swift234

Collect all of the constraints that relate directly to a type
variable T, e.g.,  T < Int or T << Int. Use this information to
eliminate redundant constraints, such as "T << Int" in the above
example (since subtyping is a stronger constraint than
convertibility). 

Today's fun little constraint system:

func f<T>(x : T, fn : (T) -> T) {}

var i : Int
var fnii : (Int) -> Int
:dump_constraints f(i, fnii)

---Initial constraints for the given expression---
(call_expr type='<null>'
  (declref_expr type='<T> (x : T, fn : (T) -> T) -> ()' decl=f)
  (tuple_expr type='<null>'
    (declref_expr type='[byref(heap)] Int' decl=i)
    (declref_expr type='[byref(heap)] (Int) -> Int' decl=fnii)))

Type Variables:
  $T0
  $T1
  $T2

Constraints:
  (x : $T0, fn : ($T0) -> $T0) -> () == $T1 -> $T2
  ([byref(heap)] Int, [byref(heap)] (Int) -> Int) << $T1
---Simplified constraints---
Type Variables:
  $T0
  $T1 as (x : $T0, fn : $T0 -> $T0)
  $T2 as ()

Constraints:
  $T0 < Int64
  Int64 < $T0

Constraint system is still viable



Swift SVN r2654