Enable UnboxedTuples in `genInst`, Fixes #20524

9 files changed, 32 insertions, 11 deletions

diff --git a/compiler/GHC/Tc/Deriv.hs b/compiler/GHC/Tc/Deriv.hs
index bf95f5c58f..e1a688cd55 100644
--- a/compiler/GHC/Tc/Deriv.hs
+++ b/compiler/GHC/Tc/Deriv.hs
@@ -1850,6 +1850,9 @@ genInst spec@(DS { ds_tvs = tvs, ds_mechanism = mechanism
           -- that bring type variables into scope.
           -- See Note [Newtype-deriving instances] in GHC.Tc.Deriv.Generate
         , LangExt.InstanceSigs
+          -- Skip unboxed tuples checking for derived instances when imported
+          -- in a different module, see #20524
+        , LangExt.UnboxedTuples
         ]
       | otherwise
       = []
diff --git a/testsuite/tests/deriving/should_fail/T15073.hs b/testsuite/tests/deriving/should_compile/T15073.hs
index b1da4bb701..b1da4bb701 100644
--- a/testsuite/tests/deriving/should_fail/T15073.hs
+++ b/testsuite/tests/deriving/should_compile/T15073.hs
diff --git a/testsuite/tests/deriving/should_fail/T15073a.hs b/testsuite/tests/deriving/should_compile/T15073a.hs
index 87e7571f50..87e7571f50 100644
--- a/testsuite/tests/deriving/should_fail/T15073a.hs
+++ b/testsuite/tests/deriving/should_compile/T15073a.hs
diff --git a/testsuite/tests/deriving/should_compile/all.T b/testsuite/tests/deriving/should_compile/all.T
index e2680a8f9d..64925923ba 100644
--- a/testsuite/tests/deriving/should_compile/all.T
+++ b/testsuite/tests/deriving/should_compile/all.T
@@ -113,6 +113,8 @@ test('T14682', normal, compile, ['-ddump-deriv -dsuppress-uniques'])
 test('T14883', normal, compile, [''])
 test('T14932', normal, compile, [''])
 test('T14933', normal, compile, [''])
+test('T15073', [extra_files(['T15073a.hs'])], multimod_compile,
+               ['T15073', '-v0'])
 test('T15290c', normal, compile, [''])
 test('T15290d', normal, compile, [''])
 test('T15398', normal, compile, [''])
diff --git a/testsuite/tests/deriving/should_fail/T15073.stderr b/testsuite/tests/deriving/should_fail/T15073.stderr
deleted file mode 100644
index 79d3a10cdc..0000000000
--- a/testsuite/tests/deriving/should_fail/T15073.stderr
+++ /dev/null
@@ -1,9 +0,0 @@
-
-T15073.hs:8:12: error:
-    • Illegal unboxed tuple type as function argument: (# Foo a #)
-    • In the type signature: p :: Foo a -> (# Foo a #)
-      When typechecking the code for ‘p’
-        in a derived instance for ‘P (Foo a)’:
-        To see the code I am typechecking, use -ddump-deriv
-      In the instance declaration for ‘P (Foo a)’
-    Suggested fix: Perhaps you intended to use UnboxedTuples
\ No newline at end of file
diff --git a/testsuite/tests/deriving/should_fail/all.T b/testsuite/tests/deriving/should_fail/all.T
index 4743d3530d..70bd0f9dbe 100644
--- a/testsuite/tests/deriving/should_fail/all.T
+++ b/testsuite/tests/deriving/should_fail/all.T
@@ -72,8 +72,6 @@ test('T14365', [extra_files(['T14365B.hs','T14365B.hs-boot'])],
 test('T14728a', normal, compile_fail, [''])
 test('T14728b', normal, compile_fail, [''])
 test('T14916', normal, compile_fail, [''])
-test('T15073', [extra_files(['T15073a.hs'])], multimod_compile_fail,
-               ['T15073', '-v0'])
 test('T16181', normal, compile_fail, [''])
 test('T16923', normal, compile_fail, [''])
 test('T18127b', normal, compile_fail, [''])
diff --git a/testsuite/tests/typecheck/T20524/T20524.hs b/testsuite/tests/typecheck/T20524/T20524.hs
new file mode 100644
index 0000000000..4313acbcef
--- /dev/null
+++ b/testsuite/tests/typecheck/T20524/T20524.hs
@@ -0,0 +1,11 @@
+{-#LANGUAGE DerivingVia, GeneralizedNewtypeDeriving#-}
+
+module T20524 where
+import UT
+
+data Foo = Foo
+  deriving Tupleable via Boring Foo
+
+newtype Bar a = Bar ()
+  deriving newtype Tupleable
+
diff --git a/testsuite/tests/typecheck/T20524/UT.hs b/testsuite/tests/typecheck/T20524/UT.hs
new file mode 100644
index 0000000000..2293f5c006
--- /dev/null
+++ b/testsuite/tests/typecheck/T20524/UT.hs
@@ -0,0 +1,15 @@
+{-#LANGUAGE UnboxedTuples#-}
+
+module UT where
+
+class Tupleable a where
+  tup :: a -> (# a #)
+
+newtype Boring a = Boring a
+instance Tupleable (Boring a) where
+  tup a = (# a #)
+
+instance Tupleable () where
+  tup _ = (# () #)
+
+
diff --git a/testsuite/tests/typecheck/T20524/all.T b/testsuite/tests/typecheck/T20524/all.T
new file mode 100644
index 0000000000..e0b595d550
--- /dev/null
+++ b/testsuite/tests/typecheck/T20524/all.T
@@ -0,0 +1 @@
+test('T20524', [extra_files(['UT.hs'])], multi_compile, ['T20524', [('UT.hs', '')], '-v0'])