Change default roles in hs-boot files. (#9204)

Test case: roles/should_compile/T9204b

12 files changed, 68 insertions, 38 deletions

diff --git a/compiler/typecheck/TcRnDriver.hs b/compiler/typecheck/TcRnDriver.hs
index 60a6860066..f75ca64c25 100644
--- a/compiler/typecheck/TcRnDriver.hs
+++ b/compiler/typecheck/TcRnDriver.hs
@@ -460,7 +460,7 @@ tcRnImports hsc_env import_decls
 ************************************************************************
 -}
 
-tcRnSrcDecls :: ModDetails 
+tcRnSrcDecls :: ModDetails
              -> Maybe (Located [LIE RdrName])   -- Exports
              -> [LHsDecl RdrName]               -- Declarations
              -> TcM TcGblEnv
@@ -736,7 +736,7 @@ checkHiBootIface' :: [ClsInst] -> TypeEnv -> [AvailInfo]
 -- Variant which doesn't require a full TcGblEnv; you could get the
 -- local components from another ModDetails.
 --
--- We return a list of "impedence-matching" bindings for the dfuns 
+-- We return a list of "impedence-matching" bindings for the dfuns
 -- defined in the hs-boot file, such as
 --           $fxEqT = $fEqT
 -- We need these because the module and hi-boot file might differ in
@@ -996,9 +996,9 @@ checkBootTyCon tc1 tc2
   where
     roles1 = tyConRoles tc1
     roles2 = tyConRoles tc2
-    roles_msg = text "The roles do not match." <+>
-                (text "Roles default to" <+>
-                 quotes (text "representational") <+> text "in boot files")
+    roles_msg = text "The roles do not match." $$
+                (text "Roles on abstract types default to" <+>
+                 quotes (text "representational") <+> text "in boot files.")
 
     eqAlgRhs tc (AbstractTyCon dis1) rhs2
       | dis1      = check (isDistinctAlgRhs rhs2)   --Check compatibility
@@ -1921,7 +1921,7 @@ getModuleInterface hsc_env mod
   = runTcInteractive hsc_env $
     loadModuleInterface (ptext (sLit "getModuleInterface")) mod
 
-tcRnLookupRdrName :: HscEnv -> Located RdrName 
+tcRnLookupRdrName :: HscEnv -> Located RdrName
                   -> IO (Messages, Maybe [Name])
 -- ^ Find all the Names that this RdrName could mean, in GHCi
 tcRnLookupRdrName hsc_env (L loc rdr_name)
diff --git a/compiler/typecheck/TcTyDecls.hs b/compiler/typecheck/TcTyDecls.hs
index 94442901a9..d279ff5ebc 100644
--- a/compiler/typecheck/TcTyDecls.hs
+++ b/compiler/typecheck/TcTyDecls.hs
@@ -684,9 +684,9 @@ initialRoleEnv1 is_boot annots_env tc
                         zipWith orElse role_annots (repeat default_role)
 
         default_role
-          | isClassTyCon tc = Nominal
-          | is_boot         = Representational
-          | otherwise       = Phantom
+          | isClassTyCon tc               = Nominal
+          | is_boot && isAbstractTyCon tc = Representational
+          | otherwise                     = Phantom
 
 irGroup :: RoleEnv -> [TyCon] -> RoleEnv
 irGroup env tcs
diff --git a/docs/users_guide/7.12.1-notes.xml b/docs/users_guide/7.12.1-notes.xml
index 5bdf96d9e1..4dbb0b20cd 100644
--- a/docs/users_guide/7.12.1-notes.xml
+++ b/docs/users_guide/7.12.1-notes.xml
@@ -59,7 +59,18 @@
                     See the release notes for base for a description of the
                     <literal>CallStack</literal> type.
                </para>
-           </listitem>
+            </listitem>
+	    <listitem>
+	      <para>
+		To conform to the common case, the default role assigned to parameters
+		of datatypes declared in <literal>hs-boot</literal> files is
+		<literal>representational</literal>. However, if the constructor(s)
+		for the datatype are given, it makes sense to do normal role inference.
+		This is now implemented, effectively making the default role for
+		non-abstract datatypes in <literal>hs-boot</literal> files to be
+		<literal>phantom</literal>, like it is in regular Haskell code.
+	      </para>
+	    </listitem>
        </itemizedlist>
     </sect3>
 
