Uast: Fix an exception while converting type alias KotlinType to PsiType (KT-21874)

plugins/uast-kotlin/tests/KotlinUastApiTest.kt

@@ -6,6 +6,7 @@ import com.intellij.testFramework.UsefulTestCase
 import org.jetbrains.kotlin.asJava.toLightAnnotation
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.psiUtil.getParentOfType
+import org.jetbrains.kotlin.psi.psiUtil.getValueParameterList
 import org.jetbrains.kotlin.test.testFramework.KtUsefulTestCase
 import org.jetbrains.kotlin.utils.addToStdlib.cast
 import org.jetbrains.uast.*
@@ -277,6 +278,16 @@ class KotlinUastApiTest : AbstractKotlinUastTest() {
         }
     }
 
+    @Test
+    fun testTypeAliases() {
+        doTest("TypeAliases") { _, file ->
+            val g = (file.psi as KtFile).declarations.single { it.name == "G" } as KtTypeAlias
+            val originalType = g.getTypeReference()!!.typeElement as KtFunctionType
+            val originalTypeParameters = originalType.parameterList.toUElement() as UDeclarationsExpression
+            Assert.assertTrue((originalTypeParameters.declarations.single() as UParameter).type.isValid)
+        }
+    }
+
     @Test
     fun testNestedAnnotation() = doTest("AnnotationComplex") { _, file ->
         file.findElementByTextFromPsi<UElement>("@AnnotationArray(value = Annotation())")