diff --git a/src/librustc_typeck/check/mod.rs b/src/librustc_typeck/check/mod.rs index a8697f45d9156..e04c6a6cc3840 100644 --- a/src/librustc_typeck/check/mod.rs +++ b/src/librustc_typeck/check/mod.rs @@ -4250,14 +4250,9 @@ pub fn check_enum_variants<'a,'tcx>(ccx: &CrateCtxt<'a,'tcx>, let def_id = ccx.tcx.map.local_def_id(id); let hint = *ccx.tcx.lookup_repr_hints(def_id).get(0).unwrap_or(&attr::ReprAny); - if hint != attr::ReprAny && vs.len() <= 1 { - if vs.len() == 1 { - span_err!(ccx.tcx.sess, sp, E0083, - "unsupported representation for univariant enum"); - } else { - span_err!(ccx.tcx.sess, sp, E0084, - "unsupported representation for zero-variant enum"); - }; + if hint != attr::ReprAny && vs.is_empty() { + span_err!(ccx.tcx.sess, sp, E0084, + "unsupported representation for zero-variant enum"); } do_check(ccx, vs, id, hint); diff --git a/src/librustc_typeck/diagnostics.rs b/src/librustc_typeck/diagnostics.rs index 8f7692c794540..df09cd261344e 100644 --- a/src/librustc_typeck/diagnostics.rs +++ b/src/librustc_typeck/diagnostics.rs @@ -1062,13 +1062,6 @@ Note also that without a representation manually defined, the compiler will optimize by using the smallest integer type possible. "##, -E0083: r##" -At present, it's not possible to define a custom representation for an enum with -a single variant. As a workaround you can add a `Dummy` variant. - -See: https://github.com/rust-lang/rust/issues/10292 -"##, - E0084: r##" It is impossible to define an integer type to be used to represent zero-variant enum values because there are no zero-variant enum values. There is no way to diff --git a/src/test/run-pass/enum-univariant-repr.rs b/src/test/run-pass/enum-univariant-repr.rs new file mode 100644 index 0000000000000..ef4cc60bf0da1 --- /dev/null +++ b/src/test/run-pass/enum-univariant-repr.rs @@ -0,0 +1,47 @@ +// Copyright 2016 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 or the MIT license +// , at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + + +use std::mem; + +// Univariant C-like enum +#[repr(i32)] +enum Univariant { + X = 17 +} + +#[repr(u16)] +enum UnivariantWithoutDescr { + Y +} + +pub fn main() { + { + assert_eq!(4, mem::size_of::()); + assert_eq!(17, Univariant::X as i32); + + let enums: &[Univariant] = + &[Univariant::X, Univariant::X, Univariant::X]; + let ints: &[i32] = unsafe { mem::transmute(enums) }; + // check it has the same memory layout as i32 + assert_eq!(&[17, 17, 17], ints); + } + + { + assert_eq!(2, mem::size_of::()); + let descr = UnivariantWithoutDescr::Y as u16; + + let enums: &[UnivariantWithoutDescr] = + &[UnivariantWithoutDescr::Y, UnivariantWithoutDescr::Y, UnivariantWithoutDescr::Y]; + let ints: &[u16] = unsafe { mem::transmute(enums) }; + // check it has the same memory layout as u16 + assert_eq!(&[descr, descr, descr], ints); + } +}