syntax_data: {"ast_node_type":"other","tokens":[{"end":37,"kind":"keyword","start":0,"text":"ty::Placeholder(lhs)"}]}
source_snippet:             ty::Placeholder(lhs) => {
context_before:             // Placeholder types don't unify with anything on their own.
context_after:                 matches!(rhs.kind(), ty::Placeholder(rhs) if lhs == rhs)