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34 lines
936 B
Rust
34 lines
936 B
Rust
// edition:2018
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#![allow(dead_code)]
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use std::future::Future;
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use std::pin::Pin;
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type BoxFuture<'a, T> = Pin<Box<dyn Future<Output = T> + Send + 'a>>;
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// ^^^^^^^^^ This would come from the `futures` crate in real code.
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fn foo<F: Future<Output=i32> + Send + 'static>(x: F) -> BoxFuture<'static, i32> {
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// We could instead use an `async` block, but this way we have no std spans.
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x //~ ERROR mismatched types
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}
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fn bar<F: Future<Output=i32> + Send + 'static>(x: F) -> BoxFuture<'static, i32> {
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Box::new(x) //~ ERROR mismatched types
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}
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fn baz<F: Future<Output=i32> + Send + 'static>(x: F) -> BoxFuture<'static, i32> {
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Pin::new(x) //~ ERROR mismatched types
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//~^ ERROR E0277
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}
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fn qux<F: Future<Output=i32> + Send + 'static>(x: F) -> BoxFuture<'static, i32> {
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Pin::new(Box::new(x)) //~ ERROR E0277
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}
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fn zap() -> BoxFuture<'static, i32> {
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async { //~ ERROR mismatched types
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42
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}
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}
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fn main() {}
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