Adding upstream version 1.66.0+dfsg1.upstream/1.66.0+dfsg1

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

4 files changed, 564 insertions, 232 deletions

diff --git a/compiler/rustc_attr/Cargo.toml b/compiler/rustc_attr/Cargo.toml
index ba310a686..6349ddf31 100644
--- a/compiler/rustc_attr/Cargo.toml
+++ b/compiler/rustc_attr/Cargo.toml
@@ -4,7 +4,6 @@ version = "0.0.0"
 edition = "2021"
 
 [lib]
-doctest = false
 
 [dependencies]
 rustc_ast_pretty = { path = "../rustc_ast_pretty" }
diff --git a/compiler/rustc_attr/src/builtin.rs b/compiler/rustc_attr/src/builtin.rs
index 10a9cfb62..753f62dd5 100644
--- a/compiler/rustc_attr/src/builtin.rs
+++ b/compiler/rustc_attr/src/builtin.rs
@@ -3,7 +3,6 @@
 use rustc_ast as ast;
 use rustc_ast::{Attribute, Lit, LitKind, MetaItem, MetaItemKind, NestedMetaItem, NodeId};
 use rustc_ast_pretty::pprust;
-use rustc_errors::{struct_span_err, Applicability};
 use rustc_feature::{find_gated_cfg, is_builtin_attr_name, Features, GatedCfg};
 use rustc_macros::HashStable_Generic;
 use rustc_session::lint::builtin::UNEXPECTED_CFGS;
@@ -14,6 +13,20 @@ use rustc_span::hygiene::Transparency;
 use rustc_span::{symbol::sym, symbol::Symbol, Span};
 use std::num::NonZeroU32;
 
+use crate::session_diagnostics::{self, IncorrectReprFormatGenericCause};
+
+/// The version placeholder that recently stabilized features contain inside the
+/// `since` field of the `#[stable]` attribute.
+///
+/// For more, see [this pull request](https://github.com/rust-lang/rust/pull/100591).
+pub const VERSION_PLACEHOLDER: &str = "CURRENT_RUSTC_VERSION";
+
+pub fn rust_version_symbol() -> Symbol {
+    let version = option_env!("CFG_VERSION").unwrap_or("<current>");
+    let version = version.split(' ').next().unwrap();
+    Symbol::intern(&version)
+}
+
 pub fn is_builtin_attr(attr: &Attribute) -> bool {
     attr.is_doc_comment() || attr.ident().filter(|ident| is_builtin_attr_name(ident.name)).is_some()
 }
@@ -25,46 +38,43 @@ enum AttrError {
     NonIdentFeature,
     MissingFeature,
     MultipleStabilityLevels,
-    UnsupportedLiteral(&'static str, /* is_bytestr */ bool),
+    UnsupportedLiteral(UnsupportedLiteralReason, /* is_bytestr */ bool),
+}
+
+pub(crate) enum UnsupportedLiteralReason {
+    Generic,
+    CfgString,
+    DeprecatedString,
+    DeprecatedKvPair,
 }
 
 fn handle_errors(sess: &ParseSess, span: Span, error: AttrError) {
-    let diag = &sess.span_diagnostic;
     match error {
         AttrError::MultipleItem(item) => {
-            struct_span_err!(diag, span, E0538, "multiple '{}' items", item).emit();
+            sess.emit_err(session_diagnostics::MultipleItem { span, item });
         }
         AttrError::UnknownMetaItem(item, expected) => {
-            let expected = expected.iter().map(|name| format!("`{}`", name)).collect::<Vec<_>>();
-            struct_span_err!(diag, span, E0541, "unknown meta item '{}'", item)
-                .span_label(span, format!("expected one of {}", expected.join(", ")))
-                .emit();
+            sess.emit_err(session_diagnostics::UnknownMetaItem { span, item, expected });
         }
         AttrError::MissingSince => {
-            struct_span_err!(diag, span, E0542, "missing 'since'").emit();
+            sess.emit_err(session_diagnostics::MissingSince { span });
         }
         AttrError::NonIdentFeature => {
-            struct_span_err!(diag, span, E0546, "'feature' is not an identifier").emit();
+            sess.emit_err(session_diagnostics::NonIdentFeature { span });
         }
         AttrError::MissingFeature => {
-            struct_span_err!(diag, span, E0546, "missing 'feature'").emit();
+            sess.emit_err(session_diagnostics::MissingFeature { span });
         }
         AttrError::MultipleStabilityLevels => {
-            struct_span_err!(diag, span, E0544, "multiple stability levels").emit();
+            sess.emit_err(session_diagnostics::MultipleStabilityLevels { span });
         }
-        AttrError::UnsupportedLiteral(msg, is_bytestr) => {
-            let mut err = struct_span_err!(diag, span, E0565, "{}", msg);
-            if is_bytestr {
-                if let Ok(lint_str) = sess.source_map().span_to_snippet(span) {
-                    err.span_suggestion(
-                        span,
-                        "consider removing the prefix",
-                        &lint_str[1..],
-                        Applicability::MaybeIncorrect,
-                    );
-                }
-            }
-            err.emit();
+        AttrError::UnsupportedLiteral(reason, is_bytestr) => {
+            sess.emit_err(session_diagnostics::UnsupportedLiteral {
+                span,
+                reason,
+                is_bytestr,
+                start_point_span: sess.source_map().start_point(span),
+            });
         }
     }
 }
@@ -131,6 +141,14 @@ impl ConstStability {
     }
 }
 
