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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:19:03 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:19:03 +0000 |
commit | 64d98f8ee037282c35007b64c2649055c56af1db (patch) | |
tree | 5492bcf97fce41ee1c0b1cc2add283f3e66cdab0 /tests/ui/variance/variance-trait-matching.rs | |
parent | Adding debian version 1.67.1+dfsg1-1. (diff) | |
download | rustc-64d98f8ee037282c35007b64c2649055c56af1db.tar.xz rustc-64d98f8ee037282c35007b64c2649055c56af1db.zip |
Merging upstream version 1.68.2+dfsg1.
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'tests/ui/variance/variance-trait-matching.rs')
-rw-r--r-- | tests/ui/variance/variance-trait-matching.rs | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/tests/ui/variance/variance-trait-matching.rs b/tests/ui/variance/variance-trait-matching.rs new file mode 100644 index 000000000..b4efee7d6 --- /dev/null +++ b/tests/ui/variance/variance-trait-matching.rs @@ -0,0 +1,38 @@ +#![allow(dead_code)] + +// Get<T> is covariant in T +trait Get<T> { + fn get(&self) -> T; +} + +struct Cloner<T:Clone> { + t: T +} + +impl<T:Clone> Get<T> for Cloner<T> { + fn get(&self) -> T { + self.t.clone() + } +} + +fn get<'a, G>(get: &G) -> i32 + where G : Get<&'a i32> +{ + // This fails to type-check because, without variance, we can't + // use `G : Get<&'a i32>` as evidence that `G : Get<&'b i32>`, + // even if `'a : 'b`. + pick(get, &22) //~ ERROR explicit lifetime required in the type of `get` [E0621] +} + +fn pick<'b, G>(get: &'b G, if_odd: &'b i32) -> i32 + where G : Get<&'b i32> +{ + let v = *get.get(); + if v % 2 != 0 { v } else { *if_odd } +} + +fn main() { + let x = Cloner { t: &23 }; + let y = get(&x); + assert_eq!(y, 23); +} |