Add case guards to parser

src/aeso_parser.erl

@@ -282,9 +282,14 @@ stmt() ->
     , {else, keyword(else), body()}
     ])).
 
-branch() ->
+branch() -> choice(unguarded_branch(), guarded_branch()).
+
+unguarded_branch() ->
     ?RULE(pattern(), keyword('=>'), body(), {'case', _2, _1, _3}).
 
+guarded_branch() ->
+    ?RULE(pattern(), tok('|'), expr(), keyword('=>'), body(), {'case', _4, _1, _3, _5}).
+
 pattern() ->
     ?LET_P(E, expr(), parse_pattern(E)).
 

src/aeso_syntax.erl

@@ -145,7 +145,8 @@
 -type stmt() :: letbind()
               | expr().
 
--type alt() :: {'case', ann(), pat(), expr()}.
+-type alt() :: {'case', ann(), pat(), expr()}
+             | {'case', ann(), pat(), expr(), expr()}.
 
 -type lvalue() :: nonempty_list(elim()).