From 3f177d363f1322d449d312c84168c1b0782f1089 Mon Sep 17 00:00:00 2001
From: Gaith Hallak <gaithhallak@gmail.com>
Date: Sat, 11 Jun 2022 17:26:13 +0400
Subject: [PATCH] Add constraints to the syntax and parser

---
 src/aeso_parser.erl | 16 ++++++++++++++--
 src/aeso_scan.erl   |  2 +-
 src/aeso_syntax.erl |  4 ++++
 3 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/src/aeso_parser.erl b/src/aeso_parser.erl
index 51b81f6..b0f0bce 100644
--- a/src/aeso_parser.erl
+++ b/src/aeso_parser.erl
@@ -134,9 +134,20 @@ fun_block(Mods, Kind, [Decl]) ->
 fun_block(Mods, Kind, Decls) ->
     {block, get_ann(Kind), [ add_modifiers(Mods, Kind, Decl) || Decl <- Decls ]}.
 
+typevar_constraint() ->
+    ?RULE(tvar(), keyword(is), choice([tok(eq), tok(ord)]),
+          {constraint, element(2, _1), element(3, _1), element(1, _3)}).
+
+typevars_constraints() ->
+    ?RULE(comma_sep1(typevar_constraint()), tok(';'), _1).
+
+fundecl() ->
+    choice([?RULE(id(), tok(':'), typevars_constraints(), type(),
+                  {fun_decl, get_ann(_1), _1, {constrained_t, get_ann(_1), _3, _4}}),
+            ?RULE(id(), tok(':'), type(), {fun_decl, get_ann(_1), _1, _3})]).
+
 fundef_or_decl() ->
-    choice([?RULE(id(), tok(':'), type(), {fun_decl, get_ann(_1), _1, _3}),
-            fundef()]).
+    choice([fundecl(), fundef()]).
 
 using() ->
     Alias = {keyword(as), con()},
@@ -527,6 +538,7 @@ parens(P)   -> between(tok('('), P, tok(')')).
 braces(P)   -> between(tok('{'), P, tok('}')).
 brackets(P) -> between(tok('['), P, tok(']')).
 comma_sep(P) -> sep(P, tok(',')).
+comma_sep1(P) -> sep1(P, tok(',')).
 
 paren_list(P)   -> parens(comma_sep(P)).
 brace_list(P)   -> braces(comma_sep(P)).
diff --git a/src/aeso_scan.erl b/src/aeso_scan.erl
index 4587efa..11900b1 100644
--- a/src/aeso_scan.erl
+++ b/src/aeso_scan.erl
@@ -45,7 +45,7 @@ lexer() ->
 
     Keywords = ["contract", "include", "let", "switch", "type", "record", "datatype", "if", "elif", "else", "function",
                 "stateful", "payable", "true", "false", "mod", "public", "entrypoint", "private", "indexed", "namespace",
-                "interface", "main", "using", "as", "for", "hiding"
+                "interface", "main", "using", "as", "for", "hiding", "is", "eq", "ord"
                ],
     KW = string:join(Keywords, "|"),
 
diff --git a/src/aeso_syntax.erl b/src/aeso_syntax.erl
index 1e01153..6461dac 100644
--- a/src/aeso_syntax.erl
+++ b/src/aeso_syntax.erl
@@ -79,11 +79,15 @@
 
 -type constructor_t() :: {constr_t, ann(), con(), [type()]}.
 
+-type tvar_constraint() :: eq | ord.
+-type constraint() :: {constraint, ann(), name(), tvar_constraint()}.
+
 -type type() :: {fun_t, ann(), [named_arg_t()], [type()], type()}
               | {app_t, ann(), type(), [type()]}
               | {tuple_t, ann(), [type()]}
               | {args_t, ann(), [type()]}   %% old tuple syntax, old for error messages
               | {bytes_t, ann(), integer() | any}
+              | {constrained_t, ann(), [constraint()], type()}
               | id()  | qid()
               | con() | qcon()  %% contracts
               | tvar().