Add regression test for #6070

Fixes #6070.

testsuite/tests/stranal/sigs/T6070.hs

+module T6070 where
+
+import qualified Data.Map as M
+
+-- Should unbox `x`, so signature 1!P(..,..)
+h :: (Int, Int) -> Int -> (Int, Int)
+h x y = if y > 10
+         then x
+         else h (case h x 0 of (y1, y2) -> (y2, y1)) (y + 1)
+
+-- Should unbox `(a,b)`, so signature 1!P(..,..)
+c :: M.Map Int Int -> (Int, Int)
+c m = M.foldrWithKey (\k v (a, b) -> if k + v > 2 then (a, b) else (b, a)) (0, 1) m

testsuite/tests/stranal/sigs/T6070.stderr

+
+==================== Strictness signatures ====================
+T6070.c: <1L>
+T6070.h: <1!P(L,L)><1!P(L)>
+
+
+
+==================== Cpr signatures ====================
+T6070.c: 1
+T6070.h: 1
+
+
+
+==================== Strictness signatures ====================
+T6070.c: <1L>
+T6070.h: <1!P(L,L)><1!P(L)>
+
+

testsuite/tests/stranal/sigs/all.T

@@ -18,6 +18,7 @@ test('DmdAnalGADTs', normal, compile, [''])
 test('T12370', normal, compile, [''])
 test('NewtypeArity', normal, compile, [''])
 test('T5075', normal, compile, [''])
+test('T6070', normal, compile, [''])
 test('T17932', normal, compile, [''])
 test('T13380c', expect_broken('!3014'), compile, [''])
 test('T13380f', normal, compile, [''])