syntax_data: {"ast_node_type":"other","tokens":[{"end":58,"kind":"keyword","start":0,"text":"Some(GenericArgKind::Const(c1))"}]}
source_snippet:                     Some(GenericArgKind::Const(c1)) => c1,
context_before:                     // opaque type.
context_after:                     Some(u) => panic!("const mapped to unexpected kind: {u:?}"),