28cf146d00
This PR fixes a bug where the monad lift coercion elaborator would partially unify expressions even if they were not monads. This could be taken advantage of to propagate information that could help elaboration make progress, for example the first `change` worked because the monad lift coercion elaborator was unifying `@Eq _ _` with `@Eq (Nat × Nat) p`: ```lean example (p : Nat × Nat) : p = p := by change _ = ⟨_, _⟩ -- used to work (yielding `p = (p.fst, p.snd)`), now it doesn't change ⟨_, _⟩ = _ -- never worked ``` As such, this is a breaking change; you may need to adjust expressions to include additional implicit arguments.
56 lines
1.2 KiB
Text
56 lines
1.2 KiB
Text
import Lean.Elab.Command
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set_option pp.mvars false
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/--
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error: application type mismatch
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⟨Nat.lt_irrefl (?_ n), Fin.is_lt ?_⟩
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argument
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Fin.is_lt ?_
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has type
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↑?_ < ?_ : Prop
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but is expected to have type
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?_ n < ?_ n : Prop
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-/
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#guard_msgs in
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def foo := fun n => (not_and_self_iff _).mp ⟨Nat.lt_irrefl _, Fin.is_lt _⟩
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/--
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error: type mismatch
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Fin.is_lt ?_
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has type
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↑?_ < ?_ : Prop
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but is expected to have type
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?_ < ?_ : Prop
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---
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error: unsolved goals
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case a
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⊢ Nat
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this : ?_ < ?_
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⊢ True
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-/
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#guard_msgs in
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def test : True := by
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have : ((?a : Nat) < ?a : Prop) := by
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refine Fin.is_lt ?_
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done
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done
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open Lean Meta
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/--
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info: Defeq?: false
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---
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info: fun x_0 x_1 => x_1
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-/
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#guard_msgs in
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run_meta do
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let mvarIdNat ← mkFreshExprMVar (.some (.const ``Nat []))
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let mvarIdFin ← mkFreshExprMVar (.some (.app (.const `Fin []) mvarIdNat))
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-- mvarIdNat.assign (.app (.const ``Fin.val []) mvaridFin))
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let b ← isDefEq mvarIdNat (mkApp2 (.const ``Fin.val []) mvarIdNat mvarIdFin)
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logInfo m!"Defeq?: {b}" -- prints true
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-- Now mvaridNat occurs in its own type
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-- This will stack overflow
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let r ← abstractMVars mvarIdFin (levels := false)
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logInfo m!"{r.expr}"
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