syntax for defining implicit funcs

Author: christoph-dfinity

doc/md/examples/grammar.txt

@@ -7,6 +7,9 @@
     X
     X SEP <list(X, SEP)>
 
+<implicit> ::= 
+    IMPLICIT
+
 <id_wild> ::= 
     '_'
 
@@ -70,6 +73,7 @@
 
 <typ_item> ::= 
     <id> ':' <typ>
+    <implicit> ':' <typ>
     <id_wild> ':' <typ>
     <typ>
 
@@ -294,7 +298,8 @@
 <pat_plain> ::= 
     '_'
     <id>
-    IMPLICIT <id> <id>
+    <implicit> <id>
+    <implicit> '(' <id> ')' <id>
     <lit>
     '(' <list(<pat_bin>, ',')> ')'
 
@@ -324,6 +329,8 @@
 
 <func_pat> ::= 
     <id>? <typ_params_opt> <pat_plain>
+    <implicit> <id> <typ_params_opt> <pat_plain>
+    <implicit> '(' <id> ')' <id> <typ_params_opt> <pat_plain>
 
 <dec_var> ::= 
     'var' <id> (':' <typ>)? '=' <exp>

src/mo_frontend/parser.mly

@@ -98,11 +98,14 @@ let rec normalize_let p e =
     | ParP p' -> normalize_let p' e
     | _ -> (p, e)
 
-let let_or_exp named x e' at =
+let let_or_exp named x implicit e' at =
   if named
-  then LetD(VarP x @! x.at, e' @? at, None) @? at
+  then match implicit with
+    | None -> LetD(VarP x @! x.at, e' @? at, None) @? at
        (* If you change the above regions,
           modify is_sugared_func_or_module to match *)
+    | Some(implicit) ->
+      LetD(ImplicitP { id = x; implicit } @! x.at, e' @? at, None) @? at
   else ExpD(e' @? at) @? at
 
 let is_sugared_func_or_module dec = match dec.it with
@@ -894,7 +897,6 @@ pat_plain :
     { VarP(x) @! at $sloc }
   | implicit x=id
     { ImplicitP { implicit = x; id = x; } @! at $sloc }
-    (* TODO *)
   | implicit LPAR x=id RPAR y=id
     { ImplicitP { implicit = x; id = y; } @! at $sloc }
   | l=lit
@@ -952,10 +954,11 @@ pat_opt :
     { fun sloc -> WildP @! sloc }
 
 func_pat :
-  | xf=id_opt ts=typ_params_opt p=pat_plain { (xf, ts, p) }
+  | xf=id_opt ts=typ_params_opt p=pat_plain { (xf, None, ts, p) }
+  | implicit x=id ts=typ_params_opt p=pat_plain { ((fun _ _ -> true, x), Some(x), ts, p) }
+  | implicit LPAR x=id RPAR y=id ts=typ_params_opt p=pat_plain { ((fun _ _ -> true, y), Some(x), ts, p) }
 
 (* Declarations *)
-
 dec_var :
   | VAR x=id t=annot_opt EQ e=exp(ob)
     { VarD(x, annot_exp e t) @? at $sloc }
@@ -971,10 +974,10 @@ dec_nonvar :
     { (* This is a hack to support local func declarations that return a computed async.
          These should be defined using RHS syntax EQ e to avoid the implicit AsyncE introduction
          around bodies declared as blocks *)
-      let xf, tps, p = xf_tps_p in
+      let xf, i, tps, p = xf_tps_p in
       let named, x = xf "func" $sloc in
       let is_sugar, e = desugar_func_body sp x t fb in
-      let_or_exp named x (func_exp x.it sp tps p t is_sugar e) (at $sloc) }
+      let_or_exp named x i (func_exp x.it sp tps p t is_sugar e) (at $sloc) }
   | eo=parenthetical_opt mk_d=obj_or_class_dec  { mk_d eo }
   | MIXIN p=pat_plain dfs=obj_body {
      let dfs = List.map (share_dec_field (Stable @@ no_region)) dfs in
@@ -1001,12 +1004,12 @@ obj_or_class_dec :
              @? at $sloc) @? at $sloc
         else objblock eo { s with note = persistent } None t efs @? at $sloc
       in
-      let_or_exp named x e.it e.at }
+      let_or_exp named x None e.it e.at }
   | sp=shared_pat_opt ds=obj_sort_opt CLASS
       xf_tps_p=func_pat t=annot_opt  cb=class_body
     { fun eo ->
       let (persistent, s) = ds in
-      let xf, tps, p = xf_tps_p in
+      let xf, _, tps, p = xf_tps_p in
       let (_, id) = xf "class" $sloc in
       let cid = id.it @= id.at in
       let x, dfs = cb in

test/run/implicit-custom-compare.mo

@@ -0,0 +1,25 @@
+import Text "../core-stub/src/Text";
+import Nat "../core-stub/src/Nat";
+import Map "../core-stub/src/Map";
+import { type Order } "../core-stub/src/Types";
+
+actor {
+  type User = { name : Text };
+  type Invoice = { id : Nat };
+
+  func implicit(compare) compareUser(self : User, other : User) : Order {
+    Text.compare(self.name, other.name)
+  };
+
+  func implicit(compare) compareInvoice(self : Invoice, other : Invoice) : Order {
+    Nat.compare(self.id, other.id)
+  };
+
+  let users = Map.empty<User, ()>();
+  let invoices = Map.empty<Invoice, ()>();
+
+  users.add({ name = "foo" }, ());
+  invoices.add({ id = 10 }, ());
+}
+
+//SKIP comp

test/run/implicit-pat.mo

@@ -16,13 +16,10 @@ two();
 assert addOne() == 1;
 
 module DumbHash {
-  func hashNat_(_ : Nat) : Nat { 1 };
-  func hashInt_(_ : Int) : Nat { 2 };
-  func hashText_(_ : Text) : Nat { 3 };
-
-  public let implicit(hashFn) hashNat : Nat -> Nat = hashNat_;
-  public let implicit(hashFn) hashInt : Int -> Nat = hashInt_;
-  public let implicit(hashFn) hashText : Text -> Nat = hashText_;
+  public func implicit(hashFn) hashNat(_ : Nat) : Nat { 1 };
+  public func implicit(hashFn) hashInt(_ : Int) : Nat { 2 };
+  public func implicit(hashFn) hashText(_ : Text) : Nat { 3 };
+  public func implicit hashFn(_ : Char) : Nat { 4 };
 };
 
 func hash<T>(self : T, hashFn : (implicit : T -> Nat)) : Nat {
@@ -32,3 +29,4 @@ func hash<T>(self : T, hashFn : (implicit : T -> Nat)) : Nat {
 assert hash(42) == 1;
 assert hash(-2) == 2;
 assert hash("Hello") == 3;
+assert hash('H') == 4;