summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
Diffstat
-rw-r--r--compiler/main/DynFlags.hs11
-rw-r--r--compiler/parser/Lexer.x35
-rw-r--r--compiler/rename/RnEnv.lhs2
-rw-r--r--docs/users_guide/flags.xml13
-rw-r--r--docs/users_guide/glasgow_exts.xml54
5 files changed, 67 insertions, 48 deletions
diff --git a/compiler/main/DynFlags.hs b/compiler/main/DynFlags.hs
index 46c9d200ac..31886581f3 100644
--- a/compiler/main/DynFlags.hs
+++ b/compiler/main/DynFlags.hs
@@ -256,6 +256,7 @@ data DynFlag
| Opt_TypeOperators
| Opt_PackageImports
| Opt_NewQualifiedOperators
+ | Opt_ExplicitForAll
| Opt_PrintExplicitForalls
@@ -1816,6 +1817,7 @@ xFlags = [
( "NPlusKPatterns", Opt_NPlusKPatterns, const Supported ),
-- On by default (which is not strictly H98):
( "MonoPatBinds", Opt_MonoPatBinds, const Supported ),
+ ( "ExplicitForAll", Opt_ExplicitForAll, const Supported ),
( "MonoLocalBinds", Opt_MonoLocalBinds, const Supported ),
( "RelaxedPolyRec", Opt_RelaxedPolyRec, const Supported ),
( "ExtendedDefaultRules", Opt_ExtendedDefaultRules, const Supported ),
@@ -1847,7 +1849,14 @@ xFlags = [
impliedFlags :: [(DynFlag, DynFlag)]
impliedFlags
- = [ (Opt_GADTs, Opt_RelaxedPolyRec) -- We want type-sig variables to
+ = [ (Opt_RankNTypes, Opt_ExplicitForAll)
+ , (Opt_Rank2Types, Opt_ExplicitForAll)
+ , (Opt_ScopedTypeVariables, Opt_ExplicitForAll)
+ , (Opt_LiberalTypeSynonyms, Opt_ExplicitForAll)
+ , (Opt_ExistentialQuantification, Opt_ExplicitForAll)
+ , (Opt_PolymorphicComponents, Opt_ExplicitForAll)
+
+ , (Opt_GADTs, Opt_RelaxedPolyRec) -- We want type-sig variables to
-- be completely rigid for GADTs
, (Opt_TypeFamilies, Opt_RelaxedPolyRec) -- Trac #2944 gives a nice example
diff --git a/compiler/parser/Lexer.x b/compiler/parser/Lexer.x
index 675b4d6fc0..fe5c693266 100644
--- a/compiler/parser/Lexer.x
+++ b/compiler/parser/Lexer.x
@@ -1753,26 +1753,21 @@ mkPState buf loc flags =
}
where
bitmap = genericsBit `setBitIf` dopt Opt_Generics flags
- .|. ffiBit `setBitIf` dopt Opt_ForeignFunctionInterface flags
- .|. parrBit `setBitIf` dopt Opt_PArr flags
- .|. arrowsBit `setBitIf` dopt Opt_Arrows flags
- .|. thBit `setBitIf` dopt Opt_TemplateHaskell flags
- .|. qqBit `setBitIf` dopt Opt_QuasiQuotes flags
- .|. ipBit `setBitIf` dopt Opt_ImplicitParams flags
- .|. explicitForallBit `setBitIf` dopt Opt_ScopedTypeVariables flags
- .|. explicitForallBit `setBitIf` dopt Opt_LiberalTypeSynonyms flags
- .|. explicitForallBit `setBitIf` dopt Opt_PolymorphicComponents flags
- .|. explicitForallBit `setBitIf` dopt Opt_ExistentialQuantification flags
- .|. explicitForallBit `setBitIf` dopt Opt_Rank2Types flags
- .|. explicitForallBit `setBitIf` dopt Opt_RankNTypes flags
- .|. bangPatBit `setBitIf` dopt Opt_BangPatterns flags
- .|. tyFamBit `setBitIf` dopt Opt_TypeFamilies flags
- .|. haddockBit `setBitIf` dopt Opt_Haddock flags
- .|. magicHashBit `setBitIf` dopt Opt_MagicHash flags
- .|. kindSigsBit `setBitIf` dopt Opt_KindSignatures flags
- .|. recursiveDoBit `setBitIf` dopt Opt_RecursiveDo flags
