GH-130: Compare type references by type's full/qualified name

Resolve weird case when imports from current file and imports from
imported file resolve to different descriptor.proto files, resulting
in broken references for custom options.

Author: kshchepanovskyi

src/main/java/io/protostuff/jetbrains/plugin/reference/TypeReference.java

@@ -3,6 +3,8 @@
 import com.intellij.openapi.util.TextRange;
 import com.intellij.psi.PsiElement;
 import com.intellij.psi.PsiReferenceBase;
+import io.protostuff.jetbrains.plugin.psi.ProtoType;
+import java.util.Objects;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
@@ -31,4 +33,16 @@ public PsiElement resolve() {
     public Object[] getVariants() {
         return new Object[0];
     }
+
+    @Override
+    public boolean isReferenceTo(@NotNull PsiElement element) {
+        if (target instanceof ProtoType) {
+            ProtoType targetType = (ProtoType) target;
+            if (element instanceof ProtoType) {
+                ProtoType elementType = (ProtoType) element;
+                return Objects.equals(targetType.getFullName(), elementType.getFullName());
+            }
+        }
+        return super.isReferenceTo(element);
+    }
 }

src/test/java/io/protostuff/jetbrains/plugin/reference/CustomOptionReferenceTest.java

@@ -46,6 +46,20 @@ public void testImportedCustomOptionReference() {
         Assert.assertTrue(field.getParent() instanceof ExtendEntryNode);
     }
 
+    public void testImportedCustomOptionReference_withDescriptorProtoImport() {
+        myFixture.configureByFiles("reference/options/custom/SimpleExtensionField.proto",
+                "google/protobuf/__descriptor.proto");
+        PsiReference reference = myFixture.getReferenceAtCaretPositionWithAssertion(
+                "reference/options/custom/ImportedExtension_withDescriptorProtoImport.proto"
+        );
+        PsiElement target = reference.resolve();
+        Assert.assertNotNull(target);
+        Assert.assertTrue(target instanceof FieldNode);
+        FieldNode field = (FieldNode) target;
+        Assert.assertEquals("bar", field.getFieldName());
+        Assert.assertTrue(field.getParent() instanceof ExtendEntryNode);
+    }
+
     public void testImportedImportedCustomOptionReference() {
         myFixture.configureByFiles(
                 "reference/options/custom/SimpleExtensionField.proto",