lean4-htt/tests/lean/struct1.lean
Kyle Miller 675d2d5a11
feat: only direct parents of classes create projections (#5920)
This PR changes the rule for which projections become instances. Before,
all parents along with all indirect ancestors that were represented as
subobject fields would have their projections become instances. Now only
projections for direct parents become instances.

Features:
- Only parents that are not ancestors of other parents get instances.
This allows "discretionary" indirect parents to be inserted for the
purpose of computing strict resolution orders when
`structure.strictResolutionOrder` is enabled, without having an impact
on typeclass synthesis.
- Non-subobject projections are now theorems if the parent is a
proposition. These are also no longer `@[reducible]`.

Closes #2905
2024-11-12 01:55:17 +00:00

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--
structure A (α : Type) where
(x : α)
structure B (α : Type) where
(x : α)
structure S : Nat where -- error expected Type
(x : Nat)
structure S extends Nat → Nat where -- error expected structure
(x : Nat)
set_option structureDiamondWarning true in
structure S' extends A Nat, B Nat where -- error field `x` already declared
(x : Nat)
structure SDup extends A Nat, A Nat where -- duplicate parent structure 'A'
structure S extends A Nat, B Bool where -- error field `x` from `B` has already been declared
(x : Nat)
structure S1 where
(_x : Nat)
structure S2 where
(x _y : Nat)
structure S where
(x : Nat)
(x : Nat) -- error
structure S extends A Nat where
(x : Nat) -- error
structure S' extends A Nat where
(x := true) -- error type mismatch
structure S extends A Nat where
(x : Bool := true) -- error omit type
structure S'' where
(x : Nat := true) -- error type mismatch
private structure S where
private mk :: (x : Nat)
private structure S where
protected mk :: (x : Nat)
private structure S where
protected (x : Nat)
private structure S where
mk2 :: (x : Nat)
#check S
#check S.mk2