syntax_data: {"ast_node_type":"other","tokens":[{"end":40,"kind":"keyword","start":0,"text":"FloatVar(ref"}]}
source_snippet:             FloatVar(ref v) => v.fmt(f),
context_before:             IntVar(ref v) => v.fmt(f),
context_after:             FreshTy(v) => write!(f, "FreshTy({v:?})"),