fix pick types to allow interfaces (#237)

src/object.ts

@@ -166,7 +166,7 @@ export const listify = <TValue, TKey extends string | number | symbol, KResult>(
  * Pick a list of properties from an object
  * into a new object
  */
-export const pick = <T extends Record<string, unknown>, TKeys extends keyof T>(
+export const pick = <T extends object, TKeys extends keyof T>(
   obj: T,
   keys: TKeys[]
 ): Pick<T, TKeys> => {

src/tests/object.test.ts

@@ -213,11 +213,11 @@ describe('object module', () => {
       assert.deepEqual(result, {})
     })
     test('handle key not in object', () => {
-      const result = _.pick({ a: 2, b: 3 } as any, ['c'])
+      const result = _.pick({ a: 2, b: 3 }, ['c'] as any)
       assert.deepEqual(result, {} as any)
     })
     test('handle one key not in object', () => {
-      const result = _.pick({ a: 2, b: 3 } as any, ['a', 'c'])
+      const result = _.pick({ a: 2, b: 3 }, ['a', 'c'] as any)
       assert.deepEqual(result, { a: 2 } as any)
     })
     test('does not ignore undefined values', () => {
@@ -230,6 +230,22 @@ describe('object module', () => {
         a: 2
       })
     })
+    test('type: accepts an interface', () => {
+      interface SomeDeclaredType {
+        a: string
+        b: Error
+        c: number[]
+      }
+      const x: SomeDeclaredType = {
+        a: 'alpha',
+        b: new Error('beta'),
+        c: [3]
+      }
+      const result = _.pick(x, ['a'])
+      assert.deepEqual(result, {
+        a: 'alpha'
+      })
+    })
   })
 
   describe('omit function', () => {