Add util class for stubbed PSI

Implement methods to find parent by stub

compiler/frontend/src/org/jetbrains/jet/lang/psi/JetStubbedPsiUtil.java

@@ -0,0 +1,57 @@
+/*
+ * Copyright 2010-2014 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 org.jetbrains.jet.lang.psi;
+
+import com.intellij.psi.PsiElement;
+import com.intellij.psi.stubs.StubElement;
+import com.intellij.psi.util.PsiTreeUtil;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+public final class JetStubbedPsiUtil {
+    @Nullable
+    public static JetDeclaration getContainingDeclaration(@NotNull PsiElement element) {
+        return getContainingDeclaration(element, JetDeclaration.class, true);
+    }
+
+    @Nullable
+    public static <T extends JetDeclaration> T getContainingDeclaration(@NotNull PsiElement element, @NotNull Class<T> declarationClass) {
+        return getContainingDeclaration(element, declarationClass, true);
+    }
+
+    @Nullable
+    public static <T extends JetDeclaration> T getContainingDeclaration(
+            @NotNull PsiElement element,
+            @NotNull Class<T> declarationClass,
+            boolean strict
+    ) {
+        if (!strict && declarationClass.isInstance(element)) {
+            //noinspection unchecked
+            return (T) element;
+        }
+        if (element instanceof JetElementImplStub) {
+            StubElement<?> stub = ((JetElementImplStub) element).getStub();
+            if (stub != null) {
+                return stub.getParentStubOfType(declarationClass);
+            }
+        }
+        return PsiTreeUtil.getParentOfType(element, declarationClass, strict);
+    }
+
+    private JetStubbedPsiUtil() {
+    }
+}