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rust-bors merged 2 commits into from
Jan 19, 2026
Merged

Factor out diagnostic slug checking from DiagnosticDerive #151338

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7216b03
Factor out diagnostic slug checking from `DiagnosticDerive` and `Lint…
JonathanBrouwer Jan 18, 2026
7ec4a8e
Update uitests
JonathanBrouwer Jan 18, 2026
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100 changes: 17 additions & 83 deletions compiler/rustc_macros/src/diagnostics/diagnostic.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,12 +4,10 @@ use std::cell::RefCell;

use proc_macro2::TokenStream;
use quote::quote;
use syn::spanned::Spanned;
use synstructure::Structure;

use crate::diagnostics::diagnostic_builder::DiagnosticDeriveKind;
use crate::diagnostics::error::{DiagnosticDeriveError, span_err};
use crate::diagnostics::utils::SetOnce;
use crate::diagnostics::error::DiagnosticDeriveError;

/// The central struct for constructing the `into_diag` method from an annotated struct.
pub(crate) struct DiagnosticDerive<'a> {
Expand All @@ -29,36 +27,16 @@ impl<'a> DiagnosticDerive<'a> {
let preamble = builder.preamble(variant);
let body = builder.body(variant);

let init = match builder.slug.value_ref() {
None => {
span_err(builder.span, "diagnostic slug not specified")
.help(
"specify the slug as the first argument to the `#[diag(...)]` \
attribute, such as `#[diag(hir_analysis_example_error)]`",
)
.emit();
return DiagnosticDeriveError::ErrorHandled.to_compile_error();
}
Some(slug)
if let Some(Mismatch { slug_name, crate_name, slug_prefix }) =
Mismatch::check(slug) =>
{
span_err(slug.span().unwrap(), "diagnostic slug and crate name do not match")
.note(format!("slug is `{slug_name}` but the crate name is `{crate_name}`"))
.help(format!("expected a slug starting with `{slug_prefix}_...`"))
.emit();
return DiagnosticDeriveError::ErrorHandled.to_compile_error();
}
Some(slug) => {
slugs.borrow_mut().push(slug.clone());
quote! {
let mut diag = rustc_errors::Diag::new(
dcx,
level,
crate::fluent_generated::#slug
);
}
}
let Some(slug) = builder.primary_message() else {
return DiagnosticDeriveError::ErrorHandled.to_compile_error();
};
slugs.borrow_mut().push(slug.clone());
let init = quote! {
let mut diag = rustc_errors::Diag::new(
dcx,
level,
crate::fluent_generated::#slug
);
};

let formatting_init = &builder.formatting_init;
Expand Down Expand Up @@ -113,32 +91,12 @@ impl<'a> LintDiagnosticDerive<'a> {
let preamble = builder.preamble(variant);
let body = builder.body(variant);

let primary_message = match builder.slug.value_ref() {
None => {
span_err(builder.span, "diagnostic slug not specified")
.help(
"specify the slug as the first argument to the attribute, such as \
`#[diag(compiletest_example)]`",
)
.emit();
DiagnosticDeriveError::ErrorHandled.to_compile_error()
}
Some(slug)
if let Some(Mismatch { slug_name, crate_name, slug_prefix }) =
Mismatch::check(slug) =>
{
span_err(slug.span().unwrap(), "diagnostic slug and crate name do not match")
.note(format!("slug is `{slug_name}` but the crate name is `{crate_name}`"))
.help(format!("expected a slug starting with `{slug_prefix}_...`"))
.emit();
DiagnosticDeriveError::ErrorHandled.to_compile_error()
}
Some(slug) => {
slugs.borrow_mut().push(slug.clone());
quote! {
diag.primary_message(crate::fluent_generated::#slug);
}
}
let Some(slug) = builder.primary_message() else {
return DiagnosticDeriveError::ErrorHandled.to_compile_error();
};
slugs.borrow_mut().push(slug.clone());
let primary_message = quote! {
diag.primary_message(crate::fluent_generated::#slug);
};

