Migrate parts of rustc_expand to session diagnostics

This migrates everything but the `mbe` and `proc_macro` modules. It also
contains a few cleanups and drive-by/accidental diagnostic improvements
which can be seen in the diff for the UI tests.

compiler/rustc_builtin_macros/src/concat.rs

@@ -11,7 +11,7 @@ pub fn expand_concat(
     sp: rustc_span::Span,
     tts: TokenStream,
 ) -> Box<dyn base::MacResult + 'static> {
-    let Some(es) = base::get_exprs_from_tts(cx, sp, tts) else {
+    let Some(es) = base::get_exprs_from_tts(cx, tts) else {
         return DummyResult::any(sp);
     };
     let mut accumulator = String::new();

compiler/rustc_builtin_macros/src/concat_bytes.rs

@@ -137,7 +137,7 @@ pub fn expand_concat_bytes(
     sp: rustc_span::Span,
     tts: TokenStream,
 ) -> Box<dyn base::MacResult + 'static> {
-    let Some(es) = base::get_exprs_from_tts(cx, sp, tts) else {
+    let Some(es) = base::get_exprs_from_tts(cx, tts) else {
         return DummyResult::any(sp);
     };
     let mut accumulator = Vec::new();

compiler/rustc_builtin_macros/src/env.rs

@@ -52,7 +52,7 @@ pub fn expand_env<'cx>(
     sp: Span,
     tts: TokenStream,
 ) -> Box<dyn base::MacResult + 'cx> {
-    let mut exprs = match get_exprs_from_tts(cx, sp, tts) {
+    let mut exprs = match get_exprs_from_tts(cx, tts) {
         Some(exprs) if exprs.is_empty() => {
             cx.span_err(sp, "env! takes 1 or 2 arguments");
             return DummyResult::any(sp);

compiler/rustc_error_messages/locales/en-US/expand.ftl

@@ -20,3 +20,110 @@ expand_var_still_repeating =
     variable '{$ident}' is still repeating at this depth
 
 expand_meta_var_dif_seq_matchers = {$msg}
+
+expand_macro_const_stability =
+    macros cannot have const stability attributes
+    .label = invalid const stability attribute
+    .label2 = const stability attribute affects this macro
+
+expand_macro_body_stability =
+    macros cannot have body stability attributes
+    .label = invalid body stability attribute
+    .label2 = body stability attribute affects this macro
+
+expand_resolve_relative_path =
+    cannot resolve relative path in non-file source `{$path}`
+
+expand_attr_no_arguments =
+    attribute must have either one or two arguments
+
+expand_not_a_meta_item =
+    not a meta item
+
+expand_only_one_word =
+    must only be one word
+
+expand_cannot_be_name_of_macro =
+    `{$trait_ident}` cannot be a name of {$macro_type} macro
+
+expand_arg_not_attributes =
+    second argument must be `attributes`
+
+expand_attributes_wrong_form =
+    attribute must be of form: `attributes(foo, bar)`
+
+expand_attribute_meta_item =
+    attribute must be a meta item, not a literal
+
+expand_attribute_single_word =
+    attribute must only be a single word
+
+expand_helper_attribute_name_invalid =
+    `{$name}` cannot be a name of derive helper attribute
+
+expand_expected_comma_in_list =
+    expected token: `,`
+
+expand_only_one_argument =
+    {$name} takes 1 argument
+
+expand_takes_no_arguments =
+    {$name} takes no arguments
+
+expand_feature_included_in_edition =
+    the feature `{$feature}` is included in the Rust {$edition} edition
+
+expand_feature_removed =
+    feature has been removed
+    .label = feature has been removed
+    .reason = {$reason}
+
+expand_feature_not_allowed =
+    the feature `{$name}` is not in the list of allowed features
+
+expand_recursion_limit_reached =
+    recursion limit reached while expanding `{$descr}`
+    .help = consider increasing the recursion limit by adding a `#![recursion_limit = "{$suggested_limit}"]` attribute to your crate (`{$crate_name}`)
+
+expand_malformed_feature_attribute =
+    malformed `feature` attribute input
+    .expected = expected just one word
+
+expand_remove_expr_not_supported =
+    removing an expression is not supported in this position
+
+expand_invalid_cfg_no_parens = `cfg` is not followed by parentheses
+expand_invalid_cfg_no_predicate = `cfg` predicate is not specified
+expand_invalid_cfg_multiple_predicates = multiple `cfg` predicates are specified
+expand_invalid_cfg_predicate_literal = `cfg` predicate key cannot be a literal
+expand_invalid_cfg_expected_syntax = expected syntax is
+
+expand_wrong_fragment_kind =
+    non-{$kind} macro in {$kind} position: {$name}
+
+expand_unsupported_key_value =
+    key-value macro attributes are not supported
+
+expand_incomplete_parse =
+    macro expansion ignores token `{$token}` and any following
+    .label = caused by the macro expansion here
+    .note = the usage of `{$macro_path}!` is likely invalid in {$kind_name} context
+    .suggestion_add_semi = you might be missing a semicolon here
+
+expand_remove_node_not_supported =
+    removing {$descr} is not supported in this position
+
+expand_module_circular =
+    circular modules: {$modules}
+
+expand_module_in_block =
+    cannot declare a non-inline module inside a block unless it has a path attribute
+    .note = maybe `use` the module `{$name}` instead of redeclaring it
+
+expand_module_file_not_found =
+    file not found for module `{$name}`
+    .help = to create the module `{$name}`, create file "{$default_path}" or "{$secondary_path}"
+
+expand_module_multiple_candidates =
+    file for module `{$name}` found at both "{$default_path}" and "{$secondary_path}"
+    .help = delete or rename one of them to remove the ambiguity

compiler/rustc_errors/src/diagnostic_impls.rs

@@ -152,6 +152,12 @@ impl IntoDiagnosticArg for ast::Path {
     }
 }
 
+impl IntoDiagnosticArg for &ast::Path {
+    fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
+        DiagnosticArgValue::Str(Cow::Owned(pprust::path_to_string(self)))
+    }
+}
+
 impl IntoDiagnosticArg for ast::token::Token {
     fn into_diagnostic_arg(self) -> DiagnosticArgValue<'static> {
         DiagnosticArgValue::Str(pprust::token_to_string(&self))

compiler/rustc_expand/src/base.rs

@@ -1,3 +1,11 @@
+#![deny(rustc::untranslatable_diagnostic)]
+
+use crate::errors::{
+    ArgumentNotAttributes, AttrNoArguments, AttributeMetaItem, AttributeSingleWord,
+    AttributesWrongForm, CannotBeNameOfMacro, ExpectedCommaInList, HelperAttributeNameInvalid,
+    MacroBodyStability, MacroConstStability, NotAMetaItem, OnlyOneArgument, OnlyOneWord,
+    ResolveRelativePath, TakesNoArguments,
+};
 use crate::expand::{self, AstFragment, Invocation};
 use crate::module::DirOwnership;
 
