<sect2 id="impredicative-polymorphism">
<title>Impredicative polymorphism
</title>
-<para><emphasis>NOTE: the impredicative-polymorphism feature is deprecated in GHC 6.12, and
-will be removed or replaced in GHC 6.14.</emphasis></para>
-
<para>GHC supports <emphasis>impredicative polymorphism</emphasis>,
enabled with <option>-XImpredicativeTypes</option>.
This means
g (x:xs) = xs ++ [ x :: a ]
</programlisting>
This program will be rejected, because "<literal>a</literal>" does not scope
-over the definition of "<literal>f</literal>", so "<literal>x::a</literal>"
+over the definition of "<literal>g</literal>", so "<literal>x::a</literal>"
means "<literal>x::forall a. a</literal>" by Haskell's usual implicit
quantification rules.
</para></listitem>
<programlisting>
f = runST ( (op >>= \(x :: STRef s Int) -> g x) :: forall s. ST s Bool )
</programlisting>
-Here, the type signature <literal>forall a. ST s Bool</literal> brings the
+Here, the type signature <literal>forall s. ST s Bool</literal> brings the
type variable <literal>s</literal> into scope, in the annotated expression
<literal>(op >>= \(x :: STRef s Int) -> g x)</literal>.
</para>