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spec: combine section on type parameters and type parameter lists

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This change moves the relevant prose of the section on type parameters
into the section on type parameter lists and eliminates the former.

With this change, the section on types now exclusively describes all
Go composite types.

User-defined named types (defined types and type parameters) are
described with their declarations.

Change-Id: I3e421cd236e8801d31a4a81ff1e5ec9933e3ed20
Reviewed-on: https://go-review.googlesource.com/c/go/+/385037
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This commit is contained in:
Robert Griesemer 2022-02-10 21:51:04 -08:00
parent ea9b1f1573
commit 18e1a5a085
1 changed files with 23 additions and 35 deletions
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58
doc/go_spec.html
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@ -1,5 +1,5 @@
<!--{
"Title": "The Go Programming Language Specification - Go 1.18 Draft (incomplete)",
"Title": "The Go Programming Language Specification - Go 1.18 Draft",
"Subtitle": "Version of Feb 11, 2022",
"Path": "/ref/spec"
}-->
@ -1688,25 +1688,6 @@ and a second goroutine receives them, the values are
received in the order sent.
</p>
<h3 id="Type_parameters">Type parameters</h3>
<p>
A <i>type parameter</i> is an (unqualified) type name declared in the
<a href="#Type_parameter_lists">type parameter list</a> of a
<a href="#Function_declarations">function declaration</a> or
<a href="#Type_definitions">type definition</a>; or in the receiver specification
of a <a href="#Method_declarations">method declaration</a> that is associated
with a generic type.
A type parameter acts as a place holder for an (as of yet) unknown type in the declaration;
the type parameter is replaced with a <i>type argument</i> upon
<a href="#Instantiations">instantiation</a> of the generic function or type.
</p>
<p>
The properties of a type parameter are determined by its
<a href="#Type_constraints">type constraint</a>.
</p>
<h2 id="Properties_of_types_and_values">Properties of types and values</h2>
<h3 id="Underlying_types">Underlying types</h3>
@ -1790,7 +1771,7 @@ depending on the direction of the directional channels present.
<p>
By definition, a core type is never a <a href="#Type_definitions">defined type</a>,
<a href="#Type_parameters">type parameter</a>, or
<a href="#Type_parameter_lists">type parameter</a>, or
<a href="#Interface_types">interface type</a>.
</p>
@ -2047,7 +2028,7 @@ to <code>T</code>.
<p>
A <a href="#Constants">constant</a> <code>x</code> is <i>representable</i>
by a value of type <code>T</code>,
where <code>T</code> is not a <a href="#Type_parameters">type parameter</a>,
where <code>T</code> is not a <a href="#Type_parameter_lists">type parameter</a>,
if one of the following conditions applies:
</p>
@ -2628,8 +2609,7 @@ func (l *List[T]) Len() int { … }
<h3 id="Type_parameter_lists">Type parameter lists</h3>
<p>
A type parameter list declares the <a href="#Type_parameters">type parameters</a>
in a generic function or type declaration.
A type parameter list declares the <i>type parameters</i> of a generic function or type declaration.
The type parameter list looks like an ordinary <a href="#Function_types">function parameter list</a>
except that the type parameter names must all be present and the list is enclosed
in square brackets rather than parentheses.
@ -2642,9 +2622,11 @@ TypeParamDecl = IdentifierList TypeConstraint .
</pre>
<p>
Each identifier declares a type parameter.
All non-blank names in the list must be unique.
Each type parameter is a new and different <a href="#Types">named type</a>.
Each name declares a type parameter, which is a new and different <a href="#Types">named type</a>
that acts as a place holder for an (as of yet) unknown type in the declaration.
The type parameter is replaced with a <i>type argument</i> upon
<a href="#Instantiations">instantiation</a> of the generic function or type.
