WIP: Error Messages: Improve response for illegal forall and GADT Syntax
This patch aims to improve the error messages emitted with illegal forall
and GADT
syntax.
Previously, using forall
in a type with -XNoExplicitForAll
Perhaps you intended to use RankNTypes
or a similar language extension to enable explicit-forall syntax: forall <tvs>. <type>
This is confusing because the actual extension to enable the syntax is ExplicitForAll
.
The new error is:
Use ExplicitForAll
to enable syntax: forall <tvs>. <type>
Similarly -XNoGADTSyntax
and data Foo where
used to say:
Perhaps you intended to use GADTs
or a similar language extension to enable syntax: data T where
this patch changes it to
Use GADTSyntax
to enable syntax: data T where
Fixes: #24448 (closed)