[FIR] Fix generic sam conversion in call completion

#KT-60903 Fixed

jps/jps-plugin/testData/incremental/pureKotlin/samConversion/observable.kt

@@ -0,0 +1,33 @@
+open class Subscription
+
+interface Observer<T> {
+    fun next(value: T)
+}
+
+open class Subscriber<T>(observer: Observer<T>? = null) : Subscription(), Observer<T> {
+    override fun next(value: T) {}
+}
+
+fun interface Subscribe<T> {
+    fun subscribe(subscriber: Subscriber<T>): Subscription
+}
+
+fun interface Operator<X, Y> {
+    fun call(source: Observable<X>): Observable<Y>
+}
+
+open class Observable<T>(private val subscribeFn: Subscribe<T>) {
+    fun <R> apply(operator: Operator<T, R>): Observable<R> {
+        return operator.call(this)
+    }
+
+    fun subscribe(observer: Observer<T>): Subscription {
+        return Subscription()
+    }
+
+    companion object {
+        fun <T> of(vararg elems: T): Observable<T> {
+            return Observable { Subscription() }
+        }
+    }
+}