+/// Represents the `#[rustc_default_body_unstable]` attribute.
+#[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, Hash)]
+#[derive(HashStable_Generic)]
+pub struct DefaultBodyStability {
+    pub level: StabilityLevel,
+    pub feature: Symbol,
+}
+
 /// The available stability levels.
 #[derive(Encodable, Decodable, PartialEq, Copy, Clone, Debug, Eq, Hash)]
 #[derive(HashStable_Generic)]
@@ -214,7 +232,8 @@ pub fn find_stability(
     sess: &Session,
     attrs: &[Attribute],
     item_sp: Span,
-) -> (Option<(Stability, Span)>, Option<(ConstStability, Span)>) {
+) -> (Option<(Stability, Span)>, Option<(ConstStability, Span)>, Option<(DefaultBodyStability, Span)>)
+{
     find_stability_generic(sess, attrs.iter(), item_sp)
 }
 
@@ -222,7 +241,7 @@ fn find_stability_generic<'a, I>(
     sess: &Session,
     attrs_iter: I,
     item_sp: Span,
-) -> (Option<(Stability, Span)>, Option<(ConstStability, Span)>)
+) -> (Option<(Stability, Span)>, Option<(ConstStability, Span)>, Option<(DefaultBodyStability, Span)>)
 where
     I: Iterator<Item = &'a Attribute>,
 {
@@ -230,11 +249,10 @@ where
 
     let mut stab: Option<(Stability, Span)> = None;
     let mut const_stab: Option<(ConstStability, Span)> = None;
+    let mut body_stab: Option<(DefaultBodyStability, Span)> = None;
     let mut promotable = false;
     let mut allowed_through_unstable_modules = false;
 
-    let diagnostic = &sess.parse_sess.span_diagnostic;
-
     'outer: for attr in attrs_iter {
         if ![
             sym::rustc_const_unstable,
@@ -243,6 +261,7 @@ where
             sym::stable,
             sym::rustc_promotable,
             sym::rustc_allowed_through_unstable_modules,
+            sym::rustc_default_body_unstable,
         ]
         .iter()
         .any(|&s| attr.has_name(s))
@@ -273,14 +292,14 @@ where
                     *item = Some(v);
                     true
                 } else {
-                    struct_span_err!(diagnostic, meta.span, E0539, "incorrect meta item").emit();
+                    sess.emit_err(session_diagnostics::IncorrectMetaItem { span: meta.span });
                     false
                 }
             };
 
             let meta_name = meta.name_or_empty();
             match meta_name {
-                sym::rustc_const_unstable | sym::unstable => {
+                sym::rustc_const_unstable | sym::rustc_default_body_unstable | sym::unstable => {
                     if meta_name == sym::unstable && stab.is_some() {
                         handle_errors(
                             &sess.parse_sess,
@@ -295,6 +314,13 @@ where
                             AttrError::MultipleStabilityLevels,
                         );
                         break;
+                    } else if meta_name == sym::rustc_default_body_unstable && body_stab.is_some() {
+                        handle_errors(
+                            &sess.parse_sess,
+                            attr.span,
+                            AttrError::MultipleStabilityLevels,
+                        );
+                        break;
                     }
 