diff --git a/docs/users_guide/separate_compilation.xml b/docs/users_guide/separate_compilation.xml
index 07cf76c6c7..f6b2cba0ce 100644
--- a/docs/users_guide/separate_compilation.xml
+++ b/docs/users_guide/separate_compilation.xml
@@ -878,7 +878,7 @@ methods entirely; but you must either omit them all or put them all in.
 </para></listitem>
 <listitem><para> You can include instance declarations just as in Haskell; but omit the "where" part.
  </para></listitem>
-<listitem><para>The default role for class and datatype parameters is now representational. To get another role, use a role annotation. (See <xref linkend="roles"/>.)</para></listitem>
+<listitem><para>The default role for abstract datatype parameters is now representational. (An abstract datatype is one with no constructors listed.) To get another role, use a role annotation. (See <xref linkend="roles"/>.)</para></listitem>
 </itemizedlist>
 </para>
     </sect2>
diff --git a/testsuite/tests/rename/should_fail/rnfail055.stderr b/testsuite/tests/rename/should_fail/rnfail055.stderr
index 05cec42788..4611e867ec 100644
--- a/testsuite/tests/rename/should_fail/rnfail055.stderr
+++ b/testsuite/tests/rename/should_fail/rnfail055.stderr
@@ -1,55 +1,57 @@
 
-RnFail055.hs:1:73: Warning:
+RnFail055.hs:1:73: warning:
     -XDatatypeContexts is deprecated: It was widely considered a misfeature, and has been removed from the Haskell language.
 
-RnFail055.hs-boot:1:73: Warning:
+RnFail055.hs-boot:1:73: warning:
     -XDatatypeContexts is deprecated: It was widely considered a misfeature, and has been removed from the Haskell language.
 
-RnFail055.hs-boot:4:1:
+RnFail055.hs-boot:4:1: error:
     Identifier ‘f1’ has conflicting definitions in the module
     and its hs-boot file
     Main module: f1 :: Int -> Float
     Boot file:   f1 :: Float -> Int
     The two types are different
 
-RnFail055.hs-boot:6:1:
+RnFail055.hs-boot:6:1: error:
     Type constructor ‘S1’ has conflicting definitions in the module
     and its hs-boot file
     Main module: type S1 a b = (a, b)
     Boot file:   type S1 a b c = (a, b)
     The types have different kinds
 
-RnFail055.hs-boot:8:1:
+RnFail055.hs-boot:8:1: error:
     Type constructor ‘S2’ has conflicting definitions in the module
     and its hs-boot file
     Main module: type S2 a b = forall a1. (a1, b)
     Boot file:   type S2 a b = forall b1. (a, b1)
-    The roles do not match. Roles default to ‘representational’ in boot files
+    The roles do not match.
+    Roles on abstract types default to ‘representational’ in boot files.
 
-RnFail055.hs-boot:12:1:
+RnFail055.hs-boot:12:1: error:
     Type constructor ‘T1’ has conflicting definitions in the module
     and its hs-boot file
     Main module: data T1 a b = T1 [b] [a]
     Boot file:   data T1 a b = T1 [a] [b]
     The constructors do not match: The types for ‘T1’ differ
 
