coq-lib.elpi

/* coq-elpi: Coq terms as the object language of elpi                        */
/* license: GNU Lesser General Public License Version 2.1 or later           */
/* ------------------------------------------------------------------------- */

shorten std.{fatal-error, fatal-error-w-data, debug-print, unsafe-cast}.
shorten std.{rev, map, append, appendR, map2, forall-ok, take, do-ok!, lift-ok}.

:before "default-fatal-error"
fatal-error Msg :- !, M is "elpi: " ^ Msg, stop M.

:before "default-fatal-error-w-data"
fatal-error-w-data Msg Data :- !,
  term_to_string Data DataS,
  M is "elpi: " ^ Msg ^ ": " ^ DataS, stop M.

:before "default-debug-print"
debug-print Msg Data :- !, M is "elpi: " ^ Msg, coq.say M Data.

% HACK: elpi's stop has no argument
type stop string -> prop.
stop S :- halt S.

% TODO: move to elpi proper
pred map-ok i:list A, i:(A -> B -> diagnostic -> prop), o:list A, o:diagnostic.
map-ok [X|L] P [Y|YS] S :- P X Y S0, if (S0 = ok) (map-ok L P YS S) (S = S0).
map-ok [] _ [] ok.


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Helpers
%
% Pure LP code that works with the data types and API above.
% Named clauses are natural extension points, eg one can extend
% subst-prod to perform reduction in order to expose a "prod" node.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% Term surgery %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

pred coq.subst-prod i:list term, i:term, o:term.
coq.subst-prod [] P P :- !.
coq.subst-prod [X|XS] (prod _ _ F) P :- !, coq.subst-prod XS (F X) P.
coq.subst-prod XS (let _ _ X F) P :- !, coq.subst-prod XS (F X) P.
:name "subst-prod:fail"
coq.subst-prod [_|_] T _ :- !,
  fatal-error-w-data "subst-prod: not a product" T.

pred coq.subst-fun i:list term, i:term, o:term.
coq.subst-fun [] T T :- !.
coq.subst-fun [X|XS] (fun _ _ F) T :- !, coq.subst-fun XS (F X) T.
coq.subst-fun XS (let _ _ X F) T :- !, coq.subst-fun XS (F X) T.
:name "subst-fun:fail"
coq.subst-fun [_|_] T _ :- !, 
  fatal-error-w-data "subst-fun: not a lambda" T.

pred coq.prod-R-fun o:term, o:term.
coq.prod-R-fun (prod N T F) (fun N T R) :- !, pi x\ coq.prod-R-fun (F x) (R x).
coq.prod-R-fun (let N T B F) (let N T B R) :- !, pi x\ coq.prod-R-fun (F x) (R x).
coq.prod-R-fun X X.

pred coq.prod->fun i:term, o:term.
coq.prod->fun (prod N T F) (fun N T R) :- !, pi x\ coq.prod->fun (F x) (R x).
coq.prod->fun (let N T B F) (let N T B R) :- !, pi x\ coq.prod->fun (F x) (R x).
coq.prod->fun X X.

pred coq.count-prods i:term, o:int.
coq.count-prods (prod _ _ B) N :- !, (pi x\ coq.count-prods (B x) M), N is M + 1.
coq.count-prods (let _ _ _ B) N :- !, (pi x\ coq.count-prods (B x) N).
:name "count-prod:end"
coq.count-prods _ 0 :- !.

pred coq.mk-n-holes  i:int, o:list A.
coq.mk-n-holes  0 [] :- !.
coq.mk-n-holes  N [HOLE_|R] :- !, M is N - 1, coq.mk-n-holes  M R.

pred coq.safe-dest-app i:term, o:term, o:list term.
coq.safe-dest-app (app [X|XS]) HD AllArgs :- !,
  coq.safe-dest-app X HD ARGS, append ARGS XS AllArgs.
coq.safe-dest-app X X [].

pred coq.mk-app i:term, i:list term, o:term.
coq.mk-app HD [] HD :- !.
coq.mk-app (app L) Args (app LArgs) :- !, append L Args LArgs.
coq.mk-app (fun _ _ F) [A|Args] R :- !, coq.mk-app (F A) Args R.
coq.mk-app (let _ _ A F) Args R :- !, coq.mk-app (F A) Args R.
coq.mk-app HD Args (app [HD|Args]).

pred coq.mk-app-uvar i:term, i:list term, o:term.
coq.mk-app-uvar HD [] HD :- !.
coq.mk-app-uvar (uvar as K) [A|Args] R :- !, unsafe-cast K K', coq.mk-app-uvar (K' A) Args R.

