Instantiate what implicit members use inside their trial

Author: lucic71

cpp2rust/converter/converter_lib.cpp

@@ -1638,7 +1638,12 @@ void DefineImplicitMembers(clang::Sema &sema, clang::CXXRecordDecl *decl) {
   sema.ForceDeclarationOfImplicitMembers(decl);
   auto define = [&](clang::FunctionDecl *fn, auto &&definer) {
     RuleDecls::Trial trial(sema);
-    definer();
+    {
+      clang::Sema::GlobalEagerInstantiationScope instantiations(
+          sema, /*Enabled=*/true, /*AtEndOfTU=*/false);
+      definer();
+      instantiations.perform();
+    }
     if (trial.failed()) {
       fn->setDeletedAsWritten(true);
     }