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Change 'switch' not to fall through between empty cases and always require at

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least one statement per case

rdar://16301313


Swift SVN r15266
This commit is contained in:
Dmitri Hrybenko
2014-03-20 11:44:59 +00:00
parent bf2568f8e9
commit 11fea869c1
16 changed files with 402 additions and 407 deletions
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27
docs/LangRefNew.rst
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@@ -1250,9 +1250,9 @@ The 'continue' statement transfers control back to the start of the enclosing
.. code-block:: none
stmt-switch ::= 'switch' expr-basic '{' stmt-switch-case* '}'
stmt-switch-case ::= (case-label+ | default-label) brace-item*
stmt-switch-case ::= (case-label | default-label) brace-item+
case-label ::= 'case' pattern (',' pattern)* ('where' expr)? ':'
case-label ::= 'case' pattern ('where' expr)? (',' pattern ('where' expr)?)* ':'
default-label ::= 'default' ':'
'switch' statements branch on the value of an expression by :ref:`pattern
@@ -1260,15 +1260,15 @@ matching <langref.pattern>`. The subject expression of the switch is evaluated
and tested against the patterns in its ``case`` labels in source order. When a
pattern is found that matches the value, control is transferred into the
matching ``case`` block. ``case`` labels may declare multiple patterns
separated by commas, and multiple ``case`` labels may cover a case block. Case
labels may optionally specify a *guard* expression, introduced by the ``where``
keyword; if present, control is transferred to the case only if the subject
value both matches one of its patterns and the guard expression evaluates to
true. Patterns are tested "as if" in source order; if multiple cases can match
a value, control is transferred only to the first matching case. The actual
execution order of pattern matching operations, and in particular the
evaluation order of :ref:`expression patterns <langref.pattern.expr>`, is
unspecified.
separated by commas. Only a single ``case`` labels may precede a block of
code. Case labels may optionally specify a *guard* expression, introduced by
the ``where`` keyword; if present, control is transferred to the case only if
the subject value both matches the corresponding pattern and the guard
expression evaluates to true. Patterns are tested "as if" in source order; if
multiple cases can match a value, control is transferred only to the first
matching case. The actual execution order of pattern matching operations, and
in particular the evaluation order of :ref:`expression patterns
<langref.pattern.expr>`, is unspecified.
A switch may also contain a ``default`` block. If present, it receives control
if no cases match the subject value. The ``default`` block must appear at the
@@ -1291,9 +1291,12 @@ transfer control among case blocks. :ref:`break <langref.stmt.break>` and
:ref:`continue <langref.stmt.continue>` within a switch will break or continue
out of an enclosing 'while' or 'for' loop, not out of the 'switch' itself.
At least one ``brace-item`` is required in every case or default block. It is
allowed to be a no-op.
::
func classifyPoint(point:(Int, Int)) {
func classifyPoint(point: (Int, Int)) {
switch point {
case (0, 0):
println("origin")