Annotations

[Edward A Kmett]

Currently, in all the cases I can think of if the splice generates something that uses an extension then the module must have that flag turned on.

Sent from my iPhone

> On Nov 6, 2013, at 6:57 AM, Gergely Risko <gergely at risko.hu> wrote:
> 
> On Wed, 6 Nov 2013 10:55:09 +0000, Simon Peyton-Jones <simonpj at microsoft.com> writes:
> 
>> I’m inclined to add a language extension “Annotations”. 
>> 
>> · Without it {-# ANN … #-} pragmas are ignored as comments
>> 
>> · With it, they are treated as annotations
>> 
>> Do you agree?
> 
> I generally agree that this should be a language extension.
> 
> My only worry is around the just implemented TH additions regarding
> annotations.  I don't clearly see what would happen if:
>  - a TH library exports a function that generates annotations when spliced.
>  - and the user uses this function in a .hs file,
>  - without specifying the language extension.
> 
> I'd it to work even in that case.
> 
> I guess the behavior in this corner case depends heavily on how this is
> actually implemented.  If e.g. the reader is the only component that
> checks if the language extension is turned on, then I imagine that the
> TH way of putting in the annotation into the AST would just work.
> 
> On the other hand if the reader recognizes the annotations either way
> and some component after TH splicing is checking for the language
> extension, then my use-case would blow up.
> 
> TH currently is lenient in cases like this.  E.g. if you know that a
> Name is exported from a module and you reference it directly, without
> importing it everything will just work.  I'd like to have the same
> behavior for annotations.
> 
> Thanks,
> Gergely
> 
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