with constraint: ignore ghost components

"With" constraint should not be able to manipulate
independently ghost signature components. For instance, in

  module type s = sig class c: object end end with type c := < >

the compiler should fail with a missing component item rather than
silently remove the ghost type of the class c.

1 files changed, 31 insertions, 0 deletions

diff --git a/testsuite/tests/typing-modules/with_ghosts.ml b/testsuite/tests/typing-modules/with_ghosts.ml
new file mode 100644
index 0000000000..bd500139ff
--- /dev/null
+++ b/testsuite/tests/typing-modules/with_ghosts.ml
@@ -0,0 +1,31 @@
+(* TEST
+   * expect
+*)
+
+(**
+   Check the behavior of with constraints with respect to
+    ghost type items introduced for class and class types
+ *)
+
+module type s = sig
+  class type c = object method m: int end
+end with type c := <m : int >
+[%%expect {|
+Lines 6-8, characters 16-29:
+6 | ................sig
+7 |   class type c = object method m: int end
+8 | end with type c := <m : int >
+Error: The signature constrained by `with' has no component named c
+|}]
+
+
+module type s = sig
+  class type ct = object method m: int end
+end with type ct := <m : int >
+[%%expect {|
+Lines 1-3, characters 16-30:
+1 | ................sig
+2 |   class type ct = object method m: int end
+3 | end with type ct := <m : int >
+Error: The signature constrained by `with' has no component named ct
+|}]