[agumonkey]

There was one attempt at creating a language splitting both pure function and effectful procedures. Any construct with a procedure call was automatically/effectively typed as a procedure. But I can't recall the name so far..

[ngruhn]

Unison is one example. Except it doesn't just differentiate between pure and effectful but also what combinations of effects are used.

[d_tr]

Never heard about this one, thanks.

[paulddraper]

That’s cool function coloring.

C++ sort of has this, with const.

[hardlianotion]

I am a fan of C++ const, but I don't really see what it has to do with effect labelling in this way.