syntax_data: {"ast_node_type":"other","tokens":[{"end":89,"kind":"keyword","start":0,"text":"|index,"}]}
source_snippet:                 |index, encoding: Option<TagEncoding<VariantIdx>>| -> Result<Self, Err> {
context_before:             let layout_of_variant =
context_after:                     let variant_layout = ty_variant(cx, (ty, layout), index);