<html><head><meta http-equiv="Content-Type" content="text/html; charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><span style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class="">Hi all,</span><br style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class=""><br style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class=""><span style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class="">On a project I'm working on, I wish to declare something like</span><br style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class=""><br style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class=""><span style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class="">data Rec = MkRec { field :: forall a. SomeConstraint a => ... }</span><br style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class=""><br style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class=""><span style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class="">where the ... contains no mention of `a`.</span><br style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class=""><br style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class=""><span style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class="">Even with </span><a href="https://github.com/ghc-proposals/ghc-proposals/pull/448" class="">https://github.com/ghc-proposals/ghc-proposals/pull/448</a><span style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class="">, I think there is no way to avoid the ambiguity when setting `field`. Is that correct? If so, what shall we do about it? The natural answer is somehow to write ... MkRec { field @a = ... } ... but that would break significant new syntactic ground. (Maybe it's good new syntactic ground, but it would still be very new.)</span><br style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class=""><br style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class=""><span style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class="">Thanks,</span><br style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class=""><span style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0);" class="">Richard</span></body></html>