Add Animated.Numeric Flow type

Summary:
Changelog: [General][Added] - Add `Animated.Numeric` Flow type

Adds a Flow type to represent the various Animated node types that evaluate to numeric values and can be `interpolate()`d.

I'm including `AnimatedInterpolation` as "numeric" here even though it can technically evaluate either to a number or to a string, depending on its config. Note that calling `interpolate()` on a string-valued `AnimatedInterpolation` is a runtime error.

In a future diff, I'm planning to add a type argument to `AnimatedInterpolation` (and its config type), at which point we can refine `Animated.Numeric` to correctly include only `AnimatedInterpolation<number>`.

Reviewed By: javache

Differential Revision: D35869375

fbshipit-source-id: 2ff6754f1a5abc68c9da2c6836872c2022b25676

Libraries/Animated/Animated.js

@@ -16,8 +16,8 @@ import typeof AnimatedSectionList from './components/AnimatedSectionList';
 import typeof AnimatedText from './components/AnimatedText';
 import typeof AnimatedView from './components/AnimatedView';
 
-const AnimatedMock = require('./AnimatedMock');
-const AnimatedImplementation = require('./AnimatedImplementation');
+import * as AnimatedMock from './AnimatedMock';
+import * as AnimatedImplementation from './AnimatedImplementation';
 
 const Animated = ((Platform.isTesting
   ? AnimatedMock

Libraries/Animated/AnimatedImplementation.js

@@ -551,6 +551,19 @@ const event = function (
   }
 };
 
+// All types of animated nodes that represent scalar numbers and can be interpolated (etc)
+type AnimatedNumeric =
+  | AnimatedAddition
+  | AnimatedDiffClamp
+  | AnimatedDivision
+  | AnimatedInterpolation
+  | AnimatedModulo
+  | AnimatedMultiplication
+  | AnimatedSubtraction
+  | AnimatedValue;
+
+export type {AnimatedNumeric as Numeric};
+
 /**
  * The `Animated` library is designed to make animations fluid, powerful, and
  * easy to build and maintain. `Animated` focuses on declarative relationships

Libraries/Animated/AnimatedMock.js

@@ -23,7 +23,7 @@ import type {EndCallback} from './animations/Animation';
 import type {TimingAnimationConfig} from './animations/TimingAnimation';
 import type {DecayAnimationConfig} from './animations/DecayAnimation';
 import type {SpringAnimationConfig} from './animations/SpringAnimation';
-
+import type {Numeric as AnimatedNumeric} from './AnimatedImplementation';
 import AnimatedColor from './nodes/AnimatedColor';
 
 /**
@@ -163,6 +163,8 @@ const loop = function (
   return emptyAnimation;
 };
 
+export type {AnimatedNumeric as Numeric};
+
 module.exports = {
   Value: AnimatedValue,
   ValueXY: AnimatedValueXY,