syntax_data: {"ast_node_type":"other","tokens":[{"end":46,"kind":"keyword","start":0,"text":"///"}]}
source_snippet: ///     - an pointee-sized type (extern types)
context_before: /// For `MetaSized`, there are only a few options for the types in the constraint:
context_after: ///     - a type parameter or projection whose sizedness can't be known