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This PR stabilizes the `#[diagnostic]` attribute namespace and a minimal
option of the `#[diagnostic::on_unimplemented]` attribute.
The `#[diagnostic]` attribute namespace is meant to provide a home for
attributes that allow users to influence error messages emitted by the
compiler. The compiler is not guaranteed to use any of this hints,
however it should accept any (non-)existing attribute in this namespace
and potentially emit lint-warnings for unused attributes and options.
This is meant to allow discarding certain attributes/options in the
future to allow fundamental changes to the compiler without the need to
keep then non-meaningful options working.
The `#[diagnostic::on_unimplemented]` attribute is allowed to appear
on a trait definition. This allows crate authors to hint the compiler
to emit a specific error message if a certain trait is not implemented.
For the `#[diagnostic::on_unimplemented]` attribute the following
options are implemented:
* `message` which provides the text for the top level error message
* `label` which provides the text for the label shown inline in the
broken code in the error message
* `note` which provides additional notes.
The `note` option can appear several times, which results in several
note messages being emitted. If any of the other options appears several
times the first occurrence of the relevant option specifies the actually
used value. Any other occurrence generates an lint warning. For any
other non-existing option a lint-warning is generated.
All three options accept a text as argument. This text is allowed to
contain format parameters referring to generic argument or `Self` by
name via the `{Self}` or `{NameOfGenericArgument}` syntax. For any
non-existing argument a lint warning is generated.
Tracking issue: #111996
48 lines
1.2 KiB
Plaintext
48 lines
1.2 KiB
Plaintext
error[E0277]: Foo
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--> $DIR/multiple_notes.rs:12:15
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LL | takes_foo(());
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| --------- ^^ Bar
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| |
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| required by a bound introduced by this call
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= help: the trait `Foo` is not implemented for `()`
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= note: Baz
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= note: Boom
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help: this trait has no implementations, consider adding one
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--> $DIR/multiple_notes.rs:2:1
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LL | trait Foo {}
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| ^^^^^^^^^
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note: required by a bound in `takes_foo`
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--> $DIR/multiple_notes.rs:8:22
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LL | fn takes_foo(_: impl Foo) {}
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| ^^^ required by this bound in `takes_foo`
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error[E0277]: Bar
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--> $DIR/multiple_notes.rs:14:15
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LL | takes_bar(());
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| --------- ^^ Foo
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| required by a bound introduced by this call
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= help: the trait `Bar` is not implemented for `()`
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= note: Baz
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= note: Baz2
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help: this trait has no implementations, consider adding one
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--> $DIR/multiple_notes.rs:6:1
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LL | trait Bar {}
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| ^^^^^^^^^
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note: required by a bound in `takes_bar`
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--> $DIR/multiple_notes.rs:9:22
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LL | fn takes_bar(_: impl Bar) {}
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| ^^^ required by this bound in `takes_bar`
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error: aborting due to 2 previous errors
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For more information about this error, try `rustc --explain E0277`.
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