675d2d5a11
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
45 lines
1.2 KiB
Text
45 lines
1.2 KiB
Text
import Lean
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/-!
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# Only direct parents of classes are instances
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https://github.com/leanprover/lean4/issues/2905
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-/
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set_option structure.strictResolutionOrder true
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class A
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class B
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class C extends A
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class D extends A, B
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class E extends C, D
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/-!
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These were or were not instances before #5902 and still are or are not.
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-/
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/-- info: some 1000 -/
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#guard_msgs in #eval return (←Lean.Meta.getInstancePriority? `E.toC)
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/-- info: some 1000 -/
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#guard_msgs in #eval return (←Lean.Meta.getInstancePriority? `E.toD)
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/-- info: none -/
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#guard_msgs in #eval return (←Lean.Meta.getInstancePriority? `E.toA)
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/-!
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This was an instance before #5902 and no longer is.
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-/
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/-- info: none -/
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#guard_msgs in #eval return (←Lean.Meta.getInstancePriority? `E.toB)
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/-!
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Check that `A` is not an instance, since it is implied by the others.
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-/
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class E' extends C, D, A
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/-- info: none -/
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#guard_msgs in #eval return (←Lean.Meta.getInstancePriority? `E'.toA_1)
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/-- info: none -/
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#guard_msgs in #eval return (←Lean.Meta.getInstancePriority? `E'.toB)
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/-- info: some 1000 -/
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#guard_msgs in #eval return (←Lean.Meta.getInstancePriority? `E'.toC)
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/-- info: some 1000 -/
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#guard_msgs in #eval return (←Lean.Meta.getInstancePriority? `E'.toD)
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