% coq.mk-eta n Ty T: performs up to n (when >= 0) eta expasion of T
% according to its type Ty. If n < 0 it makes as many step as
% products in Ty. There be dragons if T has not type Ty.
pred coq.mk-eta i:int, i:term, i:term, o:term.
coq.mk-eta 0 _ B B :- !.
coq.mk-eta N (prod Name Ty P) (fun _ _ F) (fun Name Ty F1) :- !, N1 is N - 1,
  pi x \ coq.mk-eta N1 (P x) (F x) (F1 x).
coq.mk-eta N (prod Name Ty P) B           (fun Name Ty B1) :- !, N1 is N - 1,
  pi x \ coq.mk-eta N1 (P x) {coq.mk-app B [x]} (B1 x).
:name "mk-eta:end"
coq.mk-eta _ _ B B :- !.

% copy can be used to perform a replacement, eg
%   (copy (const "foo") (const "bar) :- !) => copy T T1
% traverses T replacing foo with bar.
pred copy i:term, o:term.
:name "copy:start"
copy X Y :- name X, !, X = Y, !. % avoid loading "copy x x" at binders
copy (global _ as C) C :- !.
copy (sort _ as C) C :- !.
copy (fun N T F) (fun N T1 F1) :- !,
  copy T T1, pi x\ copy (F x) (F1 x).
copy (let N T B F) (let N T1 B1 F1) :- !,
  copy T T1, copy B B1, pi x\ copy (F x) (F1 x).
copy (prod N T F) (prod N T1 F1) :- !,
  copy T T1, (pi x\ copy (F x) (F1 x)).
copy (app L) (app L1) :- !, map L copy L1.
copy (fix N Rno Ty F) (fix N Rno Ty1 F1) :- !,
  copy Ty Ty1, pi x\ copy (F x) (F1 x).
copy (match T Rty B) (match T1 Rty1 B1) :- !,
  copy T T1, copy Rty Rty1, map B copy B1.
copy (primitive _ as C) C :- !.
copy (uvar M L as X) W :- var X, !, map L copy L1, coq.mk-app-uvar M L1 W.
% when used in CHR rules
copy (uvar X L) (uvar X L1) :- map L copy L1.

pred copy-ctx-item i:prop, o:prop.
copy-ctx-item (decl X N T) (decl X1 N T1) :- copy X X1, copy T T1.
copy-ctx-item (def X N T B) (def X1 N T1 B1) :-
  copy X X1, copy T T1, copy B B1.

pred copy-arity i:arity, o:arity.
copy-arity (parameter ID IMP T R) (parameter ID IMP T1 R1) :-
  copy T T1, pi x\ copy-arity (R x) (R1 x).
copy-arity (arity T) (arity T1) :- copy T T1.

% Bridges the gap between the data types used to read/write inductives.
% The arguments are the same of coq.env.indt plus an an extra one being
% the output (of type indt-decl).

pred coq.build-indt-decl
  i:(pair inductive id), i:bool, i:int, i:int, i:term, i:list (pair constructor id), i:list term, o:indt-decl.

coq.build-indt-decl GR IsInd Pno UPno Arity Kns Ktys Decl :-
  coq.build-indt-decl-aux GR IsInd Pno UPno Arity Kns Ktys [] Decl.

