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Rollup merge of #25283 - steveklabnik:gh24999, r=alexcrichton

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and remove references to the unit type, which no longer exists

Fixes #24999
This commit is contained in:
Steve Klabnik 2015-05-11 23:24:19 -04:00
commit adf5b84394
1 changed files with 17 additions and 20 deletions
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src/doc/reference.md
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@ -31,23 +31,27 @@ You may also be interested in the [grammar].
## Unicode productions ## Unicode productions
A few productions in Rust's grammar permit Unicode code points outside the ASCII A few productions in Rust's grammar permit Unicode code points outside the
range. We define these productions in terms of character properties specified ASCII range. We define these productions in terms of character properties
in the Unicode standard, rather than in terms of ASCII-range code points. The specified in the Unicode standard, rather than in terms of ASCII-range code
section [Special Unicode Productions](#special-unicode-productions) lists these points. The grammar has a [Special Unicode Productions][unicodeproductions]
productions. section that lists these productions.
[unicodeproductions]: grammar.html#special-unicode-productions
## String table productions ## String table productions
Some rules in the grammar — notably [unary Some rules in the grammar — notably [unary
operators](#unary-operator-expressions), [binary operators](#unary-operator-expressions), [binary
operators](#binary-operator-expressions), and [keywords](#keywords) — are operators](#binary-operator-expressions), and [keywords][keywords] — are
given in a simplified form: as a listing of a table of unquoted, printable given in a simplified form: as a listing of a table of unquoted, printable
whitespace-separated strings. These cases form a subset of the rules regarding whitespace-separated strings. These cases form a subset of the rules regarding
the [token](#tokens) rule, and are assumed to be the result of a the [token](#tokens) rule, and are assumed to be the result of a
lexical-analysis phase feeding the parser, driven by a DFA, operating over the lexical-analysis phase feeding the parser, driven by a DFA, operating over the
disjunction of all such string table entries. disjunction of all such string table entries.
[keywords]: grammar.html#keywords
When such a string enclosed in double-quotes (`"`) occurs inside the grammar, When such a string enclosed in double-quotes (`"`) occurs inside the grammar,
it is an implicit reference to a single member of such a string table it is an implicit reference to a single member of such a string table
production. See [tokens](#tokens) for more information. production. See [tokens](#tokens) for more information.
@ -75,7 +79,7 @@ An identifier is any nonempty Unicode[^non_ascii_idents] string of the following
- The first character has property `XID_start` - The first character has property `XID_start`
- The remaining characters have property `XID_continue` - The remaining characters have property `XID_continue`
that does _not_ occur in the set of [keywords](#keywords). that does _not_ occur in the set of [keywords][keywords].
> **Note**: `XID_start` and `XID_continue` as character properties cover the > **Note**: `XID_start` and `XID_continue` as character properties cover the
> character ranges used to form the more familiar C and Java language-family > character ranges used to form the more familiar C and Java language-family
@ -401,7 +405,7 @@ Symbols are a general class of printable [token](#tokens) that play structural
roles in a variety of grammar productions. They are catalogued here for roles in a variety of grammar productions. They are catalogued here for
completeness as the set of remaining miscellaneous printable tokens that do not completeness as the set of remaining miscellaneous printable tokens that do not
otherwise appear as [unary operators](#unary-operator-expressions), [binary otherwise appear as [unary operators](#unary-operator-expressions), [binary
operators](#binary-operator-expressions), or [keywords](#keywords). operators](#binary-operator-expressions), or [keywords][keywords].
## Paths ## Paths
@ -611,7 +615,7 @@ module needs its own source file: [module definitions](#modules) can be nested
within one file. within one file.
Each source file contains a sequence of zero or more `item` definitions, and Each source file contains a sequence of zero or more `item` definitions, and
may optionally begin with any number of [attributes](#Items and attributes) may optionally begin with any number of [attributes](#items-and-attributes)
that apply to the containing module, most of which influence the behavior of that apply to the containing module, most of which influence the behavior of
the compiler. The anonymous crate module can have additional attributes that the compiler. The anonymous crate module can have additional attributes that
apply to the crate as a whole. apply to the crate as a whole.
@ -653,7 +657,7 @@ There are several kinds of item:
* [`use` declarations](#use-declarations) * [`use` declarations](#use-declarations)
* [modules](#modules) * [modules](#modules)
* [functions](#functions) * [functions](#functions)
* [type aliases](#type-aliases) * [type definitions](grammar.html#type-definitions)
* [structures](#structures) * [structures](#structures)
* [enumerations](#enumerations) * [enumerations](#enumerations)
* [constant items](#constant-items) * [constant items](#constant-items)
@ -773,7 +777,7 @@ extern crate std as ruststd; // linking to 'std' under another name
A _use declaration_ creates one or more local name bindings synonymous with A _use declaration_ creates one or more local name bindings synonymous with
some other [path](#paths). Usually a `use` declaration is used to shorten the some other [path](#paths). Usually a `use` declaration is used to shorten the
path required to refer to a module item. These declarations may appear at the path required to refer to a module item. These declarations may appear at the
top of [modules](#modules) and [blocks](#blocks). top of [modules](#modules) and [blocks](grammar.html#block-expressions).
> **Note**: Unlike in many languages, > **Note**: Unlike in many languages,
> `use` declarations in Rust do *not* declare linkage dependency with external crates. > `use` declarations in Rust do *not* declare linkage dependency with external crates.
@ -1144,9 +1148,7 @@ let px: i32 = match p { Point(x, _) => x };
``` ```
A _unit-like struct_ is a structure without any fields, defined by leaving off A _unit-like struct_ is a structure without any fields, defined by leaving off
the list of fields entirely. Such types will have a single value, just like the list of fields entirely. Such types will have a single value. For example:
the [unit value `()`](#unit-and-boolean-literals) of the unit type. For
example:
``` ```
struct Cookie; struct Cookie;
@ -2436,11 +2438,6 @@ comma:
(0); // zero in parentheses (0); // zero in parentheses
``` ```
### Unit expressions
The expression `()` denotes the _unit value_, the only value of the type with
the same name.
### Structure expressions ### Structure expressions
There are several forms of structure expressions. A _structure expression_ There are several forms of structure expressions. A _structure expression_
@ -3281,7 +3278,7 @@ constructor or `struct` field may refer, directly or indirectly, to the
enclosing `enum` or `struct` type itself. Such recursion has restrictions: enclosing `enum` or `struct` type itself. Such recursion has restrictions:
* Recursive types must include a nominal type in the recursion * Recursive types must include a nominal type in the recursion
(not mere [type definitions](#type-definitions), (not mere [type definitions](grammar.html#type-definitions),
or other structural types such as [arrays](#array,-and-slice-types) or [tuples](#tuple-types)). or other structural types such as [arrays](#array,-and-slice-types) or [tuples](#tuple-types)).
* A recursive `enum` item must have at least one non-recursive constructor * A recursive `enum` item must have at least one non-recursive constructor
(in order to give the recursion a basis case). (in order to give the recursion a basis case).