Ensure parenthesis are allowed in call args

lib/elixir/src/elixir_parser.yrl

@@ -3,12 +3,12 @@
 
 Nonterminals
   grammar expr_list
-  expr block_expr fn_expr bracket_expr call_expr bracket_at_expr max_expr
+  expr paren_expr block_expr fn_expr bracket_expr call_expr bracket_at_expr max_expr
   base_expr matched_expr matched_op_expr unmatched_expr op_expr
   add_op mult_op unary_op two_op pipeline_op bin_concat_op
   match_op send_op default_op when_op pipe_op in_op inc_op stab_op range_op
   andand_op oror_op and_op or_op comp_expr_op colon_colon_op three_op at_op
-  open_paren close_paren
+  open_paren close_paren empty_paren
   open_bracket close_bracket
   open_curly close_curly
   open_bit close_bit
@@ -80,9 +80,12 @@ grammar -> '$empty' : [nil].
 
 % Note expressions are on reverse order
 expr_list -> expr : ['$1'].
-expr_list -> open_paren ')' : [nil].
+expr_list -> empty_paren : [nil].
 expr_list -> expr_list eol expr : ['$3'|'$1'].
 
+paren_expr -> empty_paren : nil.
+paren_expr -> expr : '$1'.
+
 expr -> matched_expr : '$1'.
 expr -> unmatched_expr : '$1'.
 
@@ -229,6 +232,8 @@ open_paren -> '(' eol  : '$1'.
 close_paren -> ')'     : '$1'.
 close_paren -> eol ')' : '$2'.
 
+empty_paren -> open_paren ')' : nil.
+
 open_bracket  -> '['     : '$1'.
 open_bracket  -> '[' eol : '$1'.
 close_bracket -> ']'     : '$1'.
@@ -388,17 +393,17 @@ call_args_parens_not_one -> open_paren ')' : [].
 call_args_parens_not_one -> open_paren matched_kw_base close_paren : ['$2'].
 call_args_parens_not_one -> open_paren matched_expr ',' call_args_no_parens close_paren : ['$2'|'$4'].
 
-base_comma_expr -> expr ',' : ['$1'].
-base_comma_expr -> base_comma_expr expr ',' : ['$2'|'$1'].
+base_comma_expr -> paren_expr ',' : ['$1'].
+base_comma_expr -> base_comma_expr paren_expr ',' : ['$2'|'$1'].
 
-comma_expr -> expr : ['$1'].
+comma_expr -> paren_expr : ['$1'].
 comma_expr -> kw_base : ['$1'].
 comma_expr -> base_comma_expr : '$1'.
-comma_expr -> base_comma_expr expr : ['$2'|'$1'].
+comma_expr -> base_comma_expr paren_expr : ['$2'|'$1'].
 comma_expr -> base_comma_expr kw_base : ['$2'|'$1'].
 
-optional_comma_expr -> expr : '$1'.
-optional_comma_expr -> expr ',' : '$1'.
+optional_comma_expr -> paren_expr : '$1'.
+optional_comma_expr -> paren_expr ',' : '$1'.
 
 call_args -> comma_expr : lists:reverse('$1').
 
@@ -409,7 +414,7 @@ call_args_parens -> open_paren call_args close_paren : '$2'.
 
 kw_eol  -> kw_identifier : '$1'.
 kw_eol  -> kw_identifier eol : '$1'.
-kw_expr -> kw_eol expr : { ?exprs('$1'),'$2' }.
+kw_expr -> kw_eol paren_expr : { ?exprs('$1'),'$2' }.
 
 kw_comma -> kw_expr ',' : ['$1'].
 kw_comma -> kw_comma kw_expr ',' : ['$2'|'$1'].
@@ -419,6 +424,7 @@ kw_base  -> kw_comma : lists:reverse('$1').
 kw_base  -> kw_comma kw_expr : lists:reverse(['$2'|'$1']).
 
 matched_kw_expr  -> kw_eol matched_expr : {?exprs('$1'),'$2'}.
+matched_kw_expr  -> kw_eol empty_paren : {?exprs('$1'),nil}.
 matched_kw_comma -> matched_kw_expr : ['$1'].
 matched_kw_comma -> matched_kw_expr ',' matched_kw_comma : ['$1'|'$3'].
 matched_kw_base  -> matched_kw_comma : '$1'.
@@ -432,13 +438,13 @@ bracket_access -> open_bracket kw_base close_bracket : { '$2', ?line('$1') }.
 list -> open_bracket ']' : [].
 list -> open_bracket kw_base close_bracket : '$2'.
 list -> open_bracket optional_comma_expr close_bracket : ['$2'].
-list -> open_bracket expr ',' call_args close_bracket : ['$2'|'$4'].
+list -> open_bracket paren_expr ',' call_args close_bracket : ['$2'|'$4'].
 
 % Tuple
 
 tuple -> open_curly '}' : build_tuple('$1', []).
 tuple -> open_curly optional_comma_expr close_curly : build_tuple('$1', ['$2']).
-tuple -> open_curly expr ',' call_args close_curly :  build_tuple('$1', ['$2'|'$4']).
+tuple -> open_curly paren_expr ',' call_args close_curly :  build_tuple('$1', ['$2'|'$4']).
 
 % Bitstrings
 

lib/elixir/test/elixir/kernel_test.exs

@@ -20,6 +20,13 @@ defmodule KernelTest do
     refute x([])
   end
 
+  test :paren do
+    assert nil?(())
+    assert [ 1, (), 3 ] == [1, nil, 3 ]
+    assert [do: ()] == [do: nil]
+    assert { 1, (), 3 } == { 1, nil, 3 }
+  end
+
   test :__info__ do
     assert { :in, 2 } inlist Kernel.__info__(:macros)
   end