Passes now do not return anything (they always modify the AST in-place)

src/compiler.js

@@ -23,7 +23,7 @@ PEG.compiler = {
     }
 
     for (i = 0; i < PASS_NAMES.length; i++) {
-      ast = this.passes[PASS_NAMES[i]](ast);
+      this.passes[PASS_NAMES[i]](ast);
     }
 
     var source = this.emitter(ast);

src/passes.js

@@ -1,8 +1,8 @@
 /*
  * Optimalization passes made on the grammar AST before compilation. Each pass
- * is a function that is passed the AST and returns a new AST. The AST can be
- * modified in-place by the pass. The order in which the passes are run is
- * specified in |PEG.compiler.compile| and should be the same as the order of
+ * is a function that is passed the AST and does not return anything. The AST
+ * can be modified in-place by the pass. The order in which the passes are run
+ * is specified in |PEG.compiler.compile| and should be the same as the order of
  * definitions here.
  */
 PEG.compiler.passes = {
@@ -74,8 +74,6 @@ PEG.compiler.passes = {
         delete ast.rules[name];
       }
     }
-
-    return ast;
   },
 
   /*
@@ -154,7 +152,5 @@ PEG.compiler.passes = {
     });
 
     compute(ast);
-
-    return ast;
   }
 };

test/passes-test.js

@@ -143,7 +143,9 @@ test("removes proxy rules", function() {
 
   for (var i = 0; i < cases.length; i++) {
     var ast = PEG.parser.parse(cases[i].grammar);
-    deepEqual(PEG.compiler.passes.removeProxyRules(ast), cases[i].ast);
+    PEG.compiler.passes.removeProxyRules(ast);
+
+    deepEqual(ast, cases[i].ast);
   }
 });