[Issue 6942] lazy parameters can break purity

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http://d.puremagic.com/issues/show_bug.cgi?id=6942


Kenji Hara k.hara...@gmail.com changed:

   What|Removed |Added

 Status|NEW |RESOLVED
 Resolution||INVALID


--- Comment #2 from Kenji Hara k.hara...@gmail.com 2011-12-02 18:56:15 PST ---
The pureness of lazy parameter belongs to the *caller side*, not callee side.
It is a design.

One use case is std.exception.enforce. It receives a condition as a lazy
parameter, but whole enforce function can become pure with the design.

Delegate parameter is similar to lazy parameter, but it is different in this
point.

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[Issue 6942] lazy parameters can break purity

[d-bugmail]

http://d.puremagic.com/issues/show_bug.cgi?id=6942



--- Comment #1 from timon.g...@gmx.ch 2011-11-13 04:54:18 PST ---
note that

int foo(int delegate() x) pure{
return x()+x();
}

void main(){
auto a=foo({return writeln(impure),1;});
}

fails with

Error: pure function 'foo' cannot call impure delegate 'x'

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