syntax_data: {"ast_node_type":"other","tokens":[{"end":74,"kind":"keyword","start":0,"text":"Contravariant,"}]}
source_snippet:     Contravariant, // T<A> <: T<B> iff B <: A -- e.g., function param type
context_before:     Invariant,     // T<A> <: T<B> iff B == A -- e.g., type of mutable cell
context_after:     Bivariant,     // T<A> <: T<B>            -- e.g., unused type parameter