Merging upstream version 1.69.0+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

9 files changed, 401 insertions, 289 deletions

diff --git a/compiler/rustc_macros/src/diagnostics/diagnostic.rs b/compiler/rustc_macros/src/diagnostics/diagnostic.rs
index 9ff944864..12a954258 100644
--- a/compiler/rustc_macros/src/diagnostics/diagnostic.rs
+++ b/compiler/rustc_macros/src/diagnostics/diagnostic.rs
@@ -57,7 +57,7 @@ impl<'a> DiagnosticDerive<'a> {
                 }
                 Some(slug) => {
                     quote! {
-                        let mut #diag = #handler.struct_diagnostic(rustc_errors::fluent::#slug);
+                        let mut #diag = #handler.struct_diagnostic(crate::fluent_generated::#slug);
                     }
                 }
             };
@@ -149,7 +149,7 @@ impl<'a> LintDiagnosticDerive<'a> {
                 }
                 Some(slug) => {
                     quote! {
-                        rustc_errors::fluent::#slug.into()
+                        crate::fluent_generated::#slug.into()
                     }
                 }
             }
diff --git a/compiler/rustc_macros/src/diagnostics/diagnostic_builder.rs b/compiler/rustc_macros/src/diagnostics/diagnostic_builder.rs
index e405462bb..46068f8c8 100644
--- a/compiler/rustc_macros/src/diagnostics/diagnostic_builder.rs
+++ b/compiler/rustc_macros/src/diagnostics/diagnostic_builder.rs
@@ -322,11 +322,7 @@ impl<'a> DiagnosticDeriveVariantBuilder<'a> {
                 let generated_code = self
                     .generate_inner_field_code(
                         attr,
-                        FieldInfo {
-                            binding: binding_info,
-                            ty: inner_ty.inner_type().unwrap_or(&field.ty),
-                            span: &field.span(),
-                        },
+                        FieldInfo { binding: binding_info, ty: inner_ty, span: &field.span() },
                         binding,
                     )
                     .unwrap_or_else(|v| v.to_compile_error());
@@ -418,9 +414,9 @@ impl<'a> DiagnosticDeriveVariantBuilder<'a> {
                 Ok(self.add_spanned_subdiagnostic(binding, &fn_ident, slug))
             }
             SubdiagnosticKind::Note | SubdiagnosticKind::Help | SubdiagnosticKind::Warn => {
-                if type_matches_path(info.ty, &["rustc_span", "Span"]) {
+                if type_matches_path(info.ty.inner_type(), &["rustc_span", "Span"]) {
                     Ok(self.add_spanned_subdiagnostic(binding, &fn_ident, slug))
-                } else if type_is_unit(info.ty) {
+                } else if type_is_unit(info.ty.inner_type()) {
                     Ok(self.add_subdiagnostic(&fn_ident, slug))
                 } else {
                     report_type_error(attr, "`Span` or `()`")?
@@ -432,6 +428,15 @@ impl<'a> DiagnosticDeriveVariantBuilder<'a> {
                 code_field,
                 code_init,
             } => {
+                if let FieldInnerTy::Vec(_) = info.ty {
+                    throw_invalid_attr!(attr, &meta, |diag| {
+                        diag
+                        .note("`#[suggestion(...)]` applied to `Vec` field is ambiguous")
+                        .help("to show a suggestion consisting of multiple parts, use a `Subdiagnostic` annotated with `#[multipart_suggestion(...)]`")
+                        .help("to show a variable set of suggestions, use a `Vec` of `Subdiagnostic`s annotated with `#[suggestion(...)]`")
+                    });
+                }
+
                 let (span_field, mut applicability) = self.span_and_applicability_of_ty(info)?;
 
                 if let Some((static_applicability, span)) = static_applicability {
@@ -447,7 +452,7 @@ impl<'a> DiagnosticDeriveVariantBuilder<'a> {
                 Ok(quote! {
                     #diag.span_suggestions_with_style(
                         #span_field,
-                        rustc_errors::fluent::#slug,
+                        crate::fluent_generated::#slug,
                         #code_field,
                         #applicability,
                         #style
@@ -471,7 +476,7 @@ impl<'a> DiagnosticDeriveVariantBuilder<'a> {
         quote! {
             #diag.#fn_name(
                 #field_binding,
-                rustc_errors::fluent::#fluent_attr_identifier
+                crate::fluent_generated::#fluent_attr_identifier
             );
         }
     }
@@ -481,7 +486,7 @@ impl<'a> DiagnosticDeriveVariantBuilder<'a> {
     fn add_subdiagnostic(&self, kind: &Ident, fluent_attr_identifier: Path) -> TokenStream {
         let diag = &self.parent.diag;
         quote! {
-            #diag.#kind(rustc_errors::fluent::#fluent_attr_identifier);
+            #diag.#kind(crate::fluent_generated::#fluent_attr_identifier);
         }
     }
 