</p>
<pre>
@ -2686,6 +2668,12 @@ type T[P interface{*C}] …
type T[P *C,] …
</pre>
<p>
Type parameters may also be declared by the receiver specification
of a <a href="#Method_declarations">method declaration</a> associated
with a generic type.
</p>
<h4 id="Type_constraints">Type constraints</h4>
<p>
@ -3829,7 +3817,7 @@ For <code>a</code> of <a href="#Map_types">map type</a> <code>M</code>:
</ul>
<p>
For <code>a</code> of <a href="#Type_parameters">type parameter type</a> <code>P</code>:
For <code>a</code> of <a href="#Type_parameter_lists">type parameter type</a> <code>P</code>:
</p>
<ul>
<li><code>P</code> must have <a href="#Specific_types">specific types</a>.</li>
@ -4023,7 +4011,7 @@ If the indices are out of range at run time, a <a href="#Run_time_panics">run-ti
<p>
For an expression <code>x</code> of <a href="#Interface_types">interface type</a>,
but not a <a href="#Type_parameters">type parameter</a>, and a type <code>T</code>,
but not a <a href="#Type_parameter_lists">type parameter</a>, and a type <code>T</code>,
the primary expression
</p>
@ -4840,7 +4828,7 @@ The bitwise logical and shift operators apply to integers only.
</pre>
<p>
Excluding shifts, if the operand type is a <a href="#Type_parameters">type parameter</a>,
Excluding shifts, if the operand type is a <a href="#Type_parameter_lists">type parameter</a>,
it must have <a href="#Specific_types">specific types</a>, and the operator must
apply to each specific type.
The operands are represented as values of the type argument that the type parameter
@ -5295,7 +5283,7 @@ as for non-constant <code>x</code>.
</p>
<p>
Converting a constant to a type that is not a <a href="#Type_parameters">type parameter</a>
Converting a constant to a type that is not a <a href="#Type_parameter_lists">type parameter</a>
yields a typed constant.
</p>
@ -5350,7 +5338,7 @@ in any of these cases:
<li>
ignoring struct tags (see below),
<code>x</code>'s type and <code>T</code> are not
<a href="#Type_parameters">type parameters</a> but have
<a href="#Type_parameter_lists">type parameters</a> but have
<a href="#Type_identity">identical</a> <a href="#Types">underlying types</a>.
</li>
<li>
@ -6269,7 +6257,7 @@ switch x.(type) {
Cases then match actual types <code>T</code> against the dynamic type of the
expression <code>x</code>. As with type assertions, <code>x</code> must be of
<a href="#Interface_types">interface type</a>, but not a
<a href="#Type_parameters">type parameter</a>, and each non-interface type
<a href="#Type_parameter_lists">type parameter</a>, and each non-interface type
<code>T</code> listed in a case must implement the type of <code>x</code>.
The types listed in the cases of a type switch must all be
<a href="#Type_identity">different</a>.
@ -6351,7 +6339,7 @@ if v == nil {
</pre>
<p>
A <a href="#Type_parameters">type parameter</a> or a <a href="#Type_declarations">generic type</a>
A <a href="#Type_parameter_lists">type parameter</a> or a <a href="#Type_declarations">generic type</a>
may be used as a type in a case. If upon <a href="#Instantiations">instantiation</a> that type turns
out to duplicate another entry in the switch, the first matching case is chosen.
</p>
@ -7092,7 +7080,7 @@ cap(s) [n]T, *[n]T array length (== n)
</pre>
<p>
If the argument type is a <a href="#Type_parameters">type parameter</a> <code>P</code>,
If the argument type is a <a href="#Type_parameter_lists">type parameter</a> <code>P</code>,
<code>P</code> must have <a href="#Specific_types">specific types</a>, and
the call <code>len(e)</code> (or <code>cap(e)</code> respectively) must be valid for
each specific type of <code>P</code>.
@ -7316,7 +7304,7 @@ delete(m, k) // remove element m[k] from map m
</pre>
<p>
If the type of <code>m</code> is a <a href="#Type_parameters">type parameter</a>,
If the type of <code>m</code> is a <a href="#Type_parameter_lists">type parameter</a>,
it must have <a href="#Specific_types">specific types</a>, all specific types
must be maps, and they must all have identical key types.
</p>