@@ -789,26 +797,16 @@ impl SyntaxExtension {
             .unwrap_or_else(|| (None, helper_attrs));
         let (stability, const_stability, body_stability) = attr::find_stability(&sess, attrs, span);
         if let Some((_, sp)) = const_stability {
-            sess.parse_sess
+            sess.emit_err(MacroConstStability {
-                .span_diagnostic
+                span: sp,
-                .struct_span_err(sp, "macros cannot have const stability attributes")
+                head_span: sess.source_map().guess_head_span(span),
-                .span_label(sp, "invalid const stability attribute")
+            });
-                .span_label(
-                    sess.source_map().guess_head_span(span),
-                    "const stability attribute affects this macro",
-                )
-                .emit();
         }
         if let Some((_, sp)) = body_stability {
-            sess.parse_sess
+            sess.emit_err(MacroBodyStability {
-                .span_diagnostic
+                span: sp,
-                .struct_span_err(sp, "macros cannot have body stability attributes")
+                head_span: sess.source_map().guess_head_span(span),
-                .span_label(sp, "invalid body stability attribute")
+            });
-                .span_label(
-                    sess.source_map().guess_head_span(span),
-                    "body stability attribute affects this macro",
-                )
-                .emit();
         }
 
         SyntaxExtension {
@@ -1200,13 +1198,11 @@ pub fn resolve_path(
                 .expect("attempting to resolve a file path in an external file"),
             FileName::DocTest(path, _) => path,
             other => {
-                return Err(parse_sess.span_diagnostic.struct_span_err(
+                return Err(ResolveRelativePath {
                     span,
-                    &format!(
+                    path: parse_sess.source_map().filename_for_diagnostics(&other).to_string(),
-                        "cannot resolve relative path in non-file source `{}`",
+                }
-                        parse_sess.source_map().filename_for_diagnostics(&other)
+                .into_diagnostic(&parse_sess.span_diagnostic));
-                    ),
-                ));
             }
         };
         result.pop();
@@ -1222,6 +1218,8 @@ pub fn resolve_path(
 /// The returned bool indicates whether an applicable suggestion has already been
 /// added to the diagnostic to avoid emitting multiple suggestions. `Err(None)`
 /// indicates that an ast error was encountered.
+// FIXME(Nilstrieb) Make this function setup translatable
+#[allow(rustc::untranslatable_diagnostic)]
 pub fn expr_to_spanned_string<'a>(
     cx: &'a mut ExtCtxt<'_>,
     expr: P<ast::Expr>,
@@ -1280,9 +1278,9 @@ pub fn expr_to_string(
 /// compilation should call
 /// `cx.parse_sess.span_diagnostic.abort_if_errors()` (this should be
 /// done as rarely as possible).
-pub fn check_zero_tts(cx: &ExtCtxt<'_>, sp: Span, tts: TokenStream, name: &str) {
+pub fn check_zero_tts(cx: &ExtCtxt<'_>, span: Span, tts: TokenStream, name: &str) {
     if !tts.is_empty() {
-        cx.span_err(sp, &format!("{} takes no arguments", name));
+        cx.emit_err(TakesNoArguments { span, name });
     }
 }
 
@@ -1304,31 +1302,27 @@ pub fn parse_expr(p: &mut parser::Parser<'_>) -> Option<P<ast::Expr>> {
 /// expect exactly one string literal, or emit an error and return `None`.
 pub fn get_single_str_from_tts(
     cx: &mut ExtCtxt<'_>,
-    sp: Span,
+    span: Span,
     tts: TokenStream,
     name: &str,
 ) -> Option<Symbol> {
     let mut p = cx.new_parser_from_tts(tts);
     if p.token == token::Eof {
-        cx.span_err(sp, &format!("{} takes 1 argument", name));
+        cx.emit_err(OnlyOneArgument { span, name });
         return None;
     }
     let ret = parse_expr(&mut p)?;
     let _ = p.eat(&token::Comma);
 
     if p.token != token::Eof {
-        cx.span_err(sp, &format!("{} takes 1 argument", name));
+        cx.emit_err(OnlyOneArgument { span, name });
     }
     expr_to_string(cx, ret, "argument must be a string literal").map(|(s, _)| s)
 }
 
 /// Extracts comma-separated expressions from `tts`.
 /// On error, emit it, and return `None`.
-pub fn get_exprs_from_tts(
+pub fn get_exprs_from_tts(cx: &mut ExtCtxt<'_>, tts: TokenStream) -> Option<Vec<P<ast::Expr>>> {
-    cx: &mut ExtCtxt<'_>,
-    sp: Span,
-    tts: TokenStream,
-) -> Option<Vec<P<ast::Expr>>> {
     let mut p = cx.new_parser_from_tts(tts);
     let mut es = Vec::new();
     while p.token != token::Eof {
@@ -1343,7 +1337,7 @@ pub fn get_exprs_from_tts(
             continue;
         }
         if p.token != token::Eof {
-            cx.span_err(sp, "expected token: `,`");
+            cx.emit_err(ExpectedCommaInList { span: p.token.span });
             return None;
         }
     }
@@ -1353,64 +1347,58 @@ pub fn get_exprs_from_tts(
 pub fn parse_macro_name_and_helper_attrs(
     diag: &rustc_errors::Handler,
     attr: &Attribute,
-    descr: &str,
+    macro_type: &str,
 ) -> Option<(Symbol, Vec<Symbol>)> {
     // Once we've located the `#[proc_macro_derive]` attribute, verify
     // that it's of the form `#[proc_macro_derive(Foo)]` or
     // `#[proc_macro_derive(Foo, attributes(A, ..))]`
     let list = attr.meta_item_list()?;
     if list.len() != 1 && list.len() != 2 {
-        diag.span_err(attr.span, "attribute must have either one or two arguments");
+        diag.emit_err(AttrNoArguments { span: attr.span });
         return None;
     }
     let Some(trait_attr) = list[0].meta_item() else {
-        diag.span_err(list[0].span(), "not a meta item");
+        diag.emit_err(NotAMetaItem {span: list[0].span()});
         return None;
     };
     let trait_ident = match trait_attr.ident() {
         Some(trait_ident) if trait_attr.is_word() => trait_ident,
         _ => {
-            diag.span_err(trait_attr.span, "must only be one word");
+            diag.emit_err(OnlyOneWord { span: trait_attr.span });
             return None;
         }
     };
 
