Bug featuring var, binary relations and a specific field name

[grayswandyr]

var sig T {}
one sig S { Next: T->T } 
run {} 

yields an error.

Remove var: no error.

sig T {}
one sig S { Next: T->T } 
run {} 

Rename Next: no error.

var sig T {}
one sig S { r: T->T } 
run {} 

Make Next unary: no error

var sig T {}
one sig S { Next: T } 
run {} 

Make Next ternary: no error

var sig T {}
one sig S { Next: T->T->T } 
run {}