c++/modules: Provide definitions of synthesized methods outside their defining module [PR120499]

In the PR, we're getting a linker error from _Vector_impl's destructor
never getting emitted.  This is because of a combination of factors:

1. in imp-member-4_a, the destructor is not used and so there is no
   definition generated.

2. in imp-member-4_b, the destructor gets synthesized (as part of the
   synthesis for Coll's destructor) but is not ODR-used and so does not
   get emitted.  Despite there being a definition provided in this TU,
   the destructor is still considered imported and so isn't streamed
   into the module body.

3. in imp-member-4_c, we need to ODR-use the destructor but we only got
   a forward declaration from imp-member-4_b, so we cannot emit a body.

The point of failure here is step 2; this function has effectively been
declared in the imp-member-4_b module, and so we shouldn't treat it as
imported.  This way we'll properly stream the body so that importers can
emit it.

	PR c++/120499

gcc/cp/ChangeLog:

	* method.cc (synthesize_method): Set the instantiating module.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/imp-member-4_a.C: New test.
	* g++.dg/modules/imp-member-4_b.C: New test.
	* g++.dg/modules/imp-member-4_c.C: New test.

Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>

0 files changed, 0 insertions, 0 deletions