syntax_data: {"ast_node_type":"other","tokens":[{"end":89,"kind":"keyword","start":0,"text":"if"}]}
source_snippet:     if specializing_impl_trait_header.polarity != tcx.impl_polarity(parent_impl_def_id) {
context_before:     // Currently we do not allow e.g., a negative impl to specialize a positive one
context_after:         return false;