2020-02-01 03:04:58 +00:00
error[E0038]: the trait `Trait` cannot be made into an object
Support HIR wf checking for function signatures
During function type-checking, we normalize any associated types in
the function signature (argument types + return type), and then
create WF obligations for each of the normalized types. The HIR wf code
does not currently support this case, so any errors that we get have
imprecise spans.
This commit extends `ObligationCauseCode::WellFormed` to support
recording a function parameter, allowing us to get the corresponding
HIR type if an error occurs. Function typechecking is modified to
pass this information during signature normalization and WF checking.
The resulting code is fairly verbose, due to the fact that we can
no longer normalize the entire signature with a single function call.
As part of the refactoring, we now perform HIR-based WF checking
for several other 'typed items' (statics, consts, and inherent impls).
As a result, WF and projection errors in a function signature now
have a precise span, which points directly at the responsible type.
If a function signature is constructed via a macro, this will allow
the error message to point at the code 'most responsible' for the error
(e.g. a user-supplied macro argument).
2021-07-18 16:33:49 +00:00
--> $DIR/object-unsafe-trait-should-use-where-sized.rs:9:12
2020-02-01 03:04:58 +00:00
|
2020-10-16 00:23:45 +00:00
LL | fn bar(x: &dyn Trait) {}
Support HIR wf checking for function signatures
During function type-checking, we normalize any associated types in
the function signature (argument types + return type), and then
create WF obligations for each of the normalized types. The HIR wf code
does not currently support this case, so any errors that we get have
imprecise spans.
This commit extends `ObligationCauseCode::WellFormed` to support
recording a function parameter, allowing us to get the corresponding
HIR type if an error occurs. Function typechecking is modified to
pass this information during signature normalization and WF checking.
The resulting code is fairly verbose, due to the fact that we can
no longer normalize the entire signature with a single function call.
As part of the refactoring, we now perform HIR-based WF checking
for several other 'typed items' (statics, consts, and inherent impls).
As a result, WF and projection errors in a function signature now
have a precise span, which points directly at the responsible type.
If a function signature is constructed via a macro, this will allow
the error message to point at the code 'most responsible' for the error
(e.g. a user-supplied macro argument).
2021-07-18 16:33:49 +00:00
| ^^^^^^^^^ `Trait` cannot be made into an object
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|
note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
--> $DIR/object-unsafe-trait-should-use-where-sized.rs:5:8
|
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LL | trait Trait {
| ----- this trait cannot be made into an object...
LL | fn foo() where Self: Other, { }
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| ^^^ ...because associated function `foo` has no `self` parameter
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LL | fn bar(self: ()) {}
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| ^^ ...because method `bar`'s `self` parameter cannot be dispatched on
help: consider turning `foo` into a method by giving it a `&self` argument
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|
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LL | fn foo(&self) where Self: Other, { }
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| +++++
2020-10-16 00:23:45 +00:00
help: alternatively, consider constraining `foo` so it does not apply to trait objects
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|
2022-06-25 21:59:45 +00:00
LL | fn foo() where Self: Other, Self: Sized { }
| ~~~~~~~~~~~~~
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help: consider changing method `bar`'s `self` parameter to be `&self`
|
LL | fn bar(self: &Self) {}
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| ~~~~~
2020-02-01 03:04:58 +00:00
2022-06-11 22:47:21 +00:00
error[E0307]: invalid `self` parameter type: ()
--> $DIR/object-unsafe-trait-should-use-where-sized.rs:6:18
|
LL | fn bar(self: ()) {}
| ^^
|
= note: type of `self` must be `Self` or a type that dereferences to it
= help: consider changing to `self`, `&self`, `&mut self`, `self: Box<Self>`, `self: Rc<Self>`, `self: Arc<Self>`, or `self: Pin<P>` (where P is one of the previous types except `Self`)
2020-02-01 03:04:58 +00:00
error: aborting due to 2 previous errors
Some errors have detailed explanations: E0038, E0307.
For more information about an error, try `rustc --explain E0038`.
