syntax_data: {"ast_node_type":"variable","tokens":[{"end":51,"kind":"keyword","start":0,"text":"if"}]}
source_snippet:                 if let Some(else_expr) = else_opt {
context_before:                 // If there is an `else` arm, lower it into `else_blk`.
context_after:                     else_blk = this.expr_into_dest(destination, else_blk, else_expr).into_block();