Template Haskell support for TypeApplications

Summary: Fixes #12530.

Test Plan: make test TEST=12530

Reviewers: austin, bgamari, hvr, goldfire

Reviewed By: goldfire

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2472

GHC Trac Issues: #12530

3 files changed, 26 insertions, 0 deletions

diff --git a/testsuite/tests/th/T12530.hs b/testsuite/tests/th/T12530.hs
new file mode 100644
index 0000000000..4c0e27dcbf
--- /dev/null
+++ b/testsuite/tests/th/T12530.hs
@@ -0,0 +1,15 @@
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TemplateHaskell #-}
+{-# LANGUAGE TypeApplications #-}
+module T12530 where
+
+import Language.Haskell.TH
+
+$([d|   -- Test the Template Haskell pretty-printing for TypeApplications
+        f :: Maybe Int -> Maybe Int
+        f = id @(Maybe Int)
+
+        -- Wildcards and scoped type variables too
+        g :: forall a. a
+        g = undefined @(_) @(a)
+    |])
diff --git a/testsuite/tests/th/T12530.stderr b/testsuite/tests/th/T12530.stderr
new file mode 100644
index 0000000000..0ba15360ac
--- /dev/null
+++ b/testsuite/tests/th/T12530.stderr
@@ -0,0 +1,10 @@
+T12530.hs:(8,3)-(15,6): Splicing declarations
+    [d| f :: Maybe Int -> Maybe Int
+        f = id @(Maybe Int)
+        g :: forall a. a
+        g = undefined @(_) @(a) |]
+  ======>
+    f :: Maybe Int -> Maybe Int
+    f = id @(Maybe Int)
+    g :: forall a. a
+    g = undefined @_ @a
diff --git a/testsuite/tests/th/all.T b/testsuite/tests/th/all.T
index 592e133e7d..2cfe2a509b 100644
--- a/testsuite/tests/th/all.T
+++ b/testsuite/tests/th/all.T
@@ -427,3 +427,4 @@ test('T12478_2', omit_ways(['ghci']), compile_and_run, ['-v0'])
 test('T12478_3', omit_ways(['ghci']), compile, ['-v0'])
 test('T12478_4', omit_ways(['ghci']), compile_fail, ['-v0'])
 test('T12513', omit_ways(['ghci']), compile_fail, ['-v0'])
+test('T12530', normal, compile, ['-v0 -ddump-splices -dsuppress-uniques'])