+ builders/default: implicit matches (refs #69).

doc/AST_FORMAT.md

@@ -5,7 +5,6 @@ AST and Source Location RFC
 
  * Should we handle these cases at all? They do not have special syntax associated.
    1. How to handle lvar-injecting match (`if /(?<a>foo)/ =~ bar`)?
-   1. How to handle magic match (`foo if /bar/`)?
 
 ## Literals
 
@@ -380,6 +379,15 @@ Format:
     ~~~~~ expression
 ~~~
 
+### Implicit matches
+
+Format:
+
+~~~
+(match-current-line (regexp (str "a") (regopt)))
+"if /a/; end"
+~~~
+
 ## Assignment
 
 ### To local variable

lib/parser/builders/default.rb

@@ -826,6 +826,9 @@ def check_condition(cond)
           check_condition(rhs)
         ])
 
+      when :regexp
+        n(:match_current_line, [ cond ], nil)
+
       else
         cond
       end

test/test_parser.rb

@@ -3612,6 +3612,17 @@ def test_cond_eflipflop
         |      ~~~ operator (eflipflop)})
   end
 
+  def test_cond_match_current_line
+    assert_parses(
+      s(:if,
+        s(:match_current_line,
+          s(:regexp,
+            s(:str, 'wat'),
+            s(:regopt))),
+        s(:nil), nil),
+      %q{if /wat/; end})
+  end
+
   # Case matching
 
   def test_case_expr