@@ -489,7 +494,7 @@ impl<'a> DiagnosticDeriveVariantBuilder<'a> {
         &self,
         info: FieldInfo<'_>,
     ) -> Result<(TokenStream, SpannedOption<TokenStream>), DiagnosticDeriveError> {
-        match &info.ty {
+        match &info.ty.inner_type() {
             // If `ty` is `Span` w/out applicability, then use `Applicability::Unspecified`.
             ty @ Type::Path(..) if type_matches_path(ty, &["rustc_span", "Span"]) => {
                 let binding = &info.binding.binding;
diff --git a/compiler/rustc_macros/src/diagnostics/fluent.rs b/compiler/rustc_macros/src/diagnostics/fluent.rs
index 32338f9df..38c0f4895 100644
--- a/compiler/rustc_macros/src/diagnostics/fluent.rs
+++ b/compiler/rustc_macros/src/diagnostics/fluent.rs
@@ -4,7 +4,10 @@ use annotate_snippets::{
 };
 use fluent_bundle::{FluentBundle, FluentError, FluentResource};
 use fluent_syntax::{
-    ast::{Attribute, Entry, Identifier, Message},
+    ast::{
+        Attribute, Entry, Expression, Identifier, InlineExpression, Message, Pattern,
+        PatternElement,
+    },
     parser::ParserError,
 };
 use proc_macro::{Diagnostic, Level, Span};
@@ -16,52 +19,9 @@ use std::{
     io::Read,
     path::{Path, PathBuf},
 };
-use syn::{
-    parse::{Parse, ParseStream},
-    parse_macro_input,
-    punctuated::Punctuated,
-    token, Ident, LitStr, Result,
-};
+use syn::{parse_macro_input, Ident, LitStr};
 use unic_langid::langid;
 
-struct Resource {
-    krate: Ident,
-    #[allow(dead_code)]
-    fat_arrow_token: token::FatArrow,
-    resource_path: LitStr,
-}
-
-impl Parse for Resource {
-    fn parse(input: ParseStream<'_>) -> Result<Self> {
-        Ok(Resource {
-            krate: input.parse()?,
-            fat_arrow_token: input.parse()?,
-            resource_path: input.parse()?,
-        })
-    }
-}
-
-struct Resources(Punctuated<Resource, token::Comma>);
-
-impl Parse for Resources {
-    fn parse(input: ParseStream<'_>) -> Result<Self> {
-        let mut resources = Punctuated::new();
-        loop {
-            if input.is_empty() || input.peek(token::Brace) {
-                break;
-            }
-            let value = input.parse()?;
-            resources.push_value(value);
-            if !input.peek(token::Comma) {
-                break;
-            }
-            let punct = input.parse()?;
-            resources.push_punct(punct);
-        }
-        Ok(Resources(resources))
-    }
-}
-
 /// Helper function for returning an absolute path for macro-invocation relative file paths.
 ///
 /// If the input is already absolute, then the input is returned. If the input is not absolute,
@@ -81,224 +41,285 @@ fn invocation_relative_path_to_absolute(span: Span, path: &str) -> PathBuf {
     }
 }
 
+/// Tokens to be returned when the macro cannot proceed.
+fn failed(crate_name: &Ident) -> proc_macro::TokenStream {
+    quote! {
+        pub static DEFAULT_LOCALE_RESOURCE: &'static str = "";
+
+        #[allow(non_upper_case_globals)]
+        #[doc(hidden)]
+        pub(crate) mod fluent_generated {
+            pub mod #crate_name {
+            }
+
+            pub mod _subdiag {
+                pub const help: crate::SubdiagnosticMessage =
+                    crate::SubdiagnosticMessage::FluentAttr(std::borrow::Cow::Borrowed("help"));
+                pub const note: crate::SubdiagnosticMessage =
+                    crate::SubdiagnosticMessage::FluentAttr(std::borrow::Cow::Borrowed("note"));
+                pub const warn: crate::SubdiagnosticMessage =
+                    crate::SubdiagnosticMessage::FluentAttr(std::borrow::Cow::Borrowed("warn"));
+                pub const label: crate::SubdiagnosticMessage =
+                    crate::SubdiagnosticMessage::FluentAttr(std::borrow::Cow::Borrowed("label"));
+                pub const suggestion: crate::SubdiagnosticMessage =
+                    crate::SubdiagnosticMessage::FluentAttr(std::borrow::Cow::Borrowed("suggestion"));
+            }
+        }
+    }
+    .into()
+}
+
 /// See [rustc_macros::fluent_messages].
 pub(crate) fn fluent_messages(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
-    let resources = parse_macro_input!(input as Resources);
+    let crate_name = std::env::var("CARGO_PKG_NAME")
+        // If `CARGO_PKG_NAME` is missing, then we're probably running in a test, so use
+        // `no_crate`.
+        .unwrap_or_else(|_| "no_crate".to_string())
+        .replace("rustc_", "");
 
     // Cannot iterate over individual messages in a bundle, so do that using the
     // `FluentResource` instead. Construct a bundle anyway to find out if there are conflicting
     // messages in the resources.
     let mut bundle = FluentBundle::new(vec![langid!("en-US")]);
 
-    // Map of Fluent identifiers to the `Span` of the resource that defined them, used for better
-    // diagnostics.
-    let mut previous_defns = HashMap::new();
-
     // Set of Fluent attribute names already output, to avoid duplicate type errors - any given
     // constant created for a given attribute is the same.
     let mut previous_attrs = HashSet::new();
 
-    let mut includes = TokenStream::new();
-    let mut generated = TokenStream::new();
+    let resource_str = parse_macro_input!(input as LitStr);
+    let resource_span = resource_str.span().unwrap();
+    let relative_ftl_path = resource_str.value();
+    let absolute_ftl_path = invocation_relative_path_to_absolute(resource_span, &relative_ftl_path);
 
-    for res in resources.0 {
-        let krate_span = res.krate.span().unwrap();
-        let path_span = res.resource_path.span().unwrap();
+    let crate_name = Ident::new(&crate_name, resource_str.span());
 
