Don't use PsiElement.getReference() on JetElement

compiler/frontend/src/org/jetbrains/kotlin/psi/JetElement.kt

@@ -14,16 +14,18 @@
  * limitations under the License.
  */
 
-package org.jetbrains.kotlin.psi;
+package org.jetbrains.kotlin.psi
 
-import com.intellij.psi.NavigatablePsiElement;
-import org.jetbrains.annotations.NotNull;
+import com.intellij.psi.NavigatablePsiElement
+import com.intellij.psi.PsiReference
 
-public interface JetElement extends NavigatablePsiElement {
-    @NotNull
-    JetFile getContainingJetFile();
+public interface JetElement : NavigatablePsiElement {
+    public fun getContainingJetFile(): JetFile
 
-    <D> void acceptChildren(@NotNull JetVisitor<Void, D> visitor, D data);
+    public fun <D> acceptChildren(visitor: JetVisitor<Void, D>, data: D)
 
-    <R, D> R accept(@NotNull JetVisitor<R, D> visitor, D data);
+    public fun <R, D> accept(visitor: JetVisitor<R, D>, data: D): R
+
+    @deprecated("Don't use getReference() on JetElement for the choice is unpredictable")
+    override fun getReference(): PsiReference?
 }

compiler/frontend/src/org/jetbrains/kotlin/resolve/constants/evaluate/ConstantExpressionEvaluator.kt

@@ -82,7 +82,7 @@ public class ConstantExpressionEvaluator private constructor(val trace: BindingT
         return null
     }
 
-    private val stringExpressionEvaluator = object : JetVisitor<TypedCompileTimeConstant<String>, Nothing>() {
+    private val stringExpressionEvaluator = object : JetVisitor<TypedCompileTimeConstant<String>, Nothing?>() {
         private fun createStringConstant(compileTimeConstant: CompileTimeConstant<*>): TypedCompileTimeConstant<String>? {
             val constantValue = compileTimeConstant.toConstantValue(TypeUtils.NO_EXPECTED_TYPE)
             return when (constantValue) {