PoC for emitting more than one at a time error in typechecking

[zth]

Very simple PoC so far. Idea would be to use this in the editor tooling.

[zth]

This should not affect normal operation when off except at most make exception traces look slightly different (I.raise) right? Also those exceptions I guess never surface to top level.

Pretty much, yes. But worth investigating that in practice, if it makes a difference we need/want to care about.

[github-actions[bot]]

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