-        let relative_ftl_path = res.resource_path.value();
-        let absolute_ftl_path =
-            invocation_relative_path_to_absolute(krate_span, &relative_ftl_path);
-        // As this macro also outputs an `include_str!` for this file, the macro will always be
-        // re-executed when the file changes.
-        let mut resource_file = match File::open(absolute_ftl_path) {
-            Ok(resource_file) => resource_file,
-            Err(e) => {
-                Diagnostic::spanned(path_span, Level::Error, "could not open Fluent resource")
-                    .note(e.to_string())
-                    .emit();
-                continue;
-            }
-        };
-        let mut resource_contents = String::new();
-        if let Err(e) = resource_file.read_to_string(&mut resource_contents) {
-            Diagnostic::spanned(path_span, Level::Error, "could not read Fluent resource")
+    // As this macro also outputs an `include_str!` for this file, the macro will always be
+    // re-executed when the file changes.
+    let mut resource_file = match File::open(absolute_ftl_path) {
+        Ok(resource_file) => resource_file,
+        Err(e) => {
+            Diagnostic::spanned(resource_span, Level::Error, "could not open Fluent resource")
                 .note(e.to_string())
                 .emit();
-            continue;
+            return failed(&crate_name);
         }
-        let resource = match FluentResource::try_new(resource_contents) {
-            Ok(resource) => resource,
-            Err((this, errs)) => {
-                Diagnostic::spanned(path_span, Level::Error, "could not parse Fluent resource")
-                    .help("see additional errors emitted")
-                    .emit();
-                for ParserError { pos, slice: _, kind } in errs {
-                    let mut err = kind.to_string();
-                    // Entirely unnecessary string modification so that the error message starts
-                    // with a lowercase as rustc errors do.
-                    err.replace_range(
-                        0..1,
-                        &err.chars().next().unwrap().to_lowercase().to_string(),
-                    );
+    };
+    let mut resource_contents = String::new();
+    if let Err(e) = resource_file.read_to_string(&mut resource_contents) {
+        Diagnostic::spanned(resource_span, Level::Error, "could not read Fluent resource")
+            .note(e.to_string())
+            .emit();
+        return failed(&crate_name);
+    }
+
+    let resource = match FluentResource::try_new(resource_contents) {
+        Ok(resource) => resource,
+        Err((this, errs)) => {
+            Diagnostic::spanned(resource_span, Level::Error, "could not parse Fluent resource")
+                .help("see additional errors emitted")
+                .emit();
+            for ParserError { pos, slice: _, kind } in errs {
+                let mut err = kind.to_string();
+                // Entirely unnecessary string modification so that the error message starts
+                // with a lowercase as rustc errors do.
+                err.replace_range(0..1, &err.chars().next().unwrap().to_lowercase().to_string());
 
-                    let line_starts: Vec<usize> = std::iter::once(0)
-                        .chain(
-                            this.source()
-                                .char_indices()
-                                .filter_map(|(i, c)| Some(i + 1).filter(|_| c == '\n')),
-                        )
-                        .collect();
-                    let line_start = line_starts
-                        .iter()
-                        .enumerate()
-                        .map(|(line, idx)| (line + 1, idx))
-                        .filter(|(_, idx)| **idx <= pos.start)
-                        .last()
-                        .unwrap()
-                        .0;
+                let line_starts: Vec<usize> = std::iter::once(0)
+                    .chain(
+                        this.source()
+                            .char_indices()
+                            .filter_map(|(i, c)| Some(i + 1).filter(|_| c == '\n')),
+                    )
+                    .collect();
+                let line_start = line_starts
+                    .iter()
+                    .enumerate()
+                    .map(|(line, idx)| (line + 1, idx))
+                    .filter(|(_, idx)| **idx <= pos.start)
+                    .last()
+                    .unwrap()
+                    .0;
 
-                    let snippet = Snippet {
-                        title: Some(Annotation {
-                            label: Some(&err),
-                            id: None,
+                let snippet = Snippet {
+                    title: Some(Annotation {
+                        label: Some(&err),
+                        id: None,
+                        annotation_type: AnnotationType::Error,
+                    }),
+                    footer: vec![],
+                    slices: vec![Slice {
+                        source: this.source(),
+                        line_start,
+                        origin: Some(&relative_ftl_path),
+                        fold: true,
+                        annotations: vec![SourceAnnotation {
+                            label: "",
                             annotation_type: AnnotationType::Error,
-                        }),
-                        footer: vec![],
-                        slices: vec![Slice {
-                            source: this.source(),
-                            line_start,
-                            origin: Some(&relative_ftl_path),
-                            fold: true,
-                            annotations: vec![SourceAnnotation {
-                                label: "",
-                                annotation_type: AnnotationType::Error,
-                                range: (pos.start, pos.end - 1),
-                            }],
+                            range: (pos.start, pos.end - 1),
                         }],
-                        opt: Default::default(),
-                    };
-                    let dl = DisplayList::from(snippet);
-                    eprintln!("{dl}\n");
+                    }],
+                    opt: Default::default(),
+                };
+                let dl = DisplayList::from(snippet);
+                eprintln!("{dl}\n");
+            }
+
+            return failed(&crate_name);
+        }
+    };
+
+    let mut constants = TokenStream::new();
+    let mut previous_defns = HashMap::new();
+    let mut message_refs = Vec::new();
+    for entry in resource.entries() {
+        if let Entry::Message(Message { id: Identifier { name }, attributes, value, .. }) = entry {
+            let _ = previous_defns.entry(name.to_string()).or_insert(resource_span);
+            if name.contains('-') {
+                Diagnostic::spanned(
+                    resource_span,
+                    Level::Error,
+                    format!("name `{name}` contains a '-' character"),
+                )
+                .help("replace any '-'s with '_'s")
+                .emit();
+            }
+
+            if let Some(Pattern { elements }) = value {
+                for elt in elements {
+                    if let PatternElement::Placeable {
+                        expression:
+                            Expression::Inline(InlineExpression::MessageReference { id, .. }),
+                    } = elt
+                    {
+                        message_refs.push((id.name, *name));
+                    }
                 }
+            }
+
+            // `typeck_foo_bar` => `foo_bar` (in `typeck.ftl`)
+            // `const_eval_baz` => `baz` (in `const_eval.ftl`)
+            // `const-eval-hyphen-having` => `hyphen_having` (in `const_eval.ftl`)
+            // The last case we error about above, but we want to fall back gracefully
+            // so that only the error is being emitted and not also one about the macro
+            // failing.
+            let crate_prefix = format!("{crate_name}_");
+
+            let snake_name = name.replace('-', "_");
+            if !snake_name.starts_with(&crate_prefix) {
+                Diagnostic::spanned(
+                    resource_span,
+                    Level::Error,
+                    format!("name `{name}` does not start with the crate name"),
+                )
+                .help(format!(
+                    "prepend `{crate_prefix}` to the slug name: `{crate_prefix}{snake_name}`"
+                ))
+                .emit();
+            };
+            let snake_name = Ident::new(&snake_name, resource_str.span());
+
+            if !previous_attrs.insert(snake_name.clone()) {
                 continue;
             }
-        };
 
