syntax_data: {"ast_node_type":"other","tokens":[{"end":86,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:                 // Will be the same as `ctxt` if the expn chain contains only opaques.
context_before:             Transparency::Opaque => (
context_after:                 self.alloc_ctxt(parent_opaque, expn_id, transparency),