Is it possible to declare our own utility types?

[rzvc]

I would like to create some utility types that I see Psalm is missing, and according to the discussions in the issue section, won't be implemented anytime soon.

Is it possible to do that via the plugin system? If yes, can someone please point me in the right direction?

Thank you.

[orklah]

Hi, it's not possible right now, and I don't want to give hope on that, it won't happen without a rewrite of Psalm.

Every type operation need to be aware of the other existing types. For example, if you create a new special string type, a simple thing like a concatenation need to be aware how your type must behave. Does concatenation on your type must keep your type or must it revert to a string?

Should asserting that your type is not empty change your type into a non-empty-string or do you consider that your type must prevail because it's more detailed?

Every single operation, every time a type is included in an union that could contain a parent type should have a special piece of code dedicated to handle your special type. It's a pretty massive work and each interaction need to be thought of in depth

[AndrolGenhald]

One thing to consider is conflicts between utility types and class names. Should utility types be required to include a hyphen? Instead of Partial<Type> you'd have partial-array<array>, instead of Omit<Type, "a"|"b"> maybe omit-keys<array{...}, "a"|"b"> and omit-properties<object{...}, "a"|"b">?

[orklah]

I made a mistake, Atomic::create will always return a TNamedObject when finding a string it doesn't recognize. This could be then transformed by the callbacks we talked about.

Requiring hyphens would reduce the risk of accidental collisions with user classes, but it would probably make the tool less powerful (we can probably imagine some Plugin that would replace a given class into something else entirely

[AndrolGenhald]

we can probably imagine some Plugin that would replace a given class into something else entirely

idk, that sounds like an anti-feature to me.

[orklah]

Possibly yeah, didn't put much thought into it honestly :D

[rzvc]

For that an afterNewAnalysisInterface could be useful. There's definitely a use for it - I needed it a couple of days ago.