Account for Box::new(impl Future) and emit help use Box::pin
This commit is contained in:
Esteban Küber
parent
a852fb7413
commit
80cdb0af7d
5 changed files with 84 additions and 30 deletions
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@ -24,8 +24,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
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self.annotate_expected_due_to_let_ty(err, expr);
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self.suggest_compatible_variants(err, expr, expected, expr_ty);
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self.suggest_ref_or_into(err, expr, expected, expr_ty);
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if self.suggest_calling_boxed_future_when_appropriate(err, expr, expected, expr_ty) {
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return;
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}
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self.suggest_boxing_when_appropriate(err, expr, expected, expr_ty);
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self.suggest_calling_boxed_future_when_appropriate(err, expr, expected, expr_ty);
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self.suggest_missing_await(err, expr, expected, expr_ty);
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}
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@ -5053,18 +5053,18 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
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expr: &hir::Expr<'_>,
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expected: Ty<'tcx>,
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found: Ty<'tcx>,
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) {
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) -> bool {
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// Handle #68197.
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if self.tcx.hir().is_const_context(expr.hir_id) {
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// Do not suggest `Box::new` in const context.
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return;
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return false;
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}
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let pin_did = self.tcx.lang_items().pin_type();
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match expected.kind {
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ty::Adt(def, _) if Some(def.did) != pin_did => return,
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ty::Adt(def, _) if Some(def.did) != pin_did => return false,
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// This guards the `unwrap` and `mk_box` below.
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_ if pin_did.is_none() || self.tcx.lang_items().owned_box().is_none() => return,
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_ if pin_did.is_none() || self.tcx.lang_items().owned_box().is_none() => return false,
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_ => {}
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}
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let boxed_found = self.tcx.mk_box(found);
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@ -5073,12 +5073,22 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
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self.can_coerce(new_found, expected),
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self.sess().source_map().span_to_snippet(expr.span),
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) {
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err.span_suggestion(
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expr.span,
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"you need to pin and box this expression",
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format!("Box::pin({})", snippet),
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Applicability::MachineApplicable,
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);
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match found.kind {
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ty::Adt(def, _) if def.is_box() => {
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err.help("use `Box::pin`");
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}
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_ => {
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err.span_suggestion(
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expr.span,
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"you need to pin and box this expression",
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format!("Box::pin({})", snippet),
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Applicability::MachineApplicable,
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);
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}
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}
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true
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} else {
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false
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}
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}
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@ -1,15 +0,0 @@
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// edition:2018
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// run-rustfix
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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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Box::pin(x) //~ ERROR mismatched types
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}
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fn main() {}
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@ -1,5 +1,4 @@
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// edition:2018
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// run-rustfix
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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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@ -11,5 +10,17 @@ 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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//~^ HELP use `Box::pin`
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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 the trait bound
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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 mismatched types
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//~^ ERROR the trait bound
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}
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fn main() {}
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@ -1,5 +1,5 @@
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error[E0308]: mismatched types
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--> $DIR/expected-boxed-future-isnt-pinned.rs:12:5
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--> $DIR/expected-boxed-future-isnt-pinned.rs:11:5
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LL | fn foo<F: Future<Output=i32> + Send + 'static>(x: F) -> BoxFuture<'static, i32> {
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| - this type parameter ----------------------- expected `std::pin::Pin<std::boxed::Box<(dyn std::future::Future<Output = i32> + std::marker::Send + 'static)>>` because of return type
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@ -15,6 +15,52 @@ LL | x
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= help: type parameters must be constrained to match other types
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= note: for more information, visit https://doc.rust-lang.org/book/ch10-02-traits.html#traits-as-parameters
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error: aborting due to previous error
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error[E0308]: mismatched types
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--> $DIR/expected-boxed-future-isnt-pinned.rs:14:5
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LL | fn bar<F: Future<Output=i32> + Send + 'static>(x: F) -> BoxFuture<'static, i32> {
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| ----------------------- expected `std::pin::Pin<std::boxed::Box<(dyn std::future::Future<Output = i32> + std::marker::Send + 'static)>>` because of return type
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LL | Box::new(x)
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| ^^^^^^^^^^^ expected struct `std::pin::Pin`, found struct `std::boxed::Box`
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= note: expected struct `std::pin::Pin<std::boxed::Box<(dyn std::future::Future<Output = i32> + std::marker::Send + 'static)>>`
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found struct `std::boxed::Box<F>`
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= help: use `Box::pin`
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For more information about this error, try `rustc --explain E0308`.
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error[E0308]: mismatched types
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--> $DIR/expected-boxed-future-isnt-pinned.rs:18:14
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LL | fn baz<F: Future<Output=i32> + Send + 'static>(x: F) -> BoxFuture<'static, i32> {
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| - this type parameter
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LL | Pin::new(x)
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| ^
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| |
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| expected struct `std::boxed::Box`, found type parameter `F`
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| help: store this in the heap by calling `Box::new`: `Box::new(x)`
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= note: expected struct `std::boxed::Box<dyn std::future::Future<Output = i32> + std::marker::Send>`
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found type parameter `F`
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= help: type parameters must be constrained to match other types
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= note: for more information, visit https://doc.rust-lang.org/book/ch10-02-traits.html#traits-as-parameters
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= note: for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
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error[E0277]: the trait bound `dyn std::future::Future<Output = i32> + std::marker::Send: std::marker::Unpin` is not satisfied
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--> $DIR/expected-boxed-future-isnt-pinned.rs:18:5
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LL | Pin::new(x)
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| ^^^^^^^^ the trait `std::marker::Unpin` is not implemented for `dyn std::future::Future<Output = i32> + std::marker::Send`
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= note: required by `std::pin::Pin::<P>::new`
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error[E0277]: the trait bound `dyn std::future::Future<Output = i32> + std::marker::Send: std::marker::Unpin` is not satisfied
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--> $DIR/expected-boxed-future-isnt-pinned.rs:22:5
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LL | Pin::new(Box::new(x))
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| ^^^^^^^^ the trait `std::marker::Unpin` is not implemented for `dyn std::future::Future<Output = i32> + std::marker::Send`
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= note: required by `std::pin::Pin::<P>::new`
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error: aborting due to 5 previous errors
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Some errors have detailed explanations: E0277, E0308.
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For more information about an error, try `rustc --explain E0277`.
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