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| <h1 id="diagnostic-and-subdiagnostic-structs"><a class="header" href="#diagnostic-and-subdiagnostic-structs">Diagnostic and subdiagnostic structs</a></h1> |
| <p>rustc has three diagnostic traits that can be used to create diagnostics: |
| <code>Diagnostic</code>, <code>LintDiagnostic</code>, and <code>Subdiagnostic</code>.</p> |
| <p>For simple diagnostics, |
| derived impls can be used, e.g. <code>#[derive(Diagnostic)]</code>. They are only suitable for simple diagnostics that |
| don’t require much logic in deciding whether or not to add additional |
| subdiagnostics.</p> |
| <p>In cases where diagnostics require more complex or dynamic behavior, such as conditionally adding subdiagnostics, |
| customizing the rendering logic, or selecting messages at runtime, you will need to manually implement |
| the corresponding trait (<code>Diagnostic</code>, <code>LintDiagnostic</code>, or <code>Subdiagnostic</code>). |
| This approach provides greater flexibility and is recommended for diagnostics that go beyond simple, static structures.</p> |
| <p>Diagnostic can be translated into different languages and each has a slug that uniquely identifies the diagnostic.</p> |
| <h2 id="derivediagnostic-and-derivelintdiagnostic"><a class="header" href="#derivediagnostic-and-derivelintdiagnostic"><code>#[derive(Diagnostic)]</code> and <code>#[derive(LintDiagnostic)]</code></a></h2> |
| <p>Consider the <a href="https://github.com/rust-lang/rust/blob/6201eabde85db854c1ebb57624be5ec699246b50/compiler/rustc_hir_analysis/src/errors.rs#L68-L77">definition</a> of the “field already declared” diagnostic |
| shown below:</p> |
| <pre><code class="language-rust ignore">#[derive(Diagnostic)] |
| #[diag(hir_analysis_field_already_declared, code = E0124)] |
| pub struct FieldAlreadyDeclared { |
| pub field_name: Ident, |
| #[primary_span] |
| #[label] |
| pub span: Span, |
| #[label(previous_decl_label)] |
| pub prev_span: Span, |
| }</code></pre> |
| <p><code>Diagnostic</code> can only be derived on structs and enums. |
| Attributes that are placed on the type for structs are placed on each |
| variants for enums (or vice versa). Each <code>Diagnostic</code> has to have one |
| attribute, <code>#[diag(...)]</code>, applied to the struct or each enum variant.</p> |
| <p>If an error has an error code (e.g. “E0624”), then that can be specified using |
| the <code>code</code> sub-attribute. Specifying a <code>code</code> isn’t mandatory, but if you are |
| porting a diagnostic that uses <code>Diag</code> to use <code>Diagnostic</code> |
| then you should keep the code if there was one.</p> |
| <p><code>#[diag(..)]</code> must provide a slug as the first positional argument (a path to an |
| item in <code>rustc_errors::fluent::*</code>). A slug uniquely identifies the diagnostic |
| and is also how the compiler knows what error message to emit (in the default |
| locale of the compiler, or in the locale requested by the user). See |
| <a href="./translation.html">translation documentation</a> to learn more about how |
| translatable error messages are written and how slug items are generated.</p> |
| <p>In our example, the Fluent message for the “field already declared” diagnostic |
| looks like this:</p> |
| <pre><code class="language-fluent">hir_analysis_field_already_declared = |
| field `{$field_name}` is already declared |
| .label = field already declared |
| .previous_decl_label = `{$field_name}` first declared here |
| </code></pre> |
| <p><code>hir_analysis_field_already_declared</code> is the slug from our example and is followed |
| by the diagnostic message.</p> |
| <p>Every field of the <code>Diagnostic</code> which does not have an annotation is |
| available in Fluent messages as a variable, like <code>field_name</code> in the example |
| above. Fields can be annotated <code>#[skip_arg]</code> if this is undesired.</p> |
