IsExpression

[Luís Marques]

Hello,

The documentation of IsExpression lists the following valid forms:

is ( Type )
is ( Type : TypeSpecialization )
is ( Type == TypeSpecialization )
is ( Type Identifier )
is ( Type Identifier : TypeSpecialization )
is ( Type Identifier == TypeSpecialization )

What about the form "expression is expression"? I cannot find 
documentation for that form. What are its semantics? "exp is null" is an 
obvious one. But what about other forms?

- for classes it seems that "obj1 is obj2" is equivalent to "&obj1 == 
&obj2". Can I rely on that? I have a singleton called "nil", so it's 
great being able to say "obj is nil".

- for structs "structvar1 is structvar2" is always true.

- for PODs it seems that values must be semantically equivalent. For 
instance, "1L is 1.0+0i" is true.

Could this be documented?

Also, the IsExpression docs refer to a "Type", which can be an 
identifier (e.g. "int x; writefln(is(x));" is valid, even though the 
form in question is "is(Type)"). Perhaps that could be made more clear?

Regards,
Luis