Callback arguments are inferred as any when function has multiple overloads and callback arguments are typed as tuple

[markostanimirovic]

TypeScript Version: 4.0.5 or higher

Search Terms: function overloads, tuples

Code

function f(callback: (...args: [number, string]) => void): void;
function f(callback: (...args: [number, string, boolean]) => void): void;
function f(callback: (...args: any[]) => void): void {}

// demo
f((num, str) => {}); // first signature: ok

f((num, str, bool) => {}); // second signature: all arguments have any type

Expected behavior: num, str and bool should be type of number, string and boolean.

Actual behavior: num, str and bool are type of any

Playground Link:
https://www.typescriptlang.org/play?ts=4.0.5&ssl=3&ssc=32&pln=3&pc=35#code/GYVwdgxgLglg9mABMAFBAhgG0wI3RAawC5EUA6C9AJwHMBnEgbTBAFscBTKgGkTqiowwNALoBKRAF4AfIgBucGABMxJBcoDcAKFCRYCZGiy58xUhTLV6TFuy69+g4bxxw4mDujDips9SrVFJW1daHgkVAxsPEISckpaBkQvAE9GHxl5INUs5UQAbwBfLS0AelLEJQ5WOB0UFFsHAQlMorENRHLkGCp+PhgaMHQoECoOEjgCEtQGtiaeRFd3Ftk2jq66DggEJX7B4dHx5Oxk2jYOMCg6RAALdDkOZLAUxCgUgAcOLSA

[MartinJohns]

Overload signatures should go from most specific to least specific. You should change the order of the overloads, then it works.

[markostanimirovic]

Overload signatures should go from most specific to least specific. You should change the order of the overloads, then it works.

No, then signature function f(callback: (...args: [number, string]) => void): void; will never be reached.

When you change the order and call f((num, str) => {}); it will point to the function f(callback: (...args: [number, string, boolean]) => void): void; signature.

[RyanCavanaugh]

I'd need a more realistic example to comment on what the expected behavior is here. The first overload is doing nothing; there's no reason that I can see to not just have the 3-tuple one.

[markostanimirovic]

@RyanCavanaugh
Here's a more realistic example:

https://www.typescriptlang.org/play?#code/PQKhCgAIUgVBPADgUwM5RMcyAeiD2ATgC6TFLKQDKyANsgMbFEA8VxAhscgDSQBKaAK61iAPkgBeSAApUnbgC5qC5AEopEwahHEA3NjxFS5FNTqNmhAOoBLYgAsACoXyJUbVXxdvUfbboS0jJQkGHyXMjK7JE8oWGIru7KPu7gGpJawqIGhgQkZBSQAKI4xIQcTDHcAGKuALY09ExEHrBBcJC43AB2ACao5s1WLPGQtj0AZsiEKrFjHD3w4GIA2gC6YwD8c9xjykI9ANY9+ADuPQa4+SZFpeWVxNXIdfiNFi2EqHaOqW0dsC6ZWQ-UGTUsRB+ziSHjGE2ms2ecTCYUW8GRKLRKw2212yH2kEOJ3Ol3AeWMhTM9wqVVotgYLwa4M+LHaUk63RBAyGEMILDRfHhM2odIZYlxVFF+JRkAOx1OFyuRgKpko1MekvpjLezKsUL+rIBQN63N1kPs0N8oxlAoWSwxYSFiKlKwlLplcuJirJ1wpqsgABkOPJDezAZzQZBVgA6WNOyAAfUFU2FQfk60gOzTpE9CtJ5JVdzKNOIBrNX28rgAVryAIKEADmqA65cGEdNHxGdvR3exmxlWeDxBYPhrn3rTfFHp5nzbwMj5f1MP59vGKdmfz4aLW-ZROz+BKJedyoAg0EgNUOTFs+B6GCwvoKkyvxBvPUgDEIyEi5etKNbxpcmCnasEihLyiSO4OiKWpziagwAN5jDKqwAJJrpARzIPA+CTDOVioOsyjqrSWqvO8wygSBXxoesYgGDKAC+0EBKI0HPOyJFPKo5Gtmw1HNisIQyrG0YcI2qDKDGsaoAJ0QCXwiT4GOVjKDIomoFKkkwQyqAZFkOiiJsajyZRfJgax4hKjckDPj0163h+X4-tRf5hAB7bAWZS5WmBm7gV6PRQWMo51hJgGRqsyEohpWnKEhMqJSiaEYVhOF4a2RElMWGpSrx1E+e4-FmagtH0dFYTMRVkBKckkAHjK6wsdkxDsaonE5VUPFMgJhUeK2YjQX8HUPEwZYKfV1ZhZOQljKJ4lNlJ1UaXJ+GtNBMpKSpRBqaJW3TdpoXjhJ+kCC1YzGaZvJ9Z4sSTb4-gteVj6kHZDnvp+37cOW6mxgmyhohsJmQGikAIZAjFkqeGDZRw9SIPQ97gBM3CEJMlSUBxCUopM+D4Mo8iEBMDYGJD4DQ+e5aQGcFr4EIpC1ZJMOoQz+Ao4MzBkA4lBEw2DikKgtgNj0XBCF+0aQNYRBHIMkwTMg0ZIwwt7yJAsnDDUePsp9LlmcJKJyKo0SqKdETcNGuP4HwwDAGr1FjDIp0AAzW7b6u8g7lt8D0Qj1KdMjg17kA+-UENqK7NVTZ86S5O7TCa-gAe2XjygAOQAEbianYcnmAMNUzTjiR74kAAIyKMzrPs2Q+BczzQv82rQsi8QYsK5L0uy-L1Pc++jPjIMfSMLQ4nIH0GFx1YivQFgys9Krk8J31pfa8533UfrYSG5Ext3Yzygh+nMz+4HKdq6oFt43wmeEMo-cANRl2HEeT0QDvOy-9syjIlsAELid7X2J9k74H-oQQBodGLh0gDbYu21CAxzJIvPGy8k6WzTjfbOzEy5qFzmeGABcLTF3cJAAATBXc8LMapsx6MQDmtdHD1z5gLZuotxYwwACL4DQD0VOpAzjS1st3M4vdiGDFsIPYeo9x4TDgbyZQlsQb9GDr7EGX5KSUFwko+A09MDgDngvTsS8LR-FIavL6yAfoOzNlEPEpsL5B1ga-BB38P4wLdl-A2QcQ6KRhModOeN6CLGAd43219xJ3xhM-dxcjo64KQUYlBJiYSkLQWfDOWcIZ8HRrQWS8SgA

Check the error on line 117.