[java] avoids setting a package name for module-info files

java/java-psi-api/src/com/intellij/psi/PsiJavaFile.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2011 JetBrains s.r.o.
+ * Copyright 2000-2016 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.
@@ -20,7 +20,7 @@ import org.jetbrains.annotations.Nullable;
 import com.intellij.pom.java.LanguageLevel;
 
 /**
- * Represents a Java, JSP or class file.
+ * Represents a Java, JSP or .class file.
  */
 public interface PsiJavaFile extends PsiImportHolder, PsiClassOwner {
   /**
@@ -91,4 +91,9 @@ public interface PsiJavaFile extends PsiImportHolder, PsiClassOwner {
   @Nullable PsiJavaCodeReferenceElement findImportReferenceTo(PsiClass aClass);
 
   @NotNull LanguageLevel getLanguageLevel();
-}
+
+  /**
+   * Returns a Java module declaration element, or {@code null} if the file is not a module-info one.
+   */
+  @Nullable PsiJavaModule getModuleDeclaration();
+}

java/java-psi-api/src/com/intellij/psi/util/PsiUtil.java

@@ -1281,4 +1281,8 @@ public final class PsiUtil extends PsiUtilCore {
       }
     }
   }
+
+  public static boolean isModuleFile(@NotNull PsiFile file) {
+    return file instanceof PsiJavaFile && ((PsiJavaFile)file).getModuleDeclaration() != null;
+  }
 }