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Treat selection error as ambiguous when error type is present

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This commit is contained in:
Aaron Hill 2020-06-04 21:09:31 -04:00
parent 7f7729d83b
commit 3295c262ae
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GPG Key ID: B4087E510E98B164
3 changed files with 17 additions and 181 deletions
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8
src/librustc_trait_selection/traits/select/mod.rs
View File

@ -1104,6 +1104,14 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// who might care about this case, like coherence, should use
// that function).
if candidates.is_empty() {
// If there's an error type, 'downgrade' our result from
// `Err(Unimplemented)` to `Ok(None)`. This helps us avoid
// emitting additional spurious errors, since we're guaranteed
// to have emitted at least one.
if stack.obligation.references_error() {
debug!("no results for error type, treating as ambiguous");
return Ok(None);
}
return Err(Unimplemented);
}

2
src/test/ui/impl-trait/auto-trait-leak.rs
View File

@ -11,8 +11,6 @@ fn main() {
// return type, which can't depend on the obligation.
fn cycle1() -> impl Clone {
//~^ ERROR cycle detected
//~| ERROR cycle detected
//~| ERROR cycle detected
send(cycle2().clone());
//~^ ERROR cannot be sent between threads safely

188
src/test/ui/impl-trait/auto-trait-leak.stderr
View File

@ -36,37 +36,37 @@ LL | fn cycle1() -> impl Clone {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
= note: ...which requires evaluating trait selection obligation `impl std::clone::Clone: std::marker::Send`...
note: ...which requires computing type of `cycle2::{{opaque}}#0`...
--> $DIR/auto-trait-leak.rs:22:16
--> $DIR/auto-trait-leak.rs:20:16
|
LL | fn cycle2() -> impl Clone {
| ^^^^^^^^^^
note: ...which requires borrow-checking `cycle2`...
--> $DIR/auto-trait-leak.rs:22:1
--> $DIR/auto-trait-leak.rs:20:1
|
LL | fn cycle2() -> impl Clone {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires processing `cycle2`...
--> $DIR/auto-trait-leak.rs:22:1
--> $DIR/auto-trait-leak.rs:20:1
|
LL | fn cycle2() -> impl Clone {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires processing MIR for `cycle2`...
--> $DIR/auto-trait-leak.rs:22:1
--> $DIR/auto-trait-leak.rs:20:1
|
LL | fn cycle2() -> impl Clone {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires unsafety-checking `cycle2`...
--> $DIR/auto-trait-leak.rs:22:1
--> $DIR/auto-trait-leak.rs:20:1
|
LL | fn cycle2() -> impl Clone {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires building MIR for `cycle2`...
--> $DIR/auto-trait-leak.rs:22:1
--> $DIR/auto-trait-leak.rs:20:1
|
LL | fn cycle2() -> impl Clone {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires type-checking `cycle2`...
--> $DIR/auto-trait-leak.rs:22:1
--> $DIR/auto-trait-leak.rs:20:1
|
LL | fn cycle2() -> impl Clone {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
@ -84,178 +84,8 @@ LL | | Rc::new(String::from("foo"))
LL | | }
| |_^
error[E0391]: cycle detected when computing type of `cycle1::{{opaque}}#0`
--> $DIR/auto-trait-leak.rs:12:16
|
LL | fn cycle1() -> impl Clone {
| ^^^^^^^^^^
|
note: ...which requires borrow-checking `cycle1`...
--> $DIR/auto-trait-leak.rs:12:1
|
LL | fn cycle1() -> impl Clone {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires processing `cycle1`...
--> $DIR/auto-trait-leak.rs:12:1
|
LL | fn cycle1() -> impl Clone {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires processing MIR for `cycle1`...
--> $DIR/auto-trait-leak.rs:12:1
|
LL | fn cycle1() -> impl Clone {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires unsafety-checking `cycle1`...
--> $DIR/auto-trait-leak.rs:12:1
|
LL | fn cycle1() -> impl Clone {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires building MIR for `cycle1`...
--> $DIR/auto-trait-leak.rs:12:1
|
LL | fn cycle1() -> impl Clone {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires type-checking `cycle1`...
--> $DIR/auto-trait-leak.rs:12:1
|
LL | fn cycle1() -> impl Clone {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
= note: ...which requires evaluating trait selection obligation `impl std::clone::Clone: std::marker::Send`...
note: ...which requires computing type of `cycle2::{{opaque}}#0`...
--> $DIR/auto-trait-leak.rs:22:16
|
LL | fn cycle2() -> impl Clone {
| ^^^^^^^^^^
note: ...which requires borrow-checking `cycle2`...
--> $DIR/auto-trait-leak.rs:22:1
