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Fix unused_result lint triggering when a function returns (), ! or an empty enum #43813

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Aug 13, 2017
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Fix unused_result lint triggering when a function returns (), ! or an empty enum #43813

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0b2c9f0
Fix unused_result lint triggering when a function returns `()` or `!`
pengowen123 Aug 11, 2017
eeb748a
Don't trigger unused_result on functions returning empty enums
pengowen123 Aug 12, 2017
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2 changes: 2 additions & 0 deletions src/librustc_lint/unused.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -146,6 +146,8 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedResults {

let t = cx.tables.expr_ty(&expr);
let ty_warned = match t.sty {
ty::TyTuple(ref tys, _) if tys.is_empty() => return,
ty::TyNever => return,
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Should this also apply to enum Void {}, and other such uninhabited types? (Possibly like #38069?)

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Makes sense to me. I'll add that.

ty::TyAdt(def, _) => check_must_use(cx, def.did, s.span, ""),
_ => false,
};
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26 changes: 26 additions & 0 deletions src/test/ui/issue-43806.rs
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@@ -0,0 +1,26 @@
// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

// run-pass

#![deny(unused_results)]

fn foo() {}

fn bar() -> ! {
loop {}
}

fn qux() {
foo();
bar();
}

fn main() {}