pred coq.build-indt-decl-aux
  i:pair inductive id, i:bool, i:int, i:int, i:term, i:list (pair constructor id), i:list term, i:list term, o:indt-decl.
coq.build-indt-decl-aux (pr GR I) IsInd NUPno 0 Ty Kns KtysNu Params (inductive I IsInd Arity Ks) :- !,
  coq.term->arity Ty NUPno Arity,
  std.map KtysNu (k\coq.term->arity k NUPno) Ktys,
  rev Params ParamsR,
  (pi i\ Sub i = [ % we factor uniform parameters
     (pi x l\ copy (app[global (indt GR)|l]) (app[i|x]):- !, appendR ParamsR x l),
     (copy (global (indt GR)) i :- !) ]),
  pi i\
    map2 Kns Ktys (gr_name\ ty\ res\
      sigma tmp name\
      Sub i => copy-arity ty tmp,
      gr_name = pr _ name,
      res = constructor name tmp)
    (Ks i).

coq.build-indt-decl-aux GR IsInd Pno UPno (prod N S T) Kns Ktys Params (parameter NS explicit S Res) :- Pno > 0, UPno > 0, !,
  coq.name->id N NS,
  Pno1 is Pno - 1,
  UPno1 is UPno - 1,
  pi p\
    map Ktys (coq.subst-prod [p]) (Ktys1 p),
    coq.build-indt-decl-aux GR IsInd Pno1 UPno1 (T p) Kns (Ktys1 p) [p|Params] (Res p).

:name "coq.build-indt-decl-aux:fail"
coq.build-indt-decl-aux _ _ _ _ _ _ _ _ _ :- !,
  fatal-error "coq.build-indt-decl-aux: invalid declaration".

pred coq.rename-arity
  i:(id -> id -> prop),
  i:arity,
  o:arity.
coq.rename-arity RP (parameter ID I TY In) (parameter ID1 I TY Out) :-
  RP ID ID1,
  @pi-parameter ID TY p\
    coq.rename-arity RP (In p) (Out p).
coq.rename-arity _ (arity T) (arity T).

% [coq.rename-indt-decl RenameParam RenameIndType RenameIndConstr D D1]
% can be used to rename all [id] part of an inductive type declaration
pred coq.rename-indt-decl
  i:(id -> id -> prop),
  i:(id -> id -> prop),
  i:(id -> id -> prop),
  i:indt-decl, o:indt-decl.
coq.rename-indt-decl RP RI RK (parameter ID I TY In) (parameter ID1 I TY Out) :-
  RP ID ID1,
  @pi-parameter ID TY p\
    coq.rename-indt-decl RP RI RK (In p) (Out p).
coq.rename-indt-decl RP RI RK (inductive ID Ind A In) (inductive ID1 Ind A1 Out) :-
  RI ID ID1,
  coq.rename-arity RP A A1,
  coq.id->name ID Name,
  coq.arity->term A TY,
  @pi-decl Name TY i\
    std.map (In i) (coq.rename-indt-decl.aux RP RI RK) (Out i).
coq.rename-indt-decl _ RI RK (record ID A KID F) (record ID1 A KID1 F) :-
  RI ID ID1,
  RK KID KID1.
coq.rename-indt-decl.aux RP _ RK (constructor ID A) (constructor ID1 A1) :-
  RK ID ID1,
  coq.rename-arity RP A A1.


% Lifts coq.typecheck to inductive declarations
pred coq.typecheck-indt-decl.heuristic-var-type i:term, o:diagnostic.
coq.typecheck-indt-decl.heuristic-var-type (uvar _ _ as X) D :- !,
  coq.univ.new [] U, coq.unify-eq X (sort (typ U)) D.
coq.typecheck-indt-decl.heuristic-var-type _ ok.

pred coq.typecheck-indt-decl i:indt-decl, o:diagnostic.
coq.typecheck-indt-decl (parameter ID _ T Decl) Diag :- do-ok! Diag [
  coq.typecheck-ty T _,
  (d\ @pi-parameter ID T x\ coq.typecheck-indt-decl (Decl x) d),
].
coq.typecheck-indt-decl (inductive ID _ Arity KDecl) Diag :- coq.arity->term Arity A, do-ok! Diag [
  coq.typecheck-ty A _,
  coq.typecheck-indt-decl.heuristic-var-type A,
  d\ @pi-parameter ID A i\ forall-ok (KDecl i) (coq.typecheck-indt-decl-c i A) d
].
coq.typecheck-indt-decl (record ID A _IDK FDecl) Diag :- do-ok! Diag [
  coq.typecheck-ty A _,
  d\ @pi-parameter ID A i\ do-ok! d [
    lift-ok (coq.typecheck-indt-decl-field i FDecl (K i)) "",
    coq.typecheck-indt-decl-c i A (constructor "fields" (arity (K i)))
  ]
].