| <p>Using the <code>#[primary_span]</code> attribute on a field (that has type <code>Span</code>) |
| indicates the primary span of the diagnostic which will have the main message |
| of the diagnostic.</p> |
| <p>Diagnostics are more than just their primary message, they often include |
| labels, notes, help messages and suggestions, all of which can also be |
| specified on a <code>Diagnostic</code>.</p> |
| <p><code>#[label]</code>, <code>#[help]</code>, <code>#[warning]</code> and <code>#[note]</code> can all be applied to fields which have the |
| type <code>Span</code>. Applying any of these attributes will create the corresponding |
| subdiagnostic with that <code>Span</code>. These attributes will look for their |
| diagnostic message in a Fluent attribute attached to the primary Fluent |
| message. In our example, <code>#[label]</code> will look for |
| <code>hir_analysis_field_already_declared.label</code> (which has the message “field already |
| declared”). If there is more than one subdiagnostic of the same type, then |
| these attributes can also take a value that is the attribute name to look for |
| (e.g. <code>previous_decl_label</code> in our example).</p> |
| <p>Other types have special behavior when used in a <code>Diagnostic</code> derive:</p> |
| <ul> |
| <li>Any attribute applied to an <code>Option<T></code> will only emit a |
| subdiagnostic if the option is <code>Some(..)</code>.</li> |
| <li>Any attribute applied to a <code>Vec<T></code> will be repeated for each element of the |
| vector.</li> |
| </ul> |
| <p><code>#[help]</code>, <code>#[warning]</code> and <code>#[note]</code> can also be applied to the struct itself, in which case |
| they work exactly like when applied to fields except the subdiagnostic won’t |
| have a <code>Span</code>. These attributes can also be applied to fields of type <code>()</code> for |
| the same effect, which when combined with the <code>Option</code> type can be used to |
| represent optional <code>#[note]</code>/<code>#[help]</code>/<code>#[warning]</code> subdiagnostics.</p> |
| <p>Suggestions can be emitted using one of four field attributes:</p> |
| <ul> |
| <li><code>#[suggestion(slug, code = "...", applicability = "...")]</code></li> |
| <li><code>#[suggestion_hidden(slug, code = "...", applicability = "...")]</code></li> |
| <li><code>#[suggestion_short(slug, code = "...", applicability = "...")]</code></li> |
| <li><code>#[suggestion_verbose(slug, code = "...", applicability = "...")]</code></li> |
| </ul> |
| <p>Suggestions must be applied on either a <code>Span</code> field or a <code>(Span, MachineApplicability)</code> field. Similarly to other field attributes, the slug |
| specifies the Fluent attribute with the message and defaults to the equivalent |
| of <code>.suggestion</code>. <code>code</code> specifies the code that should be suggested as a |
| replacement and is a format string (e.g. <code>{field_name}</code> would be replaced by |
| the value of the <code>field_name</code> field of the struct), not a Fluent identifier. |
| <code>applicability</code> can be used to specify the applicability in the attribute, it |
| cannot be used when the field’s type contains an <code>Applicability</code>.</p> |
| <p>In the end, the <code>Diagnostic</code> derive will generate an implementation of |
| <code>Diagnostic</code> that looks like the following:</p> |
| <pre><code class="language-rust ignore">impl<'a, G: EmissionGuarantee> Diagnostic<'a> for FieldAlreadyDeclared { |
| fn into_diag(self, dcx: &'a DiagCtxt, level: Level) -> Diag<'a, G> { |
| let mut diag = Diag::new(dcx, level, fluent::hir_analysis_field_already_declared); |
| diag.set_span(self.span); |
| diag.span_label( |
| self.span, |
| fluent::hir_analysis_label |
| ); |
| diag.span_label( |
| self.prev_span, |
| fluent::hir_analysis_previous_decl_label |
| ); |
| diag |
| } |
| }</code></pre> |
