add "pure" attribute to @Contract (IDEA-107864)

java/java-tests/testData/inspection/dataFlow/fixture/ContractAnnotation.java

@@ -46,4 +46,7 @@ public class AssertIsNotNull {
 
   @Contract(<warning descr="Method takes 2 parameters, while contract clause number 1 expects 1">"null -> _"</warning>)
   void wrongParameterCount(Object a, boolean b) {}
+  
+  @Contract(pure=<warning descr="Pure methods must return something, void is not allowed as a return type">true</warning>)
+  void voidPureMethod() {}
 }

java/java-tests/testSrc/com/intellij/codeInspection/DataFlowInspectionTest.java

@@ -39,12 +39,6 @@ public class DataFlowInspectionTest extends LightCodeInsightFixtureTestCase {
     return JAVA_1_7;
   }
 
-  @Override
-  protected void setUp() throws Exception {
-    super.setUp();
-    myFixture.addClass("package org.jetbrains.annotations; public @interface Contract { String value(); }");
-  }
-
   @Override
   protected String getTestDataPath() {
     return JavaTestUtil.getJavaTestDataPath() + "/inspection/dataFlow/fixture/";