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- Clarify that struct composite literal keys are field names not selectors.

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- Slight re-phrasing of struct type section since "field name" was not
properly introduced.

Fixes #164.

R=r, rsc, iant
https://golang.org/cl/155061
This commit is contained in:
Robert Griesemer 2009-11-16 08:58:55 -08:00
parent 0660d243b1
commit d3b1565716
1 changed files with 22 additions and 19 deletions
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41
doc/go_spec.html
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@ -694,17 +694,19 @@ new([100]int)[0:50]
<h3 id="Struct_types">Struct types</h3>
<p>
A struct is a sequence of named
elements, called fields, with various types. A struct type declares
an identifier and type for each field. Within a struct, non-<a href="#Blank_identifier">blank</a>
field identifiers must be unique.
A struct is a sequence of named elements, called fields, each of which has a
name and a type. Field names may be specified explicitly (IdentifierList) or
implicitly (AnonymousField).
Within a struct, non-<a href="#Blank_identifier">blank</a> field names must
be unique.
</p>
<pre class="ebnf">
StructType = "struct" "{" [ FieldDeclList ] "}" .
FieldDeclList = FieldDecl { ";" FieldDecl } [ ";" ] .
FieldDecl = (IdentifierList Type | [ "*" ] TypeName) [ Tag ] .
Tag = StringLit .
StructType = "struct" "{" [ FieldDeclList ] "}" .
FieldDeclList = FieldDecl { ";" FieldDecl } [ ";" ] .
FieldDecl = (IdentifierList Type | AnonymousField) [ Tag ] .
AnonymousField = [ "*" ] TypeName .
Tag = StringLit .
</pre>
<pre>
@ -722,28 +724,27 @@ struct {
</pre>
<p>
A field declared with a type but no field identifier is an <i>anonymous field</i>.
A field declared with a type but no explicit field name is an <i>anonymous field</i>.
Such a field type must be specified as
a type name <code>T</code> or as a pointer to a type name <code>*T</code>,
and <code>T</code> itself may not be
a pointer type. The unqualified type name acts as the field identifier.
a pointer type. The unqualified type name acts as the field name.
</p>
<pre>
// A struct with four anonymous fields of type T1, *T2, P.T3 and *P.T4
struct {
T1; // the field name is T1
*T2; // the field name is T2
P.T3; // the field name is T3
*P.T4; // the field name is T4
x, y int;
T1; // field name is T1
*T2; // field name is T2
P.T3; // field name is T3
*P.T4; // field name is T4
x, y int; // field names are x and y
}
</pre>
<p>
The unqualified type name of an anonymous field must be distinct from the
field identifier (or unqualified type name for an anonymous field) of every
other field within the struct. The following declaration is illegal:
The following declaration is illegal because field names must be unique
in a struct type:
</p>
<pre>
@ -778,7 +779,7 @@ a type named <code>T</code>:
</ul>
<p>
A field declaration may be followed by an optional string literal <i>tag</i>,
which becomes an attribute for all the identifiers in the corresponding
which becomes an attribute for all the fields in the corresponding
field declaration. The tags are made
visible through a <a href="#Package_unsafe">reflection interface</a>
but are otherwise ignored.
@ -1915,6 +1916,8 @@ constant key value.
For struct literals the following rules apply:
</p>
<ul>
<li>A key must be a field name declared in the LiteralType.
</li>
<li>A literal that does not contain any keys must
list an element for each struct field in the
order in which the fields are declared.