| <p>Now that we’ve defined our diagnostic, how do we <a href="https://github.com/rust-lang/rust/blob/f1112099eba41abadb6f921df7edba70affe92c5/compiler/rustc_hir_analysis/src/collect.rs#L823-L827">use it</a>? It’s quite |
| straightforward, just create an instance of the struct and pass it to |
| <code>emit_err</code> (or <code>emit_warning</code>):</p> |
| <pre><code class="language-rust ignore">tcx.dcx().emit_err(FieldAlreadyDeclared { |
| field_name: f.ident, |
| span: f.span, |
| prev_span, |
| });</code></pre> |
| <h3 id="reference-for-derivediagnostic-and-derivelintdiagnostic"><a class="header" href="#reference-for-derivediagnostic-and-derivelintdiagnostic">Reference for <code>#[derive(Diagnostic)]</code> and <code>#[derive(LintDiagnostic)]</code></a></h3> |
| <p><code>#[derive(Diagnostic)]</code> and <code>#[derive(LintDiagnostic)]</code> support the |
| following attributes:</p> |
| <ul> |
| <li><code>#[diag(slug, code = "...")]</code> |
| <ul> |
| <li><em>Applied to struct or enum variant.</em></li> |
| <li><em>Mandatory</em></li> |
| <li>Defines the text and error code to be associated with the diagnostic.</li> |
| <li>Slug (<em>Mandatory</em>) |
| <ul> |
| <li>Uniquely identifies the diagnostic and corresponds to its Fluent message, |
| mandatory.</li> |
| <li>A path to an item in <code>rustc_errors::fluent</code>, e.g. |
| <code>rustc_errors::fluent::hir_analysis_field_already_declared</code> |
| (<code>rustc_errors::fluent</code> is implicit in the attribute, so just |
| <code>hir_analysis_field_already_declared</code>).</li> |
| <li>See <a href="./translation.html">translation documentation</a>.</li> |
| </ul> |
| </li> |
| <li><code>code = "..."</code> (<em>Optional</em>) |
| <ul> |
| <li>Specifies the error code.</li> |
| </ul> |
| </li> |
| </ul> |
| </li> |
| <li><code>#[note]</code> or <code>#[note(slug)]</code> (<em>Optional</em>) |
| <ul> |
| <li><em>Applied to struct or struct fields of type <code>Span</code>, <code>Option<()></code> or <code>()</code>.</em></li> |
| <li>Adds a note subdiagnostic.</li> |
| <li>Value is a path to an item in <code>rustc_errors::fluent</code> for the note’s |
| message. |
| <ul> |
| <li>Defaults to equivalent of <code>.note</code>.</li> |
| </ul> |
| </li> |
| <li>If applied to a <code>Span</code> field, creates a spanned note.</li> |
| </ul> |
| </li> |
| <li><code>#[help]</code> or <code>#[help(slug)]</code> (<em>Optional</em>) |
| <ul> |
| <li><em>Applied to struct or struct fields of type <code>Span</code>, <code>Option<()></code> or <code>()</code>.</em></li> |
| <li>Adds a help subdiagnostic.</li> |
| <li>Value is a path to an item in <code>rustc_errors::fluent</code> for the note’s |
| message. |
| <ul> |
| <li>Defaults to equivalent of <code>.help</code>.</li> |
| </ul> |
| </li> |
| <li>If applied to a <code>Span</code> field, creates a spanned help.</li> |
| </ul> |
| </li> |
| <li><code>#[label]</code> or <code>#[label(slug)]</code> (<em>Optional</em>) |
| <ul> |
| <li><em>Applied to <code>Span</code> fields.</em></li> |
| <li>Adds a label subdiagnostic.</li> |
| <li>Value is a path to an item in <code>rustc_errors::fluent</code> for the note’s |
| message. |
| <ul> |
| <li>Defaults to equivalent of <code>.label</code>.</li> |
| </ul> |
| </li> |
| </ul> |
| </li> |
| <li><code>#[warning]</code> or <code>#[warning(slug)]</code> (<em>Optional</em>) |
| <ul> |
| <li><em>Applied to struct or struct fields of type <code>Span</code>, <code>Option<()></code> or <code>()</code>.</em></li> |
| <li>Adds a warning subdiagnostic.</li> |
| <li>Value is a path to an item in <code>rustc_errors::fluent</code> for the note’s |
| message. |
| <ul> |
| <li>Defaults to equivalent of <code>.warn</code>.</li> |
| </ul> |
| </li> |
| </ul> |
| </li> |
| <li><code>#[suggestion{,_hidden,_short,_verbose}(slug, code = "...", applicability = "...")]</code> |
| (<em>Optional</em>) |
| <ul> |