-        let mut constants = TokenStream::new();
-        for entry in resource.entries() {
-            let span = res.krate.span();
-            if let Entry::Message(Message { id: Identifier { name }, attributes, .. }) = entry {
-                let _ = previous_defns.entry(name.to_string()).or_insert(path_span);
+            let msg = format!("Constant referring to Fluent message `{name}` from `{crate_name}`");
+            constants.extend(quote! {
+                #[doc = #msg]
+                pub const #snake_name: crate::DiagnosticMessage =
+                    crate::DiagnosticMessage::FluentIdentifier(
+                        std::borrow::Cow::Borrowed(#name),
+                        None
+                    );
+            });
 
-                if name.contains('-') {
-                    Diagnostic::spanned(
-                        path_span,
-                        Level::Error,
-                        format!("name `{name}` contains a '-' character"),
-                    )
-                    .help("replace any '-'s with '_'s")
-                    .emit();
+            for Attribute { id: Identifier { name: attr_name }, .. } in attributes {
+                let snake_name = Ident::new(
+                    &format!("{}{}", &crate_prefix, &attr_name.replace('-', "_")),
+                    resource_str.span(),
+                );
+                if !previous_attrs.insert(snake_name.clone()) {
+                    continue;
                 }
 
-                // Require that the message name starts with the crate name
-                // `hir_typeck_foo_bar` (in `hir_typeck.ftl`)
-                // `const_eval_baz` (in `const_eval.ftl`)
-                // `const-eval-hyphen-having` => `hyphen_having` (in `const_eval.ftl`)
-                // The last case we error about above, but we want to fall back gracefully
-                // so that only the error is being emitted and not also one about the macro
-                // failing.
-                let crate_prefix = format!("{}_", res.krate);
-
-                let snake_name = name.replace('-', "_");
-                if !snake_name.starts_with(&crate_prefix) {
+                if attr_name.contains('-') {
                     Diagnostic::spanned(
-                        path_span,
+                        resource_span,
                         Level::Error,
-                        format!("name `{name}` does not start with the crate name"),
+                        format!("attribute `{attr_name}` contains a '-' character"),
                     )
-                    .help(format!(
-                        "prepend `{crate_prefix}` to the slug name: `{crate_prefix}{snake_name}`"
-                    ))
+                    .help("replace any '-'s with '_'s")
                     .emit();
-                };
-
-                let snake_name = Ident::new(&snake_name, span);
+                }
 
+                let msg = format!(
+                    "Constant referring to Fluent message `{name}.{attr_name}` from `{crate_name}`"
+                );
                 constants.extend(quote! {
-                    pub const #snake_name: crate::DiagnosticMessage =
-                        crate::DiagnosticMessage::FluentIdentifier(
-                            std::borrow::Cow::Borrowed(#name),
-                            None
+                    #[doc = #msg]
+                    pub const #snake_name: crate::SubdiagnosticMessage =
+                        crate::SubdiagnosticMessage::FluentAttr(
+                            std::borrow::Cow::Borrowed(#attr_name)
                         );
                 });
-
-                for Attribute { id: Identifier { name: attr_name }, .. } in attributes {
-                    let snake_name = Ident::new(&attr_name.replace('-', "_"), span);
-                    if !previous_attrs.insert(snake_name.clone()) {
-                        continue;
-                    }
-
-                    if attr_name.contains('-') {
-                        Diagnostic::spanned(
-                            path_span,
-                            Level::Error,
-                            format!("attribute `{attr_name}` contains a '-' character"),
-                        )
-                        .help("replace any '-'s with '_'s")
-                        .emit();
-                    }
-
-                    constants.extend(quote! {
-                        pub const #snake_name: crate::SubdiagnosticMessage =
-                            crate::SubdiagnosticMessage::FluentAttr(
-                                std::borrow::Cow::Borrowed(#attr_name)
-                            );
-                    });
-                }
             }
         }
+    }
 
