diff --git a/src/main/java/org/jastadd/tooling/aspect/AspectColorSettingsPage.java b/src/main/java/org/jastadd/tooling/aspect/AspectColorSettingsPage.java
index 84739a005fa10daf558ac231ec630dff95310fbf..d6e4e215c753670bc3668de1cd881aade1bcdc13 100644
--- a/src/main/java/org/jastadd/tooling/aspect/AspectColorSettingsPage.java
+++ b/src/main/java/org/jastadd/tooling/aspect/AspectColorSettingsPage.java
@@ -72,13 +72,13 @@ public class AspectColorSettingsPage implements ColorSettingsPage {
 
   @NotNull
   @Override
-  public AttributesDescriptor[] getAttributeDescriptors() {
+  public AttributesDescriptor @NotNull [] getAttributeDescriptors() {
     return DESCRIPTORS;
   }
 
   @NotNull
   @Override
-  public ColorDescriptor[] getColorDescriptors() {
+  public ColorDescriptor @NotNull [] getColorDescriptors() {
     return ColorDescriptor.EMPTY_ARRAY;
   }
 
diff --git a/src/main/java/org/jastadd/tooling/aspect/AspectSyntaxHighlighter.java b/src/main/java/org/jastadd/tooling/aspect/AspectSyntaxHighlighter.java
index f6a3c03147dfa3e1a48b0911fbef4e1f61b4764b..4f44cb07d6504401460d79fa8038bfeaaea729ee 100644
--- a/src/main/java/org/jastadd/tooling/aspect/AspectSyntaxHighlighter.java
+++ b/src/main/java/org/jastadd/tooling/aspect/AspectSyntaxHighlighter.java
@@ -131,7 +131,7 @@ public class AspectSyntaxHighlighter extends SyntaxHighlighterBase {
 
   @NotNull
   @Override
-  public TextAttributesKey[] getTokenHighlights(IElementType tokenType) {
+  public TextAttributesKey @NotNull [] getTokenHighlights(IElementType tokenType) {
     if (javaKeywords.contains(tokenType) || jastAddKeywords.contains(tokenType)) {
       return KEYWORD_KEYS;
     } else if (keywordLiterals.contains(tokenType)) {
diff --git a/src/main/java/org/jastadd/tooling/aspect/parser/AspectParserDefinition.java b/src/main/java/org/jastadd/tooling/aspect/parser/AspectParserDefinition.java
index 62cf3ab1de30577aaf7f4d84b3d5c253beeead3a..5d0c747f76aade0f26d218f63e8bbfbf1e153d1e 100644
--- a/src/main/java/org/jastadd/tooling/aspect/parser/AspectParserDefinition.java
+++ b/src/main/java/org/jastadd/tooling/aspect/parser/AspectParserDefinition.java
@@ -56,17 +56,17 @@ public class AspectParserDefinition implements ParserDefinition {
   }
 
   @Override
-  public IFileElementType getFileNodeType() {
+  public @NotNull IFileElementType getFileNodeType() {
     return FILE;
   }
 
   @Override
-  public PsiFile createFile(FileViewProvider viewProvider) {
+  public @NotNull PsiFile createFile(@NotNull FileViewProvider viewProvider) {
     return new AspectFile(viewProvider);
   }
 
   @Override
-  public SpaceRequirements spaceExistenceTypeBetweenTokens(ASTNode left, ASTNode right) {
+  public @NotNull SpaceRequirements spaceExistenceTypeBetweenTokens(ASTNode left, ASTNode right) {
     return SpaceRequirements.MAY;
   }
 
diff --git a/src/main/java/org/jastadd/tooling/grammar/GrammarChooseByNameContributor.java b/src/main/java/org/jastadd/tooling/grammar/GrammarChooseByNameContributor.java
index 972038e20013dd367a138c5f42546301843a3235..f1d88f5bdd920cd0494edf557d463572f4c8f215 100644
--- a/src/main/java/org/jastadd/tooling/grammar/GrammarChooseByNameContributor.java
+++ b/src/main/java/org/jastadd/tooling/grammar/GrammarChooseByNameContributor.java
@@ -3,6 +3,7 @@ package org.jastadd.tooling.grammar;
 import com.intellij.navigation.ChooseByNameContributor;
 import com.intellij.navigation.NavigationItem;
 import com.intellij.openapi.project.Project;
+import com.intellij.psi.PsiElement;
 import org.jastadd.tooling.grammar.psi.GrammarTypeDecl;
 import org.jetbrains.annotations.NotNull;
 
@@ -28,8 +29,13 @@ public class GrammarChooseByNameContributor implements ChooseByNameContributor {
   @Override
   public NavigationItem @NotNull [] getItemsByName(String name, String pattern, Project project, boolean includeNonProjectItems) {
     // TODO: include non project items
-    List<GrammarTypeDecl> typeDecls = GrammarUtil.findTypeDecl(project, name);
-    return typeDecls.toArray(new NavigationItem[0]);
+
+    List<NavigationItem> items = new ArrayList<>();
+    for (PsiElement typeDecl : GrammarUtil.findTypeDecl(project, name)) {
+      items.add((NavigationItem) typeDecl);
+    }
+
+    return items.toArray(new NavigationItem[0]);
   }
 
