fix some missing keywords in java completion (IDEA-175673, IDEA-175669)

java/java-impl/src/com/intellij/codeInsight/completion/JavaKeywordCompletion.java

@@ -38,6 +38,7 @@ import com.intellij.util.Consumer;
 import com.intellij.util.ObjectUtils;
 import com.intellij.util.ProcessingContext;
 import com.intellij.util.containers.ContainerUtil;
+import com.intellij.util.containers.JBIterable;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
@@ -152,7 +153,7 @@ public class JavaKeywordCompletion {
   private static final ElementPattern<PsiElement> EXPR_KEYWORDS = and(
     psiElement().withParent(psiElement(PsiReferenceExpression.class).withParent(
       not(
-        or(psiElement(PsiTypeCastExpression.class),
+        or(
            psiElement(PsiSwitchLabelStatement.class),
            psiElement(PsiExpressionStatement.class),
            psiElement(PsiPrefixExpression.class)
@@ -193,12 +194,16 @@ public class JavaKeywordCompletion {
     mySession = session;
     myPrefix = session.getMatcher().getPrefix();
     myPosition = parameters.getPosition();
-    myPrevLeaf = PsiTreeUtil.prevVisibleLeaf(myPosition);
+    myPrevLeaf = prevSignificantLeaf(myPosition);
 
     addKeywords();
     addEnumCases();
   }
 
+  private static PsiElement prevSignificantLeaf(PsiElement position) {
+    return JBIterable.generate(position, PsiTreeUtil::prevVisibleLeaf).skip(1).skipWhile(e -> e instanceof PsiComment).first();
+  }
+
   private void addKeyword(LookupElement element) {
     if (element.getLookupString().startsWith(myPrefix)) {
       myResults.add(element);
@@ -617,7 +622,7 @@ public class JavaKeywordCompletion {
       return false;
     }
 
-    PsiElement prev = PsiTreeUtil.prevVisibleLeaf(position);
+    PsiElement prev = prevSignificantLeaf(position);
     if (prev == null) {
       return true;
     }

java/java-tests/testData/codeInsight/completion/keywords/fileScopeAfterComment.java

@@ -0,0 +1,2 @@
+//comment
+<caret>package

java/java-tests/testData/codeInsight/completion/keywords/newInCast.java

@@ -0,0 +1,6 @@
+class Foo {
+
+  Object test() {
+    return (CharSequence) n<caret>
+  }
+}

java/java-tests/testSrc/com/intellij/java/codeInsight/completion/KeywordCompletionTest.java

@@ -45,6 +45,7 @@ public class KeywordCompletionTest extends LightCompletionTestCase {
   }
 
   public void testFileScope1() { doTest(8, FILE_SCOPE_KEYWORDS); }
+  public void testFileScopeAfterComment() { doTest(4, "package", "class", "import", "public", "private"); }
   public void testFileScope2() { doTest(7, CLASS_SCOPE_KEYWORDS); }
   public void testClassScope1() { doTest(5, CLASS_SCOPE_KEYWORDS); }
   public void testClassScope2() { doTest(4, CLASS_SCOPE_KEYWORDS); }
@@ -104,6 +105,7 @@ public class KeywordCompletionTest extends LightCompletionTestCase {
   public void testNullInMethodCall() { doTest(); }
   public void testNullInMethodCall2() { doTest(); }
   public void testNewInMethodRefs() { doTest(1, "new", "null", "true", "false"); }
+  public void testNewInCast() { doTest(2, "new", "null", "true", "false"); }
   public void testSpaceAfterInstanceof() { doTest(); }
   public void testInstanceofAfterUnresolved() { doTest(1, "instanceof"); }
   public void testInstanceofAfterStatementStart() { doTest(1, "instanceof"); }