Fix and document Unique generation for sum TyCon and DataCons

Test Plan: validate

Reviewers: bgamari, austin

Reviewed By: bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2420

2 files changed, 31 insertions, 0 deletions

diff --git a/testsuite/tests/unboxedsums/all.T b/testsuite/tests/unboxedsums/all.T
index 274045f393..0b948b1477 100644
--- a/testsuite/tests/unboxedsums/all.T
+++ b/testsuite/tests/unboxedsums/all.T
@@ -1,3 +1,8 @@
+test('unboxedsums_unit_tests',
+     only_ways(['normal']),
+     compile_and_run,
+     ['-package ghc'])
+
 test('unarise',       omit_ways(['ghci']), compile_and_run, [''])
 test('unboxedsums1',  omit_ways(['ghci']), compile_and_run, [''])
 test('unboxedsums2',  omit_ways(['ghci']), compile_and_run, [''])
diff --git a/testsuite/tests/unboxedsums/unboxedsums_unit_tests.hs b/testsuite/tests/unboxedsums/unboxedsums_unit_tests.hs
new file mode 100644
index 0000000000..d7a8d333a0
--- /dev/null
+++ b/testsuite/tests/unboxedsums/unboxedsums_unit_tests.hs
@@ -0,0 +1,26 @@
+module Main where
+
+import TysWiredIn
+import UniqSet
+import Unique
+
+import System.IO
+import Control.Monad
+
+main :: IO ()
+main = sequence_
+    [ uniq_tests ]
+
+
+uniq_tests :: IO ()
+uniq_tests = do
+    let tycons   = map sumTyCon [2 .. 20]
+        datacons = [ sumDataCon alt arity | arity <- [ 2 .. 20 ]
+                                          , alt   <- [ 1 .. arity ] ]
+
+        us = mkUniqSet (map getUnique tycons)
+               `unionUniqSets` mkUniqSet (map getUnique datacons)
+
+    when (sizeUniqSet us /= length tycons + length datacons) $ do
+      hPutStrLn stderr "Sum cons/tycons have same uniques."
+      hFlush stderr