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.
41 lines
1.2 KiB
Text
41 lines
1.2 KiB
Text
set_option pp.mvars false
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def Additive (α : Type) := α
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instance [OfNat α 1] : OfNat (Additive α) (nat_lit 0) := ⟨(1 : α)⟩
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example : (0 : Nat) = (0 : Additive Nat) := rfl -- Error
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def toA (a : Nat) : Additive Nat := a
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def Foo (α : Type) := α
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instance [OfNat α n] : OfNat (Foo α) n :=
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inferInstanceAs (OfNat α n)
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instance [HAdd α α α] : HMul (Foo α) (Foo α) (Foo α) where
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hMul a b := let a : α := a; let b : α := b; let x : α := a + b; x
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instance [HAdd α α α] : HSub (Foo α) (Foo α) (Foo α) where
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hSub a b := let a : α := a; let b : α := b; let x : α := a + b; x
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instance [HAdd α α α] : HAdd (Foo α) (Foo α) (Foo α) where
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hAdd a b := let a : α := a; let b : α := b; let x : α := a + b + a; x
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example : (2 : Nat) * (3 : Nat) = (2 : Foo Nat) * (3 : Foo Nat) :=
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rfl -- Error
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example : (2 : Nat) + (3 : Nat) = (2 : Foo Nat) + (3 : Foo Nat) :=
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rfl -- Error
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example : (2 : Nat) - (3 : Nat) = (2 : Foo Nat) - (3 : Foo Nat) :=
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rfl -- Error
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example : (2 : Nat) + (3 : Nat) = (2 : Foo Nat) * (3 : Foo Nat) :=
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rfl
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example : (2 : Nat) + (3 : Nat) + (2 : Nat) = (2 : Foo Nat) + (3 : Foo Nat) :=
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rfl
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example : (2 : Nat) + (3 : Nat) = (2 : Foo Nat) - (3 : Foo Nat) :=
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rfl
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