Add test for T20509

This test checks to see whether a signature can depend on another home
module. Whether it should or not is up for debate, see #20509 for
more details.

9 files changed, 80 insertions, 0 deletions

diff --git a/testsuite/tests/backpack/cabal/T20509/Makefile b/testsuite/tests/backpack/cabal/T20509/Makefile
new file mode 100644
index 0000000000..7d20e83135
--- /dev/null
+++ b/testsuite/tests/backpack/cabal/T20509/Makefile
@@ -0,0 +1,27 @@
+TOP=../../../..
+include $(TOP)/mk/boilerplate.mk
+include $(TOP)/mk/test.mk
+
+SETUP=./Setup -v0
+CONFIGURE=$(SETUP) configure $(CABAL_MINIMAL_BUILD) --with-ghc='$(TEST_HC)' --ghc-options='$(TEST_HC_OPTS)' --package-db=tmp.d --prefix='$(PWD)/inst'
+
+T20509: clean
+	$(MAKE) -s --no-print-directory clean
+	'$(GHC_PKG)' init tmp.d
+	'$(TEST_HC)' $(TEST_HC_OPTS) -v0 --make Setup
+	# typecheck p
+	$(CONFIGURE) --cid "p-0.1" p
+	$(SETUP) build
+	$(SETUP) copy
+	$(SETUP) register
+	# typecheck q
+	$(CONFIGURE) --cid "q-0.1" q
+	$(SETUP) build
+	$(SETUP) copy
+	$(SETUP) register
+ifneq "$(CLEANUP)" ""
+	$(MAKE) -s --no-print-directory clean
+endif
+
+clean :
+	$(RM) -r tmp.d inst dist Setup$(exeext)
diff --git a/testsuite/tests/backpack/cabal/T20509/Setup.hs b/testsuite/tests/backpack/cabal/T20509/Setup.hs
new file mode 100644
index 0000000000..9a994af677
--- /dev/null
+++ b/testsuite/tests/backpack/cabal/T20509/Setup.hs
@@ -0,0 +1,2 @@
+import Distribution.Simple
+main = defaultMain
diff --git a/testsuite/tests/backpack/cabal/T20509/T20509.cabal b/testsuite/tests/backpack/cabal/T20509/T20509.cabal
new file mode 100644
index 0000000000..f26ab29d66
--- /dev/null
+++ b/testsuite/tests/backpack/cabal/T20509/T20509.cabal
@@ -0,0 +1,23 @@
+cabal-version: 3.0
+name: T20509
+version: 0
+build-type: Simple
+
+common common
+  build-depends: base
+  ghc-options: -Wall
+
+library p
+  import: common
+  hs-source-dirs: p
+  signatures: H
+  exposed-modules: A
+
+library q
+  import: common
+  hs-source-dirs: q
+  build-depends: p
+  signatures: H2
+  exposed-modules: L, B
+  mixins:
+    p (A as A2) requires (H as H2)
diff --git a/testsuite/tests/backpack/cabal/T20509/all.T b/testsuite/tests/backpack/cabal/T20509/all.T
new file mode 100644
index 0000000000..d94879a8d7
--- /dev/null
+++ b/testsuite/tests/backpack/cabal/T20509/all.T
@@ -0,0 +1,10 @@
+if config.cleanup:
+   cleanup = 'CLEANUP=1'
+else:
+   cleanup = 'CLEANUP=0'
+
+test('T20509',
+     [extra_files(['p', 'q', 'T20509.cabal', 'Setup.hs']),
+      run_timeout_multiplier(2)],
+     run_command,
+     ['$MAKE -s --no-print-directory T20509 ' + cleanup])
diff --git a/testsuite/tests/backpack/cabal/T20509/p/A.hs b/testsuite/tests/backpack/cabal/T20509/p/A.hs
new file mode 100644
index 0000000000..6be0e516e5
--- /dev/null
+++ b/testsuite/tests/backpack/cabal/T20509/p/A.hs
@@ -0,0 +1,3 @@
+module A where
+    import H
+    data T = T S1 S2
diff --git a/testsuite/tests/backpack/cabal/T20509/p/H.hsig b/testsuite/tests/backpack/cabal/T20509/p/H.hsig
new file mode 100644
index 0000000000..37b8071c5c
--- /dev/null
+++ b/testsuite/tests/backpack/cabal/T20509/p/H.hsig
@@ -0,0 +1,3 @@
+signature H where
+    data S1
+    data S2
diff --git a/testsuite/tests/backpack/cabal/T20509/q/B.hs b/testsuite/tests/backpack/cabal/T20509/q/B.hs
new file mode 100644
index 0000000000..c4757b8d61
--- /dev/null
+++ b/testsuite/tests/backpack/cabal/T20509/q/B.hs
@@ -0,0 +1,5 @@
+module B where
+    import A2
+    import H2
+    t :: S1 -> S2 -> T
+    t = T :: S1 -> S2 -> T
diff --git a/testsuite/tests/backpack/cabal/T20509/q/H2.hsig b/testsuite/tests/backpack/cabal/T20509/q/H2.hsig
new file mode 100644
index 0000000000..e52c45a6e6
--- /dev/null
+++ b/testsuite/tests/backpack/cabal/T20509/q/H2.hsig
@@ -0,0 +1,4 @@
+signature H2 (S1(MkS1),S2, f) where
+    import L(S1(..))
+    data S2
+    f :: S1 -> S1
diff --git a/testsuite/tests/backpack/cabal/T20509/q/L.hs b/testsuite/tests/backpack/cabal/T20509/q/L.hs
new file mode 100644
index 0000000000..669e391739
--- /dev/null
+++ b/testsuite/tests/backpack/cabal/T20509/q/L.hs
@@ -0,0 +1,3 @@
+module L where
+  data S1 = MkS1
+