| <li><em>Applied to <code>(Span, MachineApplicability)</code> or <code>Span</code> fields.</em></li> |
| <li>Adds a suggestion subdiagnostic.</li> |
| <li>Slug (<em>Mandatory</em>) |
| <ul> |
| <li>A path to an item in <code>rustc_errors::fluent</code>, e.g. |
| <code>rustc_errors::fluent::hir_analysis_field_already_declared</code> |
| (<code>rustc_errors::fluent</code> is implicit in the attribute, so just |
| <code>hir_analysis_field_already_declared</code>). Fluent attributes for all messages |
| exist as top-level items in that module (so <code>hir_analysis_message.attr</code> is just |
| <code>attr</code>).</li> |
| <li>See <a href="./translation.html">translation documentation</a>.</li> |
| <li>Defaults to <code>rustc_errors::fluent::_subdiag::suggestion</code> (or</li> |
| <li><code>.suggestion</code> in Fluent).</li> |
| </ul> |
| </li> |
| <li><code>code = "..."</code>/<code>code("...", ...)</code> (<em>Mandatory</em>) |
| <ul> |
| <li>One or multiple format strings indicating the code to be suggested as a |
| replacement. Multiple values signify multiple possible replacements.</li> |
| </ul> |
| </li> |
| <li><code>applicability = "..."</code> (<em>Optional</em>) |
| <ul> |
| <li>String which must be one of <code>machine-applicable</code>, <code>maybe-incorrect</code>, |
| <code>has-placeholders</code> or <code>unspecified</code>.</li> |
| </ul> |
| </li> |
| </ul> |
| </li> |
| <li><code>#[subdiagnostic]</code> |
| <ul> |
| <li><em>Applied to a type that implements <code>Subdiagnostic</code> (from |
| <code>#[derive(Subdiagnostic)]</code>).</em></li> |
| <li>Adds the subdiagnostic represented by the subdiagnostic struct.</li> |
| </ul> |
| </li> |
| <li><code>#[primary_span]</code> (<em>Optional</em>) |
| <ul> |
| <li><em>Applied to <code>Span</code> fields on <code>Subdiagnostic</code>s. Not used for <code>LintDiagnostic</code>s.</em></li> |
| <li>Indicates the primary span of the diagnostic.</li> |
| </ul> |
| </li> |
| <li><code>#[skip_arg]</code> (<em>Optional</em>) |
| <ul> |
| <li><em>Applied to any field.</em></li> |
| <li>Prevents the field from being provided as a diagnostic argument.</li> |
| </ul> |
| </li> |
| </ul> |
| <h2 id="derivesubdiagnostic"><a class="header" href="#derivesubdiagnostic"><code>#[derive(Subdiagnostic)]</code></a></h2> |
| <p>It is common in the compiler to write a function that conditionally adds a |
| specific subdiagnostic to an error if it is applicable. Oftentimes these |
| subdiagnostics could be represented using a diagnostic struct even if the |
| overall diagnostic could not. In this circumstance, the <code>Subdiagnostic</code> |
| derive can be used to represent a partial diagnostic (e.g a note, label, help or |
| suggestion) as a struct.</p> |
| <p>Consider the <a href="https://github.com/rust-lang/rust/blob/f1112099eba41abadb6f921df7edba70affe92c5/compiler/rustc_hir_analysis/src/errors.rs#L221-L234">definition</a> of the “expected return type” label |
| shown below:</p> |
| <pre class="playground"><code class="language-rust"><span class="boring">#![allow(unused)] |
| </span><span class="boring">fn main() { |
| </span>#[derive(Subdiagnostic)] |
| pub enum ExpectedReturnTypeLabel<'tcx> { |
| #[label(hir_analysis_expected_default_return_type)] |
| Unit { |
| #[primary_span] |
| span: Span, |
| }, |
| #[label(hir_analysis_expected_return_type)] |
| Other { |
| #[primary_span] |
| span: Span, |
| expected: Ty<'tcx>, |
| }, |
| } |
| <span class="boring">}</span></code></pre> |
| <p>Like <code>Diagnostic</code>, <code>Subdiagnostic</code> can be derived for structs or |
| enums. Attributes that are placed on the type for structs are placed on each |
| variants for enums (or vice versa). Each <code>Subdiagnostic</code> should have one |
| attribute applied to the struct or each variant, one of:</p> |
| <ul> |
| <li><code>#[label(..)]</code> for defining a label</li> |
| <li><code>#[note(..)]</code> for defining a note</li> |
