java completion: use a single way to find previous interesting PSI (IDEA-184555)

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

@@ -12,6 +12,7 @@ import com.intellij.patterns.ElementPattern;
 import com.intellij.patterns.PsiElementPattern;
 import com.intellij.pom.java.LanguageLevel;
 import com.intellij.psi.*;
+import com.intellij.psi.filters.FilterPositionUtil;
 import com.intellij.psi.templateLanguages.OuterLanguageElement;
 import com.intellij.psi.util.InheritanceUtil;
 import com.intellij.psi.util.PsiTreeUtil;
@@ -19,7 +20,6 @@ import com.intellij.psi.util.PsiUtil;
 import com.intellij.util.Consumer;
 import com.intellij.util.ObjectUtils;
 import com.intellij.util.containers.ContainerUtil;
-import com.intellij.util.containers.JBIterable;
 import org.jetbrains.annotations.NotNull;
 
 import java.util.ArrayList;
@@ -124,7 +124,7 @@ public class JavaKeywordCompletion {
   }
 
   private static PsiElement prevSignificantLeaf(PsiElement position) {
-    return JBIterable.generate(position, PsiTreeUtil::prevVisibleLeaf).skip(1).skipWhile(e -> PsiTreeUtil.getNonStrictParentOfType(e, PsiComment.class) != null).first();
+    return FilterPositionUtil.searchNonSpaceNonCommentBack(position);
   }
 
   private void addKeyword(LookupElement element) {

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

+abstract /** javadoc */
+<caret> class Primitive {
+
+    public abstract void draw();
+
+
+}
\ No newline at end of file

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

@@ -48,6 +48,7 @@ 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 testFileScopeAfterJavaDoc() { doTest(4, "package", "class", "import", "public", "private"); }
+  public void testFileScopeAfterJavaDocInsideModifierList() { doTest(2, "class", "public"); }
   public void testFileScope2() { doTest(7, CLASS_SCOPE_KEYWORDS); }
   public void testClassScope1() { doTest(5, CLASS_SCOPE_KEYWORDS); }
   public void testClassScope2() { doTest(4, CLASS_SCOPE_KEYWORDS); }

platform/lang-impl/src/com/intellij/psi/filters/FilterPositionUtil.java

@@ -20,6 +20,7 @@ import com.intellij.psi.PsiComment;
 import com.intellij.psi.PsiElement;
 import com.intellij.psi.TokenType;
 import com.intellij.psi.impl.source.tree.TreeUtil;
+import com.intellij.psi.util.PsiTreeUtil;
 import org.jetbrains.annotations.Nullable;
 
 /**
@@ -37,7 +38,8 @@ public class FilterPositionUtil {
     ASTNode leftNeighbour = TreeUtil.prevLeaf(element.getNode());
     if (!strict) {
       while (leftNeighbour != null &&
-             (leftNeighbour.getElementType() == TokenType.WHITE_SPACE || leftNeighbour.getPsi() instanceof PsiComment)) {
+             (leftNeighbour.getElementType() == TokenType.WHITE_SPACE || 
+              PsiTreeUtil.getNonStrictParentOfType(leftNeighbour.getPsi(), PsiComment.class) != null)) {
         leftNeighbour = TreeUtil.prevLeaf(leftNeighbour);
       }
     }