     if !trait_ident.name.can_be_raw() {
-        diag.span_err(
+        diag.emit_err(CannotBeNameOfMacro { span: trait_attr.span, trait_ident, macro_type });
-            trait_attr.span,
-            &format!("`{}` cannot be a name of {} macro", trait_ident, descr),
-        );
     }
 
     let attributes_attr = list.get(1);
     let proc_attrs: Vec<_> = if let Some(attr) = attributes_attr {
         if !attr.has_name(sym::attributes) {
-            diag.span_err(attr.span(), "second argument must be `attributes`");
+            diag.emit_err(ArgumentNotAttributes { span: attr.span() });
         }
         attr.meta_item_list()
             .unwrap_or_else(|| {
-                diag.span_err(attr.span(), "attribute must be of form: `attributes(foo, bar)`");
+                diag.emit_err(AttributesWrongForm { span: attr.span() });
                 &[]
             })
             .iter()
             .filter_map(|attr| {
                 let Some(attr) = attr.meta_item() else {
-                    diag.span_err(attr.span(), "not a meta item");
+                    diag.emit_err(AttributeMetaItem { span: attr.span() });
                     return None;
                 };
 
                 let ident = match attr.ident() {
                     Some(ident) if attr.is_word() => ident,
                     _ => {
-                        diag.span_err(attr.span, "must only be one word");
+                        diag.emit_err(AttributeSingleWord { span: attr.span });
                         return None;
                     }
                 };
                 if !ident.name.can_be_raw() {
-                    diag.span_err(
+                    diag.emit_err(HelperAttributeNameInvalid { span: attr.span, name: ident });
-                        attr.span,
-                        &format!("`{}` cannot be a name of derive helper attribute", ident),
-                    );
                 }
 
                 Some(ident.name)

compiler/rustc_expand/src/config.rs

@@ -1,5 +1,9 @@
 //! Conditional compilation stripping.
 
+use crate::errors::{
+    FeatureIncludedInEdition, FeatureNotAllowed, FeatureRemoved, FeatureRemovedReason, InvalidCfg,
+    MalformedFeatureAttribute, MalformedFeatureAttributeHelp, RemoveExprNotSupported,
+};
 use rustc_ast::ptr::P;
 use rustc_ast::token::{Delimiter, Token, TokenKind};
 use rustc_ast::tokenstream::{AttrTokenStream, AttrTokenTree};
@@ -10,7 +14,6 @@ use rustc_ast::{self as ast, AttrStyle, Attribute, HasAttrs, HasTokens, MetaItem
 use rustc_attr as attr;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::map_in_place::MapInPlace;
-use rustc_errors::{error_code, struct_span_err, Applicability, Handler};
 use rustc_feature::{Feature, Features, State as FeatureState};
 use rustc_feature::{
     ACCEPTED_FEATURES, ACTIVE_FEATURES, REMOVED_FEATURES, STABLE_REMOVED_FEATURES,
@@ -33,18 +36,12 @@ pub struct StripUnconfigured<'a> {
     pub lint_node_id: NodeId,
 }
 
-fn get_features(
+fn get_features(sess: &Session, krate_attrs: &[ast::Attribute]) -> Features {
-    sess: &Session,
+    fn feature_removed(sess: &Session, span: Span, reason: Option<&str>) {
-    span_handler: &Handler,
+        sess.emit_err(FeatureRemoved {
-    krate_attrs: &[ast::Attribute],
+            span,
-) -> Features {
+            reason: reason.map(|reason| FeatureRemovedReason { reason }),
-    fn feature_removed(span_handler: &Handler, span: Span, reason: Option<&str>) {
+        });
-        let mut err = struct_span_err!(span_handler, span, E0557, "feature has been removed");
-        err.span_label(span, "feature has been removed");
-        if let Some(reason) = reason {
-            err.note(reason);
-        }
-        err.emit();
     }
 
     fn active_features_up_to(edition: Edition) -> impl Iterator<Item = &'static Feature> {
@@ -117,34 +114,34 @@ fn get_features(
             continue;
         };
 
-        let bad_input = |span| {
-            struct_span_err!(span_handler, span, E0556, "malformed `feature` attribute input")
-        };
-
         for mi in list {
             let name = match mi.ident() {
                 Some(ident) if mi.is_word() => ident.name,
                 Some(ident) => {
-                    bad_input(mi.span())
+                    sess.emit_err(MalformedFeatureAttribute {
-                        .span_suggestion(
+                        span: mi.span(),
-                            mi.span(),
+                        help: MalformedFeatureAttributeHelp::Suggestion {
-                            "expected just one word",
+                            span: mi.span(),
-                            ident.name,
+                            suggestion: ident.name,
-                            Applicability::MaybeIncorrect,
+                        },
-                        )
+                    });
-                        .emit();
                     continue;
                 }
                 None => {
-                    bad_input(mi.span()).span_label(mi.span(), "expected just one word").emit();
+                    sess.emit_err(MalformedFeatureAttribute {
+                        span: mi.span(),
+                        help: MalformedFeatureAttributeHelp::Label { span: mi.span() },
+                    });
                     continue;
                 }
             };
 
