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| 1 | +#![feature(arbitrary_self_types, coerce_unsized, dispatch_from_dyn, unsize, unsized_locals)] |
| 2 | + |
| 3 | +// This tests a few edge-cases around `arbitrary_self_types`. Most specifically, |
| 4 | +// it checks that the `ObjectCandidate` you get from method matching can't |
| 5 | +// match a trait with the same DefId as a supertrait but a bad type parameter. |
| 6 | + |
| 7 | +use std::marker::PhantomData; |
| 8 | + |
| 9 | +mod internal { |
| 10 | + use std::ops::{CoerceUnsized, Deref, DispatchFromDyn}; |
| 11 | + use std::marker::{PhantomData, Unsize}; |
| 12 | + |
| 13 | + pub struct Smaht<T: ?Sized, MISC>(pub Box<T>, pub PhantomData<MISC>); |
| 14 | + |
| 15 | + impl<T: ?Sized, MISC> Deref for Smaht<T, MISC> { |
| 16 | + type Target = T; |
| 17 | + |
| 18 | + fn deref(&self) -> &Self::Target { |
| 19 | + &self.0 |
| 20 | + } |
| 21 | + } |
| 22 | + impl<T: ?Sized + Unsize<U>, U: ?Sized, MISC> CoerceUnsized<Smaht<U, MISC>> |
| 23 | + for Smaht<T, MISC> |
| 24 | + {} |
| 25 | + impl<T: ?Sized + Unsize<U>, U: ?Sized, MISC> DispatchFromDyn<Smaht<U, MISC>> |
| 26 | + for Smaht<T, MISC> |
| 27 | + {} |
| 28 | + |
| 29 | + pub trait Foo: X<u32> {} |
| 30 | + pub trait X<T> { |
| 31 | + fn foo(self: Smaht<Self, T>) -> T; |
| 32 | + } |
| 33 | + |
| 34 | + impl X<u32> for () { |
| 35 | + fn foo(self: Smaht<Self, u32>) -> u32 { |
| 36 | + 0 |
| 37 | + } |
| 38 | + } |
| 39 | + |
| 40 | + pub trait Marker {} |
| 41 | + impl Marker for dyn Foo {} |
| 42 | + impl<T: Marker + ?Sized> X<u64> for T { |
| 43 | + fn foo(self: Smaht<Self, u64>) -> u64 { |
| 44 | + 1 |
| 45 | + } |
| 46 | + } |
| 47 | + |
| 48 | + impl Deref for dyn Foo { |
| 49 | + type Target = (); |
| 50 | + fn deref(&self) -> &() { &() } |
| 51 | + } |
| 52 | + |
| 53 | + impl Foo for () {} |
| 54 | +} |
| 55 | + |
| 56 | +pub trait FinalFoo { |
| 57 | + fn foo(&self) -> u8; |
| 58 | +} |
| 59 | + |
| 60 | +impl FinalFoo for () { |
| 61 | + fn foo(&self) -> u8 { 0 } |
| 62 | +} |
| 63 | + |
| 64 | +mod nuisance_foo { |
| 65 | + pub trait NuisanceFoo { |
| 66 | + fn foo(self); |
| 67 | + } |
| 68 | + |
| 69 | + impl<T: ?Sized> NuisanceFoo for T { |
| 70 | + fn foo(self) {} |
| 71 | + } |
| 72 | +} |
| 73 | + |
| 74 | + |
| 75 | +fn objectcandidate_impl() { |
| 76 | + let x: internal::Smaht<(), u32> = internal::Smaht(Box::new(()), PhantomData); |
| 77 | + let x: internal::Smaht<dyn internal::Foo, u32> = x; |
| 78 | + |
| 79 | + // This picks `<dyn internal::Foo as X<u32>>::foo` via `ObjectCandidate`. |
| 80 | + // |
| 81 | + // The `TraitCandidate` is not relevant because `X` is not in scope. |
| 82 | + let z = x.foo(); |
| 83 | + |
| 84 | + // Observe the type of `z` is `u32` |
| 85 | + let _seetype: () = z; //~ ERROR mismatched types |
| 86 | + //~| expected (), found u32 |
| 87 | +} |
| 88 | + |
| 89 | +fn traitcandidate_impl() { |
| 90 | + use internal::X; |
| 91 | + |
| 92 | + let x: internal::Smaht<(), u64> = internal::Smaht(Box::new(()), PhantomData); |
| 93 | + let x: internal::Smaht<dyn internal::Foo, u64> = x; |
| 94 | + |
| 95 | + // This picks `<dyn internal::Foo as X<u64>>::foo` via `TraitCandidate`. |
| 96 | + // |
| 97 | + // The `ObjectCandidate` does not apply, as it only applies to |
| 98 | + // `X<u32>` (and not `X<u64>`). |