|
LL | fn cycle2() -> impl Clone {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires processing `cycle2`...
--> $DIR/auto-trait-leak.rs:22:1
|
LL | fn cycle2() -> impl Clone {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires processing MIR for `cycle2`...
--> $DIR/auto-trait-leak.rs:22:1
|
LL | fn cycle2() -> impl Clone {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires unsafety-checking `cycle2`...
--> $DIR/auto-trait-leak.rs:22:1
|
LL | fn cycle2() -> impl Clone {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires building MIR for `cycle2`...
--> $DIR/auto-trait-leak.rs:22:1
|
LL | fn cycle2() -> impl Clone {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires type-checking `cycle2`...
--> $DIR/auto-trait-leak.rs:22:1
|
LL | fn cycle2() -> impl Clone {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
= note: ...which again requires computing type of `cycle1::{{opaque}}#0`, completing the cycle
note: cycle used when checking item types in top-level module
--> $DIR/auto-trait-leak.rs:1:1
|
LL | / use std::cell::Cell;
LL | | use std::rc::Rc;
LL | |
LL | | fn send<T: Send>(_: T) {}
... |
LL | | Rc::new(String::from("foo"))
LL | | }
| |_^
error[E0391]: cycle detected when computing type of `cycle1::{{opaque}}#0`
--> $DIR/auto-trait-leak.rs:12:16
|
LL | fn cycle1() -> impl Clone {
| ^^^^^^^^^^
|
note: ...which requires borrow-checking `cycle1`...
--> $DIR/auto-trait-leak.rs:12:1
|
LL | fn cycle1() -> impl Clone {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires processing `cycle1`...
--> $DIR/auto-trait-leak.rs:12:1
|
LL | fn cycle1() -> impl Clone {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires processing MIR for `cycle1`...
--> $DIR/auto-trait-leak.rs:12:1
|
LL | fn cycle1() -> impl Clone {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires unsafety-checking `cycle1`...
--> $DIR/auto-trait-leak.rs:12:1
|
LL | fn cycle1() -> impl Clone {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires building MIR for `cycle1`...
--> $DIR/auto-trait-leak.rs:12:1
|
LL | fn cycle1() -> impl Clone {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires type-checking `cycle1`...
--> $DIR/auto-trait-leak.rs:12:1
|
LL | fn cycle1() -> impl Clone {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
= note: ...which requires evaluating trait selection obligation `impl std::clone::Clone: std::marker::Send`...
note: ...which requires computing type of `cycle2::{{opaque}}#0`...
--> $DIR/auto-trait-leak.rs:22:16
|
LL | fn cycle2() -> impl Clone {
| ^^^^^^^^^^
note: ...which requires borrow-checking `cycle2`...
--> $DIR/auto-trait-leak.rs:22:1
|
LL | fn cycle2() -> impl Clone {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires processing `cycle2`...
--> $DIR/auto-trait-leak.rs:22:1
|
LL | fn cycle2() -> impl Clone {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires processing MIR for `cycle2`...
--> $DIR/auto-trait-leak.rs:22:1
|
LL | fn cycle2() -> impl Clone {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires unsafety-checking `cycle2`...
--> $DIR/auto-trait-leak.rs:22:1
|
LL | fn cycle2() -> impl Clone {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires building MIR for `cycle2`...
--> $DIR/auto-trait-leak.rs:22:1
|
LL | fn cycle2() -> impl Clone {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires type-checking `cycle2`...
--> $DIR/auto-trait-leak.rs:22:1
|
LL | fn cycle2() -> impl Clone {
| ^^^^^^^^^^^^^^^^^^^^^^^^^
= note: ...which again requires computing type of `cycle1::{{opaque}}#0`, completing the cycle
note: cycle used when checking item types in top-level module
--> $DIR/auto-trait-leak.rs:1:1
|
LL | / use std::cell::Cell;
LL | | use std::rc::Rc;
LL | |
LL | | fn send<T: Send>(_: T) {}
... |
LL | | Rc::new(String::from("foo"))
LL | | }
| |_^
error[E0277]: `std::rc::Rc<std::string::String>` cannot be sent between threads safely
--> $DIR/auto-trait-leak.rs:16:5
--> $DIR/auto-trait-leak.rs:14:5
|
LL | fn send<T: Send>(_: T) {}
| ---- required by this bound in `send`
@ -269,7 +99,7 @@ LL | fn cycle2() -> impl Clone {
= help: within `impl std::clone::Clone`, the trait `std::marker::Send` is not implemented for `std::rc::Rc<std::string::String>`
= note: required because it appears within the type `impl std::clone::Clone`
error: aborting due to 4 previous errors
error: aborting due to 2 previous errors
Some errors have detailed explanations: E0277, E0391.
For more information about an error, try `rustc --explain E0277`.