c++/modules: Handle exposures of TU-local types in uninstantiated member templates

Previously, 'is_tu_local_entity' wouldn't detect the exposure of the (in
practice) TU-local lambda in the following example, unless instantiated:

  struct S {
    template <typename>
    static inline decltype([]{}) x = {};
  };

This is for two reasons.  Firstly, when traversing the TYPE_FIELDS of S
we only see the TEMPLATE_DECL, and never end up building a dependency on
its DECL_TEMPLATE_RESULT (due to not being instantiated).  This patch
fixes this by stripping any templates before checking for unnamed types.

The second reason is that we currently assume all class-scope entities
are not TU-local.  Despite this being unambiguous in the standard, this
is not actually true in our implementation just yet, due to issues with
mangling lambdas in some circumstances.  Allowing these lambdas to be
exported can cause issues in importers with apparently conflicting
declarations, so this patch treats them as TU-local as well.

After these changes, we now get double diagnostics from the two ways
that we can see the above lambda being exposed, via 'S' (through
TYPE_FIELDS) or via 'S::x'.  To workaround this we hide diagnostics from
the first case, so we only get errors from 'S::x' which will be closer
to the point the offending lambda is declared.

gcc/cp/ChangeLog:

	* module.cc (trees_out::has_tu_local_dep): Also look at the
	TI_TEMPLATE if we don't find a dep for a decl.
	(depset::hash::is_tu_local_entity): Handle unnamed template
	types, treat lambdas specially.
	(is_exposure_of_member_type): New function.
	(depset::hash::add_dependency): Use it.
	(depset::hash::finalize_dependencies): Likewise.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/internal-10.C: New test.

Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
Reviewed-by: Jason Merrill <jason@redhat.com>

0 files changed, 0 insertions, 0 deletions