Default value for input argument not bound to schema

[beneshed]

I have a schema like the following

enum FooEnum {
   FOO
   BAR
}
input FooBarInput {
    foo: FooEnum! = FOO
}

extend type mutation {
foo(input: FooBarInput): Boolean!
}

But when calling the mutation FOO is not passed as an argument and the resolver fails

[rafalp]

Duplicate of #293

[rafalp]

Ok, not exact duplicate, but same source and same fix, so I've updated #293 instead to track both of those. ;)

Thanks!