Add KtTypeElement.unwrapNullability() extension function

Replace similar functions with its usage

compiler/psi/src/org/jetbrains/kotlin/psi/psiUtil/ktPsiUtil.kt

@@ -676,3 +676,11 @@ fun getTrailingCommaByElementsList(elementList: PsiElement?): PsiElement? {
 
 val KtNameReferenceExpression.isUnderscoreInBackticks
     get() = getReferencedName() == "`_`"
+
+tailrec fun KtTypeElement.unwrapNullability(): KtTypeElement? {
+    return when (this) {
+        is KtNullableType -> this.innerType?.unwrapNullability()
+        is KtDefinitelyNotNullType -> this.innerType?.unwrapNullability()
+        else -> this
+    }
+}

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/components/KtFirReferenceShortener.kt

@@ -57,6 +57,7 @@ import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.psiUtil.createSmartPointer
 import org.jetbrains.kotlin.psi.psiUtil.getQualifiedExpressionForSelector
+import org.jetbrains.kotlin.psi.psiUtil.unwrapNullability
 
 internal class KtFirReferenceShortener(
     override val analysisSession: KtFirAnalysisSession,
@@ -218,7 +219,7 @@ private class ElementsToShortenCollector(private val shorteningContext: FirShort
         val wholeTypeReference = resolvedTypeRef.psi as? KtTypeReference ?: return
 
         val wholeClassifierId = resolvedTypeRef.type.lowerBoundIfFlexible().classId ?: return
-        val wholeTypeElement = wholeTypeReference.typeElement.unwrapNullable() as? KtUserType ?: return
+        val wholeTypeElement = wholeTypeReference.typeElement?.unwrapNullability() as? KtUserType ?: return
 
         if (wholeTypeElement.qualifier == null) return
 
@@ -456,9 +457,6 @@ private fun CallableId.asImportableFqName(): FqName? = if (classId == null) pack
 private fun KtElement.getDotQualifiedExpressionForSelector(): KtDotQualifiedExpression? =
     getQualifiedExpressionForSelector() as? KtDotQualifiedExpression
 
-private tailrec fun KtTypeElement?.unwrapNullable(): KtTypeElement? =
-    if (this is KtNullableType) this.innerType.unwrapNullable() else this
-
 private fun KtDotQualifiedExpression.deleteQualifier(): KtExpression? {
     val selectorExpression = selectorExpression ?: return null
     return this.replace(selectorExpression) as KtExpression

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/references/FirReferenceResolveHelper.kt

@@ -41,6 +41,7 @@ import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.psiUtil.collectDescendantsOfType
 import org.jetbrains.kotlin.psi.psiUtil.getNonStrictParentOfType
 import org.jetbrains.kotlin.psi.psiUtil.getQualifiedExpressionForSelector
+import org.jetbrains.kotlin.psi.psiUtil.unwrapNullability
 import org.jetbrains.kotlin.utils.addToStdlib.firstNotNullResult
 
 internal object FirReferenceResolveHelper {
@@ -420,7 +421,7 @@ internal object FirReferenceResolveHelper {
         // FIXME make it work with generics in functional types (like () -> AA.BB<CC, AA.DD>)
         val wholeType = when (val psi = wholeTypeFir.psi) {
             is KtUserType -> psi
-            is KtTypeReference -> psi.typeElement?.unwrapNullable() as? KtUserType
+            is KtTypeReference -> psi.typeElement?.unwrapNullability() as? KtUserType
             else -> null
         } ?: return null
 
@@ -447,9 +448,5 @@ internal object FirReferenceResolveHelper {
         return qualifierIndex
     }
 
-    private tailrec fun KtTypeElement.unwrapNullable(): KtTypeElement? {
-        return if (this is KtNullableType) innerType?.unwrapNullable() else this
-    }
-
     private val syntheticTokenTypes = TokenSet.create(KtTokens.ELVIS, KtTokens.EXCLEXCL)
 }