syntax_data: {"ast_node_type":"other","tokens":[{"end":67,"kind":"keyword","start":0,"text":"mapped_types:"}]}
source_snippet:         mapped_types: FxIndexMap<ty::PlaceholderType, ty::BoundTy>,
context_before:         mapped_regions: FxIndexMap<ty::PlaceholderRegion, ty::BoundRegion>,
context_after:         mapped_consts: FxIndexMap<ty::PlaceholderConst, ty::BoundConst>,