Special case type constraint to just _ (underscore)

[robfletcher]

Originally reported on Google Code with ID 376

`as Foo` has a special meaning in an argument constraint, namely “argument of type Foo".
The common way to use it is `_ as Set` (“any argument of type Foo”). Perhaps we should
limit the special meaning to `_`, as I don't see much value in mixing a type constraint
with equality or closure constraints. (from pniederw@gmail.com)

Reported by quidryan on 2014-10-13 04:26:55

[robfletcher]

I'm trying to match a Set as an argument, e.g.

    class Container {
        def call(Set<String> args) {
            println args
        }
    }

    def 'simple argument constraint'() {
        setup:
        def container = Mock(Container)

        when:
        container.call(['val1'] as Set)

        then:
        1 * container.call(['val1'] as Set)
    }

But it results in a failure:

Too few invocations for:

1 * container.call(['val1'] as Set)   (0 invocations)

Unmatched invocations (ordered by similarity):

1 * container.call(['val1'])

A little investigation shows that the constraint in TypeArgumentConstraint has the
type correct as Set, but the constraint is an EqualArgumentConstraint with a List in
it. I've tried some variations, like parentheses, but Spock is just too smart. I can
assign the argument to a variable first or use the closure syntax for the argument,
but I'd like to avoid doing it and keep it simple like above. Any suggestions?

Reported by quidryan on 2014-10-13 04:27:33

[robfletcher]

A good workaround is to use `['val1'].toSet()`, rather than `['val1'] as Set`.

Reported by pniederw on 2015-03-03 02:56:48