syntax_data: {"ast_node_type":"other","tokens":[{"end":58,"kind":"keyword","start":0,"text":"ty::ConstKind::Placeholder(_)"}]}
source_snippet:                         ty::ConstKind::Placeholder(_) => {
context_before:                         ty::ConstKind::Expr(_) => return Ok(EvaluatedToOk),
context_after:                             bug!("placeholder const {:?} in old solver", ct)