| <li><code>#[help(..)]</code> for defining a help</li> |
| <li><code>#[warning(..)]</code> for defining a warning</li> |
| <li><code>#[suggestion{,_hidden,_short,_verbose}(..)]</code> for defining a suggestion</li> |
| </ul> |
| <p>All of the above must provide a slug as the first positional argument (a path |
| to an item in <code>rustc_errors::fluent::*</code>). A slug uniquely identifies the |
| diagnostic and is also how the compiler knows what error message to emit (in |
| the default locale of the compiler, or in the locale requested by the user). |
| See <a href="./translation.html">translation documentation</a> to learn more about how |
| translatable error messages are written and how slug items are generated.</p> |
| <p>In our example, the Fluent message for the “expected return type” label |
| looks like this:</p> |
| <pre><code class="language-fluent">hir_analysis_expected_default_return_type = expected `()` because of default return type |
| |
| hir_analysis_expected_return_type = expected `{$expected}` because of return type |
| </code></pre> |
| <p>Using the <code>#[primary_span]</code> attribute on a field (with type <code>Span</code>) will denote |
| the primary span of the subdiagnostic. A primary span is only necessary for a |
| label or suggestion, which can not be spanless.</p> |
| <p>Every field of the type/variant which does not have an annotation is available |
| in Fluent messages as a variable. Fields can be annotated <code>#[skip_arg]</code> if this |
| is undesired.</p> |
| <p>Like <code>Diagnostic</code>, <code>Subdiagnostic</code> supports <code>Option<T></code> and |
| <code>Vec<T></code> fields.</p> |
| <p>Suggestions can be emitted using one of four attributes on the type/variant:</p> |
| <ul> |
| <li><code>#[suggestion(..., code = "...", applicability = "...")]</code></li> |
| <li><code>#[suggestion_hidden(..., code = "...", applicability = "...")]</code></li> |
| <li><code>#[suggestion_short(..., code = "...", applicability = "...")]</code></li> |
| <li><code>#[suggestion_verbose(..., code = "...", applicability = "...")]</code></li> |
| </ul> |
| <p>Suggestions require <code>#[primary_span]</code> be set on a field and can have the |
| following sub-attributes:</p> |
| <ul> |
| <li>The first positional argument specifies the path to a item in |
| <code>rustc_errors::fluent</code> corresponding to the Fluent attribute with the message |
| and defaults to the equivalent of <code>.suggestion</code>.</li> |
| <li><code>code</code> specifies the code that should be suggested as a replacement and is a |
| format string (e.g. <code>{field_name}</code> would be replaced by the value of the |
| <code>field_name</code> field of the struct), not a Fluent identifier.</li> |
| <li><code>applicability</code> can be used to specify the applicability in the attribute, it |
| cannot be used when the field’s type contains an <code>Applicability</code>.</li> |
| </ul> |
| <p>Applicabilities can also be specified as a field (of type <code>Applicability</code>) |
| using the <code>#[applicability]</code> attribute.</p> |
| <p>In the end, the <code>Subdiagnostic</code> derive will generate an implementation |
| of <code>Subdiagnostic</code> that looks like the following:</p> |
| <pre class="playground"><code class="language-rust"><span class="boring">#![allow(unused)] |
| </span><span class="boring">fn main() { |
| </span>impl<'tcx> Subdiagnostic for ExpectedReturnTypeLabel<'tcx> { |
| fn add_to_diag(self, diag: &mut rustc_errors::Diagnostic) { |
| use rustc_errors::{Applicability, IntoDiagArg}; |
| match self { |
| ExpectedReturnTypeLabel::Unit { span } => { |
| diag.span_label(span, rustc_errors::fluent::hir_analysis_expected_default_return_type) |
| } |
| ExpectedReturnTypeLabel::Other { span, expected } => { |
| diag.set_arg("expected", expected); |
| diag.span_label(span, rustc_errors::fluent::hir_analysis_expected_return_type) |