- .|. unicodeSyntaxBit `setBitIf` dopt Opt_UnicodeSyntax flags
- .|. unboxedTuplesBit `setBitIf` dopt Opt_UnboxedTuples flags
+ .|. ffiBit `setBitIf` dopt Opt_ForeignFunctionInterface flags
+ .|. parrBit `setBitIf` dopt Opt_PArr flags
+ .|. arrowsBit `setBitIf` dopt Opt_Arrows flags
+ .|. thBit `setBitIf` dopt Opt_TemplateHaskell flags
+ .|. qqBit `setBitIf` dopt Opt_QuasiQuotes flags
+ .|. ipBit `setBitIf` dopt Opt_ImplicitParams flags
+ .|. explicitForallBit `setBitIf` dopt Opt_ExplicitForAll flags
+ .|. bangPatBit `setBitIf` dopt Opt_BangPatterns flags
+ .|. tyFamBit `setBitIf` dopt Opt_TypeFamilies flags
+ .|. haddockBit `setBitIf` dopt Opt_Haddock flags
+ .|. magicHashBit `setBitIf` dopt Opt_MagicHash flags
+ .|. kindSigsBit `setBitIf` dopt Opt_KindSignatures flags
+ .|. recursiveDoBit `setBitIf` dopt Opt_RecursiveDo flags
+ .|. unicodeSyntaxBit `setBitIf` dopt Opt_UnicodeSyntax flags
+ .|. unboxedTuplesBit `setBitIf` dopt Opt_UnboxedTuples flags
.|. standaloneDerivingBit `setBitIf` dopt Opt_StandaloneDeriving flags
.|. transformComprehensionsBit `setBitIf` dopt Opt_TransformListComp flags
.|. rawTokenStreamBit `setBitIf` dopt Opt_KeepRawTokenStream flags
diff --git a/compiler/rename/RnEnv.lhs b/compiler/rename/RnEnv.lhs
index 64e299e876..20d221857f 100644
--- a/compiler/rename/RnEnv.lhs
+++ b/compiler/rename/RnEnv.lhs
@@ -1089,7 +1089,7 @@ unknownNameErr rdr_name
perhapsForallMsg :: SDoc
perhapsForallMsg
- = vcat [ ptext (sLit "Perhaps you intended to use -XRankNTypes or similar flag")
+ = vcat [ ptext (sLit "Perhaps you intended to use -XExplicitForAll or similar flag")
, ptext (sLit "to enable explicit-forall syntax: forall <tvs>. <type>")]
unknownSubordinateErr :: SDoc -> RdrName -> SDoc
diff --git a/docs/users_guide/flags.xml b/docs/users_guide/flags.xml
index b87044f5ac..aae0f59de5 100644
--- a/docs/users_guide/flags.xml
+++ b/docs/users_guide/flags.xml
@@ -820,6 +820,19 @@
<entry><option>-XNoNewQualifiedOperators</option></entry>
</row>
<row>
+ <entry><option>-XExplicitForALl</option></entry>
+ <entry>Enable <link linkend="explicit-foralls">explicit universal quantification</link>.
+ Implied by <option>-XScopedTypeVariables</option>,
+ <option>-XLiberalTypeSynonyms</option>,
+ <option>-XRank2Types</option>,
+ <option>-XRankNTypes</option>,
+ <option>-XPolymorphicComponents</option>,
+ <option>-XExistentialQuantification</option>
+ </entry>
+ <entry>dynamic</entry>
+ <entry><option>-XNoExplicitForAll</option></entry>
+ </row>
+ <row>
<entry><option>-XPolymorphicComponents</option></entry>
<entry>Enable <link linkend="universal-quantification">polymorphic components for data constructors</link>.</entry>
<entry>dynamic</entry>
diff --git a/docs/users_guide/glasgow_exts.xml b/docs/users_guide/glasgow_exts.xml
index befb416fc7..093858bb0e 100644
--- a/docs/users_guide/glasgow_exts.xml
+++ b/docs/users_guide/glasgow_exts.xml
@@ -78,6 +78,7 @@ documentation</ulink> describes all the libraries that come with GHC.
