Replace kotlin reference contributor written in kotlin with one in java

There is some breaking change in Kotlin that causes the kotlin code to throw an exception when used in earlier IntelliJ versions

Author: filiphr

gradle.properties

@@ -2,7 +2,7 @@
 # https://www.jetbrains.com/intellij-repository/releases
 # https://www.jetbrains.com/intellij-repository/snapshots
 
-ideaVersion = 2020.3.3
+ideaVersion = 2019.1
 ideaType = IC
 sources = true
 isEAP = false

src/main/java/org/mapstruct/intellij/codeinsight/references/KtMapstructReferenceContributor.kt

@@ -0,0 +1,43 @@
+/*
+ * Copyright MapStruct Authors.
+ *
+ * Licensed under the Apache License version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0
+ */
+package org.mapstruct.intellij.codeinsight.references;
+
+import com.intellij.psi.PsiReferenceContributor;
+import com.intellij.psi.PsiReferenceRegistrar;
+import org.jetbrains.annotations.NotNull;
+
+import static org.mapstruct.intellij.util.MapstructKotlinElementUtils.mappingElementPattern;
+import static org.mapstruct.intellij.util.MapstructKotlinElementUtils.valueMappingElementPattern;
+
+/**
+ * {@link PsiReferenceContributor} for MapStruct annotations in Kotlin code.
+ *
+ * @author Frank Wang
+ * @author Filip Hrisafov
+ */
+public class MapstructKotlinReferenceContributor extends PsiReferenceContributor {
+
+    @Override
+    public void registerReferenceProviders(@NotNull PsiReferenceRegistrar registrar) {
+        registrar.registerReferenceProvider(
+            mappingElementPattern( "target" ),
+            new MappingTargetReferenceProvider( MapstructTargetReference::create )
+        );
+        registrar.registerReferenceProvider(
+            mappingElementPattern( "source" ),
+            new MappingTargetReferenceProvider( MapstructSourceReference::create )
+        );
+        registrar.registerReferenceProvider(
+            valueMappingElementPattern( "target" ),
+            new MappingTargetReferenceProvider( ValueMappingSourceReference::create )
+        );
+        registrar.registerReferenceProvider(
+            valueMappingElementPattern( "source" ),
+            new MappingTargetReferenceProvider( ValueMappingTargetReference::create )
+        );
+    }
+
+}

src/main/java/org/mapstruct/intellij/codeinsight/references/MapstructKotlinReferenceContributor.java

@@ -7,6 +7,6 @@
 -->
 <idea-plugin>
     <extensions defaultExtensionNs="com.intellij">
-        <psi.referenceContributor language="kotlin" implementation="org.mapstruct.intellij.codeinsight.references.KtMapstructReferenceContributor" />
+        <psi.referenceContributor language="kotlin" implementation="org.mapstruct.intellij.codeinsight.references.MapstructKotlinReferenceContributor" />
     </extensions>
 </idea-plugin>