[ember] refine types for Ember.tryInvoke (#28693)

* [ember] refine types for Ember.tryInvoke

* [ember] tryInvoke as three function heads

types/ember/index.d.ts

@@ -28,6 +28,20 @@ declare module 'ember' {
     // Get an alias to the global Array type to use in inner scope below.
     type GlobalArray<T> = T[];
 
+    // TODO: TypeScript 3.0
+    // type FunctionArgs<F extends (...args: any[]) => any> = F extends (...args: infer ARGS) => any ? ARGS : never;
+    type FunctionArgs<F> =
+        F extends (a: infer A) => any
+            ? [A]
+            : F extends (a: infer A, b: infer B) => any
+                ? [A, B]
+                : F extends (a: infer A, b: infer B, c: infer C) => any
+                    ? [A, B, C]
+                    : F extends (a: infer A, b: infer B, c: infer C, d: infer D) => any
+                        ? [A, B, C, D]
+                        : F extends (a: infer A, b: infer B, c: infer C, d: infer D, e: infer E) => any
+                            ? [A, B, C, D, E]
+                            : never;
     /**
      * Deconstructs computed properties into the types which would be returned by `.get()`.
      */
@@ -3320,7 +3334,14 @@ declare module 'ember' {
          * Checks to see if the `methodName` exists on the `obj`,
          * and if it does, invokes it with the arguments passed.
          */
-        function tryInvoke(obj: any, methodName: string, args?: any[]): any;
+        function tryInvoke<FNAME extends keyof T, T extends object>(
+            obj: T,
+            methodName: FNAME,
+            args: FunctionArgs<T[FNAME]>): T[FNAME] extends ((...args: any[]) => any)
+                ? ReturnType<T[FNAME]>
+                : undefined;
+        function tryInvoke<FNAME extends keyof T, T extends object>(obj: T, methodName: FNAME): T[FNAME] extends (() => any) ? ReturnType<T[FNAME]> : undefined;
+        function tryInvoke(obj: object, methodName: string, args?: any[]): undefined;
         /**
          * Forces the passed object to be part of an array. If the object is already
          * an array, it will return the object. Otherwise, it will add the object to

types/ember/test/utils.ts

@@ -99,3 +99,31 @@ function testDefineProperty() {
         return `${this.firstName} ${this.lastName}`;
     }));
 }
+
+function testTryInvoke() {
+    class Foo {
+        hello() { return ['world']; }
+        add(x: number, y: string) { return x + parseInt(y, 10); }
+        apples(n: number) { return `${n} apples`; }
+    }
+    // zero-argument function
+    Ember.tryInvoke(new Foo(), 'hello'); // $ExpectType string[]
+    // one-argument function
+    Ember.tryInvoke(new Foo(), 'apples', [4]); // $ExpectType string
+    // multi-argument function with different types (reversed types negative test case below)
+    Ember.tryInvoke(new Foo(), 'add', [4, '3']); // $ExpectType number
+
+    // Cases that should return undefined
+    // No args provided
+    Ember.tryInvoke(new Foo(), 'apples'); // $ExpectType undefined
+    // Function does not exist
+    Ember.tryInvoke(new Foo(), 'doesNotExist'); // $ExpectType undefined
+    // Empty args provided
+    Ember.tryInvoke(new Foo(), 'apples', []); // $ExpectType undefined
+    // Wrong args provided
+    Ember.tryInvoke(new Foo(), 'apples', ['']); // $ExpectType undefined
+    // Wrong arg types
+    Ember.tryInvoke(new Foo(), 'add', [4, 3]); // $ExpectType undefined
+    // Reversed arg types
+    Ember.tryInvoke(new Foo(), 'add', ['4', 3]); // $ExpectType undefined
+}