Re: A question about roles.

If you're trying to understand core, check out https://github.com/ghc/ghc/blob/master/docs/core-spec/core-spec.pdf which has all the typing rules. It might be helpful. But your analysis below is spot on. Richard On Aug 16, 2015, at 10:19 AM, Alexander Eyers-Taylor wrote:

Hello

I have reread the comment about TyConAppCo and I now understand how it works and this is all how it should work. I was just slightly confused to start with. The coercion was representational but the arguments were nominal.

Thanks

Alex

On 16/08/15 13:34, Richard Eisenberg wrote:

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Hi Alex,

Do you have a concrete example? With the -dcore-lint flag, the Core is checked, including all the roles.

Thanks, Richard

On Aug 16, 2015, at 7:47 AM, Alexander Eyers-Taylor wrote:

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Hello

I have noticed in looking at some core that GADT type constructors are often applied with a representational role. These constructors are explicitly marked as nominal.

Is this information just ignored at a Core level or is this invalid core?

Looking at the code a see that we if we downgrade a TyConAppCo we unconditionally change it to a representational role after changing its children. I think this is where it is introduced.

Alex ET _______________________________________________ ghc-devs mailing list ghc-devs@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs