Narrow scope of special-case for unqualified printing of names in core libraries

Commit 547c597112954353cef7157cb0a389bc4f6303eb modifies the
pretty-printer to render names from a set of core packages (`base`,
`ghc-prim`, `template-haskell`) as unqualified. The idea here was that
many of these names typically are not in scope but are well-known by the
user and therefore qualification merely introduces noise.

This, however, is a very large hammer and potentially breaks any
consumer who relies on parsing GHC output (hence #11208). This commit
partially reverts this change, now only printing `Constraint` (which
appears quite often in errors) as unqualified.

Fixes #11208.

Updates tests in `array` submodule.

Test Plan: validate

Reviewers: hvr, thomie, austin

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1619

GHC Trac Issues: #11208

2 files changed, 48 insertions, 43 deletions

diff --git a/testsuite/tests/overloadedlists/should_fail/overloadedlistsfail01.stderr b/testsuite/tests/overloadedlists/should_fail/overloadedlistsfail01.stderr
index dbc250d794..7a43f4f778 100644
--- a/testsuite/tests/overloadedlists/should_fail/overloadedlistsfail01.stderr
+++ b/testsuite/tests/overloadedlists/should_fail/overloadedlistsfail01.stderr
@@ -1,38 +1,41 @@
 
 overloadedlistsfail01.hs:5:8: error:
-    Ambiguous type variable ‘a0’ arising from a use of ‘print’
-    prevents the constraint ‘(Show a0)’ from being solved.
-    Probable fix: use a type annotation to specify what ‘a0’ should be.
-    These potential instances exist:
-      instance [safe] Show Version -- Defined in ‘Data.Version’
-      instance Show Module -- Defined in ‘GHC.Show’
-      instance Show Ordering -- Defined in ‘GHC.Show’
-      ...plus 26 others
-      (use -fprint-potential-instances to see them all)
-    In the expression: print [1]
-    In an equation for ‘main’: main = print [1]
+    • Ambiguous type variable ‘a0’ arising from a use of ‘print’
+      prevents the constraint ‘(Show a0)’ from being solved.
+      Probable fix: use a type annotation to specify what ‘a0’ should be.
+      These potential instances exist:
+        instance Show Ordering -- Defined in ‘GHC.Show’
+        instance Show Integer -- Defined in ‘GHC.Show’
+        instance Show a => Show (Maybe a) -- Defined in ‘GHC.Show’
+        ...plus 22 others
+        ...plus four instance involving out-of-scope typess
+        (use -fprint-potential-instances to see them all)
+    • In the expression: print [1]
+      In an equation for ‘main’: main = print [1]
 
 overloadedlistsfail01.hs:5:14: error:
-    Ambiguous type variable ‘a0’ arising from an overloaded list
-    prevents the constraint ‘(IsList a0)’ from being solved.
-    Probable fix: use a type annotation to specify what ‘a0’ should be.
-    These potential instances exist:
-      instance IsList Version -- Defined in ‘GHC.Exts’
-      instance IsList [a] -- Defined in ‘GHC.Exts’
-    In the first argument of ‘print’, namely ‘[1]’
-    In the expression: print [1]
-    In an equation for ‘main’: main = print [1]
+    • Ambiguous type variable ‘a0’ arising from an overloaded list
+      prevents the constraint ‘(GHC.Exts.IsList a0)’ from being solved.
+      Probable fix: use a type annotation to specify what ‘a0’ should be.
+      These potential instances exist:
+        instance GHC.Exts.IsList [a] -- Defined in ‘GHC.Exts’
+        ...plus one instance involving out-of-scope types
+        (use -fprint-potential-instances to see them all)
+    • In the first argument of ‘print’, namely ‘[1]’
+      In the expression: print [1]
+      In an equation for ‘main’: main = print [1]
 
 overloadedlistsfail01.hs:5:15: error:
-    Ambiguous type variable ‘a0’ arising from the literal ‘1’
-    prevents the constraint ‘(Num (Item a0))’ from being solved.
-    Probable fix: use a type annotation to specify what ‘a0’ should be.
-    These potential instances exist:
-      instance Num Integer -- Defined in ‘GHC.Num’
-      instance Num Double -- Defined in ‘GHC.Float’
-      instance Num Float -- Defined in ‘GHC.Float’
-      ...plus two others
-      (use -fprint-potential-instances to see them all)
-    In the expression: 1
-    In the first argument of ‘print’, namely ‘[1]’
-    In the expression: print [1]
+    • Ambiguous type variable ‘a0’ arising from the literal ‘1’
+      prevents the constraint ‘(Num
+                                  (GHC.Exts.Item a0))’ from being solved.
+      Probable fix: use a type annotation to specify what ‘a0’ should be.
+      These potential instances exist:
+        instance Num Integer -- Defined in ‘GHC.Num’
+        instance Num Double -- Defined in ‘GHC.Float’
+        instance Num Float -- Defined in ‘GHC.Float’
+        ...plus two others
+        (use -fprint-potential-instances to see them all)
+    • In the expression: 1
+      In the first argument of ‘print’, namely ‘[1]’
+      In the expression: print [1]
diff --git a/testsuite/tests/overloadedlists/should_fail/overloadedlistsfail02.stderr b/testsuite/tests/overloadedlists/should_fail/overloadedlistsfail02.stderr
index 4597e1ce56..e0be7ab4e5 100644
--- a/testsuite/tests/overloadedlists/should_fail/overloadedlistsfail02.stderr
+++ b/testsuite/tests/overloadedlists/should_fail/overloadedlistsfail02.stderr
@@ -1,11 +1,13 @@
-

-overloadedlistsfail02.hs:6:8:

-    No instance for (IsList Foo) arising from an overloaded list

-    In the expression: [7]

-    In an equation for ‘test’: test = [7]

-

-overloadedlistsfail02.hs:6:9:

-    No instance for (Num (Item Foo)) arising from the literal ‘7’

-    In the expression: 7

-    In the expression: [7]

-    In an equation for ‘test’: test = [7]

+
+overloadedlistsfail02.hs:6:8: error:
+    • No instance for (GHC.Exts.IsList Foo)
+        arising from an overloaded list
+    • In the expression: [7]
+      In an equation for ‘test’: test = [7]
+
+overloadedlistsfail02.hs:6:9: error:
+    • No instance for (Num (GHC.Exts.Item Foo))
+        arising from the literal ‘7’
+    • In the expression: 7
+      In the expression: [7]
+      In an equation for ‘test’: test = [7]