-        if let Err(errs) = bundle.add_resource(resource) {
-            for e in errs {
-                match e {
-                    FluentError::Overriding { kind, id } => {
-                        Diagnostic::spanned(
-                            path_span,
-                            Level::Error,
-                            format!("overrides existing {kind}: `{id}`"),
-                        )
-                        .span_help(previous_defns[&id], "previously defined in this resource")
-                        .emit();
-                    }
-                    FluentError::ResolverError(_) | FluentError::ParserError(_) => unreachable!(),
+    for (mref, name) in message_refs.into_iter() {
+        if !previous_defns.contains_key(mref) {
+            Diagnostic::spanned(
+                resource_span,
+                Level::Error,
+                format!("referenced message `{mref}` does not exist (in message `{name}`)"),
+            )
+            .help(&format!("you may have meant to use a variable reference (`{{${mref}}}`)"))
+            .emit();
+        }
+    }
+
+    if let Err(errs) = bundle.add_resource(resource) {
+        for e in errs {
+            match e {
+                FluentError::Overriding { kind, id } => {
+                    Diagnostic::spanned(
+                        resource_span,
+                        Level::Error,
+                        format!("overrides existing {kind}: `{id}`"),
+                    )
+                    .emit();
                 }
+                FluentError::ResolverError(_) | FluentError::ParserError(_) => unreachable!(),
             }
         }
-
-        includes.extend(quote! { include_str!(#relative_ftl_path), });
-
-        generated.extend(constants);
     }
 
     quote! {
+        /// Raw content of Fluent resource for this crate, generated by `fluent_messages` macro,
+        /// imported by `rustc_driver` to include all crates' resources in one bundle.
+        pub static DEFAULT_LOCALE_RESOURCE: &'static str = include_str!(#relative_ftl_path);
+
         #[allow(non_upper_case_globals)]
         #[doc(hidden)]
-        pub mod fluent_generated {
-            pub static DEFAULT_LOCALE_RESOURCES: &'static [&'static str] = &[
-                #includes
-            ];
-
-            #generated
+        /// Auto-generated constants for type-checked references to Fluent messages.
+        pub(crate) mod fluent_generated {
+            #constants
 
+            /// Constants expected to exist by the diagnostic derive macros to use as default Fluent
+            /// identifiers for different subdiagnostic kinds.
             pub mod _subdiag {
+                /// Default for `#[help]`
                 pub const help: crate::SubdiagnosticMessage =
                     crate::SubdiagnosticMessage::FluentAttr(std::borrow::Cow::Borrowed("help"));
+                /// Default for `#[note]`
                 pub const note: crate::SubdiagnosticMessage =
                     crate::SubdiagnosticMessage::FluentAttr(std::borrow::Cow::Borrowed("note"));
+                /// Default for `#[warn]`
                 pub const warn: crate::SubdiagnosticMessage =
                     crate::SubdiagnosticMessage::FluentAttr(std::borrow::Cow::Borrowed("warn"));
+                /// Default for `#[label]`
                 pub const label: crate::SubdiagnosticMessage =
                     crate::SubdiagnosticMessage::FluentAttr(std::borrow::Cow::Borrowed("label"));
+                /// Default for `#[suggestion]`
                 pub const suggestion: crate::SubdiagnosticMessage =
                     crate::SubdiagnosticMessage::FluentAttr(std::borrow::Cow::Borrowed("suggestion"));
             }
diff --git a/compiler/rustc_macros/src/diagnostics/subdiagnostic.rs b/compiler/rustc_macros/src/diagnostics/subdiagnostic.rs
index baffd3cec..90660fc1f 100644
--- a/compiler/rustc_macros/src/diagnostics/subdiagnostic.rs
+++ b/compiler/rustc_macros/src/diagnostics/subdiagnostic.rs
@@ -247,11 +247,7 @@ impl<'parent, 'a> SubdiagnosticDeriveVariantBuilder<'parent, 'a> {
                     return quote! {};
                 }
 
-                let info = FieldInfo {
-                    binding,
-                    ty: inner_ty.inner_type().unwrap_or(&ast.ty),
-                    span: &ast.span(),
-                };
+                let info = FieldInfo { binding, ty: inner_ty, span: &ast.span() };
 
                 let generated = self
                     .generate_field_code_inner(kind_stats, attr, info, inner_ty.will_iterate())
@@ -312,6 +308,21 @@ impl<'parent, 'a> SubdiagnosticDeriveVariantBuilder<'parent, 'a> {
                     let binding = info.binding.binding.clone();
                     // FIXME(#100717): support `Option<Span>` on `primary_span` like in the
                     // diagnostic derive
+                    if !matches!(info.ty, FieldInnerTy::Plain(_)) {
+                        throw_invalid_attr!(attr, &Meta::Path(path), |diag| {
+                            let diag = diag.note("there must be exactly one primary span");
+
+                            if kind_stats.has_normal_suggestion {
+                                diag.help(
+                                    "to create a suggestion with multiple spans, \
+                                     use `#[multipart_suggestion]` instead",
+                                )
+                            } else {
+                                diag
+                            }
+                        });
+                    }
+
                     self.span_field.set_once(binding, span);
                 }
 
@@ -501,7 +512,9 @@ impl<'parent, 'a> SubdiagnosticDeriveVariantBuilder<'parent, 'a> {
         let mut calls = TokenStream::new();
         for (kind, slug) in kind_slugs {
             let message = format_ident!("__message");
-            calls.extend(quote! { let #message = #f(#diag, rustc_errors::fluent::#slug.into()); });
+            calls.extend(
+                quote! { let #message = #f(#diag, crate::fluent_generated::#slug.into()); },
+            );
 
             let name = format_ident!("{}{}", if span_field.is_some() { "span_" } else { "" }, kind);
             let call = match kind {
diff --git a/compiler/rustc_macros/src/diagnostics/utils.rs b/compiler/rustc_macros/src/diagnostics/utils.rs
index 6f52a3de1..27b8f676f 100644
--- a/compiler/rustc_macros/src/diagnostics/utils.rs
+++ b/compiler/rustc_macros/src/diagnostics/utils.rs
@@ -80,7 +80,7 @@ fn report_error_if_not_applied_to_ty(
     path: &[&str],
     ty_name: &str,
 ) -> Result<(), DiagnosticDeriveError> {
-    if !type_matches_path(info.ty, path) {
+    if !type_matches_path(info.ty.inner_type(), path) {
         report_type_error(attr, ty_name)?;
     }
 
@@ -105,8 +105,8 @@ pub(crate) fn report_error_if_not_applied_to_span(
     attr: &Attribute,
     info: &FieldInfo<'_>,
 ) -> Result<(), DiagnosticDeriveError> {
-    if !type_matches_path(info.ty, &["rustc_span", "Span"])
-        && !type_matches_path(info.ty, &["rustc_errors", "MultiSpan"])
+    if !type_matches_path(info.ty.inner_type(), &["rustc_span", "Span"])
+        && !type_matches_path(info.ty.inner_type(), &["rustc_errors", "MultiSpan"])
     {
         report_type_error(attr, "`Span` or `MultiSpan`")?;
     }
@@ -115,44 +115,50 @@ pub(crate) fn report_error_if_not_applied_to_span(
 }
 
 /// Inner type of a field and type of wrapper.
+#[derive(Copy, Clone)]
 pub(crate) enum FieldInnerTy<'ty> {
     /// Field is wrapped in a `Option<$inner>`.
     Option(&'ty Type),
     /// Field is wrapped in a `Vec<$inner>`.
     Vec(&'ty Type),
     /// Field isn't wrapped in an outer type.
-    None,
+    Plain(&'ty Type),
 }
 
 impl<'ty> FieldInnerTy<'ty> {
     /// Returns inner type for a field, if there is one.
     ///
-    /// - If `ty` is an `Option`, returns `FieldInnerTy::Option { inner: (inner type) }`.
-    /// - If `ty` is a `Vec`, returns `FieldInnerTy::Vec { inner: (inner type) }`.
-    /// - Otherwise returns `None`.
+    /// - If `ty` is an `Option<Inner>`, returns `FieldInnerTy::Option(Inner)`.
+    /// - If `ty` is a `Vec<Inner>`, returns `FieldInnerTy::Vec(Inner)`.
+    /// - Otherwise returns `FieldInnerTy::Plain(ty)`.
     pub(crate) fn from_type(ty: &'ty Type) -> Self {
-        let variant: &dyn Fn(&'ty Type) -> FieldInnerTy<'ty> =
-            if type_matches_path(ty, &["std", "option", "Option"]) {
-                &FieldInnerTy::Option
-            } else if type_matches_path(ty, &["std", "vec", "Vec"]) {
-                &FieldInnerTy::Vec
-            } else {
-                return FieldInnerTy::None;
+        fn single_generic_type(ty: &Type) -> &Type {
+            let Type::Path(ty_path) = ty else {
+                panic!("expected path type");
             };
 
-        if let Type::Path(ty_path) = ty {
             let path = &ty_path.path;
             let ty = path.segments.iter().last().unwrap();
-            if let syn::PathArguments::AngleBracketed(bracketed) = &ty.arguments {
-                if bracketed.args.len() == 1 {
-                    if let syn::GenericArgument::Type(ty) = &bracketed.args[0] {
-                        return variant(ty);
-                    }
-                }
-            }
+            let syn::PathArguments::AngleBracketed(bracketed) = &ty.arguments else {
+                panic!("expected bracketed generic arguments");
+            };
+
+            assert_eq!(bracketed.args.len(), 1);
+
+            let syn::GenericArgument::Type(ty) = &bracketed.args[0] else {
+                panic!("expected generic parameter to be a type generic");
+            };
+
+            ty
         }
 
-        unreachable!();
+        if type_matches_path(ty, &["std", "option", "Option"]) {
+            FieldInnerTy::Option(single_generic_type(ty))
+        } else if type_matches_path(ty, &["std", "vec", "Vec"]) {
+            FieldInnerTy::Vec(single_generic_type(ty))
+        } else {
+            FieldInnerTy::Plain(ty)
+        }
     }
 
     /// Returns `true` if `FieldInnerTy::with` will result in iteration for this inner type (i.e.
@@ -160,15 +166,16 @@ impl<'ty> FieldInnerTy<'ty> {
     pub(crate) fn will_iterate(&self) -> bool {
         match self {
             FieldInnerTy::Vec(..) => true,
-            FieldInnerTy::Option(..) | FieldInnerTy::None => false,
+            FieldInnerTy::Option(..) | FieldInnerTy::Plain(_) => false,
         }
     }
 
-    /// Returns `Option` containing inner type if there is one.
-    pub(crate) fn inner_type(&self) -> Option<&'ty Type> {
+    /// Returns the inner type.
+    pub(crate) fn inner_type(&self) -> &'ty Type {
         match self {
-            FieldInnerTy::Option(inner) | FieldInnerTy::Vec(inner) => Some(inner),
-            FieldInnerTy::None => None,
+            FieldInnerTy::Option(inner) | FieldInnerTy::Vec(inner) | FieldInnerTy::Plain(inner) => {
+                inner
+            }
         }
     }
 