pred coq.typecheck-indt-decl-c i:term, i:term, i:indc-decl, o:diagnostic.
coq.typecheck-indt-decl-c I S (constructor _ID Arity) Diag :- coq.arity->term Arity T, do-ok! Diag [
  coq.typecheck-ty T KS,
  coq.typecheck-indt-decl-c.unify-arrow-tgt I S T,
  lift-ok (coq.arity->sort S IS) "",
  lift-ok (if (IS = typ U1, KS = typ U2) (coq.univ.leq U2 U1) true) "constructor universe too large"
].

pred coq.typecheck-indt-decl-c.unify-arrow-tgt i:term, i:term, i:term, o:diagnostic.
coq.typecheck-indt-decl-c.unify-arrow-tgt I A (prod N S T) D :-
  @pi-decl N S x\ coq.typecheck-indt-decl-c.unify-arrow-tgt I A (T x) D.
coq.typecheck-indt-decl-c.unify-arrow-tgt I A (let N S B T) D :-
  @pi-def N S B x\ coq.typecheck-indt-decl-c.unify-arrow-tgt I A (T x) D.
coq.typecheck-indt-decl-c.unify-arrow-tgt I A Concl D :-
  coq.count-prods A N,
  coq.mk-n-holes  N Args,
  coq.mk-app I Args IArgs,
  coq.unify-eq Concl IArgs D.

pred coq.typecheck-indt-decl-field i:term, i:record-decl, o:term.
coq.typecheck-indt-decl-field I end-record I.
coq.typecheck-indt-decl-field I (field _ ID T F) (prod N T F1) :-
  coq.id->name ID N,
  @pi-decl N T a\ coq.typecheck-indt-decl-field I (F a) (F1 a).

% Lifts coq.elaborate-skeleton to inductive declarations
pred coq.elaborate-indt-decl-skeleton i:indt-decl, o:indt-decl, o:diagnostic.
coq.elaborate-indt-decl-skeleton (parameter ID Imp T Decl) (parameter ID Imp T1 Decl1) Diag :- do-ok! Diag [
  coq.elaborate-ty-skeleton T _ T1,
  (d\ @pi-parameter ID T1 x\ coq.elaborate-indt-decl-skeleton (Decl x) (Decl1 x) d),
].
coq.elaborate-indt-decl-skeleton (inductive ID I Arity KDecl) (inductive ID I Arity1 KDecl1) Diag :- do-ok! Diag [
  coq.elaborate-arity-skeleton Arity _ Arity1,
  d\ coq.arity->term Arity1 A1, do-ok! d [
       coq.typecheck-indt-decl.heuristic-var-type A1,
       d\ @pi-parameter ID A1 i\ map-ok (KDecl i) (coq.elaborate-indt-decl-skeleton-c i A1) (KDecl1 i) d
  ]
].
coq.elaborate-indt-decl-skeleton (record ID A IDK FDecl) (record ID A1 IDK FDecl1) Diag :- do-ok! Diag [
  coq.elaborate-ty-skeleton A _ A1,
  lift-ok (A1 = sort U) "record type is not a sort",
  d\ @pi-parameter ID A1 i\ coq.elaborate-indt-decl-skeleton-fields U FDecl FDecl1 d
].

pred coq.elaborate-indt-decl-skeleton-fields i:universe, i:record-decl, o:record-decl, o:diagnostic.
coq.elaborate-indt-decl-skeleton-fields _ end-record end-record ok.
coq.elaborate-indt-decl-skeleton-fields U (field Att ID A Fields) (field Att ID A1 Fields1) Diag :- do-ok! Diag [
  coq.elaborate-ty-skeleton A UA A1,
  lift-ok (if (U = typ U1, UA = typ U2) (coq.univ.leq U2 U1) true) "constructor universe too large",
  d\ @pi-parameter ID A1 p\
       coq.elaborate-indt-decl-skeleton-fields U (Fields p) (Fields1 p) d
].

