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new, stricter interface rule:

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in x.(T) x cannot be a nil (uninitialized) interface variable.

remove TODO per discussion.

DELTA=3  (1 added, 1 deleted, 1 changed)
OCL=29123
CL=29134
This commit is contained in:
Russ Cox 2009-05-20 18:16:04 -07:00
parent 787dd4d3f3
commit b89a54e5c6
1 changed files with 2 additions and 2 deletions
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doc/go_spec.html
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@ -2210,7 +2210,8 @@ x.(T)
</pre> </pre>
<p> <p>
asserts that the value stored in <code>x</code> is of type <code>T</code>. asserts that <code>x</code> is not the zero interface value
and that the value stored in <code>x</code> is of type <code>T</code>.
The notation <code>x.(T)</code> is called a <i>type assertion</i>. The notation <code>x.(T)</code> is called a <i>type assertion</i>.
The type of <code>x</code> must be an interface type. The type of <code>x</code> must be an interface type.
</p> </p>
@ -2220,7 +2221,6 @@ that the dynamic type of <code>x</code> is identical to the type <code>T</code>
(§Type identity and compatibility). (§Type identity and compatibility).
If <code>T</code> is an interface type, <code>x.(T)</code> asserts that the dynamic type If <code>T</code> is an interface type, <code>x.(T)</code> asserts that the dynamic type
of <code>T</code> implements the interface <code>T</code> (§Interface types). of <code>T</code> implements the interface <code>T</code> (§Interface types).
<font color=red>TODO: gri wants an error if x is already of type T.</font>
</p> </p>
<p> <p>
If the type assertion holds, the value of the expression is the value If the type assertion holds, the value of the expression is the value