Scala 2 macros

Problem
-------
Scala 2 macro definition is not supported.

Solution
--------
This adds macro_body as an expression.

corpus/expressions.txt

@@ -1522,6 +1522,30 @@ def main() {
         (identifier)
         (identifier)))))
 
+================================================================================
+Macros (Scala 2 syntax)
+================================================================================
+
+class Foo {
+  def a: A =
+    macro B.b
+}
+
+--------------------------------------------------------------------------------
+
+(compilation_unit
+  (class_definition
+    (identifier)
+    (template_body
+      (function_definition
+        (identifier)
+        (type_identifier)
+        (indented_block
+          (macro_body
+            (field_expression
+              (identifier)
+              (identifier))))))))
+
 ================================================================================
 Macros (Scala 3 syntax)
 ================================================================================

grammar.js

@@ -1019,6 +1019,7 @@ module.exports = grammar({
         $.while_expression,
         $.do_while_expression,
         $.for_expression,
+        $.macro_body,
         $._simple_expression,
       ),
 
@@ -1306,6 +1307,15 @@ module.exports = grammar({
         ),
       ),
 
+    macro_body: $ =>
+      prec.left(
+        PREC.macro,
+        seq(
+          "macro",
+          choice($.infix_expression, $.prefix_expression, $._simple_expression),
+        )
+      ),
+
     /**
      * PrefixExpr        ::=  [PrefixOperator] SimpleExpr
      */