reference_contributor.md: Use PsiPolyVariantReferenceBase

code_samples/simple_language_plugin/src/main/java/org/intellij/sdk/language/SimpleReference.java

@@ -6,47 +6,43 @@
 import com.intellij.codeInsight.lookup.LookupElementBuilder;
 import com.intellij.openapi.project.Project;
 import com.intellij.openapi.util.TextRange;
-import com.intellij.psi.*;
+import com.intellij.psi.PsiElement;
+import com.intellij.psi.PsiElementResolveResult;
+import com.intellij.psi.PsiPolyVariantReferenceBase;
+import com.intellij.psi.ResolveResult;
 import org.intellij.sdk.language.psi.SimpleProperty;
 import org.jetbrains.annotations.NotNull;
-import org.jetbrains.annotations.Nullable;
 
 import java.util.ArrayList;
 import java.util.List;
 
-final class SimpleReference extends PsiReferenceBase<PsiElement> implements PsiPolyVariantReference {
+final class SimpleReference extends PsiPolyVariantReferenceBase<PsiElement> {
 
   private final String key;
 
   SimpleReference(@NotNull PsiElement element, TextRange textRange) {
     super(element, textRange);
-    key = element.getText().substring(textRange.getStartOffset(), textRange.getEndOffset());
+    key = element.getText()
+        .substring(textRange.getStartOffset(), textRange.getEndOffset());
   }
 
   @Override
   public ResolveResult @NotNull [] multiResolve(boolean incompleteCode) {
     Project project = myElement.getProject();
-    final List<SimpleProperty> properties = SimpleUtil.findProperties(project, key);
+    List<SimpleProperty> properties = SimpleUtil.findProperties(project, key);
     List<ResolveResult> results = new ArrayList<>();
     for (SimpleProperty property : properties) {
       results.add(new PsiElementResolveResult(property));
     }
     return results.toArray(new ResolveResult[0]);
   }
 
-  @Nullable
-  @Override
-  public PsiElement resolve() {
-    ResolveResult[] resolveResults = multiResolve(false);
-    return resolveResults.length == 1 ? resolveResults[0].getElement() : null;
-  }
-
   @Override
   public Object @NotNull [] getVariants() {
     Project project = myElement.getProject();
     List<SimpleProperty> properties = SimpleUtil.findProperties(project);
     List<LookupElement> variants = new ArrayList<>();
-    for (final SimpleProperty property : properties) {
+    for (SimpleProperty property : properties) {
       if (property.getKey() != null && !property.getKey().isEmpty()) {
         variants.add(LookupElementBuilder
             .create(property).withIcon(SimpleIcons.FILE)

topics/tutorials/custom_language_support/reference_contributor.md

@@ -121,8 +121,9 @@ property ::= (KEY? SEPARATOR VALUE?) | KEY {
 ## Define a Reference
 
 Now define a reference class [`SimpleReference.java`](%gh-sdk-samples-master%/simple_language_plugin/src/main/java/org/intellij/sdk/language/SimpleReference.java) to resolve a property from its usage.
-This requires extending [`PsiReferenceBase`](%gh-ic%/platform/core-api/src/com/intellij/psi/PsiReferenceBase.java) and implementing [`PsiPolyVariantReference`](%gh-ic%/platform/core-api/src/com/intellij/psi/PsiPolyVariantReference.java).
-The latter enables the reference to resolve to more than one element or to resolve result(s) for a superset of valid resolve cases.
+As a single reference can [resolve to multiple](references_and_resolve.md#resolving-to-multiple-targets) Simple properties, it implements [`PsiPolyVariantReference`](%gh-ic%/platform/core-api/src/com/intellij/psi/PsiPolyVariantReference.java).
+To simplify the implementation, [`PsiPolyVariantReferenceBase`](%gh-ic%/platform/core-api/src/com/intellij/psi/PsiPolyVariantReferenceBase.java) is used as a base class.
+
 
 ```java
 ```