<option>-XPostfixOperators</option>,
<option>-XPatternGuards</option>,
<option>-XLiberalTypeSynonyms</option>,
+ <option>-XExplicitForAll</option>,
<option>-XRankNTypes</option>,
<option>-XImpredicativeTypes</option>,
<option>-XTypeOperators</option>,
@@ -1664,7 +1665,8 @@ The following syntax is stolen:
<indexterm><primary><literal>forall</literal></primary></indexterm>
</term>
<listitem><para>
- Stolen (in types) by: <option>-XScopedTypeVariables</option>,
+ Stolen (in types) by: <option>-XExplicitForAll</option>, and hence by
+ <option>-XScopedTypeVariables</option>,
<option>-XLiberalTypeSynonyms</option>,
<option>-XRank2Types</option>,
<option>-XRankNTypes</option>,
@@ -4713,10 +4715,30 @@ might be in another module, or even in a module that is not yet written.
<sect1 id="other-type-extensions">
<title>Other type system extensions</title>
-<sect2 id="type-restrictions">
-<title>Type signatures</title>
+<sect2 id="explicit-foralls"><title>Explicit universal quantification (forall)</title>
+<para>
+Haskell type signatures are implicitly quantified. When the language option <option>-XExplicitForAll</option>
+is used, the keyword <literal>forall</literal>
+allows us to say exactly what this means. For example:
+</para>
+<para>
+<programlisting>
+ g :: b -> b
+</programlisting>
+means this:
+<programlisting>
+ g :: forall b. (b -> b)
+</programlisting>
+The two are treated identically.
+</para>
+<para>
+Of course <literal>forall</literal> becomes a keyword; you can't use <literal>forall</literal> as
+a type variable any more!
+</para>
+</sect2>
+
-<sect3 id="flexible-contexts"><title>The context of a type signature</title>
+<sect2 id="flexible-contexts"><title>The context of a type signature</title>
<para>
The <option>-XFlexibleContexts</option> flag lifts the Haskell 98 restriction
that the type-class constraints in a type signature must have the
@@ -4745,7 +4767,7 @@ Consider the type:
language omits them; in Haskell 98, all the free type variables of an
explicit source-language type signature are universally quantified,
except for the class type variables in a class declaration. However,
-in GHC, you can give the foralls if you want. See <xref linkend="universal-quantification"/>).
+in GHC, you can give the foralls if you want. See <xref linkend="explicit-foralls"/>).
</para>
<para>
@@ -4833,9 +4855,6 @@ territory free in case we need it later.
</orderedlist>
</para>
-</sect3>
-
-
</sect2>
@@ -5313,22 +5332,7 @@ The parentheses are required.
</title>
<para>
-Haskell type signatures are implicitly quantified. The new keyword <literal>forall</literal>
-allows us to say exactly what this means. For example:
-</para>
-<para>
-<programlisting>
- g :: b -> b
-</programlisting>
-means this:
-<programlisting>
- g :: forall b. (b -> b)
-</programlisting>
-The two are treated identically.
-</para>
-
-<para>
-However, GHC's type system supports <emphasis>arbitrary-rank</emphasis>
+GHC's type system supports <emphasis>arbitrary-rank</emphasis>
explicit universal quantification in
types.
For example, all the following types are legal:
@@ -5383,8 +5387,6 @@ field type signatures.</para> </listitem>
</itemizedlist>
</para></listitem>
</itemizedlist>
-Of course <literal>forall</literal> becomes a keyword; you can't use <literal>forall</literal> as
-a type variable any more!
</para>
View Lorry Controller Status