mirror of https://github.com/rust-lang/rust
112 lines
2.3 KiB
Rust
112 lines
2.3 KiB
Rust
pub trait Get<T> {
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fn get(self) -> T;
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}
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struct Foo {
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x: usize,
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}
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impl Get<usize> for Foo {
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fn get(self) -> usize {
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self.x
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}
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}
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fn foo<G, T>(g: G, dest: &mut T) -> impl FnOnce()
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where
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G: Get<T>,
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{
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move || {
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//~^ ERROR hidden type for `impl FnOnce()` captures lifetime
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*dest = g.get();
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}
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}
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// After applying suggestion for `foo`:
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fn bar<G, T>(g: G, dest: &mut T) -> impl FnOnce() + '_
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where
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G: Get<T>,
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{
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move || {
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//~^ ERROR the parameter type `G` may not live long enough
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*dest = g.get();
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}
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}
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// After applying suggestion for `bar`:
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fn baz<G: 'a, T>(g: G, dest: &mut T) -> impl FnOnce() + '_
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//~^ ERROR undeclared lifetime name `'a`
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where
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G: Get<T>,
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{
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move || {
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*dest = g.get();
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}
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}
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// After applying suggestion for `baz`:
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fn qux<'a, G: 'a, T>(g: G, dest: &mut T) -> impl FnOnce() + '_
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where
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G: Get<T>,
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{
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move || {
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//~^ ERROR the parameter type `G` may not live long enough
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*dest = g.get();
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}
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}
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// Same as above, but show that we pay attention to lifetime names from parent item
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impl<'a> Foo {
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fn qux<'b, G: Get<T> + 'b, T>(g: G, dest: &mut T) -> impl FnOnce() + '_ {
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move || {
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//~^ ERROR the parameter type `G` may not live long enough
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*dest = g.get();
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}
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}
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}
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// After applying suggestion for `qux`:
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fn bat<'a, G: 'a, T>(g: G, dest: &mut T) -> impl FnOnce() + '_ + 'a
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where
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G: Get<T>,
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{
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move || {
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//~^ ERROR the parameter type `G` may not live long enough
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//~| ERROR explicit lifetime required
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*dest = g.get();
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}
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}
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// Potential incorrect attempt:
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fn bak<'a, G, T>(g: G, dest: &'a mut T) -> impl FnOnce() + 'a
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where
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G: Get<T>,
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{
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move || {
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//~^ ERROR the parameter type `G` may not live long enough
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*dest = g.get();
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}
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}
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// We need to tie the lifetime of `G` with the lifetime of `&mut T` and the returned closure:
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fn ok<'a, G: 'a, T>(g: G, dest: &'a mut T) -> impl FnOnce() + 'a
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where
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G: Get<T>,
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{
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move || {
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*dest = g.get();
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}
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}
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// This also works. The `'_` isn't necessary but it's where we arrive to following the suggestions:
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fn ok2<'a, G: 'a, T>(g: G, dest: &'a mut T) -> impl FnOnce() + '_ + 'a
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where
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G: Get<T>,
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{
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move || {
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*dest = g.get();
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}
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}
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fn main() {}
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