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

plugins/uast-kotlin/src/org/jetbrains/uast/kotlin/internal/kotlinInternalUastUtils.kt

@@ -36,6 +36,7 @@ import org.jetbrains.kotlin.builtins.isBuiltinFunctionalTypeOrSubtype
 import org.jetbrains.kotlin.codegen.signature.BothSignatureWriter
 import org.jetbrains.kotlin.descriptors.ClassDescriptor
 import org.jetbrains.kotlin.descriptors.DeclarationDescriptor
+import org.jetbrains.kotlin.descriptors.TypeAliasDescriptor
 import org.jetbrains.kotlin.load.kotlin.TypeMappingMode
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.resolve.BindingContext
@@ -74,6 +75,10 @@ internal fun <T> lz(initializer: () -> T) = lazy(LazyThreadSafetyMode.NONE, init
 internal fun KotlinType.toPsiType(source: UElement, element: KtElement, boxed: Boolean): PsiType {
     if (this.isError) return UastErrorType
 
+    (constructor.declarationDescriptor as? TypeAliasDescriptor)?.let { typeAlias ->
+        return typeAlias.expandedType.toPsiType(source, element, boxed)
+    }
+
     if (arguments.isEmpty()) {
         val typeFqName = this.constructor.declarationDescriptor?.fqNameSafe?.asString()
         fun PsiPrimitiveType.orBoxed() = if (boxed) getBoxedType(element) else this

plugins/uast-kotlin/testData/TypeAliases.kt

@@ -0,0 +1,3 @@
+class A
+typealias F = A.(A) -> A
+typealias G = (F) -> F

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())")