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Use general uninhabitedness checking

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This commit is contained in:
varkor 2018-11-03 19:23:05 +00:00
parent 9e8a982a23
commit b55717f9b0
1 changed files with 10 additions and 14 deletions
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24
src/librustc_lint/unused.rs
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@ -60,19 +60,15 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedResults {
}
let t = cx.tables.expr_ty(&expr);
// FIXME(varkor): replace with `t.is_unit() || t.conservative_is_uninhabited()`.
let type_permits_no_use = match t.sty {
ty::Tuple(ref tys) if tys.is_empty() => true,
ty::Never => true,
ty::Adt(def, _) => {
if def.variants.is_empty() {
true
} else {
check_must_use(cx, def.did, s.span, "")
}
let type_permits_lack_of_use = if t.is_unit()
|| cx.tcx.is_ty_uninhabited_from(cx.tcx.hir.get_module_parent(expr.id), t) {
true
} else {
match t.sty {
ty::Adt(def, _) => check_must_use(cx, def.did, s.span, ""),
_ => false,
}
_ => false,
};
}
let mut fn_warned = false;
let mut op_warned = false;
@ -99,7 +95,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedResults {
if let Some(def) = maybe_def {
let def_id = def.def_id();
fn_warned = check_must_use(cx, def_id, s.span, "return value of ");
} else if type_permits_no_use {
} else if type_permits_lack_of_use {
// We don't warn about unused unit or uninhabited types.
// (See https://github.com/rust-lang/rust/issues/43806 for details.)
return;
@ -148,7 +144,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedResults {
op_warned = true;
}
if !(type_permits_no_use || fn_warned || op_warned) {
if !(type_permits_lack_of_use || fn_warned || op_warned) {
cx.span_lint(UNUSED_RESULTS, s.span, "unused result");
}