d: Fix ICE in dwarf2out_imported_module_or_decl, at dwarf2out.cc:27676 [PR119817]

The ImportVisitor method for handling the importing of overload sets was
pushing NULL_TREE to the array of import decls, which in turn got passed
to `debug_hooks->imported_module_or_decl', triggering the observed
internal compiler error.

NULL_TREE is returned from `build_import_decl' when the symbol was
ignored for being non-trivial to represent in debug, for example,
template or tuple declarations.  So similarly "skip" adding the symbol
when this is the case for overload sets too.

	PR d/119817

gcc/d/ChangeLog:

	* imports.cc (ImportVisitor::visit (OverloadSet *)): Don't push
	NULL_TREE to vector of import symbols.

gcc/testsuite/ChangeLog:

	* gdc.dg/debug/imports/m119817/a.d: New test.
	* gdc.dg/debug/imports/m119817/b.d: New test.
	* gdc.dg/debug/imports/m119817/package.d: New test.
	* gdc.dg/debug/pr119817.d: New test.

1 files changed, 5 insertions, 1 deletions

diff --git a/gcc/d/imports.cc b/gcc/d/imports.cc
index 776caaf..16e4df6 100644
--- a/gcc/d/imports.cc
+++ b/gcc/d/imports.cc
@@ -182,7 +182,11 @@ public:
     vec_alloc (tset, d->a.length);
 
     for (size_t i = 0; i < d->a.length; i++)
-      vec_safe_push (tset, build_import_decl (d->a[i]));
+      {
+	tree overload = build_import_decl (d->a[i]);
+	if (overload != NULL_TREE)
+	  vec_safe_push (tset, overload);
+      }
 
     this->result_ = build_tree_list_vec (tset);
     tset->truncate (0);