Fix unparseable pretty-printing of promoted data cons

Previously we would print code which would not round-trip:
```
> :set -XDataKinds
> :set -XPolyKinds
> data Proxy k = Proxy
> _ :: Proxy '[ 'True ]
error:
  Found hole: _ :: Proxy '['True]
> _ :: Proxy '['True]
error:
    Invalid type signature: _ :: ...
    Should be of form <variable> :: <type>
```

Test Plan: Validate with T14343

Reviewers: RyanGlScott, goldfire, bgamari, tdammers

Reviewed By: RyanGlScott, bgamari

Subscribers: tdammers, rwbarton, thomie, carter

GHC Trac Issues: #14343

Differential Revision: https://phabricator.haskell.org/D4746

6 files changed, 109 insertions, 0 deletions

diff --git a/testsuite/tests/printer/Makefile b/testsuite/tests/printer/Makefile
index 17fc65215f..044e44332e 100644
--- a/testsuite/tests/printer/Makefile
+++ b/testsuite/tests/printer/Makefile
@@ -229,3 +229,11 @@ T14289c:
 .PHONY: T14306
 T14306:
 	$(CHECK_PPR) "`'$(TEST_HC)' $(TEST_HC_OPTS) --print-libdir | tr -d '\r'`" T14306.hs
+
+.PHONY: T14343
+T14343:
+	$(CHECK_PPR) "`'$(TEST_HC)' $(TEST_HC_OPTS) --print-libdir | tr -d '\r'`" T14343.hs
+
+.PHONY: T14343b
+T14343b:
+	$(CHECK_PPR) "`'$(TEST_HC)' $(TEST_HC_OPTS) --print-libdir | tr -d '\r'`" T14343b.hs
diff --git a/testsuite/tests/printer/T14343.hs b/testsuite/tests/printer/T14343.hs
new file mode 100644
index 0000000000..1fe6a9660b
--- /dev/null
+++ b/testsuite/tests/printer/T14343.hs
@@ -0,0 +1,12 @@
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE PolyKinds #-}
+{-# OPTIONS_GHC -Werror=typed-holes #-}
+
+main :: IO ()
+main = undefined
+
+data Proxy k = Proxy
+
+test1 = _ :: Proxy '[ 'True ]
+test2 = _ :: Proxy '[ '[ 1 ] ]
+test3 = _ :: Proxy '[ '( "Symbol", 1 ) ]
diff --git a/testsuite/tests/printer/T14343.stderr b/testsuite/tests/printer/T14343.stderr
new file mode 100644
index 0000000000..1bceb67403
--- /dev/null
+++ b/testsuite/tests/printer/T14343.stderr
@@ -0,0 +1,36 @@
+
+T14343.hs:10:9: error:
+    • Found hole: _ :: Proxy '[ 'True]
+    • In the expression: _ :: Proxy '[ 'True]
+      In an equation for ‘test1’: test1 = _ :: Proxy '[ 'True]
+    • Relevant bindings include
+        test1 :: Proxy '[ 'True] (bound at T14343.hs:10:1)
+      Valid hole fits include
+        test1 :: Proxy '[ 'True] (defined at T14343.hs:10:1)
+        Proxy :: forall k1 (k2 :: k1). Proxy k2
+          with Proxy @[Bool] @'[ 'True]
+          (defined at T14343.hs:8:16)
+
+T14343.hs:11:9: error:
+    • Found hole: _ :: Proxy '[ '[1]]
+    • In the expression: _ :: Proxy '['[1]]
+      In an equation for ‘test2’: test2 = _ :: Proxy '['[1]]
+    • Relevant bindings include
+        test2 :: Proxy '[ '[1]] (bound at T14343.hs:11:1)
+      Valid hole fits include
+        test2 :: Proxy '[ '[1]] (defined at T14343.hs:11:1)
+        Proxy :: forall k1 (k2 :: k1). Proxy k2
+          with Proxy @[[GHC.Types.Nat]] @'[ '[1]]
+          (defined at T14343.hs:8:16)
+
+T14343.hs:12:9: error:
+    • Found hole: _ :: Proxy '[ '("Symbol", 1)]
+    • In the expression: _ :: Proxy '['("Symbol", 1)]
+      In an equation for ‘test3’: test3 = _ :: Proxy '['("Symbol", 1)]
+    • Relevant bindings include
+        test3 :: Proxy '[ '("Symbol", 1)] (bound at T14343.hs:12:1)
+      Valid hole fits include
+        test3 :: Proxy '[ '("Symbol", 1)] (defined at T14343.hs:12:1)
