syntax_data: {"ast_node_type":"other","tokens":[{"end":85,"kind":"keyword","start":0,"text":"self.alloc_ctxt(parent_opaque_and_semiopaque,"}]}
source_snippet:                 self.alloc_ctxt(parent_opaque_and_semiopaque, expn_id, transparency),
context_before:                 // Will be the same as `ctxt` if the expn chain contains only (semi-)opaques.
context_after:             ),