mirror of https://github.com/rust-lang/rust
65 lines
2.0 KiB
Rust
65 lines
2.0 KiB
Rust
// A test exploiting the bug behind #25860 except with
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// implied trait bounds which currently don't exist.
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use std::marker::PhantomData;
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struct Foo<'a, 'b, T>(PhantomData<(&'a (), &'b (), T)>)
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where
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T: Convert<'a, 'b>;
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trait Convert<'a, 'b>: Sized {
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fn cast(&'a self) -> &'b Self;
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}
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impl<'long: 'short, 'short, T> Convert<'long, 'short> for T {
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fn cast(&'long self) -> &'short T {
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self
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}
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}
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// This function will compile once we add implied trait bounds.
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//
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// If we're not careful with our impl, the transformations
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// in `bad` would succeed, which is unsound ✨
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//
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// FIXME: the error is pretty bad, this should say
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//
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// `T: Convert<'in_, 'out>` is not implemented
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//
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// help: needed by `Foo<'in_, 'out, T>`
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//
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// Please ping @lcnr if your changes end up causing `badboi` to compile.
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fn badboi<'in_, 'out, T>(x: Foo<'in_, 'out, T>, sadness: &'in_ T) -> &'out T {
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//~^ ERROR lifetime mismatch
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sadness.cast()
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//~^ ERROR may not live long enough
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}
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fn badboi2<'in_, 'out, T>(x: Foo<'in_, 'out, T>, sadness: &'in_ T) {
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//~^ ERROR lifetime mismatch
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let _: &'out T = sadness.cast();
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//~^ ERROR may not live long enough
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}
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fn badboi3<'in_, 'out, T>(a: Foo<'in_, 'out, (&'in_ T, &'out T)>, sadness: &'in_ T) {
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//~^ ERROR lifetime mismatch
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let _: &'out T = sadness.cast();
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//~^ ERROR may not live long enough
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}
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fn bad<'short, T>(value: &'short T) -> &'static T {
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let x: for<'in_, 'out> fn(Foo<'in_, 'out, T>, &'in_ T) -> &'out T = badboi;
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let x: for<'out> fn(Foo<'short, 'out, T>, &'short T) -> &'out T = x;
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let x: for<'out> fn(Foo<'static, 'out, T>, &'short T) -> &'out T = x;
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let x: fn(Foo<'static, 'static, T>, &'short T) -> &'static T = x;
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x(Foo(PhantomData), value)
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}
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// Use `bad` to cause a segfault.
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fn main() {
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let mut outer: Option<&'static u32> = Some(&3);
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let static_ref: &'static &'static u32 = match outer {
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Some(ref reference) => bad(reference),
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None => unreachable!(),
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};
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outer = None;
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println!("{}", static_ref);
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}
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