introduce LightPsiParser

platform/core-api/src/com/intellij/lang/LightPsiParser.java

@@ -0,0 +1,24 @@
+/*
+ * Copyright 2000-2014 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.intellij.lang;
+
+import com.intellij.psi.tree.IElementType;
+
+public interface LightPsiParser {
+
+  void parseLight(IElementType root, PsiBuilder builder);
+}

platform/core-api/src/com/intellij/psi/tree/ILightStubFileElementType.java

@@ -48,7 +48,12 @@ public class ILightStubFileElementType<T extends PsiFileStub> extends IStubFileE
     final ParserDefinition parserDefinition = LanguageParserDefinitions.INSTANCE.forLanguage(getLanguage());
     assert parserDefinition != null : this;
     final PsiParser parser = parserDefinition.createParser(project);
-    parser.parse(this, builder);
+    if (parser instanceof LightPsiParser) {
+      ((LightPsiParser)parser).parseLight(this, builder);
+    }
+    else {
+      parser.parse(this, builder);
+    }
     return builder.getLightTree();
   }
 }