pred coq.elaborate-indt-decl-skeleton-c i:term, i:term, i:indc-decl, o:indc-decl, o:diagnostic.
coq.elaborate-indt-decl-skeleton-c I S (constructor ID Arity) (constructor ID Arity1) Diag :- do-ok! Diag [
  coq.elaborate-arity-skeleton Arity KS Arity1,
  coq.typecheck-indt-decl-c.unify-arity-tgt I S Arity1,
  lift-ok (coq.arity->sort S IS) "",
  lift-ok (if (IS = typ U1, KS = typ U2) (coq.univ.leq U2 U1) true) "constructor universe too large"
].

pred coq.typecheck-indt-decl-c.unify-arity-tgt i:term, i:term, i:arity, o:diagnostic.
coq.typecheck-indt-decl-c.unify-arity-tgt I A (parameter ID _ T C) D :-
  @pi-parameter ID T p\ coq.typecheck-indt-decl-c.unify-arity-tgt I A (C p) D.
coq.typecheck-indt-decl-c.unify-arity-tgt I A (arity C) D :-
  coq.typecheck-indt-decl-c.unify-arrow-tgt I A C D.

% Lifts coq.elaborate-skeleton to arity
pred coq.elaborate-arity-skeleton i:arity, o:universe, o:arity, o:diagnostic.
coq.elaborate-arity-skeleton (parameter ID Imp T A) U (parameter ID Imp T1 A1) Diag :- do-ok! Diag [
  coq.elaborate-ty-skeleton T _ T1, % parameters don't count
  d\ @pi-parameter ID T1 i\ coq.elaborate-arity-skeleton (A i) U (A1 i) d
].
coq.elaborate-arity-skeleton (arity A) U (arity A1) Diag :-
  coq.elaborate-ty-skeleton A U A1 Diag.

% Converts an arity to a term
pred coq.arity->term i:arity, o:term.
coq.arity->term (parameter ID _ Ty Rest) (prod Name Ty R) :-
  coq.id->name ID Name,
  @pi-decl Name Ty x\ coq.arity->term (Rest x) (R x).
coq.arity->term (arity A) A.

pred coq.term->arity i:term, i:int, o:arity.
coq.term->arity T 0 (arity T).
coq.term->arity (prod Name S T) N (parameter ID explicit S R) :-
  M is N - 1,
  coq.name->id Name ID,
  @pi-decl Name S x\ coq.term->arity (T x) M (R x).

% extracts the sort at the end of an arity
pred coq.arity->sort i:term, o:universe.
coq.arity->sort (prod N S X) Y :- !, @pi-decl N S x\ coq.arity->sort (X x) Y.
coq.arity->sort (sort X) X :- !.
:name "arity->sort:fail"
coq.arity->sort T _ :- fatal-error-w-data "arity->sort: not a sort or prod" T.

% Counts how many parameters are there
pred coq.arity->nparams i:arity, o:int.
coq.arity->nparams (parameter _ _ _ In) O :-
  pi x\ coq.arity->nparams (In x) O1, O is O1 + 1.
coq.arity->nparams (arity _) 0.

% extract gref from terms that happen to have one
pred coq.term->gref i:term, o:gref.
coq.term->gref (global GR) GR :- !.
coq.term->gref (app [Hd|_]) GR :- !, coq.term->gref Hd GR.
:name "term->gref:fail"
coq.term->gref Term _ :-
  fatal-error-w-data "term->gref: input has no global reference" Term.

pred coq.fresh-type o:term.
coq.fresh-type (sort (typ U)) :- coq.univ.new [] U.

