Reification of out-of-scope variables?

Simon Peyton Jones simonpj at
Fri Apr 15 15:51:06 UTC 2016

|  a TExp rather than an Exp. Turns out the example from my first email
|  does work if you adapt it to use typed splices:
|  f :: Int -> Int
|  f x = $$(do let {name = mkName x}; info <- reify name; runIO (print
|  info) [|| x ||])

Hang on!  The design for typed splices, describe here,
says "Unlike TH, the only way to construct a value of type TExp is with a quote. You cannot drop into do-notation, nor use explicit construction of the values in the Exp algebraic data type. That restriction limits expressiveness, but it enables the strong typing guarantees." 

So why does the above work?  $$(e) requires a TExp, and do-notation doesn’t produce a TExp.

|  * Should we consider it a bug (and file a ticket) that reification in
|  typed splices is able to observe the order of type checking, just like
|  reify used to do in untyped splices?

Yes I think so!!!


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