method refs: turn highlighting on; check valid context

java/java-impl/src/com/intellij/codeInsight/daemon/impl/analysis/HighlightUtil.java

@@ -339,6 +339,9 @@ public class HighlightUtil {
     if (operandType == null) return null;
     if (operandType instanceof PsiLambdaExpressionType) {
       return HighlightInfo.createHighlightInfo(HighlightInfoType.ERROR, expression, "Lambda expression is not expected here");
+    } 
+    if (operandType instanceof PsiMethodReferenceType) {
+      return HighlightInfo.createHighlightInfo(HighlightInfoType.ERROR, expression, "Method reference expression is not expected here");
     }
     if (TypeConversionUtil.isPrimitiveAndNotNull(operandType)
         || TypeConversionUtil.isPrimitiveAndNotNull(checkType)
@@ -2633,11 +2636,7 @@ public class HighlightUtil {
 
   @Nullable
   public static HighlightInfo checkMethodReferencesFeature(final PsiMethodReferenceExpression expression) {
-    final HighlightInfo info = checkFeature(expression, Feature.METHOD_REFERENCES);
-    if (info != null) return info;
-    // todo[r.sh] stub; remove after implementing support in TypeConversionUtil
-    final String message = "Method references type check is not yet implemented";
-    return HighlightInfo.createHighlightInfo(HighlightInfoType.WEAK_WARNING, expression, message);
+    return checkFeature(expression, Feature.METHOD_REFERENCES);
   }
 
   @Nullable

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/advHighlighting7/MethodReferences.java

@@ -22,7 +22,7 @@ class C {
   void use(Simplest s) { }
 
   void test() {
-    Simplest simplest = <weak_warning descr="Method references type check is not yet implemented">this::simplest</weak_warning>;
-    use(<weak_warning descr="Method references type check is not yet implemented">this::simplest</weak_warning>);
+    Simplest simplest = this::simplest;
+    use(this::simplest);
   }
 }

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/lambda/methodRef/ValidContext.java

@@ -0,0 +1,17 @@
+public class Test {
+  {
+    if (<error descr="Method reference expression is not expected here">Test::length instanceof String</error>) {
+    }
+    bar(Test::length);
+  }
+
+  public static Integer length(String s) {
+    return s.length();
+  }
+  
+  public static void bar(Bar bar) {}
+  
+  interface Bar {
+    Integer _(String s);
+  }
+}

java/java-tests/testSrc/com/intellij/codeInsight/daemon/lambda/MethodRefHighlightingTest.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2000-2012 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.codeInsight.daemon.lambda;
+
+import com.intellij.codeInsight.daemon.LightDaemonAnalyzerTestCase;
+import org.jetbrains.annotations.NonNls;
+
+public class MethodRefHighlightingTest extends LightDaemonAnalyzerTestCase {
+  @NonNls static final String BASE_PATH = "/codeInsight/daemonCodeAnalyzer/lambda/methodRef";
+
+  public void testValidContext() throws Exception {
+    doTest();
+  }
+
+  private void doTest() throws Exception {
+    doTest(BASE_PATH + "/" + getTestName(false) + ".java", false, false);
+  }
+}