let formatting_init = &builder.formatting_init;
Expand Down Expand Up @@ -172,30 +130,6 @@ impl<'a> LintDiagnosticDerive<'a> {
}
}

struct Mismatch {
slug_name: String,
crate_name: String,
slug_prefix: String,
}

impl Mismatch {
/// Checks whether the slug starts with the crate name it's in.
fn check(slug: &syn::Path) -> Option<Mismatch> {
// If this is missing we're probably in a test, so bail.
let crate_name = std::env::var("CARGO_CRATE_NAME").ok()?;

// If we're not in a "rustc_" crate, bail.
let Some(("rustc", slug_prefix)) = crate_name.split_once('_') else { return None };

let slug_name = slug.segments.first()?.ident.to_string();
if !slug_name.starts_with(slug_prefix) {
Some(Mismatch { slug_name, slug_prefix: slug_prefix.to_string(), crate_name })
} else {
None
}
}
}

/// Generates a `#[test]` that verifies that all referenced variables
/// exist on this structure.
fn generate_test(slug: &syn::Path, structure: &Structure<'_>) -> TokenStream {
Expand Down
49 changes: 49 additions & 0 deletions compiler/rustc_macros/src/diagnostics/diagnostic_builder.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -110,6 +110,31 @@ impl DiagnosticDeriveKind {
}

impl DiagnosticDeriveVariantBuilder {
pub(crate) fn primary_message(&self) -> Option<&Path> {
match self.slug.value_ref() {
None => {
span_err(self.span, "diagnostic slug not specified")
.help(
"specify the slug as the first argument to the `#[diag(...)]` \
attribute, such as `#[diag(hir_analysis_example_error)]`",
)
.emit();
None
}
Some(slug)
if let Some(Mismatch { slug_name, crate_name, slug_prefix }) =
Mismatch::check(slug) =>
{
span_err(slug.span().unwrap(), "diagnostic slug and crate name do not match")
.note(format!("slug is `{slug_name}` but the crate name is `{crate_name}`"))
.help(format!("expected a slug starting with `{slug_prefix}_...`"))
.emit();
None
}
Some(slug) => Some(slug),
}
}

/// Generates calls to `code` and similar functions based on the attributes on the type or
/// variant.
pub(crate) fn preamble(&mut self, variant: &VariantInfo<'_>) -> TokenStream {
Expand Down Expand Up @@ -504,3 +529,27 @@ impl DiagnosticDeriveVariantBuilder {
}
}
}

struct Mismatch {
slug_name: String,
crate_name: String,
slug_prefix: String,
}

impl Mismatch {
/// Checks whether the slug starts with the crate name it's in.
fn check(slug: &syn::Path) -> Option<Mismatch> {
// If this is missing we're probably in a test, so bail.
let crate_name = std::env::var("CARGO_CRATE_NAME").ok()?;

// If we're not in a "rustc_" crate, bail.
let Some(("rustc", slug_prefix)) = crate_name.split_once('_') else { return None };

let slug_name = slug.segments.first()?.ident.to_string();
if slug_name.starts_with(slug_prefix) {
return None;
}

Some(Mismatch { slug_name, slug_prefix: slug_prefix.to_string(), crate_name })
}
}
2 changes: 1 addition & 1 deletion tests/ui-fulldeps/session-diagnostic/diagnostic-derive.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -384,7 +384,7 @@ error: derive(Diagnostic): diagnostic slug not specified
LL | #[lint(no_crate_example, code = E0123)]
| ^
|
= help: specify the slug as the first argument to the attribute, such as `#[diag(compiletest_example)]`
= help: specify the slug as the first argument to the `#[diag(...)]` attribute, such as `#[diag(hir_analysis_example_error)]`

error: derive(Diagnostic): attribute specified multiple times
--> $DIR/diagnostic-derive.rs:613:53
Expand Down
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