@@ -185,7 +192,7 @@ impl<'ty> FieldInnerTy<'ty> {
                     #inner
                 }
             },
-            FieldInnerTy::None => quote! { #inner },
+            FieldInnerTy::Plain(..) => quote! { #inner },
         }
     }
 }
@@ -194,7 +201,7 @@ impl<'ty> FieldInnerTy<'ty> {
 /// `generate_*` methods from walking the attributes themselves.
 pub(crate) struct FieldInfo<'a> {
     pub(crate) binding: &'a BindingInfo<'a>,
-    pub(crate) ty: &'a Type,
+    pub(crate) ty: FieldInnerTy<'a>,
     pub(crate) span: &'a proc_macro2::Span,
 }
 
diff --git a/compiler/rustc_macros/src/lib.rs b/compiler/rustc_macros/src/lib.rs
index bb3722fe1..737500cc2 100644
--- a/compiler/rustc_macros/src/lib.rs
+++ b/compiler/rustc_macros/src/lib.rs
@@ -61,9 +61,7 @@ pub fn newtype_index(input: TokenStream) -> TokenStream {
 /// For example, given the following invocation of the macro..
 ///
 /// ```ignore (rust)
-/// fluent_messages! {
-///     typeck => "./typeck.ftl",
-/// }
+/// fluent_messages! { "./typeck.ftl" }
 /// ```
 /// ..where `typeck.ftl` has the following contents..
 ///
@@ -77,9 +75,7 @@ pub fn newtype_index(input: TokenStream) -> TokenStream {
 /// will generate the following code:
 ///
 /// ```ignore (rust)
-/// pub static DEFAULT_LOCALE_RESOURCES: &'static [&'static str] = &[
-///     include_str!("./typeck.ftl"),
-/// ];
+/// pub static DEFAULT_LOCALE_RESOURCE: &'static [&'static str] = include_str!("./typeck.ftl");
 ///
 /// mod fluent_generated {
 ///     mod typeck {
@@ -124,8 +120,27 @@ decl_derive!([TyDecodable] => serialize::type_decodable_derive);
 decl_derive!([TyEncodable] => serialize::type_encodable_derive);
 decl_derive!([MetadataDecodable] => serialize::meta_decodable_derive);
 decl_derive!([MetadataEncodable] => serialize::meta_encodable_derive);
-decl_derive!([TypeFoldable, attributes(type_foldable)] => type_foldable::type_foldable_derive);
-decl_derive!([TypeVisitable, attributes(type_visitable)] => type_visitable::type_visitable_derive);
+decl_derive!(
+    [TypeFoldable, attributes(type_foldable)] =>
+    /// Derives `TypeFoldable` for the annotated `struct` or `enum` (`union` is not supported).
+    ///
+    /// The fold will produce a value of the same struct or enum variant as the input, with
+    /// each field respectively folded using the `TypeFoldable` implementation for its type.
+    /// However, if a field of a struct or an enum variant is annotated with
+    /// `#[type_foldable(identity)]` then that field will retain its incumbent value (and its
+    /// type is not required to implement `TypeFoldable`).
+    type_foldable::type_foldable_derive
+);
+decl_derive!(
+    [TypeVisitable, attributes(type_visitable)] =>
+    /// Derives `TypeVisitable` for the annotated `struct` or `enum` (`union` is not supported).
+    ///
+    /// Each field of the struct or enum variant will be visited in definition order, using the
+    /// `TypeVisitable` implementation for its type. However, if a field of a struct or an enum
+    /// variant is annotated with `#[type_visitable(ignore)]` then that field will not be
+    /// visited (and its type is not required to implement `TypeVisitable`).
+    type_visitable::type_visitable_derive
+);
 decl_derive!([Lift, attributes(lift)] => lift::lift_derive);
 decl_derive!(
     [Diagnostic, attributes(
diff --git a/compiler/rustc_macros/src/serialize.rs b/compiler/rustc_macros/src/serialize.rs
index 82e6972d0..8d017d149 100644
--- a/compiler/rustc_macros/src/serialize.rs
+++ b/compiler/rustc_macros/src/serialize.rs
@@ -42,6 +42,12 @@ fn decodable_body(
     }
     let ty_name = s.ast().ident.to_string();
     let decode_body = match s.variants() {
+        [] => {
+            let message = format!("`{}` has no variants to decode", ty_name);
+            quote! {
+                panic!(#message)
+            }
+        }
         [vi] => vi.construct(|field, _index| decode_field(field)),
         variants => {
             let match_inner: TokenStream = variants
@@ -139,6 +145,11 @@ fn encodable_body(
     });
 
