0xDE01).unwrap();
/// ```
///
/// ```
/// // Undefined behaviour
/// unsafe { char::from_u32_unchecked(0x110000) };
/// ```
///
/// USVs are also the exact set of values that may be encoded in UTF-8. Because
/// `char` values are USVs and `str` values are valid UTF-8, it is safe to store
/// any `char` in a `str` or read any character from a `str` as a `char`.
///
/// The gap in valid `char` values is understood by the compiler, so in the
/// below example the two ranges are understood to cover the whole range of
/// possible `char` values and there is no error for a [non-exhaustive match].
///
/// ```
/// let c: char = 'a';
/// match c {
/// '\0' ..= '\u{D7FF}' => false,
/// '\u{E000}' ..= '\u{10FFFF}' => true,
/// };
/// ```
///
/// All USVs are valid `char` values, but not all of them represent a real
/// character. Many USVs are not currently assigned to a character, but may be
/// in the future ("reserved"); some will never be a character
/// ("noncharacters"); and some may be given different meanings by different
/// users ("private use").
///
/// [Unicode scalar value]: https://www.unicode.org/glossary/#unicode_scalar_value
/// [Unicode code point]: https://www.unicode.org/glossary/#code_point
/// [Unicode scalar value]: https://www.unicode.org/glossary/#unicode_scalar_value
/// [non-exhaustive match]: ../book/ch06-02-match.html#matches-are-exhaustive
/// [surrogate code point]: https://www.unicode.org/glossary/#surrogate_code_point
///
/// # Representation