Fix tidy issues
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@ -1,4 +1,5 @@
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A constant item was initialized with something that is not a constant expression.
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A constant item was initialized with something that is not a constant
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expression.
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Erroneous code example:
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@ -25,4 +25,3 @@ fn main() {
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// expected 0, found 1
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}
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```
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@ -26,4 +26,3 @@ left and may require reallocation. This requires ownership of the string
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on the left. If something should be added to a string literal, move the
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literal to the heap by allocating it with `to_owned()` like in
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`"Your text".to_owned()`.
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@ -41,4 +41,3 @@ trait Foo {
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fn bar<T: Foo>(t: T) {} // ok!
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```
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@ -10,4 +10,3 @@ Please specify a valid "kind" value, from one of the following:
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* static
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* dylib
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* framework
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@ -21,4 +21,3 @@ The `#[unwind]` attribute should be used as follows:
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NB. The default behavior here is "allowed", but this is unspecified
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and likely to change in the future.
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@ -5,4 +5,3 @@ Erroneous code example:
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```compile_fail,E0635
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#![feature(nonexistent_rust_feature)] // error: unknown feature
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```
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@ -7,4 +7,3 @@ Erroneous code example:
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#![feature(rust1)]
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#![feature(rust1)] // error: the feature `rust1` has already been declared
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```
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@ -27,4 +27,3 @@ closure call itself by capturing a `&Fn()` object or `fn()` pointer
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that refers to itself. That is permitting, since the closure would be
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invoking itself via a virtual call, and hence does not directly
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reference its own *type*.
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@ -10,7 +10,8 @@ trait T {
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}
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```
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`async fn`s return an `impl Future`, making the following two examples equivalent:
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`async fn`s return an `impl Future`, making the following two examples
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equivalent:
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```edition2018,ignore (example-of-desugaring-equivalence)
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async fn foo() -> User {
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@ -23,8 +24,8 @@ fn foo(&self) -> impl Future<Output = User> + '_ {
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```
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But when it comes to supporting this in traits, there are [a few implementation
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issues][async-is-hard]. One of them is returning `impl Trait` in traits is not supported,
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as it would require [Generic Associated Types] to be supported:
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issues][async-is-hard]. One of them is returning `impl Trait` in traits is not
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supported, as it would require [Generic Associated Types] to be supported:
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```edition2018,ignore (example-of-desugaring-equivalence)
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impl MyDatabase {
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@ -40,13 +41,14 @@ impl MyDatabase {
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}
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```
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Until these issues are resolved, you can use the [`async-trait` crate], allowing you to use
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`async fn` in traits by desugaring to "boxed futures"
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Until these issues are resolved, you can use the [`async-trait` crate], allowing
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you to use `async fn` in traits by desugaring to "boxed futures"
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(`Pin<Box<dyn Future + Send + 'async>>`).
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Note that using these trait methods will result in a heap allocation per-function-call. This is not
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a significant cost for the vast majority of applications, but should be considered when deciding
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whether to use this functionality in the public API of a low-level function that is expected to be
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Note that using these trait methods will result in a heap allocation
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per-function-call. This is not a significant cost for the vast majority of
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applications, but should be considered when deciding whether to use this
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functionality in the public API of a low-level function that is expected to be
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called millions of times a second.
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You might be interested in visiting the [async book] for further information.
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@ -11,7 +11,7 @@ fn temp_address() {
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To avoid the error, first bind the temporary to a named local variable.
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```ignore
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```ignore (not yet implemented)
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# #![feature(raw_ref_op)]
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fn temp_address() {
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let val = 2;
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