-RnFail055.hs-boot:14:1:
+RnFail055.hs-boot:14:1: error:
     Type constructor ‘T2’ has conflicting definitions in the module
     and its hs-boot file
     Main module: type role T2 representational nominal
                  data Eq b => T2 a b = T2 a
-    Boot file:   type role T2 nominal representational
+    Boot file:   type role T2 nominal phantom
                  data Eq a => T2 a b = T2 a
-    The roles do not match. Roles default to ‘representational’ in boot files
+    The roles do not match.
+    Roles on abstract types default to ‘representational’ in boot files.
     The datatype contexts do not match
 
-RnFail055.hs-boot:16:11:
+RnFail055.hs-boot:16:11: error:
     ‘T3’ is exported by the hs-boot file, but not exported by the module
 
-RnFail055.hs-boot:17:12:
+RnFail055.hs-boot:17:12: error:
     ‘T3'’ is exported by the hs-boot file, but not exported by the module
 
-RnFail055.hs-boot:21:1:
+RnFail055.hs-boot:21:1: error:
     Type constructor ‘T5’ has conflicting definitions in the module
     and its hs-boot file
     Main module: data T5 a = T5 {field5 :: a}
@@ -57,7 +59,7 @@ RnFail055.hs-boot:21:1:
     The constructors do not match:
       The record label lists for ‘T5’ differ
 
-RnFail055.hs-boot:23:1:
+RnFail055.hs-boot:23:1: error:
     Type constructor ‘T6’ has conflicting definitions in the module
     and its hs-boot file
     Main module: data T6 = T6 Int
@@ -65,20 +67,21 @@ RnFail055.hs-boot:23:1:
     The constructors do not match:
       The strictness annotations for ‘T6’ differ
 
-RnFail055.hs-boot:25:1:
+RnFail055.hs-boot:25:1: error:
     Type constructor ‘T7’ has conflicting definitions in the module
     and its hs-boot file
     Main module: type role T7 phantom
                  data T7 a where
                    T7 :: a1 -> T7 a
     Boot file:   data T7 a = T7 a
-    The roles do not match. Roles default to ‘representational’ in boot files
+    The roles do not match.
+    Roles on abstract types default to ‘representational’ in boot files.
     The constructors do not match: The types for ‘T7’ differ
 
-RnFail055.hs-boot:27:22:
+RnFail055.hs-boot:27:22: error:
     ‘RnFail055.m1’ is exported by the hs-boot file, but not exported by the module
 
-RnFail055.hs-boot:28:1:
+RnFail055.hs-boot:28:1: error:
     Class ‘C2’ has conflicting definitions in the module
     and its hs-boot file
     Main module: class C2 a b where
@@ -88,7 +91,7 @@ RnFail055.hs-boot:28:1:
                    m2 :: a -> b
     The methods do not match: There are different numbers of methods
 
