From 768cbbcd9e21c75565dad4714346b0d0028d331c Mon Sep 17 00:00:00 2001 From: varkor Date: Fri, 19 Jan 2018 19:58:46 +0000 Subject: [PATCH 1/2] Fix type inhabitedness check for arrays Arrays of uninhabited types were considered to also be uninhabited if their length had not been evaluated, causing unsoundness. --- src/librustc/ty/inhabitedness/mod.rs | 9 ++++---- src/test/compile-fail/empty-never-array.rs | 26 ++++++++++++++++++++++ 2 files changed, 31 insertions(+), 4 deletions(-) create mode 100644 src/test/compile-fail/empty-never-array.rs diff --git a/src/librustc/ty/inhabitedness/mod.rs b/src/librustc/ty/inhabitedness/mod.rs index 0072512464a0e..8cf5b431cf12d 100644 --- a/src/librustc/ty/inhabitedness/mod.rs +++ b/src/librustc/ty/inhabitedness/mod.rs @@ -262,10 +262,11 @@ impl<'a, 'gcx, 'tcx> TyS<'tcx> { })) }, TyArray(ty, len) => { - if len.val.to_const_int().and_then(|i| i.to_u64()) == Some(0) { - DefIdForest::empty() - } else { - ty.uninhabited_from(visited, tcx) + match len.val.to_const_int().and_then(|i| i.to_u64()) { + Some(n) if n != 0 => ty.uninhabited_from(visited, tcx), + // If the array is definitely non-empty, it's uninhabited if + // the type of its elements is uninhabited. + _ => DefIdForest::empty() } } TyRef(_, ref tm) => { diff --git a/src/test/compile-fail/empty-never-array.rs b/src/test/compile-fail/empty-never-array.rs new file mode 100644 index 0000000000000..1dc45a1a88458 --- /dev/null +++ b/src/test/compile-fail/empty-never-array.rs @@ -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 or the MIT license +// , at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + +#![feature(never_type)] + +enum Helper { + T(T, [!; 0]), + #[allow(dead_code)] + U(U), +} + +fn transmute(t: T) -> U { + let Helper::U(u) = Helper::T(t, []); //~ ERROR refutable pattern in local binding: `T(_, _)` not covered + u +} + +fn main() { + println!("{:?}", transmute::<&str, (*const u8, u64)>("type safety")); +} From c4d0bb398b548dafba2346f3f3be9284909643f0 Mon Sep 17 00:00:00 2001 From: varkor Date: Fri, 19 Jan 2018 21:00:35 +0000 Subject: [PATCH 2/2] Fix tidy error --- src/librustc/ty/inhabitedness/mod.rs | 2 +- src/test/compile-fail/empty-never-array.rs | 3 ++- 2 files changed, 3 insertions(+), 2 deletions(-) diff --git a/src/librustc/ty/inhabitedness/mod.rs b/src/librustc/ty/inhabitedness/mod.rs index 8cf5b431cf12d..93e4cd9adf888 100644 --- a/src/librustc/ty/inhabitedness/mod.rs +++ b/src/librustc/ty/inhabitedness/mod.rs @@ -263,9 +263,9 @@ impl<'a, 'gcx, 'tcx> TyS<'tcx> { }, TyArray(ty, len) => { match len.val.to_const_int().and_then(|i| i.to_u64()) { - Some(n) if n != 0 => ty.uninhabited_from(visited, tcx), // If the array is definitely non-empty, it's uninhabited if // the type of its elements is uninhabited. + Some(n) if n != 0 => ty.uninhabited_from(visited, tcx), _ => DefIdForest::empty() } } diff --git a/src/test/compile-fail/empty-never-array.rs b/src/test/compile-fail/empty-never-array.rs index 1dc45a1a88458..53b24e1731932 100644 --- a/src/test/compile-fail/empty-never-array.rs +++ b/src/test/compile-fail/empty-never-array.rs @@ -17,7 +17,8 @@ enum Helper { } fn transmute(t: T) -> U { - let Helper::U(u) = Helper::T(t, []); //~ ERROR refutable pattern in local binding: `T(_, _)` not covered + let Helper::U(u) = Helper::T(t, []); + //~^ ERROR refutable pattern in local binding: `T(_, _)` not covered u }