Add inline syntax for diagnostic messages

Cargo.lock

@@ -4229,6 +4229,8 @@ dependencies = [
 name = "rustc_macros"
 version = "0.0.0"
 dependencies = [
+ "fluent-bundle",
+ "fluent-syntax",
  "proc-macro2",
  "quote",
  "syn 2.0.110",

compiler/rustc_error_messages/src/lib.rs

@@ -247,6 +247,9 @@ pub enum SubdiagMessage {
     /// Identifier of a Fluent message. Instances of this variant are generated by the
     /// `Subdiagnostic` derive.
     FluentIdentifier(FluentId),
+    /// An inline Fluent message. Instances of this variant are generated by the
+    /// `Subdiagnostic` derive.
+    Inline(Cow<'static, str>),
     /// Attribute of a Fluent message. Needs to be combined with a Fluent identifier to produce an
     /// actual translated message. Instances of this variant are generated by the `fluent_messages`
     /// macro.
@@ -291,6 +294,8 @@ pub enum DiagMessage {
     /// <https://projectfluent.org/fluent/guide/hello.html>
     /// <https://projectfluent.org/fluent/guide/attributes.html>
     FluentIdentifier(FluentId, Option<FluentId>),
+    /// An inline Fluent message, containing the to be translated diagnostic message.
+    Inline(Cow<'static, str>),
 }
 
 impl DiagMessage {
@@ -305,21 +310,22 @@ impl DiagMessage {
             SubdiagMessage::FluentIdentifier(id) => {
                 return DiagMessage::FluentIdentifier(id, None);
             }
+            SubdiagMessage::Inline(s) => return DiagMessage::Inline(s),
             SubdiagMessage::FluentAttr(attr) => attr,
         };
 
         match self {
-            DiagMessage::Str(s) => DiagMessage::Str(s.clone()),
             DiagMessage::FluentIdentifier(id, _) => {
                 DiagMessage::FluentIdentifier(id.clone(), Some(attr))
             }
+            _ => panic!("Tried to add a subdiagnostic to a message without a fluent identifier"),
         }
     }
 
     pub fn as_str(&self) -> Option<&str> {
         match self {
             DiagMessage::Str(s) => Some(s),
-            DiagMessage::FluentIdentifier(_, _) => None,
+            DiagMessage::FluentIdentifier(_, _) | DiagMessage::Inline(_) => None,
         }
     }
 }
@@ -353,6 +359,7 @@ impl From<DiagMessage> for SubdiagMessage {
             // There isn't really a sensible behaviour for this because it loses information but
             // this is the most sensible of the behaviours.
             DiagMessage::FluentIdentifier(_, Some(attr)) => SubdiagMessage::FluentAttr(attr),
+            DiagMessage::Inline(s) => SubdiagMessage::Inline(s),
         }
     }
 }

compiler/rustc_errors/src/translation.rs

@@ -3,11 +3,13 @@ use std::env;
 use std::error::Report;
 use std::sync::Arc;
 
+use rustc_error_messages::langid;
 pub use rustc_error_messages::{FluentArgs, LazyFallbackBundle};
 use tracing::{debug, trace};
 
 use crate::error::{TranslateError, TranslateErrorKind};
-use crate::{DiagArg, DiagMessage, FluentBundle, Style};
+use crate::fluent_bundle::FluentResource;
+use crate::{DiagArg, DiagMessage, FluentBundle, Style, fluent_bundle};
 
 /// Convert diagnostic arguments (a rustc internal type that exists to implement
 /// `Encodable`/`Decodable`) into `FluentArgs` which is necessary to perform translation.
@@ -79,6 +81,28 @@ impl Translator {
                 return Ok(Cow::Borrowed(msg));
             }
             DiagMessage::FluentIdentifier(identifier, attr) => (identifier, attr),
+            // This translates an inline fluent diagnostic message
+            // It does this by creating a new `FluentBundle` with only one message,
+            // and then translating using this bundle.
+            DiagMessage::Inline(msg) => {
+                const GENERATED_MSG_ID: &str = "generated_msg";
+                let resource =
+                    FluentResource::try_new(format!("{GENERATED_MSG_ID} = {msg}\n")).unwrap();
+                let mut bundle = fluent_bundle::FluentBundle::new(vec![langid!("en-US")]);
+                bundle.set_use_isolating(false);
+                bundle.add_resource(resource).unwrap();
+                let message = bundle.get_message(GENERATED_MSG_ID).unwrap();
+                let value = message.value().unwrap();
+
+                let mut errs = vec![];
+                let translated = bundle.format_pattern(value, Some(args), &mut errs).to_string();
+                debug!(?translated, ?errs);
+                return if errs.is_empty() {
+                    Ok(Cow::Owned(translated))
+                } else {
+                    Err(TranslateError::fluent(&Cow::Borrowed(GENERATED_MSG_ID), args, errs))
+                };
+            }
         };
         let translate_with_bundle =
             |bundle: &'a FluentBundle| -> Result<Cow<'_, str>, TranslateError<'_>> {

