Preconditions.checkArgument and Scala

[Blair Zajac]

With both Scala 2.7.7 and 2.8.0, the following fails to compile:

scala> import com.google.common.base.Preconditions.checkArgument
import com.google.common.base.Preconditions.checkArgument

scala> checkArgument(! Nil.isEmpty, "failure")
<console>:6: error: ambiguous reference to overloaded definition,
both method checkArgument in object Preconditions of type
(Boolean,java.lang.String,java.lang.Object*)Unit
and method checkArgument in object Preconditions of type (Boolean,Any)Unit
match argument types (Boolean,java.lang.String)
checkArgument(! Nil.isEmpty, "scdc")

It would be nice to have this cleanly work with Scala. Any suggestions besides
adding an empty array as a third argument?

BTW, I would put this up on StackOverflow, but this appears to have a change to
Guava to make this work, more than having it work in my code.

What about adding Preconditions.checkArgument() that takes a boolean and a
String, not an Object?

Blair

[Gary Pampara]

Until this is sorted in some way (although the error the scala
compiler provides is completely valid, so I don't really know if it
would be worth the effort for Guava to change to support this),
perhaps you could consider using Scala's require() instead, which is a
language feature.

Have a look here:
http://daily-scala.blogspot.com/2010/03/assert-require-assume.html

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[Kevin Bourrillion]

Shouldn't scala match Java's overload-resolution rules?

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[Blair Zajac]

On 09/13/2010 10:22 PM, Gary Pampara wrote:
> Until this is sorted in some way (although the error the scala
> compiler provides is completely valid, so I don't really know if it
> would be worth the effort for Guava to change to support this),
> perhaps you could consider using Scala's require() instead, which is a
> language feature.

The reason that I don't use require is that it prepends the some text to
the exception message text that I don't want:

def require(requirement: Boolean) {
if (!requirement)
throw new IllegalArgumentException("requirement failed")
}

def require(requirement: Boolean, message: Any) {
if (!requirement)
throw new IllegalArgumentException("requirement failed: "+ message)
}

Kinda minor thing, but it bugs me if I want to customize an exception
message that is thrown to client code.

Blair

[ray.j.greenwell]

On Sep 13, 9:16 pm, Blair Zajac <bl...@orcaware.com> wrote:

> It would be nice to have this cleanly work with Scala.  Any suggestions besides
> adding an empty array as a third argument?

checkArgument(! Nil.isEmpty, (Object) "scdc");