typecheck: Clarify errors mentioned in #14385

compiler/typecheck/TcTyClsDecls.hs

@@ -2796,7 +2796,7 @@ checkFamFlag tc_name
        ; checkTc idx_tys err_msg }
   where
     err_msg = hang (text "Illegal family declaration for" <+> quotes (ppr tc_name))
-                 2 (text "Use TypeFamilies to allow indexed type families")
+                 2 (text "Enable TypeFamilies to allow indexed type families")
 
 {- Note [Class method constraints]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -3163,20 +3163,20 @@ classArityErr n cls
   where
     mkErr howMany allowWhat =
         vcat [text (howMany ++ " parameters for class") <+> quotes (ppr cls),
-              parens (text ("Use MultiParamTypeClasses to allow "
+              parens (text ("Enable MultiParamTypeClasses to allow "
                                     ++ allowWhat ++ " classes"))]
 
 classFunDepsErr :: Class -> SDoc
 classFunDepsErr cls
   = vcat [text "Fundeps in class" <+> quotes (ppr cls),
-          parens (text "Use FunctionalDependencies to allow fundeps")]
+          parens (text "Enable FunctionalDependencies to allow fundeps")]
 
 badMethPred :: Id -> TcPredType -> SDoc
 badMethPred sel_id pred
   = vcat [ hang (text "Constraint" <+> quotes (ppr pred)
                  <+> text "in the type of" <+> quotes (ppr sel_id))
               2 (text "constrains only the class type variables")
-         , text "Use ConstrainedClassMethods to allow it" ]
+         , text "Enable ConstrainedClassMethods to allow it" ]
 
 noClassTyVarErr :: Class -> TyCon -> SDoc
 noClassTyVarErr clas fam_tc
@@ -3235,14 +3235,14 @@ badDataConTyCon data_con res_ty_tmpl actual_res_ty
 badGadtDecl :: Name -> SDoc
 badGadtDecl tc_name
   = vcat [ text "Illegal generalised algebraic data declaration for" <+> quotes (ppr tc_name)
-         , nest 2 (parens $ text "Use GADTs to allow GADTs") ]
+         , nest 2 (parens $ text "Enable the GADTs extension to allow this") ]
 
 badExistential :: DataCon -> SDoc
 badExistential con
   = hang (text "Data constructor" <+> quotes (ppr con) <+>
                 text "has existential type variables, a context, or a specialised result type")
        2 (vcat [ ppr con <+> dcolon <+> ppr (dataConUserType con)
-               , parens $ text "Use ExistentialQuantification or GADTs to allow this" ])
+               , parens $ text "Enable ExistentialQuantification or GADTs to allow this" ])
 
 badGADT :: DataCon -> [EqSpec] -> SDoc
 badGADT con eq_specs

testsuite/tests/gadt/gadtSyntaxFail001.stderr

@@ -2,6 +2,6 @@
 gadtSyntaxFail001.hs:8:5: error:
     • Data constructor ‘C2’ has existential type variables, a context, or a specialised result type
         C2 :: forall a. a -> Char -> Foo a Int
-        (Use ExistentialQuantification or GADTs to allow this)
+        (Enable ExistentialQuantification or GADTs to allow this)
     • In the definition of data constructor ‘C2’
       In the data type declaration for ‘Foo’

testsuite/tests/gadt/gadtSyntaxFail002.stderr

@@ -2,6 +2,6 @@
 gadtSyntaxFail002.hs:8:5: error:
     • Data constructor ‘C2’ has existential type variables, a context, or a specialised result type
         C2 :: forall a. a -> Char -> Foo a a
-        (Use ExistentialQuantification or GADTs to allow this)
+        (Enable ExistentialQuantification or GADTs to allow this)
     • In the definition of data constructor ‘C2’
       In the data type declaration for ‘Foo’

testsuite/tests/gadt/gadtSyntaxFail003.stderr

@@ -2,6 +2,6 @@
 gadtSyntaxFail003.hs:7:5: error:
     • Data constructor ‘C1’ has existential type variables, a context, or a specialised result type
         C1 :: forall a c b. a -> Int -> c -> Foo b a
-        (Use ExistentialQuantification or GADTs to allow this)
+        (Enable ExistentialQuantification or GADTs to allow this)
     • In the definition of data constructor ‘C1’
       In the data type declaration for ‘Foo’

testsuite/tests/ghci/scripts/T9293.stderr

 
 <interactive>:4:1: error:
     • Illegal generalised algebraic data declaration for ‘T’
-        (Use GADTs to allow GADTs)
+        (Enable the GADTs extension to allow this)
     • In the data declaration for ‘T’
 
