warn about underscore identifier

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

@@ -684,10 +684,6 @@ public class HighlightUtil extends HighlightUtilBase {
         String message = JavaErrorMessages.message("underscore.lambda.identifier");
         return HighlightInfo.newHighlightInfo(HighlightInfoType.ERROR).range(identifier).descriptionAndTooltip(message).create();
       }
-      else {
-        String message = JavaErrorMessages.message("underscore.identifier");
-        return HighlightInfo.newHighlightInfo(HighlightInfoType.WARNING).range(identifier).descriptionAndTooltip(message).create();
-      }
     }
 
     return null;

java/java-analysis-impl/src/com/intellij/codeInspection/compiler/JavacQuirksInspectionVisitor.java

@@ -15,9 +15,11 @@
  */
 package com.intellij.codeInspection.compiler;
 
+import com.intellij.codeInsight.daemon.JavaErrorMessages;
 import com.intellij.codeInspection.InspectionsBundle;
 import com.intellij.codeInspection.ProblemsHolder;
 import com.intellij.patterns.ElementPattern;
+import com.intellij.pom.java.LanguageLevel;
 import com.intellij.psi.*;
 import com.intellij.psi.util.PsiTreeUtil;
 import com.intellij.psi.util.PsiUtil;
@@ -63,4 +65,14 @@ public class JavacQuirksInspectionVisitor extends JavaElementVisitor {
       });
     }
   }
+
+  @Override
+  public void visitIdentifier(PsiIdentifier identifier) {
+    super.visitIdentifier(identifier);
+    if (PsiUtil.getLanguageLevel(identifier).isAtLeast(LanguageLevel.JDK_1_8)) {
+      if ("_".equals(identifier.getText())) {
+        myHolder.registerProblem(identifier, JavaErrorMessages.message("underscore.identifier"));
+      }
+    }
+  }
 }

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/lambda/advHighlighting/Underscore.java

@@ -0,0 +1,3 @@
+class Test {
+  void <warning descr="Use of '_' as an identifier might not be supported in releases after Java 8">_</warning>(){}
+}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/lambda/highlighting/Underscores.java

@@ -1,10 +1,5 @@
 class C {
   void test() {
-    {
-      I <warning descr="Use of '_' as an identifier might not be supported in releases after Java 8">_</warning> = new I() { public void f(int i) { } };
-      accept(_);
-    }
-
     {
       accept(<error descr="Use of '_' as a lambda parameter name is not allowed">_</error> -> System.out.println(_));
       accept((int <error descr="Use of '_' as a lambda parameter name is not allowed">_</error>) -> System.out.println(_));

java/java-tests/testSrc/com/intellij/codeInsight/daemon/lambda/LightAdvHighlightingJdk8Test.java

@@ -0,0 +1,52 @@
+/*
+ * 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.codeInsight.daemon.lambda;
+
+import com.intellij.codeInsight.daemon.LightDaemonAnalyzerTestCase;
+import com.intellij.codeInspection.LocalInspectionTool;
+import com.intellij.codeInspection.compiler.JavacQuirksInspection;
+import com.intellij.codeInspection.unusedSymbol.UnusedSymbolLocalInspection;
+import com.intellij.openapi.projectRoots.JavaSdkVersion;
+import com.intellij.openapi.projectRoots.Sdk;
+import com.intellij.testFramework.IdeaTestUtil;
+import org.jetbrains.annotations.NonNls;
+import org.jetbrains.annotations.NotNull;
+
+public class LightAdvHighlightingJdk8Test extends LightDaemonAnalyzerTestCase {
+  @NonNls static final String BASE_PATH = "/codeInsight/daemonCodeAnalyzer/lambda/advHighlighting";
+
+  @NotNull
+  @Override
+  protected LocalInspectionTool[] configureLocalInspectionTools() {
+    return new LocalInspectionTool[]{
+      new JavacQuirksInspection(),
+    };
+  }
+
+  public void testUnderscore() throws Exception {
+    doTest();
+  }
+
+  private void doTest() {
+    IdeaTestUtil.setTestVersion(JavaSdkVersion.JDK_1_8, getModule(), getTestRootDisposable());
+    doTestNewInference(BASE_PATH + "/" + getTestName(false) + ".java", true, false);
+  }
+
+  @Override
+  protected Sdk getProjectJDK() {
+    return IdeaTestUtil.getMockJdk18();
+  }
+}