syntax_data: {"ast_node_type":"other","tokens":[{"end":78,"kind":"keyword","start":0,"text":"(Variance::Covariant,"}]}
source_snippet:             (Variance::Covariant, Variance::Covariant) => Variance::Covariant,
context_before:             // Figure 1, column 1.
context_after:             (Variance::Covariant, Variance::Contravariant) => Variance::Contravariant,