compiler/rustc_macros/Cargo.toml

@@ -8,6 +8,8 @@ proc-macro = true
 
 [dependencies]
 # tidy-alphabetical-start
+fluent-bundle = "0.16"
+fluent-syntax = "0.12"
 proc-macro2 = "1"
 quote = "1"
 syn = { version = "2.0.9", features = ["full"] }

compiler/rustc_macros/src/diagnostics/diagnostic.rs

@@ -22,20 +22,22 @@ impl<'a> DiagnosticDerive<'a> {
     pub(crate) fn into_tokens(self) -> TokenStream {
         let DiagnosticDerive { mut structure } = self;
         let kind = DiagnosticDeriveKind::Diagnostic;
-        let slugs = RefCell::new(Vec::new());
+        let messages = RefCell::new(Vec::new());
         let implementation = kind.each_variant(&mut structure, |mut builder, variant| {
             let preamble = builder.preamble(variant);
             let body = builder.body(variant);
 
-            let Some(slug) = builder.primary_message() else {
+            let Some(message) = builder.primary_message() else {
                 return DiagnosticDeriveError::ErrorHandled.to_compile_error();
             };
-            slugs.borrow_mut().push(slug.clone());
+            messages.borrow_mut().push(message.clone());
+            let message = message.diag_message(variant);
+
             let init = quote! {
                 let mut diag = rustc_errors::Diag::new(
                     dcx,
                     level,
-                    crate::fluent_generated::#slug
+                    #message
                 );
             };
 
@@ -66,7 +68,7 @@ impl<'a> DiagnosticDerive<'a> {
                 }
             }
         });
-        for test in slugs.borrow().iter().map(|s| generate_test(s, &structure)) {
+        for test in messages.borrow().iter().map(|s| s.generate_test(&structure)) {
             imp.extend(test);
         }
         imp
@@ -86,17 +88,18 @@ impl<'a> LintDiagnosticDerive<'a> {
     pub(crate) fn into_tokens(self) -> TokenStream {
         let LintDiagnosticDerive { mut structure } = self;
         let kind = DiagnosticDeriveKind::LintDiagnostic;
-        let slugs = RefCell::new(Vec::new());
+        let messages = RefCell::new(Vec::new());
         let implementation = kind.each_variant(&mut structure, |mut builder, variant| {
             let preamble = builder.preamble(variant);
             let body = builder.body(variant);
 
-            let Some(slug) = builder.primary_message() else {
+            let Some(message) = builder.primary_message() else {
                 return DiagnosticDeriveError::ErrorHandled.to_compile_error();
             };
-            slugs.borrow_mut().push(slug.clone());
+            messages.borrow_mut().push(message.clone());
+            let message = message.diag_message(variant);
             let primary_message = quote! {
-                diag.primary_message(crate::fluent_generated::#slug);
+                diag.primary_message(#message);
             };
 
             let formatting_init = &builder.formatting_init;
@@ -122,47 +125,10 @@ impl<'a> LintDiagnosticDerive<'a> {
                 }
             }
         });
-        for test in slugs.borrow().iter().map(|s| generate_test(s, &structure)) {
+        for test in messages.borrow().iter().map(|s| s.generate_test(&structure)) {
             imp.extend(test);
         }
 
         imp
     }
 }
-
-/// Generates a `#[test]` that verifies that all referenced variables
-/// exist on this structure.
-fn generate_test(slug: &syn::Path, structure: &Structure<'_>) -> TokenStream {
-    // FIXME: We can't identify variables in a subdiagnostic
-    for field in structure.variants().iter().flat_map(|v| v.ast().fields.iter()) {
-        for attr_name in field.attrs.iter().filter_map(|at| at.path().get_ident()) {
-            if attr_name == "subdiagnostic" {
-                return quote!();
-            }
-        }
-    }
-    use std::sync::atomic::{AtomicUsize, Ordering};
-    // We need to make sure that the same diagnostic slug can be used multiple times without
-    // causing an error, so just have a global counter here.
-    static COUNTER: AtomicUsize = AtomicUsize::new(0);
-    let slug = slug.get_ident().unwrap();
-    let ident = quote::format_ident!("verify_{slug}_{}", COUNTER.fetch_add(1, Ordering::Relaxed));
-    let ref_slug = quote::format_ident!("{slug}_refs");
-    let struct_name = &structure.ast().ident;
-    let variables: Vec<_> = structure
-        .variants()
-        .iter()
-        .flat_map(|v| v.ast().fields.iter().filter_map(|f| f.ident.as_ref().map(|i| i.to_string())))
-        .collect();
-    // tidy errors on `#[test]` outside of test files, so we use `#[test ]` to work around this
-    quote! {
-        #[cfg(test)]
-        #[test ]
-        fn #ident() {
-            let variables = [#(#variables),*];
-            for vref in crate::fluent_generated::#ref_slug {
-                assert!(variables.contains(vref), "{}: variable `{vref}` not found ({})", stringify!(#struct_name), stringify!(#slug));
-            }
-        }
-    }
-}