Wrong return type when mapping multi-dimensional arrays

[dapullar]

TypeScript Version: 2.1.6

Code

const findByGroup = (key: string) => {
  return otherObj.filter(obj => obj.Name === key)
}

// expected return type to be: [[string, any[]]] but type checker shows [(string|any)[][]]
// this is evaluated correctly at runtime
const groupData = groups
  .map(group => group.Name)
  .map(name => [name, findByGroup(name)]);

// force type checker
const map = new Map<string, any[]>(groupData as [[string, any[]]]); // works

Expected behavior:

groupData should return [[string, any[]]]

Actual behavior:

groupData returns [(string|any)[][]]

[RyanCavanaugh]

See #13151 and its links regarding automatic tuple inference