-            if let Some(edition) = edition_enabled_features.get(&name) {
+            if let Some(&edition) = edition_enabled_features.get(&name) {
-                let msg =
+                sess.emit_warning(FeatureIncludedInEdition {
-                    &format!("the feature `{}` is included in the Rust {} edition", name, edition);
+                    span: mi.span(),
-                span_handler.struct_span_warn_with_code(mi.span(), msg, error_code!(E0705)).emit();
+                    feature: name,
+                    edition,
+                });
                 continue;
             }
 
@@ -159,7 +156,7 @@ fn get_features(
                 if let FeatureState::Removed { reason } | FeatureState::Stabilized { reason } =
                     state
                 {
-                    feature_removed(span_handler, mi.span(), *reason);
+                    feature_removed(sess, mi.span(), *reason);
                     continue;
                 }
             }
@@ -173,14 +170,7 @@ fn get_features(
 
             if let Some(allowed) = sess.opts.unstable_opts.allow_features.as_ref() {
                 if allowed.iter().all(|f| name.as_str() != f) {
-                    struct_span_err!(
+                    sess.emit_err(FeatureNotAllowed { span: mi.span(), name });
-                        span_handler,
-                        mi.span(),
-                        E0725,
-                        "the feature `{}` is not in the list of allowed features",
-                        name
-                    )
-                    .emit();
                     continue;
                 }
             }
@@ -221,7 +211,7 @@ pub fn features(
         }
         Some(attrs) => {
             krate.attrs = attrs;
-            let features = get_features(sess, diag, &krate.attrs);
+            let features = get_features(sess, &krate.attrs);
             if err_count == diag.err_count() {
                 // Avoid reconfiguring malformed `cfg_attr`s.
                 strip_unconfigured.features = Some(&features);
@@ -503,8 +493,7 @@ impl<'a> StripUnconfigured<'a> {
         // N.B., this is intentionally not part of the visit_expr() function
         //     in order for filter_map_expr() to be able to avoid this check
         if let Some(attr) = expr.attrs().iter().find(|a| is_cfg(*a)) {
-            let msg = "removing an expression is not supported in this position";
+            self.sess.emit_err(RemoveExprNotSupported { span: attr.span });
-            self.sess.parse_sess.span_diagnostic.span_err(attr.span, msg);
         }
 
         self.process_cfg_attrs(expr);
@@ -513,27 +502,26 @@ impl<'a> StripUnconfigured<'a> {
 }
 
 pub fn parse_cfg<'a>(meta_item: &'a MetaItem, sess: &Session) -> Option<&'a MetaItem> {
-    let error = |span, msg, suggestion: &str| {
-        let mut err = sess.parse_sess.span_diagnostic.struct_span_err(span, msg);
-        if !suggestion.is_empty() {
-            err.span_suggestion(
-                span,
-                "expected syntax is",
-                suggestion,
-                Applicability::HasPlaceholders,
-            );
-        }
-        err.emit();
-        None
-    };
     let span = meta_item.span;
     match meta_item.meta_item_list() {
-        None => error(span, "`cfg` is not followed by parentheses", "cfg(/* predicate */)"),
+        None => {
-        Some([]) => error(span, "`cfg` predicate is not specified", ""),
+            sess.emit_err(InvalidCfg::NotFollowedByParens { span });
-        Some([_, .., l]) => error(l.span(), "multiple `cfg` predicates are specified", ""),
+            None
+        }
+        Some([]) => {
+            sess.emit_err(InvalidCfg::NoPredicate { span });
+            None
+        }
+        Some([_, .., l]) => {
+            sess.emit_err(InvalidCfg::MultiplePredicates { span: l.span() });
+            None
+        }
         Some([single]) => match single.meta_item() {
             Some(meta_item) => Some(meta_item),
-            None => error(single.span(), "`cfg` predicate key cannot be a literal", ""),
+            None => {
+                sess.emit_err(InvalidCfg::PredicateLiteral { span: single.span() });
+                None
+            }
         },
     }
 }

compiler/rustc_expand/src/errors.rs

@@ -1,6 +1,10 @@
+use rustc_ast::ast;
 use rustc_macros::Diagnostic;
-use rustc_span::symbol::MacroRulesNormalizedIdent;
+use rustc_session::Limit;
-use rustc_span::Span;
+use rustc_span::edition::Edition;
+use rustc_span::symbol::{Ident, MacroRulesNormalizedIdent};
+use rustc_span::{Span, Symbol};
+use std::borrow::Cow;
 