 }
diff --git a/src/main/java/org/jastadd/tooling/grammar/GrammarColorSettingsPage.java b/src/main/java/org/jastadd/tooling/grammar/GrammarColorSettingsPage.java
index dd5ee32d608935199ff563f6d51b997c1a8069cf..e1c1519f67cca6840e08ca9045fae4d508f463bf 100644
--- a/src/main/java/org/jastadd/tooling/grammar/GrammarColorSettingsPage.java
+++ b/src/main/java/org/jastadd/tooling/grammar/GrammarColorSettingsPage.java
@@ -13,6 +13,7 @@ import org.jetbrains.annotations.Nullable;
 import javax.swing.*;
 import java.util.Map;
 
+@SuppressWarnings("DialogTitleCapitalization")
 public class GrammarColorSettingsPage implements ColorSettingsPage {
 
   private static final AttributesDescriptor[] DESCRIPTORS = new AttributesDescriptor[]{
diff --git a/src/main/java/org/jastadd/tooling/grammar/GrammarFormattingModelBuilder.java b/src/main/java/org/jastadd/tooling/grammar/GrammarFormattingModelBuilder.java
index 8df61fa224a9b1bbd31feb21319a55d35147b765..4567ebcc9cfa6c082fca0314687432e78812088e 100644
--- a/src/main/java/org/jastadd/tooling/grammar/GrammarFormattingModelBuilder.java
+++ b/src/main/java/org/jastadd/tooling/grammar/GrammarFormattingModelBuilder.java
@@ -3,7 +3,6 @@ package org.jastadd.tooling.grammar;
 import com.intellij.formatting.*;
 import com.intellij.lang.ASTNode;
 import com.intellij.openapi.util.TextRange;
-import com.intellij.psi.PsiElement;
 import com.intellij.psi.PsiFile;
 import com.intellij.psi.codeStyle.CodeStyleSettings;
 import com.intellij.psi.codeStyle.CommonCodeStyleSettings;
diff --git a/src/main/java/org/jastadd/tooling/grammar/GrammarLineMarkerProvider.java b/src/main/java/org/jastadd/tooling/grammar/GrammarLineMarkerProvider.java
index 169e72996d265f3e821121eb368287295823b17b..756de68899f5730212585c6658098559b383d979 100644
--- a/src/main/java/org/jastadd/tooling/grammar/GrammarLineMarkerProvider.java
+++ b/src/main/java/org/jastadd/tooling/grammar/GrammarLineMarkerProvider.java
@@ -28,7 +28,7 @@ public class GrammarLineMarkerProvider extends RelatedItemLineMarkerProvider {
 
     Optional<PsiClass> classOptional = asReferenceToTypeDecl(element.getParent());
 
-    if (classOptional.isEmpty()) {
+    if (!classOptional.isPresent()) {
       return;
     }
 
diff --git a/src/main/java/org/jastadd/tooling/grammar/GrammarStructureViewModel.java b/src/main/java/org/jastadd/tooling/grammar/GrammarStructureViewModel.java
index 98994e47225077bdee1313c0afd24171ba54e220..255a47ec525752a02d84427cf3f17e9f397ce3fe 100644
--- a/src/main/java/org/jastadd/tooling/grammar/GrammarStructureViewModel.java
+++ b/src/main/java/org/jastadd/tooling/grammar/GrammarStructureViewModel.java
@@ -16,7 +16,7 @@ public class GrammarStructureViewModel extends StructureViewModelBase implements
   }
 
   @NotNull
-  public Sorter[] getSorters() {
+  public Sorter @NotNull [] getSorters() {
     return new Sorter[]{Sorter.ALPHA_SORTER};
   }
 
diff --git a/src/main/java/org/jastadd/tooling/grammar/GrammarUtil.java b/src/main/java/org/jastadd/tooling/grammar/GrammarUtil.java
index 9c4f0cfaef630597f805789cc6061adca844382e..46280add83e0070bbd7fb11e397b23c2a042b3d6 100644
--- a/src/main/java/org/jastadd/tooling/grammar/GrammarUtil.java
+++ b/src/main/java/org/jastadd/tooling/grammar/GrammarUtil.java
@@ -76,7 +76,7 @@ public class GrammarUtil {
 
   public static Optional<PsiClass> asReferenceToTypeDecl(@NotNull final PsiElement element) {
 
-    // Ensure the Psi Element is an reference
+    // Ensure the Psi Element is a reference
     if (!(element instanceof PsiJavaCodeReferenceElement)) {
       return Optional.empty();
     }
diff --git a/src/main/java/org/jastadd/tooling/grammar/parser/GrammarParserDefinition.java b/src/main/java/org/jastadd/tooling/grammar/parser/GrammarParserDefinition.java
index 5f2ee175e52ac39418bc94f0a50c2d5e80ade941..dd1fc894e2c318f01f1d926c85fa9b096aa8f39c 100644
--- a/src/main/java/org/jastadd/tooling/grammar/parser/GrammarParserDefinition.java
+++ b/src/main/java/org/jastadd/tooling/grammar/parser/GrammarParserDefinition.java
@@ -55,17 +55,17 @@ public class GrammarParserDefinition implements ParserDefinition {
   }
 
   @Override
-  public IFileElementType getFileNodeType() {
+  public @NotNull IFileElementType getFileNodeType() {
     return FILE;
   }
 
   @Override
-  public PsiFile createFile(FileViewProvider viewProvider) {
+  public @NotNull PsiFile createFile(@NotNull FileViewProvider viewProvider) {
     return new GrammarFile(viewProvider);
   }
 
   @Override
-  public SpaceRequirements spaceExistenceTypeBetweenTokens(ASTNode left, ASTNode right) {
+  public @NotNull SpaceRequirements spaceExistenceTypeBetweenTokens(ASTNode left, ASTNode right) {
     return SpaceRequirements.MAY;
   }