                     let mut feature = None;
@@ -308,7 +334,7 @@ where
                             handle_errors(
                                 &sess.parse_sess,
                                 meta.span(),
-                                AttrError::UnsupportedLiteral("unsupported literal", false),
+                                AttrError::UnsupportedLiteral(UnsupportedLiteralReason::Generic, false),
                             );
                             continue 'outer;
                         };
@@ -332,39 +358,28 @@ where
                                 // is a name/value pair string literal.
                                 issue_num = match issue.unwrap().as_str() {
                                     "none" => None,
-                                    issue => {
-                                        let emit_diag = |msg: &str| {
-                                            struct_span_err!(
-                                                diagnostic,
-                                                mi.span,
-                                                E0545,
-                                                "`issue` must be a non-zero numeric string \
-                                                or \"none\"",
-                                            )
-                                            .span_label(mi.name_value_literal_span().unwrap(), msg)
-                                            .emit();
-                                        };
-                                        match issue.parse() {
-                                            Ok(0) => {
-                                                emit_diag(
-                                                    "`issue` must not be \"0\", \
-                                                    use \"none\" instead",
-                                                );
-                                                continue 'outer;
-                                            }
-                                            Ok(num) => NonZeroU32::new(num),
-                                            Err(err) => {
-                                                emit_diag(&err.to_string());
-                                                continue 'outer;
-                                            }
+                                    issue => match issue.parse::<NonZeroU32>() {
+                                        Ok(num) => Some(num),
+                                        Err(err) => {
+                                            sess.emit_err(
+                                                session_diagnostics::InvalidIssueString {
+                                                    span: mi.span,
+                                                    cause: session_diagnostics::InvalidIssueStringCause::from_int_error_kind(
+                                                        mi.name_value_literal_span().unwrap(),
+                                                        err.kind(),
+                                                    ),
+                                                },
+                                            );
+                                            continue 'outer;
                                         }
-                                    }
+                                    },
                                 };
                             }
                             sym::soft => {
                                 if !mi.is_word() {
-                                    let msg = "`soft` should not have any arguments";
-                                    sess.parse_sess.span_diagnostic.span_err(mi.span, msg);
+                                    sess.emit_err(session_diagnostics::SoftNoArgs {
+                                        span: mi.span,
+                                    });
                                 }
                                 is_soft = true;
                             }
@@ -405,11 +420,16 @@ where
                             };
                             if sym::unstable == meta_name {
                                 stab = Some((Stability { level, feature }, attr.span));
-                            } else {
+                            } else if sym::rustc_const_unstable == meta_name {
                                 const_stab = Some((
                                     ConstStability { level, feature, promotable: false },
                                     attr.span,
                                 ));
+                            } else if sym::rustc_default_body_unstable == meta_name {
+                                body_stab =
+                                    Some((DefaultBodyStability { level, feature }, attr.span));
+                            } else {
+                                unreachable!("Unknown stability attribute {meta_name}");
                             }
                         }
                         (None, _, _) => {
@@ -417,8 +437,7 @@ where
                             continue;
                         }
                         _ => {
-                            struct_span_err!(diagnostic, attr.span, E0547, "missing 'issue'")
-                                .emit();
+                            sess.emit_err(session_diagnostics::MissingIssue { span: attr.span });
                             continue;
                         }
                     }
@@ -471,13 +490,20 @@ where
                                 handle_errors(
                                     &sess.parse_sess,
                                     lit.span,
-                                    AttrError::UnsupportedLiteral("unsupported literal", false),
+                                    AttrError::UnsupportedLiteral(
+                                        UnsupportedLiteralReason::Generic,
+                                        false,
+                                    ),
                                 );
                                 continue 'outer;
                             }
                         }
                     }
 
+                    if let Some(s) = since && s.as_str() == VERSION_PLACEHOLDER {
+                        since = Some(rust_version_symbol());
+                    }
+
                     match (feature, since) {
                         (Some(feature), Some(since)) => {
                             let level = Stable { since, allowed_through_unstable_modules: false };
@@ -510,14 +536,7 @@ where
         if let Some((ref mut stab, _)) = const_stab {
             stab.promotable = promotable;
         } else {
-            struct_span_err!(
-                diagnostic,
-                item_sp,
-                E0717,
-                "`rustc_promotable` attribute must be paired with either a `rustc_const_unstable` \
-                or a `rustc_const_stable` attribute"
-            )
-            .emit();
+            sess.emit_err(session_diagnostics::RustcPromotablePairing { span: item_sp });
         }
     }
 
@@ -532,17 +551,11 @@ where
         {
             *allowed_through_unstable_modules = true;
         } else {
-            struct_span_err!(
-                diagnostic,
-                item_sp,
-                E0789,
-                "`rustc_allowed_through_unstable_modules` attribute must be paired with a `stable` attribute"
-            )
-            .emit();
+            sess.emit_err(session_diagnostics::RustcAllowedUnstablePairing { span: item_sp });
         }
     }
 
