kill-split: split() -> preg_split()

Test Plan:
~ cat a.php
<?php
if (4 >= $a) {
  echo $lol;
}
if ($a === $b) {
  echo $lol;
}
split('l\\\\o/l', 'aaal\\o/lbbb');

~ lex-pass kill-split
Checking (1/1) a.php
- Parsing
- Saving

~ cat a.php
<?php
if (4 >= $a) {
  echo $lol;
}
if ($a === $b) {
  echo $lol;
}
preg_split('/l\\\\o\/l/', 'aaal\\o/lbbb');

~ phpsh
php> =split('l\\\\o/l', 'aaal\\o/lbbb')
PHP Deprecated:  Function split() is deprecated in /usr/lib/python2.6/site-packages/phpsh/phpsh.php(534) : eval()'d code on line 1
array(
  0 => "aaa",
  1 => "bbb",
)
php> =preg_split('/l\\\\o\/l/', 'aaal\\o/lbbb');
array(
  0 => "aaa",
  1 => "bbb",
)

src/Lang/Php/Ast.hs

@@ -3,6 +3,7 @@
 module Lang.Php.Ast (
   module Lang.Php.Ast.Common,
   module Lang.Php.Ast.Expr,
+  module Lang.Php.Ast.Lex,
   module Lang.Php.Ast.Stmt,
   Ast
   ) where

src/Transf/AntiPattern.hs

@@ -14,11 +14,14 @@ transfs :: [Transf]
 transfs = [
   "assignables-go-right" -:- ftype -?-
   "\"if ($x == true)\" -> \"if (true == $x)\" etc"
-  -=- (\ [] -> lexPass $ assignablesGoRight)]
+  -=- (\ [] -> lexPass $ assignablesGoRight),
+  "kill-split" -:- ftype -?-
+  "split() becomes preg_split()"
+  -- TODO: detect non-regex case and go to explode() instead of preg_split()?
+  -=- (\ [] -> lexPass $ killSplit)]
 
-exprIsLRVal :: Expr -> Bool
-exprIsLRVal (ExprRVal (RValLRVal _)) = True
-exprIsLRVal _ = False
+assignablesGoRight :: Ast -> Transformed Ast
+assignablesGoRight = modAll . modIfBlockExpr $ modWSCap2 exprLRValToRight
 
 exprLRValToRight :: Expr -> Transformed Expr
 exprLRValToRight (ExprBinOp op e1 w e2)
@@ -34,6 +37,31 @@ exprLRValToRight (ExprBinOp op e1 w e2)
     else transfNothing
 exprLRValToRight _ = transfNothing
 
-assignablesGoRight :: Ast -> Transformed Ast
-assignablesGoRight = modAll . modIfBlockExpr $ modWSCap2 exprLRValToRight
+exprIsLRVal :: Expr -> Bool
+exprIsLRVal (ExprRVal (RValLRVal _)) = True
+exprIsLRVal _ = False
+
+killSplit :: Ast -> Transformed Ast
+killSplit = modAll $ \ a -> case a of
+  ROnlyValFunc _c@(Right (Const [] "split")) w (Right (arg0:args)) ->
+    case arg0 of
+      WSCap w1 (Left (ExprStrLit (StrLit s))) w2 ->
+        pure . ROnlyValFunc c' w . Right $ arg0':args
+        where
+        c' = Right (Const [] "preg_split")
+        arg0' = WSCap w1 (Left (ExprStrLit (StrLit s'))) w2
+        s' = onTail (onInit $ delimify '/' '\\') s
+      _ -> transfNothing
+  _ -> transfNothing
+
+delimify :: (Eq a) => a -> a -> [a] -> [a]
+delimify delim esc s = [delim] ++ concatMap doEsc s ++ [delim] where
+  doEsc c = if c == delim then [esc, c] else [c]
+
+onTail :: ([a] -> [a]) -> [a] -> [a]
+onTail f (x:l) = x : f l
+onTail _f l = l
+
+onInit :: ([a] -> [a]) -> [a] -> [a]
+onInit = reversify . onTail . reversify