lean4-htt/tests/lean/439.lean
2021-08-03 09:13:18 +02:00

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set_option pp.analyze.trustCoe true
universe u
structure Fn (E I : Sort u) := (exp : E) (imp : I)
instance (E I : Sort u) : CoeFun (Fn E I) (fun _ => I) := {coe := fun K => K.imp}
class Bar.{w} (P : Sort u) :=
fn : P -> Sort w
variable {P : Sort u} (B : Bar P)
variable (fn : Fn ((p : P) -> B.fn p) ({p : P} -> B.fn p))
#check coeFun fn -- Result is as expected (implicit)
/-
fn : {p : P} → Bar.fn p
-/
variable (p : P)
variable (Bp : Bar.fn p)
#check fn Bp
/-
application type mismatch
Fn.imp fn Bp
argument
Bp
has type
Bar.fn p : Sort ?u.635
but is expected to have type
P : Sort u
-/
#check fn p
#check fn (p := p)
variable (fn' : Fn ((p : P) -> B.fn p -> B.fn p) ({p : P} -> B.fn p -> B.fn p))
-- Expect no error
#check fn' Bp
-- Expect error
#check fn' p