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The attributes postprocess_with and postprocess_for_extraction_with allow a user to use a custom tactic to transform a definition after typechecking (to something equivalent); usually the used tactic does some controlled normalization and unfolding. However, the tactic is only applied on the body of a letbinding and not the type. This patch adds an attribute `postprocess_type` to indicate that the tactic should be applied to the type too.
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| (* | ||
| Copyright 2008-2018 Microsoft Research | ||
| Licensed under the Apache License, Version 2.0 (the "License"); | ||
| you may not use this file except in compliance with the License. | ||
| You may obtain a copy of the License at | ||
| http://www.apache.org/licenses/LICENSE-2.0 | ||
| Unless required by applicable law or agreed to in writing, software | ||
| distributed under the License is distributed on an "AS IS" BASIS, | ||
| WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| See the License for the specific language governing permissions and | ||
| limitations under the License. | ||
| *) | ||
| module Postprocess | ||
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| open FStar.Tactics.V2 | ||
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| assume val foo : int -> int | ||
| assume val lem : unit -> Lemma (foo 1 == foo 2) | ||
| let tau () = | ||
| grewrite (`(foo 1)) (`(foo 2)); | ||
| trefl (); | ||
| apply_lemma (`lem); | ||
| () | ||
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| [@@postprocess_with tau] | ||
| let x : int = foo 1 | ||
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| [@@postprocess_with tau] | ||
| let x' : (z:int{z == foo 1}) = foo 1 | ||
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| [@@postprocess_with tau; postprocess_type] | ||
| let x'' : (z:int{z == foo 1}) = foo 1 | ||
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| [@@(postprocess_for_extraction_with tau)] | ||
| let y : int = foo 1 | ||
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| let _ = assert (x == foo 2) | ||
| let _ = assert (y == foo 1) // but `foo 2` in extracted code | ||
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| (* More hardcore transformations *) | ||
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| noeq | ||
| type t1 = | ||
| | A1 : t1 | ||
| | B1 : int -> t1 | ||
| | C1 : (int -> t1) -> t1 | ||
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| noeq | ||
| type t2 = | ||
| | A2 : t2 | ||
| | B2 : int -> t2 | ||
| | C2 : (int -> t2) -> t2 | ||
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| let rec lift : t1 -> t2 = | ||
| function | ||
| | A1 -> A2 | ||
| | B1 i -> B2 i | ||
| | C1 f -> C2 (fun x -> lift (f x)) | ||
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| let lemA () : Lemma (lift A1 == A2) = () | ||
| let lemB x : Lemma (lift (B1 x) == (B2 x)) = () | ||
| let lemC ($f: int -> t1) : Lemma (lift (C1 f) == C2 (fun x -> lift (f x))) by (compute ()) = () | ||
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| (* These could really be polymorphic *) | ||
| let congB #i #j (_ : squash (i == j)) : Lemma (B2 i == B2 j) = () | ||
| let congC #f #g (_ : squash (f == g)) : Lemma (C2 f == C2 g) = () | ||
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| let xx = C1 (function | ||
| | 0 -> A1 | ||
| | 5 -> B1 42 | ||
| | x -> B1 24) | ||
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| open FStar.FunctionalExtensionality | ||
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| let q_as_lem (#a:Type) (#b:a -> Type) (p:squash (forall x. b x)) (x:a) | ||
| : Lemma (b x) | ||
| = () | ||
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| let congruence_fun #a (#b:a -> Type) (f g:(x:a -> b x)) (x:squash (forall x. f x == g x)) : | ||
| Lemma (ensures (fun (x:a) -> f x) == (fun (x:a) -> g x)) = | ||
| assert ((fun (x:a) -> f x) == (fun (x:a) -> g x)) | ||
| by (l_to_r [quote (q_as_lem x)]; | ||
| trefl()) | ||
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| let apply_feq_lem #a #b ($f $g : a -> b) : Lemma (requires (forall x. f x == g x)) | ||
| (ensures ((fun x -> f x) == (fun x -> g x))) = congruence_fun f g () | ||
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| let fext () = apply_lemma (`apply_feq_lem); dismiss (); ignore (forall_intros ()) | ||
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| let _onL a b c (_ : squash (a == b)) (_ : squash (b == c)) : Lemma (a == c) = () | ||
| let onL () = apply_lemma (`_onL) | ||
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| // invariant: takes goals of shape squash (E == ?u) and solves them | ||
| let rec push_lifts' (u:unit) : Tac unit = | ||
| match term_as_formula (cur_goal ()) with | ||
| | Comp (Eq _) lhs rhs -> | ||
| begin | ||
| match inspect lhs with | ||
| | Tv_App h t -> | ||
| begin match inspect h with | ||
| | Tv_FVar fv -> | ||
| if fv_to_string fv = `%lift | ||
| then case_analyze (fst t) | ||
| else fail "not a lift (1)" | ||
| | _ -> fail "not a lift (2)" | ||
| end | ||
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| | Tv_Abs _ _ -> | ||
| fext (); | ||
| push_lifts' () | ||
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| | _ -> fail "not a lift (3)" | ||
| end | ||
| | _ -> | ||
| fail "not an equality" | ||
| and case_analyze (lhs:term) : Tac unit = | ||
| let ap l = | ||
| onL (); apply_lemma l | ||
| in | ||
| let lhs = norm_term [weak;hnf;primops;delta] lhs in | ||
| let head, args = collect_app lhs in | ||
| begin match inspect head with | ||
| | Tv_FVar fv -> | ||
| if fv_to_string fv = `%A1 then (apply_lemma (`lemA)) | ||
| else if fv_to_string fv = `%B1 then (ap (`lemB); apply_lemma (`congB); push_lifts' ()) | ||
| else if fv_to_string fv = `%C1 then (ap (`lemC); apply_lemma (`congC); push_lifts' ()) | ||
| else (tlabel "unknown fv"; trefl ()) | ||
| | _ -> | ||
| tlabel "head unk"; | ||
| trefl () | ||
| end | ||
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| let push_lifts () : Tac unit = | ||
| push_lifts' (); | ||
| (* dump "after"; *) | ||
| () | ||
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| //#push-options "--tactic_trace_d 2" | ||
| [@@(postprocess_with push_lifts)] | ||
| let yy = lift xx | ||
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| [@@(postprocess_with push_lifts)] | ||
| let zz1 = lift (C1 (fun y -> (C1 (fun x -> A1)))) | ||
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| [@@(postprocess_for_extraction_with push_lifts)] | ||
| let zz2 = lift (C1 (fun y -> (C1 (fun x -> A1)))) |
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