 ghci057.hs:3:3: error:
     • Data constructor ‘C’ has existential type variables, a context, or a specialised result type
         C :: T Int
-        (Use ExistentialQuantification or GADTs to allow this)
+        (Enable ExistentialQuantification or GADTs to allow this)
     • In the definition of data constructor ‘C’
       In the data type declaration for ‘T’
 
 ghci057.hs:3:3: error:
     • Data constructor ‘C’ has existential type variables, a context, or a specialised result type
         C :: T Int
-        (Use ExistentialQuantification or GADTs to allow this)
+        (Enable ExistentialQuantification or GADTs to allow this)
     • In the definition of data constructor ‘C’
       In the data type declaration for ‘T’

testsuite/tests/ghci/scripts/ghci057.stderr

 
 <interactive>:4:1: error:
     • Illegal generalised algebraic data declaration for ‘T’
-        (Use GADTs to allow GADTs)
+        (Enable the GADTs extension to allow this)
     • In the data declaration for ‘T’
 
 ghci057.hs:3:3: error:
     • Data constructor ‘C’ has existential type variables, a context, or a specialised result type
         C :: T Int
-        (Use ExistentialQuantification or GADTs to allow this)
+        (Enable ExistentialQuantification or GADTs to allow this)
     • In the definition of data constructor ‘C’
       In the data type declaration for ‘T’
 
 ghci057.hs:3:3: error:
     • Data constructor ‘C’ has existential type variables, a context, or a specialised result type
         C :: T Int
-        (Use ExistentialQuantification or GADTs to allow this)
+        (Enable ExistentialQuantification or GADTs to allow this)
     • In the definition of data constructor ‘C’
       In the data type declaration for ‘T’

testsuite/tests/module/mod39.stderr

@@ -2,6 +2,6 @@
 mod39.hs:3:17: error:
     • Constraint ‘Eq a’ in the type of ‘f’
         constrains only the class type variables
-      Use ConstrainedClassMethods to allow it
+      Enable ConstrainedClassMethods to allow it
     • When checking the class method: f :: forall a. (C a, Eq a) => a
       In the class declaration for ‘C’

testsuite/tests/parser/should_fail/readFail037.stderr

 
-readFail037.hs:4:1:
-    Too many parameters for class ‘Foo’
-    (Use MultiParamTypeClasses to allow multi-parameter classes)
-    In the class declaration for ‘Foo’
+readFail037.hs:4:1: error:
+    • Too many parameters for class ‘Foo’
+      (Enable MultiParamTypeClasses to allow multi-parameter classes)
+    • In the class declaration for ‘Foo’

testsuite/tests/parser/should_fail/readFail041.stderr

 
-readFail041.hs:6:1:
-    Fundeps in class ‘Foo’
-    (Use FunctionalDependencies to allow fundeps)
-    In the class declaration for ‘Foo’
+readFail041.hs:6:1: error:
+    • Fundeps in class ‘Foo’
+      (Enable FunctionalDependencies to allow fundeps)
+    • In the class declaration for ‘Foo’

testsuite/tests/typecheck/should_fail/T12083a.stderr

@@ -7,6 +7,6 @@ T12083a.hs:5:1: error:
 T12083a.hs:9:26: error:
     • Data constructor ‘ExistentiallyLost’ has existential type variables, a context, or a specialised result type
         ExistentiallyLost :: forall u. TC u => u -> ExistentiallyLost
-        (Use ExistentialQuantification or GADTs to allow this)
+        (Enable ExistentialQuantification or GADTs to allow this)
     • In the definition of data constructor ‘ExistentiallyLost’
       In the data type declaration for ‘ExistentiallyLost’

testsuite/tests/typecheck/should_fail/TcNoNullaryTC.stderr

 
-TcNoNullaryTC.hs:3:1:
-    No parameters for class ‘A’
-    (Use MultiParamTypeClasses to allow no-parameter classes)
-    In the class declaration for ‘A’
+TcNoNullaryTC.hs:3:1: error:
+    • No parameters for class ‘A’
+      (Enable MultiParamTypeClasses to allow no-parameter classes)
+    • In the class declaration for ‘A’

testsuite/tests/typecheck/should_fail/tcfail150.stderr

@@ -2,7 +2,7 @@
 tcfail150.hs:6:3: error:
     • Constraint ‘Eq a’ in the type of ‘op’
         constrains only the class type variables
-      Use ConstrainedClassMethods to allow it
+      Enable ConstrainedClassMethods to allow it
     • When checking the class method:
         op :: forall a. (Foo a, Eq a) => a -> a
       In the class declaration for ‘Foo’