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spec: terminating statements for functions

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The only functional change is the new section
on terminating statements.

There is a minor syntax rewrite (not change)
of function declarations to make it easier to
refer to the notion of a function from all places
where it is used (function decls, method decls,
and function literals).

Includes some minor fixes/additions of missing links.

Based closely on Russ' proposal.

Fixes #65.

R=rsc, r, iant, ken, bradfitz
CC=golang-dev
https://golang.org/cl/7415050
This commit is contained in:
Robert Griesemer 2013-03-04 13:55:35 -08:00
parent 4be38dde84
commit 9905cec0dc
1 changed files with 105 additions and 17 deletions
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122
doc/go_spec.html
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@ -1469,12 +1469,13 @@ Any value may be assigned to the <a href="#Blank_identifier">blank identifier</a
<h2 id="Blocks">Blocks</h2>
<p>
A <i>block</i> is a sequence of declarations and statements within matching
brace brackets.
A <i>block</i> is a possibly empty sequence of declarations and statements
within matching brace brackets.
</p>
<pre class="ebnf">
Block = "{" { Statement ";" } "}" .
Block = "{" StatementList "}" .
StatementList = { Statement ";" } .
</pre>
<p>
@ -1490,10 +1491,13 @@ In addition to explicit blocks in the source code, there are implicit blocks:
<li>Each file has a <i>file block</i> containing all Go source text
in that file.</li>
<li>Each <code>if</code>, <code>for</code>, and <code>switch</code>
<li>Each <a href="#If_statements">"if"</a>,
<a href="#For_statements">"for"</a>, and
<a href="#Switch_statements">"switch"</a>
statement is considered to be in its own implicit block.</li>
<li>Each clause in a <code>switch</code> or <code>select</code> statement
<li>Each clause in a <a href="#Switch_statements">"switch"</a>
or <a href="#Select_statements">"select"</a> statement
acts as an implicit block.</li>
</ol>
@ -1948,11 +1952,18 @@ to a function.
</p>
<pre class="ebnf">
FunctionDecl = "func" FunctionName Signature [ Body ] .
FunctionDecl = "func" FunctionName ( Function | Signature ) .
FunctionName = identifier .
Body = Block .
Function = Signature FunctionBody .
FunctionBody = Block .
</pre>
<p>
If the function's <a href="#Function_types">signature</a> declares
result parameters, the function body's statement list must end in
a <a href="#Terminating_statements">terminating statement</a>.
</p>
<p>
A function declaration may omit the body. Such a declaration provides the
signature for a function implemented outside Go, such as an assembly routine.
@ -1972,13 +1983,13 @@ func flushICache(begin, end uintptr) // implemented externally
<h3 id="Method_declarations">Method declarations</h3>
<p>
A method is a function with a <i>receiver</i>.
A method declaration binds an identifier, the <i>method name</i>, to a method.
It also associates the method with the receiver's <i>base type</i>.
A method is a <a href="#Function_declarations">function</a> with a <i>receiver</i>.
A method declaration binds an identifier, the <i>method name</i>, to a method,
and associates the method with the receiver's <i>base type</i>.
</p>
<pre class="ebnf">
MethodDecl = "func" Receiver MethodName Signature [ Body ] .
MethodDecl = "func" Receiver MethodName ( Function | Signature ) .
Receiver = "(" [ identifier ] [ "*" ] BaseTypeName ")" .
BaseTypeName = identifier .
</pre>
@ -2284,12 +2295,11 @@ noteFrequency := map[string]float32{
<h3 id="Function_literals">Function literals</h3>
<p>
A function literal represents an anonymous function.
It consists of a specification of the function type and a function body.
A function literal represents an anonymous <a href="#Function_declarations">function</a>.
</p>
<pre class="ebnf">
FunctionLit = FunctionType Body .
FunctionLit = "func" Function .
</pre>
<pre>
@ -3843,6 +3853,84 @@ Statement =
SimpleStmt = EmptyStmt | ExpressionStmt | SendStmt | IncDecStmt | Assignment | ShortVarDecl .
</pre>
<h3 id="Terminating_statements">Terminating statements</h3>
<p>
A terminating statement is one of the following:
</p>
<ol>
<li>
A <a href="#Return_statements">"return"</a> or
<a href="#Goto_statements">"goto"</a> statement.
<!-- ul below only for regular layout -->
<ul> </ul>
</li>
<li>
A call to the built-in function
<a href="#Handling_panics"><code>panic</code></a>.
<!-- ul below only for regular layout -->
<ul> </ul>
</li>
<li>
A <a href="#Blocks">block</a> in which the statement list ends in a terminating statement.
<!-- ul below only for regular layout -->
<ul> </ul>
</li>
<li>
An <a href="#If_statements">"if" statement</a> in which:
<ul>
<li>the "else" branch is present, and</li>
<li>both branches are terminating statements.</li>
</ul>
</li>
<li>
A <a href="#For_statements">"for" statement</a> in which:
<ul>
<li>there are no "break" statements referring to the "for" statement, and</li>
<li>the loop condition is absent.</li>
</ul>
</li>
<li>
A <a href="#Switch_statements">"switch" statement</a> in which:
<ul>
<li>there are no "break" statements referring to the "switch" statement,</li>
<li>there is a default case, and</li>
<li>the statement lists in each case, including the default, end in a terminating
statement, or a possibly labeled <a href="#Fallthrough_statements">"fallthrough"
statement</a>.</li>
</ul>
</li>
<li>
A <a href="#Select_statements">"select" statement</a> in which:
<ul>
<li>there are no "break" statements referring to the "select" statement, and</li>
<li>the statement lists in each case, including the default if present,
end in a terminating statement.</li>
</ul>
</li>
<li>
A <a href="#Labeled_statements">labeled statement</a> labeling
a terminating statement.
</li>
</ol>
<p>
All other statements are not terminating.
</p>
<p>
A <a href="#Blocks">statement list</a> ends in a terminating statement if the list
is not empty and its final statement is terminating.
</p>
<h3 id="Empty_statements">Empty statements</h3>
@ -4149,7 +4237,7 @@ the expression <code>true</code>.
<pre class="ebnf">
ExprSwitchStmt = "switch" [ SimpleStmt ";" ] [ Expression ] "{" { ExprCaseClause } "}" .
ExprCaseClause = ExprSwitchCase ":" { Statement ";" } .
ExprCaseClause = ExprSwitchCase ":" StatementList .
ExprSwitchCase = "case" ExpressionList | "default" .
</pre>
@ -4213,7 +4301,7 @@ expression <code>x</code>. As with type assertions, <code>x</code> must be of
<pre class="ebnf">
TypeSwitchStmt = "switch" [ SimpleStmt ";" ] TypeSwitchGuard "{" { TypeCaseClause } "}" .
TypeSwitchGuard = [ identifier ":=" ] PrimaryExpr "." "(" "type" ")" .
TypeCaseClause = TypeSwitchCase ":" { Statement ";" } .
TypeCaseClause = TypeSwitchCase ":" StatementList .
TypeSwitchCase = "case" TypeList | "default" .
TypeList = Type { "," Type } .
</pre>
@ -4536,7 +4624,7 @@ cases all referring to communication operations.
<pre class="ebnf">
SelectStmt = "select" "{" { CommClause } "}" .
CommClause = CommCase ":" { Statement ";" } .
CommClause = CommCase ":" StatementList .
CommCase = "case" ( SendStmt | RecvStmt ) | "default" .
RecvStmt = [ ExpressionList "=" | IdentifierList ":=" ] RecvExpr .
RecvExpr = Expression .