implicitly shared type variable

[Roger-luo]

if two parameteric types are used within same statement, e.g

class MyStatemet:
    lhs: ir.SSAValue = info.argument(ilist.IListType[Tuple[Float, Float]])
    rhs: ir.SSAValue = info.argument(ilist.IListType[Tuple[Float, Float]])

this implicitly shared the length parameter because IListType is declared with the same object, however, if not explicitly specified one would expect this not sharing the same type variable. This should be considered a bug and we should fix it.

cc: @kaihsin