syntax_data: {"ast_node_type":"variable","tokens":[{"end":39,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                 let mut place_builder =
context_before:                 let lhs_expr = &this.thir[lhs];
context_after:                     unpack!(block = this.expr_as_place(block, lhs, mutability, fake_borrow_temps,));