54 lines
1.3 KiB
Rust
54 lines
1.3 KiB
Rust
#![feature(rustc_attrs)]
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#![allow(unused,dead_code)]
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fn tuple_struct() {
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#[rustc_layout_scalar_valid_range_start(1)]
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struct NonZero<T>(T);
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let mut foo = unsafe { NonZero((1,)) };
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let a = &mut foo.0.0;
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//~^ ERROR: mutation of layout constrained field is unsafe
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}
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fn slice() {
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#[rustc_layout_scalar_valid_range_start(1)]
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struct NonZero<'a, T>(&'a mut [T]);
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let mut nums = [1, 2, 3, 4];
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let mut foo = unsafe { NonZero(&mut nums[..]) };
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let a = &mut foo.0[2];
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// ^ not unsafe because there is an implicit dereference here
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}
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fn array() {
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#[rustc_layout_scalar_valid_range_start(1)]
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struct NonZero<T>([T; 4]);
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let nums = [1, 2, 3, 4];
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let mut foo = unsafe { NonZero(nums) };
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let a = &mut foo.0[2];
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//~^ ERROR: mutation of layout constrained field is unsafe
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}
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fn block() {
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#[rustc_layout_scalar_valid_range_start(1)]
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struct NonZero<T>(T);
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let foo = unsafe { NonZero((1,)) };
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&mut { foo.0 }.0;
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// ^ not unsafe because the result of the block expression is a new place
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}
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fn mtch() {
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#[rustc_layout_scalar_valid_range_start(1)]
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struct NonZero<T>(T);
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let mut foo = unsafe { NonZero((1,)) };
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match &mut foo {
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NonZero((a,)) => *a = 0,
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//~^ ERROR: mutation of layout constrained field is unsafe
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}
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}
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fn main() {}
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