Issue type:

[ ] question
[x] bug report
[ ] feature request
[ ] documentation issue

Database system/driver:

[ ] cordova
[ ] mongodb
[ ] mssql
[ ] mysql / mariadb
[ ] oracle
[ ] postgres
[ ] cockroachdb
[ ] sqlite
[ ] sqljs
[ ] react-native
[ ] expo

TypeORM version:

[x] latest
[ ] @next
[ ] 0.x.x (or put your version here)

Steps to reproduce or a small repository showing the problem:

Decorators should implement a specific interface provided by TypeScript.

https://github.com/microsoft/TypeScript/blob/9684bb21e1afe7cf08611fa0930867bf71bcfeff/lib/lib.es5.d.ts#L1396

Because TypeORM decorators do not implement said interface, they do not play nice with the ecosystem:

See: tannerntannern/ts-mixer#23

I can contribute a PR if it will be merged.