-RnFail055.hs-boot:29:1:
+RnFail055.hs-boot:29:1: error:
     Class ‘C3’ has conflicting definitions in the module
     and its hs-boot file
     Main module: class (Eq a, Ord a) => C3 a
diff --git a/testsuite/tests/roles/should_compile/T9204b.hs b/testsuite/tests/roles/should_compile/T9204b.hs
new file mode 100644
index 0000000000..d3c974f10c
--- /dev/null
+++ b/testsuite/tests/roles/should_compile/T9204b.hs
@@ -0,0 +1,5 @@
+module T9204b where
+
+import T9204b2
+
+data P a = P
diff --git a/testsuite/tests/roles/should_compile/T9204b.hs-boot b/testsuite/tests/roles/should_compile/T9204b.hs-boot
new file mode 100644
index 0000000000..fab2a86168
--- /dev/null
+++ b/testsuite/tests/roles/should_compile/T9204b.hs-boot
@@ -0,0 +1,3 @@
+module T9204b where
+
+data P a = P
diff --git a/testsuite/tests/roles/should_compile/T9204b2.hs b/testsuite/tests/roles/should_compile/T9204b2.hs
new file mode 100644
index 0000000000..607192254b
--- /dev/null
+++ b/testsuite/tests/roles/should_compile/T9204b2.hs
@@ -0,0 +1,3 @@
+module T9204b2 where
+
+import {-# SOURCE #-} T9204b
diff --git a/testsuite/tests/roles/should_compile/all.T b/testsuite/tests/roles/should_compile/all.T
index 2e0d8ea01c..b740d8ad3e 100644
--- a/testsuite/tests/roles/should_compile/all.T
+++ b/testsuite/tests/roles/should_compile/all.T
@@ -6,3 +6,4 @@ test('Roles13', only_ways('normal'), compile, ['-ddump-simpl -dsuppress-uniques'
 test('Roles14', only_ways('normal'), compile, ['-ddump-tc'])
 test('T8958', [normalise_fun(normalise_errmsg), only_ways('normal')], compile, ['-ddump-tc -dsuppress-uniques'])
 test('T10263', normal, compile, [''])
+test('T9204b', extra_clean(['T9204b.o-boot', 'T9204b.hi-boot', 'T9204b2.hi', 'T9204b2.o']), multimod_compile, ['T9204b', '-v0'])
diff --git a/testsuite/tests/roles/should_fail/Roles12.stderr b/testsuite/tests/roles/should_fail/Roles12.stderr
index 874ddca1d3..7dff7f97ec 100644
--- a/testsuite/tests/roles/should_fail/Roles12.stderr
+++ b/testsuite/tests/roles/should_fail/Roles12.stderr
@@ -1,8 +1,9 @@
 
-Roles12.hs:5:1:
+Roles12.hs:5:1: error:
     Type constructor ‘T’ has conflicting definitions in the module
     and its hs-boot file
     Main module: type role T phantom
                  data T a
     Boot file:   abstract T a
-    The roles do not match. Roles default to ‘representational’ in boot files
+    The roles do not match.
+    Roles on abstract types default to ‘representational’ in boot files.
diff --git a/testsuite/tests/roles/should_fail/T9204.stderr b/testsuite/tests/roles/should_fail/T9204.stderr
index 9936839284..721e74e74b 100644
--- a/testsuite/tests/roles/should_fail/T9204.stderr
+++ b/testsuite/tests/roles/should_fail/T9204.stderr
@@ -1,8 +1,9 @@
 
-T9204.hs:6:1:
+T9204.hs:6:1: error:
     Type constructor ‘D’ has conflicting definitions in the module
     and its hs-boot file
     Main module: type role D phantom
                  data D a
     Boot file:   abstract D a
-    The roles do not match. Roles default to ‘representational’ in boot files
+    The roles do not match.
+    Roles on abstract types default to ‘representational’ in boot files.
diff --git a/testsuite/tests/typecheck/should_fail/tcfail220.stderr b/testsuite/tests/typecheck/should_fail/tcfail220.stderr
index dcb6fbc2e4..6a4e87382d 100644
--- a/testsuite/tests/typecheck/should_fail/tcfail220.stderr
+++ b/testsuite/tests/typecheck/should_fail/tcfail220.stderr
@@ -1,15 +1,17 @@
 [1 of 1] Compiling ShouldFail[sig of Prelude] ( tcfail220.hsig, nothing )
 
-tcfail220.hsig:4:1:
+tcfail220.hsig:4:1: error:
     Type constructor ‘Bool’ has conflicting definitions in the module
     and its hsig file
     Main module: data Bool = False | True
-    Hsig file:  data Bool a b c d = False
+    Hsig file:  type role Bool phantom phantom phantom phantom
+                data Bool a b c d = False
     The types have different kinds
 
-tcfail220.hsig:5:1:
+tcfail220.hsig:5:1: error:
     Type constructor ‘Maybe’ has conflicting definitions in the module
     and its hsig file
     Main module: data Maybe a = Nothing | Just a
-    Hsig file:  data Maybe a b = Nothing
+    Hsig file:  type role Maybe phantom phantom
+                data Maybe a b = Nothing
     The types have different kinds