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Revert "spec: add new language for alias declarations"

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This reverts commit aff37662d1.

Reason: Decision to back out current alias implementation.
https://github.com/golang/go/issues/16339#issuecomment-258527920

Fixes #16339.
Fixes #17746.
Fixes #17784.

Change-Id: I5737b830d7f6fb79cf36f26403b4ad8533ba1dfe
Reviewed-on: https://go-review.googlesource.com/32813
Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
This commit is contained in:
Robert Griesemer 2016-11-04 12:38:53 -07:00
parent 585a0b03b2
commit 87f4e36ce7
1 changed files with 6 additions and 69 deletions
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73
doc/go_spec.html
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@ -1,6 +1,6 @@
<!--{
"Title": "The Go Programming Language Specification",
"Subtitle": "Version of October 28, 2016",
"Subtitle": "Version of November 4, 2016",
"Path": "/ref/spec"
}-->
@ -1726,12 +1726,8 @@ the left is bound to the value of the <i>n</i>th expression on the
right.
</p>
<p>
For constant <i>aliases</i>, see the section on <a href="#Alias_declarations">alias declarations</a>.
</p>
<pre class="ebnf">
ConstDecl = "const" ( ConstSpec | AliasSpec | "(" { ( ConstSpec | AliasSpec ) ";" } ")" ) .
ConstDecl = "const" ( ConstSpec | "(" { ConstSpec ";" } ")" ) .
ConstSpec = IdentifierList [ [ Type ] "=" ExpressionList ] .
IdentifierList = identifier { "," identifier } .
@ -1850,12 +1846,8 @@ and operations defined for the existing type are also defined for the new type.
The new type is <a href="#Type_identity">different</a> from the existing type.
</p>
<p>
For type <i>aliases</i>, see the section on <a href="#Alias_declarations">alias declarations</a>.
</p>
<pre class="ebnf">
TypeDecl = "type" ( TypeSpec | AliasSpec | "(" { ( TypeSpec | AliasSpec ) ";" } ")" ) .
TypeDecl = "type" ( TypeSpec | "(" { TypeSpec ";" } ")" ) .
TypeSpec = identifier Type .
</pre>
@ -1936,12 +1928,8 @@ A variable declaration creates one or more variables, binds corresponding
identifiers to them, and gives each a type and an initial value.
</p>
<p>
For variable <i>aliases</i>, see the section on <a href="#Alias_declarations">alias declarations</a>.
</p>
<pre class="ebnf">
VarDecl = "var" ( VarSpec | AliasSpec | "(" { ( VarSpec | AliasSpec ) ";" } ")" ) .
VarDecl = "var" ( VarSpec | "(" { VarSpec ";" } ")" ) .
VarSpec = IdentifierList ( Type [ "=" ExpressionList ] | "=" ExpressionList ) .
</pre>
@ -1988,7 +1976,6 @@ inside a <a href="#Function_declarations">function body</a> if the variable is
never used.
</p>
<h3 id="Short_variable_declarations">Short variable declarations</h3>
<p>
@ -2047,12 +2034,8 @@ A function declaration binds an identifier, the <i>function name</i>,
to a function.
</p>
<p>
For function <i>aliases</i>, see the section on <a href="#Alias_declarations">alias declarations</a>.
</p>
<pre class="ebnf">
FunctionDecl = "func" ( FunctionName ( Function | Signature ) ) | AliasSpec .
FunctionDecl = "func" FunctionName ( Function | Signature ) .
FunctionName = identifier .
Function = Signature FunctionBody .
FunctionBody = Block .
@ -2165,52 +2148,6 @@ However, a function declared this way is not a method.
</p>
<h3 id="Alias_declarations">Alias declarations</h3>
<p>
An alias declaration binds an identifier, the <i>alias</i>, to a
<a href="#Constant_declarations">constant</a>,
<a href="#Type_declarations">type</a>,
<a href="#Variable_declarations">variable</a>, or
<a href="#Function_declarations">function</a>
denoted by a <a href="#Qualified_identifiers">qualified identifier</a> and
declared in a different package.
</p>
<pre class="ebnf">
AliasSpec = identifier "=&gt;" QualifiedIdent .
</pre>
<p>
The effect of referring to a constant, type, variable, or function by an alias
is indistinguishable from referring to it by its original name.
For example, the type denoted by a type alias and the aliased type are
<a href="#Type_identity">identical</a>.
</p>
<p>
An alias declaration may appear only as a form of constant, type, variable,
or function declaration at the package level, and the aliased entity must be
a constant, type, variable, or function respectively. Alias declarations inside
functions are not permitted.
</p>
<pre>
const (
G = 6.67408e-11 // regular and alias declarations may be grouped
Pi =&gt; math.Pi // same effect as: Pi = math.Pi
)
type Struct =&gt; types.Struct // re-export of types.Struct
func sin =&gt; math.Sin // non-exported shortcut for frequently used function
</pre>
<p>
An alias declaration may not refer to package <a href="#Package_unsafe">unsafe</a>.
</p>
<h2 id="Expressions">Expressions</h2>
<p>