 #[derive(Diagnostic)]
 #[diag(expand_expr_repeat_no_syntax_vars)]
@@ -46,3 +50,321 @@ pub(crate) struct MetaVarsDifSeqMatchers {
     pub span: Span,
     pub msg: String,
 }
+
+#[derive(Diagnostic)]
+#[diag(expand_resolve_relative_path)]
+pub(crate) struct ResolveRelativePath {
+    #[primary_span]
+    pub span: Span,
+    pub path: String,
+}
+
+#[derive(Diagnostic)]
+#[diag(expand_macro_const_stability)]
+pub(crate) struct MacroConstStability {
+    #[primary_span]
+    #[label]
+    pub span: Span,
+    #[label(label2)]
+    pub head_span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(expand_macro_body_stability)]
+pub(crate) struct MacroBodyStability {
+    #[primary_span]
+    #[label]
+    pub span: Span,
+    #[label(label2)]
+    pub head_span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(expand_attr_no_arguments)]
+pub(crate) struct AttrNoArguments {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(expand_not_a_meta_item)]
+pub(crate) struct NotAMetaItem {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(expand_only_one_word)]
+pub(crate) struct OnlyOneWord {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(expand_cannot_be_name_of_macro)]
+pub(crate) struct CannotBeNameOfMacro<'a> {
+    #[primary_span]
+    pub span: Span,
+    pub trait_ident: Ident,
+    pub macro_type: &'a str,
+}
+
+#[derive(Diagnostic)]
+#[diag(expand_arg_not_attributes)]
+pub(crate) struct ArgumentNotAttributes {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(expand_attributes_wrong_form)]
+pub(crate) struct AttributesWrongForm {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(expand_attribute_meta_item)]
+pub(crate) struct AttributeMetaItem {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(expand_attribute_single_word)]
+pub(crate) struct AttributeSingleWord {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(expand_helper_attribute_name_invalid)]
+pub(crate) struct HelperAttributeNameInvalid {
+    #[primary_span]
+    pub span: Span,
+    pub name: Ident,
+}
+
+#[derive(Diagnostic)]
+#[diag(expand_expected_comma_in_list)]
+pub(crate) struct ExpectedCommaInList {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(expand_only_one_argument)]
+pub(crate) struct OnlyOneArgument<'a> {
+    #[primary_span]
+    pub span: Span,
+    pub name: &'a str,
+}
+
+#[derive(Diagnostic)]
+#[diag(expand_takes_no_arguments)]
+pub(crate) struct TakesNoArguments<'a> {
+    #[primary_span]
+    pub span: Span,
+    pub name: &'a str,
+}
+
+#[derive(Diagnostic)]
+#[diag(expand_feature_included_in_edition, code = "E0705")]
+pub(crate) struct FeatureIncludedInEdition {
+    #[primary_span]
+    pub span: Span,
+    pub feature: Symbol,
+    pub edition: Edition,
+}
+
+#[derive(Diagnostic)]
+#[diag(expand_feature_removed, code = "E0557")]
+pub(crate) struct FeatureRemoved<'a> {
+    #[primary_span]
+    #[label]
+    pub span: Span,
+    #[subdiagnostic]
+    pub reason: Option<FeatureRemovedReason<'a>>,
+}
+
+#[derive(Subdiagnostic)]
+#[note(reason)]
+pub(crate) struct FeatureRemovedReason<'a> {
+    pub reason: &'a str,
+}
+
+#[derive(Diagnostic)]
+#[diag(expand_feature_not_allowed, code = "E0725")]
+pub(crate) struct FeatureNotAllowed {
+    #[primary_span]
+    pub span: Span,
+    pub name: Symbol,
+}
+
+#[derive(Diagnostic)]
+#[diag(expand_recursion_limit_reached)]
+#[help]
+pub(crate) struct RecursionLimitReached<'a> {
+    #[primary_span]
+    pub span: Span,
+    pub descr: String,
+    pub suggested_limit: Limit,
+    pub crate_name: &'a str,
+}
+
+#[derive(Diagnostic)]
+#[diag(expand_malformed_feature_attribute, code = "E0556")]
+pub(crate) struct MalformedFeatureAttribute {
+    #[primary_span]
+    pub span: Span,
+    #[subdiagnostic]
+    pub help: MalformedFeatureAttributeHelp,
+}
+
+#[derive(Subdiagnostic)]
+pub(crate) enum MalformedFeatureAttributeHelp {
+    #[label(expected)]
+    Label {
+        #[primary_span]
+        span: Span,
+    },
+    #[suggestion(expected, code = "{suggestion}", applicability = "maybe-incorrect")]
+    Suggestion {
+        #[primary_span]
+        span: Span,
+        suggestion: Symbol,
+    },
+}
+
+#[derive(Diagnostic)]
+#[diag(expand_remove_expr_not_supported)]
+pub(crate) struct RemoveExprNotSupported {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+pub(crate) enum InvalidCfg {
+    #[diag(expand_invalid_cfg_no_parens)]
+    NotFollowedByParens {
+        #[primary_span]
+        #[suggestion(
+            expand_invalid_cfg_expected_syntax,
+            code = "cfg(/* predicate */)",
+            applicability = "has-placeholders"
+        )]
+        span: Span,
+    },
+    #[diag(expand_invalid_cfg_no_predicate)]
+    NoPredicate {
+        #[primary_span]
+        #[suggestion(
+            expand_invalid_cfg_expected_syntax,
+            code = "cfg(/* predicate */)",
+            applicability = "has-placeholders"
+        )]
+        span: Span,
+    },
+    #[diag(expand_invalid_cfg_multiple_predicates)]
+    MultiplePredicates {
+        #[primary_span]
+        span: Span,
+    },
+    #[diag(expand_invalid_cfg_predicate_literal)]
+    PredicateLiteral {
+        #[primary_span]
+        span: Span,
+    },
+}
+
+#[derive(Diagnostic)]
+#[diag(expand_wrong_fragment_kind)]
+pub(crate) struct WrongFragmentKind<'a> {
+    #[primary_span]
+    pub span: Span,
+    pub kind: &'a str,
+    pub name: &'a ast::Path,
+}
+
+#[derive(Diagnostic)]
+#[diag(expand_unsupported_key_value)]
+pub(crate) struct UnsupportedKeyValue {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(expand_incomplete_parse)]
+#[note]
+pub(crate) struct IncompleteParse<'a> {
+    #[primary_span]
+    pub span: Span,
+    pub token: Cow<'a, str>,
+    #[label]
+    pub label_span: Span,
+    pub macro_path: &'a ast::Path,
+    pub kind_name: &'a str,
+
+    #[suggestion(
+        suggestion_add_semi,
+        style = "verbose",
+        code = ";",
+        applicability = "maybe-incorrect"
+    )]
+    pub add_semicolon: Option<Span>,
+}
+
+#[derive(Diagnostic)]
+#[diag(expand_remove_node_not_supported)]
+pub(crate) struct RemoveNodeNotSupported {
+    #[primary_span]
+    pub span: Span,
+    pub descr: &'static str,
+}
+
+#[derive(Diagnostic)]
+#[diag(expand_module_circular)]
+pub(crate) struct ModuleCircular {
+    #[primary_span]
+    pub span: Span,
+    pub modules: String,
+}
+
+#[derive(Diagnostic)]
+#[diag(expand_module_in_block)]
+pub(crate) struct ModuleInBlock {
+    #[primary_span]
+    pub span: Span,
+    #[subdiagnostic]
+    pub name: Option<ModuleInBlockName>,
+}
+
+#[derive(Subdiagnostic)]
+#[note(note)]
+pub(crate) struct ModuleInBlockName {
+    #[primary_span]
+    pub span: Span,
+    pub name: Ident,
+}
+
+#[derive(Diagnostic)]
+#[diag(expand_module_file_not_found, code = "E0583")]
+#[help]
+pub(crate) struct ModuleFileNotFound {
+    #[primary_span]
+    pub span: Span,
+    pub name: Ident,
+    pub default_path: String,
+    pub secondary_path: String,
+}
+
+#[derive(Diagnostic)]
+#[diag(expand_module_multiple_candidates, code = "E0761")]
+#[help]
+pub(crate) struct ModuleMultipleCandidates {
+    #[primary_span]
+    pub span: Span,
+    pub name: Ident,
+    pub default_path: String,
+    pub secondary_path: String,
+}