| 99 | + let z = x.foo(); |
| 100 | + |
| 101 | + // Observe the type of `z` is `u64` |
| 102 | + let _seetype: () = z; //~ ERROR mismatched types |
| 103 | + //~| expected (), found u64 |
| 104 | +} |
| 105 | + |
| 106 | +fn traitcandidate_impl_with_nuisance() { |
| 107 | + use internal::X; |
| 108 | + use nuisance_foo::NuisanceFoo; |
| 109 | + |
| 110 | + let x: internal::Smaht<(), u64> = internal::Smaht(Box::new(()), PhantomData); |
| 111 | + let x: internal::Smaht<dyn internal::Foo, u64> = x; |
| 112 | + |
| 113 | + // This picks `<dyn internal::Foo as X<u64>>::foo` via `TraitCandidate`. |
| 114 | + // |
| 115 | + // The `ObjectCandidate` does not apply, as it only applies to |
| 116 | + // `X<u32>` (and not `X<u64>`). |
| 117 | + // |
| 118 | + // The NuisanceFoo impl has the same priority as the `X` impl, |
| 119 | + // so we get a conflict. |
| 120 | + let z = x.foo(); //~ ERROR multiple applicable items in scope |
| 121 | +} |
| 122 | + |
| 123 | + |
| 124 | +fn neither_impl() { |
| 125 | + let x: internal::Smaht<(), u64> = internal::Smaht(Box::new(()), PhantomData); |
| 126 | + let x: internal::Smaht<dyn internal::Foo, u64> = x; |
| 127 | + |
| 128 | + // This can't pick the `TraitCandidate` impl, because `Foo` is not |
| 129 | + // imported. However, this also can't pick the `ObjectCandidate` |
| 130 | + // impl, because it only applies to `X<u32>` (and not `X<u64>`). |
| 131 | + // |
| 132 | + // Therefore, neither of the candidates is applicable, and we pick |
| 133 | + // the `FinalFoo` impl after another deref, which will return `u8`. |
| 134 | + let z = x.foo(); |
| 135 | + |
| 136 | + // Observe the type of `z` is `u8` |
| 137 | + let _seetype: () = z; //~ ERROR mismatched types |
| 138 | + //~| expected (), found u8 |
| 139 | +} |
| 140 | + |
| 141 | +fn both_impls() { |
| 142 | + use internal::X; |
| 143 | + |
| 144 | + let x: internal::Smaht<(), u32> = internal::Smaht(Box::new(()), PhantomData); |
| 145 | + let x: internal::Smaht<dyn internal::Foo, u32> = x; |
| 146 | + |
| 147 | + // This can pick both the `TraitCandidate` and the `ObjectCandidate` impl. |
| 148 | + // |
| 149 | + // However, the `ObjectCandidate` is considered an "inherent candidate", |
| 150 | + // and therefore has priority over both the `TraitCandidate` as well as |
| 151 | + // any other "nuisance" candidate" (if present). |
| 152 | + let z = x.foo(); |
| 153 | + |
| 154 | + // Observe the type of `z` is `u32` |
| 155 | + let _seetype: () = z; //~ ERROR mismatched types |
| 156 | + //~| expected (), found u32 |
| 157 | +} |
| 158 | + |
| 159 | + |
| 160 | +fn both_impls_with_nuisance() { |
| 161 | + // Similar to the `both_impls` example, except with a nuisance impl to |
| 162 | + // make sure the `ObjectCandidate` indeed has a higher priority. |
| 163 | + |
| 164 | + use internal::X; |
| 165 | + use nuisance_foo::NuisanceFoo; |
| 166 | + |
| 167 | + let x: internal::Smaht<(), u32> = internal::Smaht(Box::new(()), PhantomData); |
| 168 | + let x: internal::Smaht<dyn internal::Foo, u32> = x; |
| 169 | + let z = x.foo(); |
| 170 | + |
| 171 | + // Observe the type of `z` is `u32` |
| 172 | + let _seetype: () = z; //~ ERROR mismatched types |
| 173 | + //~| expected (), found u32 |
| 174 | +} |
| 175 | + |
| 176 | +fn main() { |
| 177 | +} |
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