| } |
| } |
| } |
| } |
| <span class="boring">}</span></code></pre> |
| <p>Once defined, a subdiagnostic can be used by passing it to the <code>subdiagnostic</code> |
| function (<a href="https://github.com/rust-lang/rust/blob/f1112099eba41abadb6f921df7edba70affe92c5/compiler/rustc_hir_analysis/src/check/fn_ctxt/suggestions.rs#L670-L674">example</a> and <a href="https://github.com/rust-lang/rust/blob/f1112099eba41abadb6f921df7edba70affe92c5/compiler/rustc_hir_analysis/src/check/fn_ctxt/suggestions.rs#L704-L707">example</a>) on a |
| diagnostic or by assigning it to a <code>#[subdiagnostic]</code>-annotated field of a |
| diagnostic struct.</p> |
| <h3 id="argument-sharing-and-isolation"><a class="header" href="#argument-sharing-and-isolation">Argument sharing and isolation</a></h3> |
| <p>Subdiagnostics add their own arguments (i.e., certain fields in their structure) to the <code>Diag</code> structure before rendering the information. |
| <code>Diag</code> structure also stores the arguments from the main diagnostic, so the subdiagnostic can also use the arguments from the main diagnostic.</p> |
| <p>However, when a subdiagnostic is added to a main diagnostic by implementing <code>#[derive(Subdiagnostic)]</code>, |
| the following rules, introduced in <a href="https://github.com/rust-lang/rust/pull/142724">rust-lang/rust#142724</a> |
| apply to the handling of arguments (i.e., variables used in Fluent messages):</p> |
| <p><strong>Argument isolation between sub diagnostics</strong>: |
| Arguments set by a subdiagnostic are only available during the rendering of that subdiagnostic. |
| After the subdiagnostic is rendered, all arguments it introduced are restored from the main diagnostic. |
| This ensures that multiple subdiagnostics do not pollute each other’s argument scope. |
| For example, when using a <code>Vec<Subdiag></code>, it iteratively adds the same argument over and over again.</p> |
| <p><strong>Same argument override between sub and main diagnostics</strong>: |
| If a subdiagnostic sets a argument with the same name as a arguments already in the main diagnostic, |
| it will report an error at runtime unless both have exactly the same value. |
| It has two benefits:</p> |
| <ul> |
| <li>preserves the flexibility that arguments in the main diagnostic are allowed to appear in the attributes of the subdiagnostic. |
| For example, There is an attribute <code>#[suggestion(code = "{new_vis}")]</code> in the subdiagnostic, but <code>new_vis</code> is the field in the main diagnostic struct.</li> |
| <li>prevents accidental overwriting or deletion of arguments required by the main diagnostic or other subdiagnostics.</li> |
| </ul> |
| <p>These rules guarantee that arguments injected by subdiagnostics are strictly scoped to their own rendering. |
| The main diagnostic’s arguments remain unaffected by subdiagnostic logic, even in the presence of name collisions. |
| Additionally, subdiagnostics can access arguments from the main diagnostic with the same name when needed.</p> |
| <h3 id="reference-for-derivesubdiagnostic"><a class="header" href="#reference-for-derivesubdiagnostic">Reference for <code>#[derive(Subdiagnostic)]</code></a></h3> |
| <p><code>#[derive(Subdiagnostic)]</code> supports the following attributes:</p> |
| <ul> |
| <li><code>#[label(slug)]</code>, <code>#[help(slug)]</code>, <code>#[warning(slug)]</code> or <code>#[note(slug)]</code> |
| <ul> |
| <li><em>Applied to struct or enum variant. Mutually exclusive with struct/enum variant attributes.</em></li> |
| <li><em>Mandatory</em></li> |
| <li>Defines the type to be representing a label, help or note.</li> |
| <li>Slug (<em>Mandatory</em>) |
| <ul> |
| <li>Uniquely identifies the diagnostic and corresponds to its Fluent message, |
| mandatory.</li> |
| <li>A path to an item in <code>rustc_errors::fluent</code>, e.g. |
| <code>rustc_errors::fluent::hir_analysis_field_already_declared</code> |