compiler/rustc_expand/src/expand.rs

@@ -1,5 +1,9 @@
 use crate::base::*;
 use crate::config::StripUnconfigured;
+use crate::errors::{
+    IncompleteParse, RecursionLimitReached, RemoveExprNotSupported, RemoveNodeNotSupported,
+    UnsupportedKeyValue, WrongFragmentKind,
+};
 use crate::hygiene::SyntaxContext;
 use crate::mbe::diagnostics::annotate_err_with_kind;
 use crate::module::{mod_dir_path, parse_external_mod, DirOwnership, ParsedExternalMod};
@@ -18,7 +22,7 @@ use rustc_ast::{NestedMetaItem, NodeId, PatKind, StmtKind, TyKind};
 use rustc_ast_pretty::pprust;
 use rustc_data_structures::map_in_place::MapInPlace;
 use rustc_data_structures::sync::Lrc;
-use rustc_errors::{Applicability, PResult};
+use rustc_errors::PResult;
 use rustc_feature::Features;
 use rustc_parse::parser::{
     AttemptLocalParseRecovery, CommaRecoveryMode, ForceCollect, Parser, RecoverColon, RecoverComma,
@@ -606,29 +610,22 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
             Limit(0) => Limit(2),
             limit => limit * 2,
         };
-        self.cx
+
-            .struct_span_err(
+        self.cx.emit_err(RecursionLimitReached {
-                expn_data.call_site,
+            span: expn_data.call_site,
-                &format!("recursion limit reached while expanding `{}`", expn_data.kind.descr()),
+            descr: expn_data.kind.descr(),
-            )
+            suggested_limit,
-            .help(&format!(
+            crate_name: &self.cx.ecfg.crate_name,
-                "consider increasing the recursion limit by adding a \
+        });
-                 `#![recursion_limit = \"{}\"]` attribute to your crate (`{}`)",
+
-                suggested_limit, self.cx.ecfg.crate_name,
-            ))
-            .emit();
         self.cx.trace_macros_diag();
     }
 
     /// A macro's expansion does not fit in this fragment kind.
     /// For example, a non-type macro in a type position.
     fn error_wrong_fragment_kind(&mut self, kind: AstFragmentKind, mac: &ast::MacCall, span: Span) {
-        let msg = format!(
+        self.cx.emit_err(WrongFragmentKind { span, kind: kind.name(), name: &mac.path });
-            "non-{kind} macro in {kind} position: {path}",
+
-            kind = kind.name(),
-            path = pprust::path_to_string(&mac.path),
-        );
-        self.cx.span_err(span, &msg);
         self.cx.trace_macros_diag();
     }
 
@@ -707,7 +704,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                     };
                     let attr_item = attr.unwrap_normal_item();
                     if let AttrArgs::Eq(..) = attr_item.args {
-                        self.cx.span_err(span, "key-value macro attributes are not supported");
+                        self.cx.emit_err(UnsupportedKeyValue { span });
                     }
                     let inner_tokens = attr_item.args.inner_tokens();
                     let Ok(tok_result) = expander.expand(self.cx, span, inner_tokens, tokens) else {
@@ -729,9 +726,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                                 }
                             };
                             if fragment_kind == AstFragmentKind::Expr && items.is_empty() {
-                                let msg =
+                                self.cx.emit_err(RemoveExprNotSupported { span });
-                                    "removing an expression is not supported in this position";
-                                self.cx.span_err(span, msg);
                                 fragment_kind.dummy(span)
                             } else {
                                 fragment_kind.expect_from_annotatables(items)
@@ -939,38 +934,32 @@ pub fn parse_ast_fragment<'a>(
 }
 
 pub fn ensure_complete_parse<'a>(
-    this: &mut Parser<'a>,
+    parser: &mut Parser<'a>,
     macro_path: &ast::Path,
     kind_name: &str,
     span: Span,
 ) {
-    if this.token != token::Eof {
+    if parser.token != token::Eof {
-        let token = pprust::token_to_string(&this.token);
+        let token = pprust::token_to_string(&parser.token);
-        let msg = format!("macro expansion ignores token `{}` and any following", token);
         // Avoid emitting backtrace info twice.
-        let def_site_span = this.token.span.with_ctxt(SyntaxContext::root());
+        let def_site_span = parser.token.span.with_ctxt(SyntaxContext::root());
-        let mut err = this.struct_span_err(def_site_span, &msg);
-        err.span_label(span, "caused by the macro expansion here");
-        let msg = format!(
-            "the usage of `{}!` is likely invalid in {} context",
-            pprust::path_to_string(macro_path),
-            kind_name,
-        );
-        err.note(&msg);
 
-        let semi_span = this.sess.source_map().next_point(span);
+        let semi_span = parser.sess.source_map().next_point(span);
-        match this.sess.source_map().span_to_snippet(semi_span) {
+        let add_semicolon = match parser.sess.source_map().span_to_snippet(semi_span) {
             Ok(ref snippet) if &snippet[..] != ";" && kind_name == "expression" => {
-                err.span_suggestion(
+                Some(span.shrink_to_hi())
-                    span.shrink_to_hi(),
-                    "you might be missing a semicolon here",
-                    ";",
-                    Applicability::MaybeIncorrect,
-                );
             }
-            _ => {}
+            _ => None,
-        }
+        };
-        err.emit();
+
+        parser.sess.emit_err(IncompleteParse {
+            span: def_site_span,
+            token,
+            label_span: span,
+            macro_path,
+            kind_name,
+            add_semicolon,
+        });
     }
 }
 
