[Agda] parsing reports
Nils Anders Danielsson
nad at chalmers.se
Mon Jan 28 15:32:11 CET 2013
On 2013-01-01 13:38, Serge D. Mechveliani wrote:
> A minor note on Agda-2.3.2 MAlonzo:
> when a type constructor is not in scope, the type checker reports
> "could not parse this expression ...",
> -- without explaining the reason any more precisely.
> Why the checker does not report, say, "... not in scope" ?
> For example,
> open import Data.Maybe using (Maybe) -- `just' is forgotten
> f : Maybe Bool -> Bool
> f (just _) = true
> f _ = false
> causes "could not parse (just _)"
> rather than "not in scope: just"
> For the examples with a complex expression this leads to difficulty in
> finding the source of this kind of error.
In many cases it is hard to determine what the problem is. Let me modify
f : Maybe Bool -> Bool
f (just x) = true
f _ = false
The problem could be that "just" is not in scope, but it could also be
that "_x" is not in scope.
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