Suggest FFI extensions as hints (#20116)

- Use extension suggestion hints instead of suggesting extensions in the
error message body for several FFI errors.
- Adds a test case for `TcRnForeignImportPrimExtNotSet`

4 files changed, 21 insertions, 5 deletions

diff --git a/testsuite/tests/ffi/should_fail/T10461.stderr b/testsuite/tests/ffi/should_fail/T10461.stderr
index 3421467715..47df47b97f 100644
--- a/testsuite/tests/ffi/should_fail/T10461.stderr
+++ b/testsuite/tests/ffi/should_fail/T10461.stderr
@@ -1,7 +1,8 @@
 
 T10461.hs:6:1: error:
-    Unacceptable result type in foreign declaration:
-      ‘Word#’ cannot be marshalled in a foreign call
-      To marshal unlifted types, use UnliftedFFITypes
-    When checking declaration:
-      foreign import prim safe cheneycopy :: Any -> Word#
+    • Unacceptable result type in foreign declaration:
+        ‘Word#’ cannot be marshalled in a foreign call
+        UnliftedFFITypes is required to marshal unlifted types
+    • When checking declaration:
+        foreign import prim safe cheneycopy :: Any -> Word#
+    Suggested fix: Perhaps you intended to use UnliftedFFITypes
diff --git a/testsuite/tests/ffi/should_fail/T20116.hs b/testsuite/tests/ffi/should_fail/T20116.hs
new file mode 100644
index 0000000000..ca8c4fbbdf
--- /dev/null
+++ b/testsuite/tests/ffi/should_fail/T20116.hs
@@ -0,0 +1,8 @@
+{-# LANGUAGE MagicHash #-}
+{-# LANGUAGE ForeignFunctionInterface #-}
+
+module Foo where
+
+import GHC.Exts
+
+foreign import prim "test_lt" lt_s :: Int64# -> Int64# -> Int#
diff --git a/testsuite/tests/ffi/should_fail/T20116.stderr b/testsuite/tests/ffi/should_fail/T20116.stderr
new file mode 100644
index 0000000000..dbc06bf9a0
--- /dev/null
+++ b/testsuite/tests/ffi/should_fail/T20116.stderr
@@ -0,0 +1,6 @@
+
+T20116.hs:8:1: error:
+    • `foreign import prim' requires GHCForeignImportPrim.
+    • When checking declaration:
+        foreign import prim safe "test_lt" lt_s :: Int64# -> Int64# -> Int#
+    Suggested fix: Perhaps you intended to use GHCForeignImportPrim
diff --git a/testsuite/tests/ffi/should_fail/all.T b/testsuite/tests/ffi/should_fail/all.T
index ce1c10534e..24210dcca6 100644
--- a/testsuite/tests/ffi/should_fail/all.T
+++ b/testsuite/tests/ffi/should_fail/all.T
@@ -16,6 +16,7 @@ test('T7506', normal, compile_fail, [''])
 test('T7243', normal, compile_fail, [''])
 test('T10461', normal, compile_fail, [''])
 test('T16702', normal, compile_fail, [''])
+test('T20116', normal, compile_fail, [''])
 
 # UnsafeReenter tests implementation of an undefined behavior (calling Haskell
 # from an unsafe foreign function) and only makes sense in non-threaded way