syntax_data: {"ast_node_type":"other","tokens":[{"end":25,"kind":"keyword","start":0,"text":"{"}]}
source_snippet:                         {
context_before:                             if !self.thir[arg].ty.is_freeze(self.tcx, self.typing_env) =>
context_after:                             self.requires_unsafe(expr.span, BorrowOfLayoutConstrainedField)