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spec: fallthrough may not appear in last clause of a switch

Replacement for CL 7370053 which attempted to make fallthrough's
syntactically a part of switch statements. Because they may be
labeled, fixing that CL completely would require too much spec
surgery.

Fixes #4923.

R=r, iant, rsc, ken
CC=golang-dev
https://golang.org/cl/7416048
This commit is contained in:
Robert Griesemer 2013-03-01 16:45:14 -08:00
parent f235d5d8d7
commit 67a6b4f0ef

View File

@ -1,6 +1,6 @@
<!--{
"Title": "The Go Programming Language Specification",
"Subtitle": "Version of February 11, 2013",
"Subtitle": "Version of March 1, 2013",
"Path": "/ref/spec"
}-->
@ -4154,12 +4154,14 @@ ExprSwitchCase = "case" ExpressionList | "default" .
</pre>
<p>
In a case or default clause,
the last statement only may be a "fallthrough" statement
<a href="#Fallthrough_statements">Fallthrough statement</a>) to
In a case or default clause, the last non-empty statement
may be a (possibly <a href="#Labeled_statements">labeled</a>)
<a href="#Fallthrough_statements">"fallthrough" statement</a> to
indicate that control should flow from the end of this clause to
the first statement of the next clause.
Otherwise control flows to the end of the "switch" statement.
A "fallthrough" statement may appear as the last statement of all
but the last clause of an expression switch.
</p>
<p>
@ -4798,9 +4800,8 @@ the "for" statement's block but the <code>goto</code> is not.
<p>
A "fallthrough" statement transfers control to the first statement of the
next case clause in a expression "switch" statement (§<a href="#Expression_switches">Expression switches</a>). It may
be used only as the final non-empty statement in a case or default clause in an
expression "switch" statement.
next case clause in a <a href="#Expression_switches">expression "switch" statement</a>.
It may be used only as the final non-empty statement in such a clause.
</p>
<pre class="ebnf">