d85c30fde1
Without these annotations, Lean will timeout when trying to synthesize the type class instance `decidable_eq uint32`. The type class resolution problem will produce the unification problem: ``` decidable (@eq uint32 a b) =?= decidable (@eq usize ?x ?y) ``` which Lean tries to solve by assigning `?x := a`. During the assignment, the types of `?x` and `a` are unified with "full force". Thus, we get the constraint ``` usize_sz =?= uint32_sz ``` which will take forever to be solved when peforming the computation in unary arithmetic. Remark: this commit also makes sure that `type_context` will not unfold irreducible definitions when trying to unify/match the types. The new test `type_class_performance1.lean` exposes the problem fixed by this commit.
77 lines
2.6 KiB
Text
77 lines
2.6 KiB
Text
/-
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Copyright (c) 2016 Microsoft Corporation. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Author: Leonardo de Moura
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-/
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prelude
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import init.data.string.basic init.data.uint init.data.nat.div init.data.repr
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open sum subtype nat
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universes u v
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class has_to_string (α : Type u) :=
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(to_string : α → string)
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def to_string {α : Type u} [has_to_string α] : α → string :=
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has_to_string.to_string
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instance : has_to_string string :=
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⟨λ s, s⟩
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instance : has_to_string string.iterator :=
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⟨λ it, it.next_to_string⟩
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instance : has_to_string bool :=
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⟨λ b, cond b "tt" "ff"⟩
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instance {p : Prop} : has_to_string (decidable p) :=
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-- Remark: type class inference will not consider local instance `b` in the new elaborator
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⟨λ b : decidable p, @ite p b _ "tt" "ff"⟩
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protected def list.to_string_aux {α : Type u} [has_to_string α] : bool → list α → string
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| b [] := ""
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| tt (x::xs) := to_string x ++ list.to_string_aux ff xs
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| ff (x::xs) := ", " ++ to_string x ++ list.to_string_aux ff xs
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protected def list.to_string {α : Type u} [has_to_string α] : list α → string
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| [] := "[]"
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| (x::xs) := "[" ++ list.to_string_aux tt (x::xs) ++ "]"
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instance {α : Type u} [has_to_string α] : has_to_string (list α) :=
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⟨list.to_string⟩
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instance : has_to_string unit :=
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⟨λ u, "()"⟩
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instance : has_to_string nat :=
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⟨λ n, repr n⟩
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instance : has_to_string char :=
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⟨λ c, c.to_string⟩
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instance (n : nat) : has_to_string (fin n) :=
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⟨λ f, to_string (fin.val f)⟩
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instance : has_to_string uint16 :=
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⟨λ n, to_string n.to_nat⟩
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instance : has_to_string uint32 :=
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⟨λ n, to_string n.to_nat⟩
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instance : has_to_string uint64 :=
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⟨λ n, to_string n.to_nat⟩
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instance {α : Type u} [has_to_string α] : has_to_string (option α) :=
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⟨λ o, match o with | none := "none" | (some a) := "(some " ++ to_string a ++ ")"⟩
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instance {α : Type u} {β : Type v} [has_to_string α] [has_to_string β] : has_to_string (α ⊕ β) :=
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⟨λ s, match s with | (inl a) := "(inl " ++ to_string a ++ ")" | (inr b) := "(inr " ++ to_string b ++ ")"⟩
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instance {α : Type u} {β : Type v} [has_to_string α] [has_to_string β] : has_to_string (α × β) :=
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⟨λ ⟨a, b⟩, "(" ++ to_string a ++ ", " ++ to_string b ++ ")"⟩
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instance {α : Type u} {β : α → Type v} [has_to_string α] [s : ∀ x, has_to_string (β x)] : has_to_string (sigma β) :=
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⟨λ ⟨a, b⟩, "⟨" ++ to_string a ++ ", " ++ to_string b ++ "⟩"⟩
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instance {α : Type u} {p : α → Prop} [has_to_string α] : has_to_string (subtype p) :=
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⟨λ s, to_string (val s)⟩
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