% Map the term under a spine of fun nodes
pred coq.map-under-fun i:term,
  % InputTermUnderLams LamBoundVars TheirTypes Result
  i:(term -> list term -> list term -> term -> prop),
  o:term.
coq.map-under-fun T F R :- map-under-fun.aux T [] [] F R.
map-under-fun.aux (fun N T B) AccT AccTy F (fun N T R) :- !,
  @pi-decl N T x\ map-under-fun.aux (B x) [x|AccT] [T|AccTy] F (R x).
map-under-fun.aux (let _ _ X B) AccT AccTy F R :- !,
  map-under-fun.aux (B X) AccT AccTy F R.
map-under-fun.aux End AccT AccTy F R :- F End {rev AccT} {rev AccTy} R.

pred coq.iter-under-fun i:term,
  % InputTermUnderLams LamBoundVars TheirTypes
  i:(term -> list term -> list term -> prop).
coq.iter-under-fun T F :- iter-under-fun.aux T [] [] F.
iter-under-fun.aux (fun N T B) AccT AccTy F :- !,
  @pi-decl N T x\ iter-under-fun.aux (B x) [x|AccT] [T|AccTy] F.
iter-under-fun.aux (let _ _ X B) AccT AccTy F :- !,
  iter-under-fun.aux (B X) AccT AccTy F.
iter-under-fun.aux End AccT AccTy F :- F End {rev AccT} {rev AccTy}.

% Build a match given the term and function to build the return type and the
% branches
pred coq.build-match
  i:term, % T, the term being matched
  i:term, % the type of T, expected to be an inductive, eventually applied
  % MkRty: InputTermUnderLams LamBoundVars TheirTypes Result
  i:(term -> list term -> list term -> term -> prop),
  % MkBranch: Constructor ConstructorTyUnderLams LamBoundVars TheirTypes Result
  i:(term -> term -> list term -> list term -> term -> prop),
  o:term. % match T (.. MkRty) [ .. MkBranch K1, .. MkBranch K2, ..]
coq.build-match T Tty RtyF BranchF (match T Rty Bs) :-
  whd Tty [] (global (indt GR)) Args,
  coq.env.indt GR _ Lno _ Arity Kn Kt,
  take Lno Args LArgs,
  coq.mk-app (global (indt GR)) LArgs IndtLArgs,
  % Rty
  coq.subst-prod LArgs Arity ArityArgs,
  coq.bind-ind-arity IndtLArgs ArityArgs RtyF Rty,
  % Bs
  map Kt (coq.subst-prod LArgs) KtArgs,
  map KtArgs coq.prod->fun KtArgsLam,
  map Kn (k\ coq.mk-app (global (indc k)) LArgs) KnArgs,
  map2 KnArgs KtArgsLam (k\t\coq.map-under-fun t (BranchF k)) Bs.

% XXX the list of arguments are often needed in reverse order
pred coq.bind-ind-arity % calls K under (fun Arity (x : Ity Arity) =>..)
  i:term, % the inductive type
  i:term, % the arity
  i:(term -> list term -> list term -> term -> prop), % Sort Vars Tys Out
  o:term. %
bind-ind-arity.aux (prod N T B) (fun N T F) AccT AccTy IT K :- !,
  @pi-decl N T x\ bind-ind-arity.aux (B x) (F x) [x|AccT] [T|AccTy] IT K.
bind-ind-arity.aux (let _ _ X B) F AccT AccTy IT K :- !,
  bind-ind-arity.aux (B X) F AccT AccTy IT K.
bind-ind-arity.aux (sort _ as Sort) (fun `i` ITy F) AccT AccTy IT K :-
  rev AccT Vars,
  coq.mk-app IT Vars ITy,
  @pi-decl `i` ITy x\ K Sort {append Vars [x]} {rev [ITy|AccTy]} (F x).
coq.bind-ind-arity IT Arity F R :- bind-ind-arity.aux Arity R [] [] IT F.

