Rewrite dead-code pass to avoid fetching HIR. This allows to get a more uniform handling of spans, and to simplify the grouping of diagnostics for variants and fields.
&str
String
MultiSpan::push_span_label
#[default..]
#[const_trait]
#[main]
#[rustc_main]
hir_id
visit_attribute
ExprKind::Closure
to_string
String::new