[Ur] typechecker rejects form handler
adamc at csail.mit.edu
Sun Jan 5 13:15:46 EST 2014
On 01/04/2014 02:43 PM, Jason Gross wrote:
> As an idea to improve error messages, would it be possible to tag
> unification hints with where they come from, so that the error message
> would include something like "... constraint comes from passing
> 's.Text' as an argument to postfix '!'" or something?
That's an interesting idea. My first reaction is that the extra
information you're suggesting is easy to deduce by inspecting the code.
A unification failure for an expression is only triggered in the context
of its immediately enclosing parent expression.
However, I'd never before considered the consequences of parsing
misunderstandings like this one! Effectively, shouting out the kind of
enclosing parent expression could help the user see how the code is
really being parsed.
At the same time, chattier type inference output can make messages
harder to read in the common case, and I've never seen this particular
kind of error come up in the wild before. So, for now, I think I'll
leave the error messages alone, but I'll keep your suggestion in mind.
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