FIR IDE: fix IDE exception in presence of non-top-level type alias

Finding type alias doesn't work if it's not top level because the class
ID doesn't match. There doesn't seem to be a easy way to make it work
so this commit simply makes the IDE tolerate it.

idea/idea-frontend-fir/idea-fir-low-level-api/src/org/jetbrains/kotlin/idea/fir/low/level/api/util/declarationUtils.kt

@@ -124,11 +124,11 @@ private fun KtClassOrObject.findFir(firSymbolProvider: FirSymbolProvider): FirRe
     }
 }
 
-private fun KtTypeAlias.findFir(firSymbolProvider: FirSymbolProvider): FirTypeAlias {
+private fun KtTypeAlias.findFir(firSymbolProvider: FirSymbolProvider): FirTypeAlias? {
     val typeAlias = ClassId(containingKtFile.packageFqName, nameAsSafeName)
     return executeWithoutPCE {
+        // Finding a non-top-level type alias won't work
         firSymbolProvider.getClassLikeSymbolByFqName(typeAlias)?.fir as? FirTypeAlias
-            ?: error("Could not find type alias $typeAlias")
     }
 }
 

idea/idea-frontend-fir/idea-fir-low-level-api/src/org/jetbrains/kotlin/idea/fir/low/level/api/util/utils.kt

@@ -28,10 +28,11 @@ internal inline fun <T> executeOrReturnDefaultValueOnPCE(defaultValue: T, action
         defaultValue
     }
 
-internal inline fun <T : Any> executeWithoutPCE(crossinline action: () -> T): T {
+internal inline fun <T> executeWithoutPCE(crossinline action: () -> T): T {
     var result: T? = null
     ProgressManager.getInstance().executeNonCancelableSection { result = action() }
-    return result!!
+    @Suppress("UNCHECKED_CAST")
+    return result as T
 }
 
 internal inline fun <T> Lock.lockWithPCECheck(lockingIntervalMs: Long, action: () -> T): T {