syntax_data: {"ast_node_type":"other","tokens":[{"end":80,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:     // necessary. If this isn't possible, then we probably should turn this into
context_before:     // a function of `typing_env`. See the HACK comment below for why this is
context_after:     // a `NeedsDropMode` so that we can have a variant like `CollectAllSignificantDrops`,