     let encode_body = match s.variants() {
+        [] => {
+            quote! {
+                match *self {}
+            }
+        }
         [_] => {
             let encode_inner = s.each_variant(|vi| {
                 vi.bindings()
@@ -160,6 +171,23 @@ fn encodable_body(
             }
         }
         _ => {
+            let disc = {
+                let mut variant_idx = 0usize;
+                let encode_inner = s.each_variant(|_| {
+                    let result = quote! {
+                        #variant_idx
+                    };
+                    variant_idx += 1;
+                    result
+                });
+                quote! {
+                    let disc = match *self {
+                        #encode_inner
+                    };
+                    ::rustc_serialize::Encoder::emit_usize(__encoder, disc);
+                }
+            };
+
             let mut variant_idx = 0usize;
             let encode_inner = s.each_variant(|vi| {
                 let encode_fields: TokenStream = vi
@@ -176,26 +204,11 @@ fn encodable_body(
                         result
                     })
                     .collect();
-
-                let result = if !vi.bindings().is_empty() {
-                    quote! {
-                        ::rustc_serialize::Encoder::emit_enum_variant(
-                            __encoder,
-                            #variant_idx,
-                            |__encoder| { #encode_fields }
-                        )
-                    }
-                } else {
-                    quote! {
-                        ::rustc_serialize::Encoder::emit_fieldless_enum_variant::<#variant_idx>(
-                            __encoder,
-                        )
-                    }
-                };
                 variant_idx += 1;
-                result
+                encode_fields
             });
             quote! {
+                #disc
                 match *self {
                     #encode_inner
                 }
diff --git a/compiler/rustc_macros/src/type_foldable.rs b/compiler/rustc_macros/src/type_foldable.rs
index 23e619221..388e254cd 100644
--- a/compiler/rustc_macros/src/type_foldable.rs
+++ b/compiler/rustc_macros/src/type_foldable.rs
@@ -1,5 +1,5 @@
-use quote::quote;
-use syn::parse_quote;
+use quote::{quote, ToTokens};
+use syn::{parse_quote, Attribute, Meta, NestedMeta};
 
 pub fn type_foldable_derive(mut s: synstructure::Structure<'_>) -> proc_macro2::TokenStream {
     if let syn::Data::Union(_) = s.ast().data {
@@ -16,16 +16,37 @@ pub fn type_foldable_derive(mut s: synstructure::Structure<'_>) -> proc_macro2::
         let bindings = vi.bindings();
         vi.construct(|_, index| {
             let bind = &bindings[index];
-            quote! {
-                ::rustc_middle::ty::fold::TypeFoldable::try_fold_with(#bind, __folder)?
+
+            // retain value of fields with #[type_foldable(identity)]
+            let fixed = bind
+                .ast()
+                .attrs
+                .iter()
+                .map(Attribute::parse_meta)
+                .filter_map(Result::ok)
+                .flat_map(|attr| match attr {
+                    Meta::List(list) if list.path.is_ident("type_foldable") => list.nested,
+                    _ => Default::default(),
+                })
+                .any(|nested| match nested {
+                    NestedMeta::Meta(Meta::Path(path)) => path.is_ident("identity"),
+                    _ => false,
+                });
+
+            if fixed {
+                bind.to_token_stream()
+            } else {
+                quote! {
+                    ::rustc_middle::ty::fold::TypeFoldable::try_fold_with(#bind, __folder)?
+                }
             }
         })
     });
 
     s.bound_impl(
-        quote!(::rustc_middle::ty::fold::TypeFoldable<'tcx>),
+        quote!(::rustc_middle::ty::fold::TypeFoldable<::rustc_middle::ty::TyCtxt<'tcx>>),
         quote! {
-            fn try_fold_with<__F: ::rustc_middle::ty::fold::FallibleTypeFolder<'tcx>>(
+            fn try_fold_with<__F: ::rustc_middle::ty::fold::FallibleTypeFolder<::rustc_middle::ty::TyCtxt<'tcx>>>(
                 self,
                 __folder: &mut __F
             ) -> Result<Self, __F::Error> {
diff --git a/compiler/rustc_macros/src/type_visitable.rs b/compiler/rustc_macros/src/type_visitable.rs
index 1f95661ce..f6f4c4779 100644
--- a/compiler/rustc_macros/src/type_visitable.rs
+++ b/compiler/rustc_macros/src/type_visitable.rs
@@ -1,11 +1,28 @@
 use quote::quote;
-use syn::parse_quote;
+use syn::{parse_quote, Attribute, Meta, NestedMeta};
 
 pub fn type_visitable_derive(mut s: synstructure::Structure<'_>) -> proc_macro2::TokenStream {
     if let syn::Data::Union(_) = s.ast().data {
         panic!("cannot derive on union")
     }
 
+    // ignore fields with #[type_visitable(ignore)]
+    s.filter(|bi| {
+        !bi.ast()
+            .attrs
+            .iter()
+            .map(Attribute::parse_meta)
+            .filter_map(Result::ok)
+            .flat_map(|attr| match attr {
+                Meta::List(list) if list.path.is_ident("type_visitable") => list.nested,
+                _ => Default::default(),
+            })
+            .any(|nested| match nested {
+                NestedMeta::Meta(Meta::Path(path)) => path.is_ident("ignore"),
+                _ => false,
+            })
+    });
+
     if !s.ast().generics.lifetimes().any(|lt| lt.lifetime.ident == "tcx") {
         s.add_impl_generic(parse_quote! { 'tcx });
     }
@@ -19,9 +36,9 @@ pub fn type_visitable_derive(mut s: synstructure::Structure<'_>) -> proc_macro2:
     s.bind_with(|_| synstructure::BindStyle::Move);
 
     s.bound_impl(
-        quote!(::rustc_middle::ty::visit::TypeVisitable<'tcx>),
+        quote!(::rustc_middle::ty::visit::TypeVisitable<::rustc_middle::ty::TyCtxt<'tcx>>),
         quote! {
-            fn visit_with<__V: ::rustc_middle::ty::visit::TypeVisitor<'tcx>>(
+            fn visit_with<__V: ::rustc_middle::ty::visit::TypeVisitor<::rustc_middle::ty::TyCtxt<'tcx>>>(
                 &self,
                 __visitor: &mut __V
             ) -> ::std::ops::ControlFlow<__V::BreakTy> {