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use rustc::lint::*;
use rustc::hir::*;
use utils::span_lint_and_then;
declare_lint! {
pub EMPTY_ENUM,
Allow,
"enum with no variants"
}
#[derive(Copy,Clone)]
pub struct EmptyEnum;
impl LintPass for EmptyEnum {
fn get_lints(&self) -> LintArray {
lint_array!(EMPTY_ENUM)
}
}
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for EmptyEnum {
fn check_item(&mut self, cx: &LateContext, item: &Item) {
let did = cx.tcx.hir.local_def_id(item.id);
if let ItemEnum(..) = item.node {
let ty = cx.tcx.type_of(did);
let adt = ty.ty_adt_def().expect("already checked whether this is an enum");
if adt.variants.is_empty() {
span_lint_and_then(cx, EMPTY_ENUM, item.span, "enum with no variants", |db| {
db.span_help(item.span, "consider using the uninhabited type `!` or a wrapper around it");
});
}
}
}
}