2f5c7d0465
This PR fixes a bug with the `structure`/`class` command where if there are parents that are not represented as subobjects but which used other parents as instances, then there would be a kernel error. Closes #2611. Note: there is still the limitation that parents that are not represented as subobjects do not themselves provide instances to other parents.
50 lines
1.3 KiB
Text
50 lines
1.3 KiB
Text
/-!
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# Structure copied parents should be able to refer to other parents as instances
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Issue: https://github.com/leanprover/lean4/issues/2611
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-/
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/-!
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Example that worked before the fixes for 2611. The projection `D.toC` refers to `D.toA` for the `A` instance.
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This is a natural consequence to the way subobject projection functions are added by `mkProjections`.
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-/
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class A
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class C [A]
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class D extends A, C
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/-!
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This example did not work. Since `C` provides a `B` field, it's a copied parent.
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Now there is a step where the fvar for the `A` instance is replaced by the `D.toA` constant.
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-/
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namespace Ex2
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class A
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class B
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class C [A] extends B
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class D extends A, B, C
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end Ex2
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/-!
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A test that this still works even when there are parameters on the structure.
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-/
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namespace Ex3
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class A where
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x : Nat
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class B [A] where
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x : Nat
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class C (α : Type) extends A, B where
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y : α
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/-- info: Ex3.C.toB {α : Type} [self : C α] : @B (@C.toA α self) -/
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#guard_msgs in set_option pp.explicit true in #check C.toB
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end Ex3
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/-!
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A test that this still works even when there are parameters on the parents.
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-/
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namespace Ex4
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class A (n : Nat) where
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x : Nat
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class B (n : Nat) [A n] where
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x : Nat
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class C extends A 3, B 3
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/-- info: Ex4.C.toB [self : C] : @B (@OfNat.ofNat Nat 3 (instOfNatNat 3)) (@C.toA self) -/
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#guard_msgs in set_option pp.explicit true in #check C.toB
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end Ex4
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