% coq.with-TC Class Instance->Clause Code: runs Code under a context augmented with
% all instances for Class transformed by Instance->Clause.
pred coq.with-TC i:term, i:(tc-instance -> prop -> prop), i:prop.
coq.with-TC Class Instance->Clause Code :-
  coq.TC.db-for {coq.term->gref Class} Instances,
  map Instances Instance->Clause Hyps, !,
  Hyps => Code.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% Coq attribute parser, eg [#[attribute=value] Command]
%
% Usage:
%   main _ :-
%     attributes A,                                     % fetch
%     coq.parse-attributes A Spec Opts,                     % parse/validate
%     Opts => (mycode, get-option "foo" V, mycode).     % use
%
% where [Opts] is a list of clauses [get-option StringName Value], where value
% can have any type and [Spec] is a list of [attribute-sigmature].
% Example of an attribute signature:
%   [
%    att "this" bool,
%    att "that.thing" int,
%    att "algebraic" (oneof ["foo" `-> foo-thing, "bar" `-> barbar]),
%   ]

type get-option string -> A -> prop.

kind attribute-signature type.
type att string -> attribute-type -> attribute-signature.
type att-ignore-unknown attribute-signature.

type supported-attribute attribute-signature -> prop.

kind attribute-type type.
type int attribute-type.
type string attribute-type.
type bool attribute-type.
type oneof list attribute-mapping -> attribute-type.

kind attribute-mapping type.
type (`->) string -> any -> attribute-mapping.

pred coq.valid-attribute i:string, i:string, o:option any, o:diagnostic.
coq.valid-attribute Name Value V Diag :-
  if (supported-attribute (att Name Type))
     (coq.typecheck-attribute Name Type Value LPV Diag, V = some LPV)
     (if (supported-attribute att-ignore-unknown) (V = none, Diag = ok)
         (Diag = error {calc ( "Attribute " ^ Name ^ " is not supported")})).

:index (_ 1 1)
pred coq.typecheck-attribute i:string, i:attribute-type, i:string, o:any, o:diagnostic.

coq.typecheck-attribute _ int Value V ok :- V is string_to_int Value, !.
coq.typecheck-attribute N int Value _ (error Msg) :-
  Msg is "Attribute " ^ N ^ " takes an integer, got: " ^ Value.

coq.typecheck-attribute _ string V V ok.

coq.typecheck-attribute _ bool "true"  tt ok.
coq.typecheck-attribute _ bool "tt"    tt ok.
coq.typecheck-attribute _ bool "True"  tt ok.
coq.typecheck-attribute _ bool "on"    tt ok.
coq.typecheck-attribute _ bool ""      tt ok.
coq.typecheck-attribute _ bool "false" ff ok.
coq.typecheck-attribute _ bool "False" ff ok.
coq.typecheck-attribute _ bool "off"   ff ok.
coq.typecheck-attribute _ bool "ff"    ff ok.
coq.typecheck-attribute N bool Value _ (error Msg) :-
  Msg is "Attribute " ^ N ^ " takes an boolean, got: " ^ Value.

pred coq.is-one-of i:string, o:any, i:attribute-mapping.
coq.is-one-of K V (K `-> V).

coq.typecheck-attribute _ (oneof L) K V ok :- std.exists L (coq.is-one-of K V), !.
coq.typecheck-attribute N (oneof L) K _ (error Msg) :-
  std.map L (x\r\ sigma tmp\ x = r `-> tmp) S,
  std.fold S "" (s\ a\ calc (a ^ " " ^ s)) OneOf,
  Msg is "Attribute " ^ N ^ " takes one of " ^  OneOf ^ ", got: " ^ K.

pred coq.parse-attributes i:list attribute, i:list attribute-signature, o:list prop.

coq.parse-attributes L S O :-
  std.map S (x\r\ r = supported-attribute x) CS,
  CS => parse-attributes.aux L "" O, !.
parse-attributes.aux [] _ [].
parse-attributes.aux [attribute S (node L)|AS] Prefix R :- !,
  parse-attributes.aux AS Prefix R1,
  if (Prefix = "") (PS = S) (PS is Prefix ^ "." ^ S),
  parse-attributes.aux L PS R2,
  std.append R1 R2 R.
parse-attributes.aux [attribute S (leaf V)|AS] Prefix CLS :- !,
  if (Prefix = "") (PS = S) (PS is Prefix ^ "." ^ S),
  coq.valid-attribute PS V V1 Diag,
  if (Diag = error Msg) (coq.error Msg) true,
  if (V1 = some Val) (CLS = [get-option PS Val|R]) (CLS = R), % ignored
  parse-attributes.aux AS Prefix R.