Providers should return a list of alternates to @proposal or %NULL if there are no alternates available.
This can be used by the completion view to allow the user to move laterally through similar proposals, such as overrides of methods by the same name.
a #GtkSourceCompletionContext
a #GtkSourceCompletionProposal
a #GPtrArray of #GtkSourceCompletionProposal or %NULL.
See Implementation
Providers should return a list of alternates to @proposal or %NULL if there are no alternates available.
This can be used by the completion view to allow the user to move laterally through similar proposals, such as overrides of methods by the same name.