@@ -1766,9 +1755,8 @@ impl<'a, 'b> InvocationCollector<'a, 'b> {
                         if self.expand_cfg_true(node, attr, pos) {
                             continue;
                         }
-                        let msg =
+
-                            format!("removing {} is not supported in this position", Node::descr());
+                        self.cx.emit_err(RemoveNodeNotSupported { span, descr: Node::descr() });
-                        self.cx.span_err(span, &msg);
                         continue;
                     }
                     sym::cfg_attr => {

compiler/rustc_expand/src/lib.rs

@@ -10,6 +10,7 @@
 #![feature(rustc_attrs)]
 #![feature(try_blocks)]
 #![recursion_limit = "256"]
+#![deny(rustc::untranslatable_diagnostic)]
 
 #[macro_use]
 extern crate rustc_macros;
@@ -31,8 +32,13 @@ pub mod config;
 pub mod errors;
 pub mod expand;
 pub mod module;
+
+// FIXME(Nilstrieb) Translate proc_macro diagnostics
+#[allow(rustc::untranslatable_diagnostic)]
 pub mod proc_macro;
 
+// FIXME(Nilstrieb) Translate macro_rules diagnostics
+#[allow(rustc::untranslatable_diagnostic)]
 pub(crate) mod mbe;
 
 // HACK(Centril, #64197): These shouldn't really be here.

compiler/rustc_expand/src/module.rs

@@ -1,13 +1,17 @@
 use crate::base::ModuleData;
+use crate::errors::{
+    ModuleCircular, ModuleFileNotFound, ModuleInBlock, ModuleInBlockName, ModuleMultipleCandidates,
+};
 use rustc_ast::ptr::P;
 use rustc_ast::{token, AttrVec, Attribute, Inline, Item, ModSpans};
-use rustc_errors::{struct_span_err, DiagnosticBuilder, ErrorGuaranteed};
+use rustc_errors::{DiagnosticBuilder, ErrorGuaranteed};
 use rustc_parse::new_parser_from_file;
 use rustc_parse::validate_attr;
 use rustc_session::parse::ParseSess;
 use rustc_session::Session;
 use rustc_span::symbol::{sym, Ident};
 use rustc_span::Span;
+use std::iter::once;
 
 use std::path::{self, Path, PathBuf};
 
@@ -242,57 +246,41 @@ pub fn default_submod_path<'a>(
 
 impl ModError<'_> {
     fn report(self, sess: &Session, span: Span) -> ErrorGuaranteed {
-        let diag = &sess.parse_sess.span_diagnostic;
         match self {
             ModError::CircularInclusion(file_paths) => {
-                let mut msg = String::from("circular modules: ");
+                let path_to_string = |path: &PathBuf| path.display().to_string();
-                for file_path in &file_paths {
+
-                    msg.push_str(&file_path.display().to_string());
+                let paths = file_paths
-                    msg.push_str(" -> ");
+                    .iter()
-                }
+                    .map(path_to_string)
-                msg.push_str(&file_paths[0].display().to_string());
+                    .chain(once(path_to_string(&file_paths[0])))
-                diag.struct_span_err(span, &msg)
+                    .collect::<Vec<_>>();
+
+                let modules = paths.join(" -> ");
+
+                sess.emit_err(ModuleCircular { span, modules })
             }
-            ModError::ModInBlock(ident) => {
+            ModError::ModInBlock(ident) => sess.emit_err(ModuleInBlock {
-                let msg = "cannot declare a non-inline module inside a block unless it has a path attribute";
+                span,
-                let mut err = diag.struct_span_err(span, msg);
+                name: ident.map(|name| ModuleInBlockName { span, name }),
-                if let Some(ident) = ident {
+            }),
-                    let note =
+            ModError::FileNotFound(name, default_path, secondary_path) => {
-                        format!("maybe `use` the module `{}` instead of redeclaring it", ident);
+                sess.emit_err(ModuleFileNotFound {
-                    err.span_note(span, &note);
-                }
-                err
-            }
-            ModError::FileNotFound(ident, default_path, secondary_path) => {
-                let mut err = struct_span_err!(
-                    diag,
                     span,
-                    E0583,
+                    name,
-                    "file not found for module `{}`",
+                    default_path: default_path.display().to_string(),
-                    ident,
+                    secondary_path: secondary_path.display().to_string(),
-                );
+                })
-                err.help(&format!(
-                    "to create the module `{}`, create file \"{}\" or \"{}\"",
-                    ident,
-                    default_path.display(),
-                    secondary_path.display(),
-                ));
-                err
             }
-            ModError::MultipleCandidates(ident, default_path, secondary_path) => {
+            ModError::MultipleCandidates(name, default_path, secondary_path) => {
-                let mut err = struct_span_err!(
+                sess.emit_err(ModuleMultipleCandidates {
-                    diag,
                     span,
-                    E0761,
+                    name,
-                    "file for module `{}` found at both \"{}\" and \"{}\"",
+                    default_path: default_path.display().to_string(),
-                    ident,
+                    secondary_path: secondary_path.display().to_string(),
-                    default_path.display(),
+                })
-                    secondary_path.display(),
-                );
-                err.help("delete or rename one of them to remove the ambiguity");
-                err
             }
-            ModError::ParserError(err) => err,
+            ModError::ParserError(mut err) => err.emit(),
-        }.emit()
+        }
     }
 }

compiler/rustc_expand/src/tests.rs

@@ -154,6 +154,7 @@ fn test_harness(file_text: &str, span_labels: Vec<SpanLabel>, expected_output: &
             false,
         );
         let handler = Handler::with_emitter(true, None, Box::new(emitter));
+        #[allow(rustc::untranslatable_diagnostic)]
         handler.span_err(msp, "foo");
 
         assert!(

src/test/rustdoc-ui/doc-cfg.stderr

@@ -2,7 +2,7 @@ error: `cfg` predicate is not specified
   --> $DIR/doc-cfg.rs:3:7
    |
 LL | #[doc(cfg(), cfg(foo, bar))]
-   |       ^^^^^
+   |       ^^^^^ help: expected syntax is: `cfg(/* predicate */)`
 
 error: multiple `cfg` predicates are specified
   --> $DIR/doc-cfg.rs:3:23
@@ -14,7 +14,7 @@ error: `cfg` predicate is not specified
   --> $DIR/doc-cfg.rs:7:7
    |
 LL | #[doc(cfg())]
-   |       ^^^^^
+   |       ^^^^^ help: expected syntax is: `cfg(/* predicate */)`
 
