36 lines
830 B
Text
36 lines
830 B
Text
structure A :=
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(a : Nat)
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structure B :=
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(a : Nat)
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structure C :=
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(a : Nat)
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instance : Coe A B := ⟨fun s => ⟨s.1⟩⟩
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instance : Coe A C := ⟨fun s => ⟨s.1⟩⟩
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def f {α} (a b : α) := a
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def forceB {α} (b : B) (a : α) := a
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def forceC {α} (c : C) (a : α) := a
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def forceA {α} (a : A) (o : α) := o
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def f1 (x : _) (y : _) (z : _) :=
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let a1 := f x y;
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let a2 := f y z;
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forceB x a1 -- works
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def f2 (x : _) (y : _) (z : _) :=
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let a1 := f x ↑y;
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let a2 := f ↑y z;
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forceB x (forceC z (forceA y (a1, a2))) -- works because we manually added the coercions above
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#exit
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def f3 (x : _) (y : _) (z : _) :=
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let a1 := f x y;
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let a2 := f y z;
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/- Fails because we "missed" the opportunity to insert coercions around `y`.
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I think we should **not** support this kind of example. -/
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forceB x (forceC z (forceA y (a1, a2)))
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