diff --git a/src/expressions/literal-expr.md b/src/expressions/literal-expr.md index e5bc2dff4..703b55880 100644 --- a/src/expressions/literal-expr.md +++ b/src/expressions/literal-expr.md @@ -8,6 +8,8 @@ >    | [BYTE_LITERAL]\ >    | [BYTE_STRING_LITERAL]\ >    | [RAW_BYTE_STRING_LITERAL]\ +>    | [C_STRING_LITERAL]\ +>    | [RAW_C_STRING_LITERAL]\ >    | [INTEGER_LITERAL]\ >    | [FLOAT_LITERAL]\ >    | `true` | `false` @@ -48,6 +50,12 @@ A string literal expression consists of a single [BYTE_STRING_LITERAL] or [RAW_B > **Note**: This section is incomplete. +## C string literal expressions + +A C string literal expression consists of a single [C_STRING_LITERAL] or [RAW_C_STRING_LITERAL] token. + +> **Note**: This section is incomplete. + ## Integer literal expressions An integer literal expression consists of a single [INTEGER_LITERAL] token. @@ -182,5 +190,7 @@ The expression's type is the primitive [boolean type], and its value is: [BYTE_LITERAL]: ../tokens.md#byte-literals [BYTE_STRING_LITERAL]: ../tokens.md#byte-string-literals [RAW_BYTE_STRING_LITERAL]: ../tokens.md#raw-byte-string-literals +[C_STRING_LITERAL]: ../tokens.md#c-string-literals +[RAW_C_STRING_LITERAL]: ../tokens.md#raw-c-string-literals [INTEGER_LITERAL]: ../tokens.md#integer-literals [FLOAT_LITERAL]: ../tokens.md#floating-point-literals diff --git a/src/patterns.md b/src/patterns.md index 370e1990c..6088973d0 100644 --- a/src/patterns.md +++ b/src/patterns.md @@ -123,6 +123,8 @@ if let (a, 3) = (1, 2) { // "(a, 3)" is refutable, and will not match >    | [RAW_STRING_LITERAL]\ >    | [BYTE_STRING_LITERAL]\ >    | [RAW_BYTE_STRING_LITERAL]\ +>    | [C_STRING_LITERAL]\ +>    | [RAW_C_STRING_LITERAL]\ >    | `-`? [INTEGER_LITERAL]\ >    | `-`? [FLOAT_LITERAL] @@ -132,6 +134,8 @@ if let (a, 3) = (1, 2) { // "(a, 3)" is refutable, and will not match [RAW_STRING_LITERAL]: tokens.md#raw-string-literals [BYTE_STRING_LITERAL]: tokens.md#byte-string-literals [RAW_BYTE_STRING_LITERAL]: tokens.md#raw-byte-string-literals +[C_STRING_LITERAL]: tokens.md#c-string-literals +[RAW_C_STRING_LITERAL]: tokens.md#raw-c-string-literals [INTEGER_LITERAL]: tokens.md#integer-literals [FLOAT_LITERAL]: tokens.md#floating-point-literals @@ -144,6 +148,14 @@ Floating-point literals are currently accepted, but due to the complexity of com +
+ +C string and raw C string literals are accepted in literal patterns, but `&CStr` +doesn't implement structural equality (`#[derive(Eq, PartialEq)]`) and therefore +any such `match` on a `&CStr` will be rejected with a type error. + +
+ Literal patterns are always refutable. Examples: diff --git a/src/tokens.md b/src/tokens.md index 0067b647d..05b4537ca 100644 --- a/src/tokens.md +++ b/src/tokens.md @@ -32,6 +32,8 @@ Literals are tokens used in [literal expressions]. | [Byte](#byte-literals) | `b'H'` | 0 | All ASCII | [Quote](#quote-escapes) & [Byte](#byte-escapes) | | [Byte string](#byte-string-literals) | `b"hello"` | 0 | All ASCII | [Quote](#quote-escapes) & [Byte](#byte-escapes) | | [Raw byte string](#raw-byte-string-literals) | `br#"hello"#` | <256 | All ASCII | `N/A` | +| [C string](#c-string-literals) | `c"hello"` | 0 | All Unicode | [Quote](#quote-escapes) & [Byte](#byte-escapes) & [Unicode](#unicode-escapes) | +| [Raw C string](#raw-c-string-literals) | `cr#"hello"#` | <256 | All Unicode | `N/A` | \* The number of `#`s on each side of the same literal must be equivalent. @@ -328,6 +330,95 @@ b"\x52"; b"R"; br"R"; // R b"\\x52"; br"\x52"; // \x52 ``` +### C string and raw C string literals + +#### C string literals + +> **Lexer**\ +> C_STRING_LITERAL :\ +>    `c"` (\ +>       ~\[`"` `\` _IsolatedCR_]\ +>       | BYTE_ESCAPE\ +>       | UNICODE_ESCAPE\ +>       | STRING_CONTINUE\ +>    )\* `"` SUFFIX? + +A _C string literal_ is a sequence of Unicode characters and _escapes_, +preceded by the characters `U+0063` (`c`) and `U+0022` (double-quote), and +followed by the character `U+0022`. If the character `U+0022` is present within +the literal, it must be _escaped_ by a preceding `U+005C` (`\`) character. +Alternatively, a C string literal can be a _raw C string literal_, defined +below. The type of a C string literal is [`&core::ffi::CStr`][CStr]. + +[CStr]: ../core/ffi/struct.CStr.html + +C strings are implicitly terminated by byte `0x00`, so the C string literal +`c""` is equivalent to manually constructing a `&CStr` from the byte string +literal `b"\x00"`. Other