[commit: ghc] master: Parenthesize pretty-printed equalities when necessary (2277172)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/2277172ac3ea0bbeddebc9999a5d8b5f9f58afc9/ghc

>---------------------------------------------------------------

commit 2277172ac3ea0bbeddebc9999a5d8b5f9f58afc9
Author: Ryan Scott <ryan.gl.scott at gmail.com>
Date:   Thu May 11 15:42:55 2017 -0400

    Parenthesize pretty-printed equalities when necessary
    
    Fixes #13677 by parenthesizing equalities in a sufficiently high
    pretty-printing context.
    
    Test Plan: make test TEST=T13677
    
    Reviewers: goldfire, austin, bgamari
    
    Reviewed By: bgamari
    
    Subscribers: rwbarton, thomie
    
    GHC Trac Issues: #13677
    
    Differential Revision: https://phabricator.haskell.org/D3570


>---------------------------------------------------------------

2277172ac3ea0bbeddebc9999a5d8b5f9f58afc9
 compiler/iface/IfaceType.hs                         |  2 +-
 testsuite/tests/typecheck/should_fail/T13677.hs     | 11 +++++++++++
 testsuite/tests/typecheck/should_fail/T13677.stderr |  4 ++++
 testsuite/tests/typecheck/should_fail/all.T         |  1 +
 4 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/compiler/iface/IfaceType.hs b/compiler/iface/IfaceType.hs
index 41cf4f6..eafd6dd 100644
--- a/compiler/iface/IfaceType.hs
+++ b/compiler/iface/IfaceType.hs
@@ -979,7 +979,7 @@ pprTyTcApp' ctxt_prec tc tys dflags style
          -> text "(TypeError ...)"
 
        | Just doc <- ppr_equality tc (tcArgsIfaceTypes tys)
-         -> doc
+         -> maybeParen ctxt_prec TyConPrec doc
 
        | otherwise
          -> ppr_iface_tc_app ppr_ty ctxt_prec tc tys_wo_kinds
diff --git a/testsuite/tests/typecheck/should_fail/T13677.hs b/testsuite/tests/typecheck/should_fail/T13677.hs
new file mode 100644
index 0000000..f452a20
--- /dev/null
+++ b/testsuite/tests/typecheck/should_fail/T13677.hs
@@ -0,0 +1,11 @@
+{-# LANGUAGE ConstraintKinds #-}
+{-# LANGUAGE GADTs #-}
+module T13677 where
+
+import GHC.Exts (Constraint)
+
+data Dict a where
+  Dict :: a => Dict a
+
+foo :: Dict (Int ~ Int) => Int
+foo = undefined
diff --git a/testsuite/tests/typecheck/should_fail/T13677.stderr b/testsuite/tests/typecheck/should_fail/T13677.stderr
new file mode 100644
index 0000000..c29aba2
--- /dev/null
+++ b/testsuite/tests/typecheck/should_fail/T13677.stderr
@@ -0,0 +1,4 @@
+
+T13677.hs:10:8: error:
+    • Expected a constraint, but ‘Dict (Int ~ Int)’ has kind ‘*’
+    • In the type signature: foo :: Dict (Int ~ Int) => Int
diff --git a/testsuite/tests/typecheck/should_fail/all.T b/testsuite/tests/typecheck/should_fail/all.T
index 4a409e0..3875063 100644
--- a/testsuite/tests/typecheck/should_fail/all.T
+++ b/testsuite/tests/typecheck/should_fail/all.T
@@ -438,3 +438,4 @@ test('T13506', normal, compile_fail, [''])
 test('T13611', expect_broken(13611), compile_fail, [''])
 test('T13320', normal, compile_fail, [''])
 test('T13640', normal, compile_fail, [''])
+test('T13677', normal, compile_fail, [''])