 error: multiple `cfg` predicates are specified
   --> $DIR/doc-cfg.rs:8:16

src/test/ui/conditional-compilation/cfg-attr-syntax-validation.stderr

@@ -14,7 +14,7 @@ error: `cfg` predicate is not specified
   --> $DIR/cfg-attr-syntax-validation.rs:7:1
    |
 LL | #[cfg()]
-   | ^^^^^^^^
+   | ^^^^^^^^ help: expected syntax is: `cfg(/* predicate */)`
 
 error: multiple `cfg` predicates are specified
   --> $DIR/cfg-attr-syntax-validation.rs:10:10

src/test/ui/macros/macro-in-expression-context.stderr

@@ -5,11 +5,13 @@ LL |         assert_eq!("B", "B");
    |         ^^^^^^^^^
 ...
 LL |     foo!()
-   |     ------- help: you might be missing a semicolon here: `;`
+   |     ------ caused by the macro expansion here
-   |     |
-   |     caused by the macro expansion here
    |
    = note: the usage of `foo!` is likely invalid in expression context
+help: you might be missing a semicolon here
+   |
+LL |     foo!();
+   |           +
 
 warning: trailing semicolon in macro used in expression position
   --> $DIR/macro-in-expression-context.rs:5:29

src/test/ui/proc-macro/attr-invalid-exprs.stderr

@@ -8,21 +8,25 @@ error: macro expansion ignores token `,` and any following
   --> $DIR/attr-invalid-exprs.rs:15:13
    |
 LL |     let _ = #[duplicate] "Hello, world!";
-   |             ^^^^^^^^^^^^- help: you might be missing a semicolon here: `;`
+   |             ^^^^^^^^^^^^ caused by the macro expansion here
-   |             |
-   |             caused by the macro expansion here
    |
    = note: the usage of `duplicate!` is likely invalid in expression context
+help: you might be missing a semicolon here
+   |
+LL |     let _ = #[duplicate]; "Hello, world!";
+   |                         +
 
 error: macro expansion ignores token `,` and any following
   --> $DIR/attr-invalid-exprs.rs:24:9
    |
 LL |         #[duplicate]
-   |         ^^^^^^^^^^^^- help: you might be missing a semicolon here: `;`
+   |         ^^^^^^^^^^^^ caused by the macro expansion here
-   |         |
-   |         caused by the macro expansion here
    |
    = note: the usage of `duplicate!` is likely invalid in expression context
+help: you might be missing a semicolon here
+   |
+LL |         #[duplicate];
+   |                     +
 
 error: aborting due to 3 previous errors
 

src/test/ui/proc-macro/attribute.rs

@@ -53,19 +53,19 @@ pub fn foo11(input: TokenStream) -> TokenStream { input }
 pub fn foo12(input: TokenStream) -> TokenStream { input }
 
 #[proc_macro_derive(d13, attributes("a"))]
-//~^ ERROR: not a meta item
+//~^ ERROR: attribute must be a meta item, not a literal
 pub fn foo13(input: TokenStream) -> TokenStream { input }
 
 #[proc_macro_derive(d14, attributes(a = ""))]
-//~^ ERROR: must only be one word
+//~^ ERROR: attribute must only be a single word
 pub fn foo14(input: TokenStream) -> TokenStream { input }
 
 #[proc_macro_derive(d15, attributes(m::a))]
-//~^ ERROR: must only be one word
+//~^ ERROR: attribute must only be a single word
 pub fn foo15(input: TokenStream) -> TokenStream { input }
 
 #[proc_macro_derive(d16, attributes(a(b)))]
-//~^ ERROR: must only be one word
+//~^ ERROR: attribute must only be a single word
 pub fn foo16(input: TokenStream) -> TokenStream { input }
 
 #[proc_macro_derive(d17, attributes(self))]

src/test/ui/proc-macro/attribute.stderr

@@ -70,25 +70,25 @@ error: attribute must be of form: `attributes(foo, bar)`
 LL | #[proc_macro_derive(d12, attributes)]
    |                          ^^^^^^^^^^
 
-error: not a meta item
+error: attribute must be a meta item, not a literal
   --> $DIR/attribute.rs:55:37
    |
 LL | #[proc_macro_derive(d13, attributes("a"))]
    |                                     ^^^
 
-error: must only be one word
+error: attribute must only be a single word
   --> $DIR/attribute.rs:59:37
    |
 LL | #[proc_macro_derive(d14, attributes(a = ""))]
    |                                     ^^^^^^
 
-error: must only be one word
+error: attribute must only be a single word
   --> $DIR/attribute.rs:63:37
    |
 LL | #[proc_macro_derive(d15, attributes(m::a))]
    |                                     ^^^^
 
-error: must only be one word
+error: attribute must only be a single word
   --> $DIR/attribute.rs:67:37
    |
 LL | #[proc_macro_derive(d16, attributes(a(b)))]

src/test/ui/proc-macro/expand-expr.stderr

@@ -26,21 +26,25 @@ error: macro expansion ignores token `hello` and any following
   --> $DIR/expand-expr.rs:115:47
    |
 LL | expand_expr_is!("string", echo_tts!("string"; hello));
-   |                           --------------------^^^^^-- help: you might be missing a semicolon here: `;`
+   |                           --------------------^^^^^- caused by the macro expansion here
-   |                           |
-   |                           caused by the macro expansion here
    |
    = note: the usage of `echo_tts!` is likely invalid in expression context
+help: you might be missing a semicolon here
+   |
+LL | expand_expr_is!("string", echo_tts!("string"; hello););
+   |                                                     +
 
 error: macro expansion ignores token `;` and any following
   --> $DIR/expand-expr.rs:116:44
    |
 LL | expand_expr_is!("string", echo_pm!("string"; hello));
-   |                           -----------------^-------- help: you might be missing a semicolon here: `;`
+   |                           -----------------^------- caused by the macro expansion here
-   |                           |
-   |                           caused by the macro expansion here
    |
    = note: the usage of `echo_pm!` is likely invalid in expression context
+help: you might be missing a semicolon here
+   |
+LL | expand_expr_is!("string", echo_pm!("string"; hello););
+   |                                                    +
 
 error: recursion limit reached while expanding `recursive_expand!`
   --> $DIR/expand-expr.rs:124:16