diamond1.lean:11:40-11:45: error: parent field type mismatch, field 'a' from parent 'Baz' has type
  α → α : Type
but is expected to have type
  α : Type
structure Foo (α : Type) : Type
number of parameters: 1
parents:
  Foo.toBar : Bar (α → α)
  Foo.toBaz : Baz α
fields:
  Bar.a : α → α
  Bar.b : Nat → α → α
  Baz.c : Bool → α
  Baz.d : Nat
constructor:
  Foo.mk {α : Type} (toBar : Bar (α → α)) (c : Bool → α) (d : Nat) : Foo α
field notation resolution order:
  Foo, Bar, Baz
def f : Nat → Foo Nat :=
fun x => { a := fun y => x + y, b := fun x1 x2 => x1 + x2, c := fun x_1 => x, d := x }
diamond1.lean:27:47-27:52: warning: field 'a' from 'Baz' has already been declared