types.union type inference is wrong

[skeate]

Bug report

• I've checked documentation and searched for existing issues
• I've made sure my project is based on the latest MST version
• Fork this code sandbox or another minimal reproduction.

Sandbox link or minimal reproduction code
https://codesandbox.io/s/cool-neumann-gd521

Describe the expected behavior
When creating instance, the property item should accept string, number, or null.

Describe the observed behavior
TS error, item only accepts null.

[xaviergonz]

Might be related to #1371

[mweststrate]

This is conceptually correct, for reasons explained here: #1403 (comment). In other words, never redeclare property types, except if you can subtime them

[lock]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs or questions.