than the implicit terminator, byte `0x00` is not +permitted within a C string. + +Some additional _escapes_ are available in non-raw C string literals. An escape +starts with a `U+005C` (`\`) and continues with one of the following forms: + +* A _byte escape_ escape starts with `U+0078` (`x`) and is followed by exactly + two _hex digits_. It denotes the byte equal to the provided hex value. +* A _24-bit code point escape_ starts with `U+0075` (`u`) and is followed + by up to six _hex digits_ surrounded by braces `U+007B` (`{`) and `U+007D` + (`}`). It denotes the Unicode code point equal to the provided hex value, + encoded as UTF-8. +* A _whitespace escape_ is one of the characters `U+006E` (`n`), `U+0072` + (`r`), or `U+0074` (`t`), denoting the bytes values `0x0A` (ASCII LF), + `0x0D` (ASCII CR) or `0x09` (ASCII HT) respectively. +* The _backslash escape_ is the character `U+005C` (`\`) which must be + escaped in order to denote its ASCII encoding `0x5C`. + +The escape sequences `\0`, `\x00`, and `\u{0000}` are permitted within the token +but will be rejected as invalid, as C strings may not contain byte `0x00` except +as the implicit terminator. + +> **Edition Differences**: C string literals are accepted in the 2021 edition or +> later. In earlier additions the token `c""` is lexed as `c ""`. + +#### Raw C string literals + +> **Lexer**\ +> RAW_C_STRING_LITERAL :\ +>    `cr` RAW_C_STRING_CONTENT SUFFIX? +> +> RAW_C_STRING_CONTENT :\ +>       `"` ( ~ _IsolatedCR_ )* (non-greedy) `"`\ +>    | `#` RAW_C_STRING_CONTENT `#` + +Raw C string literals do not process any escapes. They start with the +character `U+0063` (`c`), followed by `U+0072` (`r`), followed by fewer than 256 +of the character `U+0023` (`#`), and a `U+0022` (double-quote) character. The +_raw C string body_ can contain any sequence of Unicode characters and is +terminated only by another `U+0022` (double-quote) character, followed by the +same number of `U+0023` (`#`) characters that preceded the opening `U+0022` +(double-quote) character. + +All characters contained in the raw C string body represent themselves in UTF-8 +encoding. The characters `U+0022` (double-quote) (except when followed by at +least as many `U+0023` (`#`) characters as were used to start the raw C string +literal) or `U+005C` (`\`) do not have any special meaning. + +> **Edition Differences**: Raw C string literals are accepted in the 2021 +> edition or later. In earlier additions the token `cr""` is lexed as `cr ""`, +> and `cr#""#` is lexed as `cr #""#` (which is non-grammatical). + +#### Examples for C string and raw C string literals + +```rust +c"foo"; cr"foo"; // foo +c"\"foo\""; cr#""foo""#; // "foo" + +c"foo #\"# bar"; +cr##"foo #"# bar"##; // foo #"# bar + +c"\x52"; c"R"; cr"R"; // R +c"\\x52"; cr"\x52"; // \x52 +``` + ### Number literals A _number literal_ is either an _integer literal_ or a _floating-point @@ -628,9 +719,9 @@ them are referred to as "token trees" in [macros]. The three types of brackets ## Reserved prefixes > **Lexer 2021+**\ -> RESERVED_TOKEN_DOUBLE_QUOTE : ( IDENTIFIER_OR_KEYWORD _Except `b` or `r` or `br`_ | `_` ) `"`\ +> RESERVED_TOKEN_DOUBLE_QUOTE : ( IDENTIFIER_OR_KEYWORD _Except `b` or `c` or `r` or `br` or `cr`_ | `_` ) `"`\ > RESERVED_TOKEN_SINGLE_QUOTE : ( IDENTIFIER_OR_KEYWORD _Except `b`_ | `_` ) `'`\ -> RESERVED_TOKEN_POUND : ( IDENTIFIER_OR_KEYWORD _Except `r` or `br`_ | `_` ) `#` +> RESERVED_TOKEN_POUND : ( IDENTIFIER_OR_KEYWORD _Except `r` or `br` or `cr`_ | `_` ) `#` Some lexical forms known as _reserved prefixes_ are reserved for future use. @@ -638,7 +729,7 @@ Source input which would otherwise be lexically interpreted as a non-raw identif Note that raw identifiers, raw string literals, and raw byte string literals may contain a `#` character but are not interpreted as containing a reserved prefix. -Similarly the `r`, `b`, and `br` prefixes used in raw string literals, byte literals, byte string literals, and raw byte string literals are not interpreted as reserved prefixes. +Similarly the `r`, `b`, `br`, `c`, and `cr` prefixes used in raw string literals, byte literals, byte string literals, raw byte string literals, C string literals, and raw C string literals are not interpreted as reserved prefixes. > **Edition Differences**: Starting with the 2021 edition, reserved prefixes are reported as an error by the lexer (in particular, they cannot be passed to macros). >