references deduction in function definitions (reference modifiers can be added to argument names)

corpus/test.langexp

@@ -106,6 +106,7 @@ func_2 = {
   print t.0;
 }
 
+: operator definition example
 ( - ) 'a 'b = 'a + neg 'b;
 
 test.something = {
@@ -187,7 +188,10 @@ test_ref_access_precendence = {
 print_two 'a 'b = print 'a, print 'b;
 
 : example of reference args and comma operator
-swap 'a 'b : <> 'A <> 'A = %c := <- 'a, 'a := <- 'b, 'b := <- c; // TODO: use move in some way ??
+swap 'a 'b : <> 'A <> 'A = %c := <- 'a, 'a := <- 'b, 'b := <- c;
+
+: previous example with automatic type deduction
+swap <> 'a <> 'b = %c := <- 'a, 'a := <- 'b, 'b := <- c;
 
 : several outputs example
 scan_three : -> String -> String -> String = scan & scan & scan;
@@ -591,6 +595,7 @@ arg_deduction_example 'name 'duration : <- String <- Float -> Task = Task 'name
           (simple_name_identifier)
           (number_literal)))))
   (function_definition
+    (definition_info)
     (operator)
     (argument_name_identifier)
     (argument_name_identifier)
@@ -950,6 +955,31 @@ arg_deduction_example 'name 'duration : <- String <- Float -> Task = Task 'name
         (case
           (reference
             (simple_name_identifier))))))
+  (function_definition
+    (definition_info)
+    (simple_name_identifier)
+    (argument_name_identifier)
+    (argument_name_identifier)
+    (comma_expression
+      (comma_expression
+        (match
+          (name_definition
+            (simple_name_identifier))
+          (case
+            (reference
+              (argument_name_identifier))))
+        (match
+          (name_expression
+            (argument_name_identifier))
+          (case
+            (reference
+              (argument_name_identifier)))))
+      (match
+        (name_expression
+          (argument_name_identifier))
+        (case
+          (reference
+            (simple_name_identifier))))))
   (function_definition
     (definition_info)
     (simple_name_identifier)

grammar.js

@@ -56,6 +56,7 @@ module.exports = grammar({
       choice(field('name', $.simple_name_identifier), seq('(', field('name', $.operator), ')')),
       repeat(seq(
         optional($.annotation_identifier),
+        optional(choice(choice('->', 'out'), choice('<-', 'in'), choice('<>', 'ref'))),
         $.argument_name_identifier,
         optional('?'),
       )),