Add IsString instance for WidgetT site m ()

[andrewthad]

#1037

[snoyberg]

I think you'll get better type inference with:

instance (Monad m, a ~ ()) => IsString (WidgetT site m a)

[andrewthad]

Ah! That dumb trick I always forget.

[snoyberg]

I only remembered because the previous instance uses it

On Tue, Jul 21, 2015, 8:36 AM Andrew Martin notifications@github.com
wrote:

In yesod-core/Yesod/Core/Types.hs
#1038 (comment):

@@ -250,6 +250,10 @@ instance (a ~ (), Monad m) => Monoid (WidgetT site m a) where
mempty = return ()
mappend x y = x >> y
instance (a ~ (), Monad m) => Semigroup (WidgetT site m a)
+instance Monad m => IsString (WidgetT site m ()) where

Ah! That dumb trick I always forget.

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Reply to this email directly or view it on GitHub
https://github.com/yesodweb/yesod/pull/1038/files#r35116687.

[andrewthad]

I'll wait two days to see if there is any opposition to this, and then I'll merge the branch.

[creichert]

@andrewthad Do you mind if I push a doc string for the new instance?

[andrewthad]

@creichert That would be wonderful.

[andrewthad]

@creichert I think you might have typoed the docstring a little. It reads:

Any type with an 'IsString' instance can be trivially promoted to a widget.

I think it was supposed to be:

A 'String' can be trivially promoted to a widget.

Or something like that. Because there are lots of types (ByteString for example) that have IsString instances but can't be trivially promoted to a widget.

[creichert]

Yea, my mistake, thanks. I pushed a fix.

On Tue, Jul 21 2015, Andrew Martin notifications@github.com wrote:

@creichert I think you might have typoed the docstring a little. It reads:

Any type with an 'IsString' instance can be trivially promoted to a widget.

I think it was supposed to be:

An 'String' can be trivially promoted to a widget.

Or something like that. Because there are lots of types (ByteString for example) that have IsString instances but can't be trivially promoted to a widget.

---

Reply to this email directly or view it on GitHub:
#1038 (comment)