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Merge pull request #1457 from mattheww/2024-01_c_string_literal_expr
C string literal expressions
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@ -252,7 +252,48 @@ b"\\x52"; br"\x52"; // \x52
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A C string literal expression consists of a single [C_STRING_LITERAL] or [RAW_C_STRING_LITERAL] token.
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> **Note**: This section is incomplete.
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The expression's type is a shared reference (with `static` lifetime) to the standard library [CStr] type.
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That is, the type is `&'static core::ffi::CStr`.
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The token must not have a suffix.
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The token's _literal content_ is the sequence of characters following the first `"` and preceding the last `"` in the string representation of the token.
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The literal expression's _represented bytes_ are a sequence of bytes derived from the literal content as follows:
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* If the token is a [C_STRING_LITERAL], the literal content is treated as a sequence of items, each of which is either a single Unicode character other than `\` or an [escape].
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The sequence of items is converted to a sequence of bytes as follows:
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* Each single Unicode character contributes its UTF-8 representation.
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* Each [simple escape] contributes the [Unicode scalar value] of its escaped value.
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* Each [8-bit escape] contributes a single byte containing the [Unicode scalar value] of its escaped value.
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* Each [unicode escape] contributes the UTF-8 representation of its escaped value.
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* Each [string continuation escape] contributes no bytes.
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* If the token is a [RAW_C_STRING_LITERAL], the represented bytes are the UTF-8 encoding of the literal content.
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> **Note**: the permitted forms of [C_STRING_LITERAL] and [RAW_C_STRING_LITERAL] tokens ensure that the represented bytes never include a null byte.
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The expression's value is a reference to a statically allocated [CStr] whose array of bytes contains the represented bytes followed by a null byte.
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Examples of C string literal expressions:
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```rust
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c"foo"; cr"foo"; // foo
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c"\"foo\""; cr#""foo""#; // "foo"
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c"foo #\"# bar";
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cr##"foo #"# bar"##; // foo #"# bar
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c"\x52"; c"R"; cr"R"; // R
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c"\\x52"; cr"\x52"; // \x52
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c"æ"; // LATIN SMALL LETTER AE (U+00E6)
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c"\u{00E6}"; // LATIN SMALL LETTER AE (U+00E6)
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c"\xC3\xA6"; // LATIN SMALL LETTER AE (U+00E6)
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c"\xE6".to_bytes(); // [230]
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c"\u{00E6}".to_bytes(); // [195, 166]
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```
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## Integer literal expressions
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@ -365,13 +406,20 @@ The expression's type is the primitive [boolean type], and its value is:
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* false if the keyword is `false`
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[Escape]: #escapes
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[Simple escape]: #simple-escapes
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[Simple escapes]: #simple-escapes
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[8-bit escape]: #8-bit-escapes
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[8-bit escapes]: #8-bit-escapes
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[7-bit escape]: #7-bit-escapes
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[7-bit escapes]: #7-bit-escapes
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[Unicode escape]: #unicode-escapes
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[Unicode escapes]: #unicode-escapes
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[String continuation escape]: #string-continuation-escapes
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[String continuation escapes]: #string-continuation-escapes
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[boolean type]: ../types/boolean.md
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[constant expression]: ../const_eval.md#constant-expressions
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[CStr]: ../../core/ffi/struct.CStr.html
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[floating-point types]: ../types/numeric.md#floating-point-types
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[lint check]: ../attributes/diagnostics.md#lint-check-attributes
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[literal tokens]: ../tokens.md#literals
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@ -330,8 +330,7 @@ A _C string literal_ is a sequence of Unicode characters and _escapes_,
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preceded by the characters `U+0063` (`c`) and `U+0022` (double-quote), and
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followed by the character `U+0022`. If the character `U+0022` is present within
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the literal, it must be _escaped_ by a preceding `U+005C` (`\`) character.
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Alternatively, a C string literal can be a _raw C string literal_, defined
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below. The type of a C string literal is [`&core::ffi::CStr`][CStr].
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Alternatively, a C string literal can be a _raw C string literal_, defined below.
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[CStr]: ../core/ffi/struct.CStr.html
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