| (<code>rustc_errors::fluent</code> is implicit in the attribute, so just |
| <code>hir_analysis_field_already_declared</code>).</li> |
| <li>See <a href="./translation.html">translation documentation</a>.</li> |
| </ul> |
| </li> |
| </ul> |
| </li> |
| <li><code>#[suggestion{,_hidden,_short,_verbose}(slug, code = "...", applicability = "...")]</code> |
| <ul> |
| <li><em>Applied to struct or enum variant. Mutually exclusive with struct/enum variant attributes.</em></li> |
| <li><em>Mandatory</em></li> |
| <li>Defines the type to be representing a suggestion.</li> |
| <li>Slug (<em>Mandatory</em>) |
| <ul> |
| <li>A path to an item in <code>rustc_errors::fluent</code>, e.g. |
| <code>rustc_errors::fluent::hir_analysis_field_already_declared</code> |
| (<code>rustc_errors::fluent</code> is implicit in the attribute, so just |
| <code>hir_analysis::field_already_declared</code>). Fluent attributes for all messages |
| exist as top-level items in that module (so <code>hir_analysis_message.attr</code> is just |
| <code>hir_analysis::attr</code>).</li> |
| <li>See <a href="./translation.html">translation documentation</a>.</li> |
| <li>Defaults to <code>rustc_errors::fluent::_subdiag::suggestion</code> (or</li> |
| <li><code>.suggestion</code> in Fluent).</li> |
| </ul> |
| </li> |
| <li><code>code = "..."</code>/<code>code("...", ...)</code> (<em>Mandatory</em>) |
| <ul> |
| <li>One or multiple format strings indicating the code to be suggested as a |
| replacement. Multiple values signify multiple possible replacements.</li> |
| </ul> |
| </li> |
| <li><code>applicability = "..."</code> (<em>Optional</em>) |
| <ul> |
| <li><em>Mutually exclusive with <code>#[applicability]</code> on a field.</em></li> |
| <li>Value is the applicability of the suggestion.</li> |
| <li>String which must be one of: |
| <ul> |
| <li><code>machine-applicable</code></li> |
| <li><code>maybe-incorrect</code></li> |
| <li><code>has-placeholders</code></li> |
| <li><code>unspecified</code></li> |
| </ul> |
| </li> |
| </ul> |
| </li> |
| </ul> |
| </li> |
| <li><code>#[multipart_suggestion{,_hidden,_short,_verbose}(slug, applicability = "...")]</code> |
| <ul> |
| <li><em>Applied to struct or enum variant. Mutually exclusive with struct/enum variant attributes.</em></li> |
| <li><em>Mandatory</em></li> |
| <li>Defines the type to be representing a multipart suggestion.</li> |
| <li>Slug (<em>Mandatory</em>): see <code>#[suggestion]</code></li> |
| <li><code>applicability = "..."</code> (<em>Optional</em>): see <code>#[suggestion]</code></li> |
| </ul> |
| </li> |
| <li><code>#[primary_span]</code> (<em>Mandatory</em> for labels and suggestions; <em>optional</em> otherwise; not applicable |
| to multipart suggestions) |
| <ul> |
| <li><em>Applied to <code>Span</code> fields.</em></li> |
| <li>Indicates the primary span of the subdiagnostic.</li> |
| </ul> |
| </li> |
| <li><code>#[suggestion_part(code = "...")]</code> (<em>Mandatory</em>; only applicable to multipart suggestions) |
| <ul> |
| <li><em>Applied to <code>Span</code> fields.</em></li> |
| <li>Indicates the span to be one part of the multipart suggestion.</li> |
| <li><code>code = "..."</code> (<em>Mandatory</em>) |
| <ul> |
| <li>Value is a format string indicating the code to be suggested as a |
| replacement.</li> |
| </ul> |
| </li> |
| </ul> |
| </li> |
| <li><code>#[applicability]</code> (<em>Optional</em>; only applicable to (simple and multipart) suggestions) |
| <ul> |
| <li><em>Applied to <code>Applicability</code> fields.</em></li> |
| <li>Indicates the applicability of the suggestion.</li> |
| </ul> |
| </li> |
| <li><code>#[skip_arg]</code> (<em>Optional</em>) |
| <ul> |
| <li><em>Applied to any field.</em></li> |
| <li>Prevents the field from being provided as a diagnostic argument.</li> |
| </ul> |
| </li> |
| </ul> |
| |
| </main> |
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