lean2/tests/lean/cast4.lean

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import cast
set::option pp::colors false
check fun (A A': TypeM)
(B : A -> TypeM)
(B' : A' -> TypeM)
(f : forall x : A, B x)
(g : forall x : A', B' x)
(a : A)
(b : A')
(H1 : (forall x : A, B x) == (forall x : A', B' x))
(H2 : f == g)
(H3 : a == b),
let
S1 : (forall x : A', B' x) == (forall x : A, B x) := symm H1,
L2 : A' == A := dominj S1,
b' : A := cast L2 b,
L3 : b == b' := cast::eq L2 b,
L4 : a == b' := htrans H3 L3,
L5 : f a == f b' := congr2 f L4,
g' : (forall x : A, B x) := cast S1 g,
L6 : g == g' := cast::eq S1 g,
L7 : f == g' := htrans H2 L6,
L8 : f b' == g' b' := congr1 b' L7,
L9 : f a == g' b' := htrans L5 L8,
L10 : g' b' == g b := cast::app S1 L2 g b
in htrans L9 L10