+        Proxy :: forall k1 (k2 :: k1). Proxy k2
+          with Proxy @[(GHC.Types.Symbol, GHC.Types.Nat)] @'[ '("Symbol", 1)]
+          (defined at T14343.hs:8:16)
diff --git a/testsuite/tests/printer/T14343b.hs b/testsuite/tests/printer/T14343b.hs
new file mode 100644
index 0000000000..6596a7a486
--- /dev/null
+++ b/testsuite/tests/printer/T14343b.hs
@@ -0,0 +1,12 @@
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE PolyKinds #-}
+{-# OPTIONS_GHC -Werror=typed-holes #-}
+
+main :: IO ()
+main = undefined
+
+data Proxy k = Proxy
+
+test1 = _ :: Proxy '( 'True, 'False )
+test2 = _ :: Proxy '( '( 'True, 'False ), 'False )
+test3 = _ :: Proxy '( '[ 1 ], 'False )
diff --git a/testsuite/tests/printer/T14343b.stderr b/testsuite/tests/printer/T14343b.stderr
new file mode 100644
index 0000000000..1954f9465a
--- /dev/null
+++ b/testsuite/tests/printer/T14343b.stderr
@@ -0,0 +1,39 @@
+
+T14343b.hs:10:9: error:
+    • Found hole: _ :: Proxy '( 'True, 'False)
+    • In the expression: _ :: Proxy '( 'True,  'False)
+      In an equation for ‘test1’: test1 = _ :: Proxy '( 'True,  'False)
+    • Relevant bindings include
+        test1 :: Proxy '( 'True, 'False) (bound at T14343b.hs:10:1)
+      Valid hole fits include
+        test1 :: Proxy '( 'True, 'False) (defined at T14343b.hs:10:1)
+        Proxy :: forall k1 (k2 :: k1). Proxy k2
+          with Proxy @(Bool, Bool) @'( 'True, 'False)
+          (defined at T14343b.hs:8:16)
+
+T14343b.hs:11:9: error:
+    • Found hole: _ :: Proxy '( '( 'True, 'False), 'False)
+    • In the expression: _ :: Proxy '('( 'True,  'False),  'False)
+      In an equation for ‘test2’:
+          test2 = _ :: Proxy '('( 'True,  'False),  'False)
+    • Relevant bindings include
+        test2 :: Proxy '( '( 'True, 'False), 'False)
+          (bound at T14343b.hs:11:1)
+      Valid hole fits include
+        test2 :: Proxy '( '( 'True, 'False), 'False)
+          (defined at T14343b.hs:11:1)
+        Proxy :: forall k1 (k2 :: k1). Proxy k2
+          with Proxy @((Bool, Bool), Bool) @'( '( 'True, 'False), 'False)
+          (defined at T14343b.hs:8:16)
+
+T14343b.hs:12:9: error:
+    • Found hole: _ :: Proxy '( '[1], 'False)
+    • In the expression: _ :: Proxy '('[1],  'False)
+      In an equation for ‘test3’: test3 = _ :: Proxy '('[1],  'False)
+    • Relevant bindings include
+        test3 :: Proxy '( '[1], 'False) (bound at T14343b.hs:12:1)
+      Valid hole fits include
+        test3 :: Proxy '( '[1], 'False) (defined at T14343b.hs:12:1)
+        Proxy :: forall k1 (k2 :: k1). Proxy k2
+          with Proxy @([GHC.Types.Nat], Bool) @'( '[1], 'False)
+          (defined at T14343b.hs:8:16)
diff --git a/testsuite/tests/printer/all.T b/testsuite/tests/printer/all.T
index 7dda6b36fa..203efa4be4 100644
--- a/testsuite/tests/printer/all.T
+++ b/testsuite/tests/printer/all.T
@@ -54,3 +54,5 @@ test('T14289', ignore_stderr, run_command, ['$MAKE -s --no-print-directory T1428
 test('T14289b', ignore_stderr, run_command, ['$MAKE -s --no-print-directory T14289b'])
 test('T14289c', ignore_stderr, run_command, ['$MAKE -s --no-print-directory T14289c'])
 test('T14306', ignore_stderr, run_command, ['$MAKE -s --no-print-directory T14306'])
+test('T14343', normal, compile_fail, [''])
+test('T14343b', normal, compile_fail, [''])