Allow &1.foo syntax inside capture

Author: José Valim

lib/elixir/lib/kernel/special_forms.ex

@@ -897,6 +897,12 @@ defmodule Kernel.SpecialForms do
       iex> fun.(1, 2, 3)
       6
 
+  Record-like calls are also allowed:
+
+      iex> fun = &(&1.first)
+      iex> fun.(1..3)
+      1
+
   Remember tuple and lists are represented as calls in the AST and
   therefore are also allowed:
 

lib/elixir/src/elixir_parser.yrl

@@ -33,7 +33,7 @@ Terminals
   comp_op at_op unary_op and_op or_op arrow_op match_op
   range_op in_op inc_op when_op than_op default_op tail_op
   dual_op add_op mult_op exp_op two_op type_op stab_op
-  'true' 'false' 'nil' 'do' eol ',' '.'
+  'true' 'false' 'nil' 'do' eol ',' '.' '&'
   '(' ')' '[' ']' '{' '}' '<<' '>>'
   .
 
@@ -205,6 +205,7 @@ base_expr -> bin_string  : build_bin_string('$1').
 base_expr -> list_string : build_list_string('$1').
 base_expr -> bit_string : '$1'.
 base_expr -> sigil : build_sigil('$1').
+base_expr -> '&' number : { '&', [{line,?line('$1')}], [?exprs('$2')] }.
 
 %% Blocks
 
@@ -490,7 +491,7 @@ build_op({ _Kind, Line, '/' }, { '&', _, [{ { '.', _, [_, _] }, _, [] } = Left]
 build_op({ _Kind, Line, BOp }, { UOp, _, [Left] }, Right) when ?rearrange_bop(BOp), ?rearrange_uop(UOp) ->
   { UOp, [{line,Line}], [{ BOp, [{line,Line}], [Left, Right] }] };
 
-build_op({ _Kind, Line, Op } = A, Left, Right) ->
+build_op({ _Kind, Line, Op }, Left, Right) ->
   { Op, [{line,Line}], [Left, Right] }.
 
 build_unary_op({ _Kind, Line, Op }, Expr) ->

lib/elixir/src/elixir_tokenizer.erl

@@ -423,6 +423,11 @@ tokenize([T1,T2|Rest], Line, Scope, Tokens) when ?type_op(T1, T2) ->
   handle_op(Rest, Line, type_op, list_to_atom([T1, T2]), Scope, Tokens);
 
 % ## Single Token Operators
+
+%% Handle &1 and friends with special precedence.
+tokenize([$&,D|Rest], Line, Scope, Tokens) when ?is_digit(D) ->
+  tokenize([D|Rest], Line, Scope, [{ '&', Line }|Tokens]);
+
 tokenize([T|Rest], Line, Scope, Tokens) when ?at_op(T) ->
   handle_nonl_op(Rest, Line, at_op, list_to_atom([T]), Scope, Tokens);
 

lib/elixir/test/elixir/kernel/fn_test.exs

@@ -60,6 +60,11 @@ defmodule Kernel.FnTest do
     assert (&[&1|&2]).(1, 2) == [1|2]
   end
 
+  test "capture and partially apply on call" do
+    assert (&(&1.file)).(__ENV__) == __FILE__
+    assert (&(&1.file(&2))).(__ENV__, "Hello").file == "Hello"
+  end
+
   test "failure on non-continuous" do
     assert_compile_fail CompileError, "nofile:1: capture &2 cannot be defined without &1", "&(&2)"
   end