Use UAST instead of Kotlin plugin APIs

Fixes #69

build.gradle

@@ -5,7 +5,7 @@ plugins {
     id "org.jetbrains.intellij" version "0.4.21"
     id "com.github.hierynomus.license" version "0.14.0"
     id "de.undercouch.download" version "4.0.4"
-    id 'org.jetbrains.kotlin.jvm' version '1.3.71'
+    id 'org.jetbrains.kotlin.jvm' version '1.4.31'
 }
 
 

gradle.properties

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

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

@@ -7,13 +7,14 @@
 
 import com.intellij.openapi.util.TextRange;
 import com.intellij.psi.PsiElement;
-import com.intellij.psi.PsiLiteral;
 import com.intellij.psi.PsiMethod;
 import com.intellij.psi.PsiReferenceBase;
-import com.intellij.psi.util.PsiTreeUtil;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
-import org.mapstruct.intellij.util.MapstructUtilKt;
+import org.jetbrains.uast.ULiteralExpression;
+import org.jetbrains.uast.UMethod;
+import org.jetbrains.uast.UastContextKt;
+import org.jetbrains.uast.UastUtils;
 
 /**
  * Base Reference for MapStruct.
@@ -43,14 +44,13 @@ abstract class BaseReference extends PsiReferenceBase<PsiElement> {
     @Nullable
     PsiMethod getMappingMethod() {
         PsiElement element = getElement();
-        if ( element instanceof PsiLiteral ) {
-            return PsiTreeUtil.getParentOfType( element, PsiMethod.class );
+        ULiteralExpression expression = UastContextKt.toUElement( element, ULiteralExpression.class );
+        if ( expression != null ) {
+            UMethod parent = UastUtils.getParentOfType( expression, UMethod.class );
+            if ( parent != null ) {
+                return parent.getJavaPsi();
+            }
         }
-        else if ( "KtStringTemplateExpression".equals( element.getClass().getSimpleName() ) ) {
-            // We cannot do an instanceOf check here because the kotlin class is optional
-            return MapstructUtilKt.getPsiMethod( element );
-        }
-
         return null;
     }
 }