4606c35c40
This PR adds the new transparency setting `@[instance_reducible]`. We
used to check whether a declaration had `instance` reducibility by using
the `isInstance` predicate. However, this was not a robust solution
because:
- We have scoped instances, and `isInstance` returns `true` only if the
scope is active.
- We have auxiliary declarations used to construct instances manually,
such as:
```lean
def lt_wfRel : WellFoundedRelation Nat
```
`isInstance` also returns `false` for this kind of declaration.
In both cases, the declaration may be (or may have been) used to
construct an instance, but `isInstance`
returns `false`. Thus, we claim it is a mistake to check the
reducibility status using `isInstance`.
`isInstance` indicates whether a declaration is available for the type
class resolution mechanism,
not its transparency status.
**We are decoupling whether a declaration is available for type class
resolution from its transparency status.**
**Remak**: We need a update stage0 to complete this feature.
---------
Co-authored-by: Sebastian Ullrich <sebasti@nullri.ch>
65 lines
1.9 KiB
Text
65 lines
1.9 KiB
Text
import Lean
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namespace A
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structure A (α : Type u) where
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a : α
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deriving Lean.ToExpr, Inhabited
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-- same namespace for instance and aux decls
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/--
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info: @[instance_reducible] def A.instToExprA.{u} : {α : Type u} → [Lean.ToExpr α] → [Lean.ToLevel] → Lean.ToExpr (A α) :=
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fun {α} [Lean.ToExpr α] [inst_1 : Lean.ToLevel] =>
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{ toExpr := instToExprA.toExpr inst_1, toTypeExpr := (Lean.Expr.const `A.A [Lean.toLevel]).app (Lean.toTypeExpr α) }
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-/
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#guard_msgs in #print A.instToExprA
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/--
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info: @[instance_reducible] def A.instInhabitedA.{u_1} : {a : Type u_1} → [Inhabited a] → Inhabited (A a) :=
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fun {a} [Inhabited a] => { default := instInhabitedA.default }
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-/
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#guard_msgs in #print A.instInhabitedA
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end A
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mutual
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inductive B (α : Type u) : Type _ where
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| leaf
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| mk (a : C α)
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deriving Lean.ToExpr, Inhabited
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inductive C (α : Type u) : Type _ where
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| mk (b : B α)
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deriving Lean.ToExpr, Inhabited
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end
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/--
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info: @[instance_reducible] def instToExprB.{u} : {α : Type u} → [Lean.ToExpr α] → [Lean.ToLevel] → Lean.ToExpr (B α) :=
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fun {α} [Lean.ToExpr α] [inst_1 : Lean.ToLevel] =>
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{ toExpr := instToExprB.toExpr_1 inst_1, toTypeExpr := (Lean.Expr.const `B [Lean.toLevel]).app (Lean.toTypeExpr α) }
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-/
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#guard_msgs in
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#print instToExprB
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/--
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info: @[instance_reducible] def instToExprC.{u} : {α : Type u} → [Lean.ToExpr α] → [Lean.ToLevel] → Lean.ToExpr (C α) :=
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fun {α} [Lean.ToExpr α] [inst_1 : Lean.ToLevel] =>
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{ toExpr := instToExprB.toExpr_2 inst_1, toTypeExpr := (Lean.Expr.const `C [Lean.toLevel]).app (Lean.toTypeExpr α) }
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-/
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#guard_msgs in
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#print instToExprC
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/--
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info: @[instance_reducible] def instInhabitedB.{u_1} : {a : Type u_1} → Inhabited (B a) :=
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fun {a} => { default := instInhabitedB.default_1 }
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-/
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#guard_msgs in
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#print instInhabitedB
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/--
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info: @[instance_reducible] def instInhabitedC.{u_1} : {a : Type u_1} → Inhabited (C a) :=
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fun {a} => { default := instInhabitedC.default_1 }
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-/
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#guard_msgs in
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#print instInhabitedC
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