chore(strawman): proposal for toPromise replacement

src/internal/finalResult.ts

@@ -0,0 +1,23 @@
+import { Observable } from './Observable';
+import { EmptyError } from './util/EmptyError';
+
+export function finalResult<T>(source: Observable<T>) {
+  return new Promise<T>((resolve, reject) => {
+    let _hasValue = false;
+    let _value: T;
+    source.subscribe({
+      next: value => {
+        _value = value;
+        _hasValue = true;
+      },
+      error: reject,
+      complete: () => {
+        if (_hasValue) {
+          resolve(_value);
+        } else {
+          reject(new EmptyError());
+        }
+      },
+    });
+  });
+}

src/internal/firstResult.ts

@@ -0,0 +1,14 @@
+import { Observable } from './Observable';
+import { EmptyError } from './util/EmptyError';
+
+export function firstResult<T>(source$: Observable<T>) {
+  return new Promise<T>((resolve, reject) => {
+    source$.subscribe({
+      next: value => resolve(value),
+      error: reject,
+      complete: () => {
+        reject(new EmptyError());
+      },
+    });
+  });
+}