-    (stab, const_stab)
+    (stab, const_stab, body_stab)
 }
 
 pub fn find_crate_name(sess: &Session, attrs: &[Attribute]) -> Option<Symbol> {
@@ -652,25 +665,18 @@ pub fn eval_condition(
                     NestedMetaItem::Literal(Lit { span, .. })
                     | NestedMetaItem::MetaItem(MetaItem { span, .. }),
                 ] => {
-                    sess.span_diagnostic
-                        .struct_span_err(*span, "expected a version literal")
-                        .emit();
+                    sess.emit_err(session_diagnostics::ExpectedVersionLiteral { span: *span });
                     return false;
                 }
                 [..] => {
-                    sess.span_diagnostic
-                        .struct_span_err(cfg.span, "expected single version literal")
-                        .emit();
+                    sess.emit_err(session_diagnostics::ExpectedSingleVersionLiteral {
+                        span: cfg.span,
+                    });
                     return false;
                 }
             };
             let Some(min_version) = parse_version(min_version.as_str(), false) else {
-                sess.span_diagnostic
-                    .struct_span_warn(
-                        *span,
-                        "unknown version literal format, assuming it refers to a future version",
-                    )
-                    .emit();
+                sess.emit_warning(session_diagnostics::UnknownVersionLiteral { span: *span });
                 return false;
             };
             let rustc_version = parse_version(env!("CFG_RELEASE"), true).unwrap();
@@ -688,7 +694,7 @@ pub fn eval_condition(
                     handle_errors(
                         sess,
                         mi.span(),
-                        AttrError::UnsupportedLiteral("unsupported literal", false),
+                        AttrError::UnsupportedLiteral(UnsupportedLiteralReason::Generic, false),
                     );
                     return false;
                 }
@@ -713,13 +719,9 @@ pub fn eval_condition(
                     }),
                 sym::not => {
                     if mis.len() != 1 {
-                        struct_span_err!(
-                            sess.span_diagnostic,
-                            cfg.span,
-                            E0536,
-                            "expected 1 cfg-pattern"
-                        )
-                        .emit();
+                        sess.emit_err(session_diagnostics::ExpectedOneCfgPattern {
+                            span: cfg.span,
+                        });
                         return false;
                     }
 
@@ -745,21 +747,16 @@ pub fn eval_condition(
                     })
                 }
                 _ => {
-                    struct_span_err!(
-                        sess.span_diagnostic,
-                        cfg.span,
-                        E0537,
-                        "invalid predicate `{}`",
-                        pprust::path_to_string(&cfg.path)
-                    )
-                    .emit();
+                    sess.emit_err(session_diagnostics::InvalidPredicate {
+                        span: cfg.span,
+                        predicate: pprust::path_to_string(&cfg.path),
+                    });
                     false
                 }
             }
         }
         ast::MetaItemKind::Word | MetaItemKind::NameValue(..) if cfg.path.segments.len() != 1 => {
-            sess.span_diagnostic
-                .span_err(cfg.path.span, "`cfg` predicate key must be an identifier");
+            sess.emit_err(session_diagnostics::CfgPredicateIdentifier { span: cfg.path.span });
             true
         }
         MetaItemKind::NameValue(ref lit) if !lit.kind.is_str() => {
@@ -767,7 +764,7 @@ pub fn eval_condition(
                 sess,
                 lit.span,
                 AttrError::UnsupportedLiteral(
-                    "literal in `cfg` predicate value must be a string",
+                    UnsupportedLiteralReason::CfgString,
                     lit.kind.is_bytestr(),
                 ),
             );
@@ -811,7 +808,6 @@ where
     I: Iterator<Item = &'a Attribute>,
 {
     let mut depr: Option<(Deprecation, Span)> = None;
-    let diagnostic = &sess.parse_sess.span_diagnostic;
     let is_rustc = sess.features_untracked().staged_api;
 
     'outer: for attr in attrs_iter {
@@ -847,14 +843,14 @@ where
                                 &sess.parse_sess,
                                 lit.span,
                                 AttrError::UnsupportedLiteral(
-                                    "literal in `deprecated` \
-                                    value must be a string",
+                                    UnsupportedLiteralReason::DeprecatedString,
                                     lit.kind.is_bytestr(),
                                 ),
                             );
                         } else {
-                            struct_span_err!(diagnostic, meta.span, E0551, "incorrect meta item")
-                                .emit();
+                            sess.emit_err(session_diagnostics::IncorrectMetaItem2 {
+                                span: meta.span,
+                            });
                         }
 
                         false
@@ -876,14 +872,11 @@ where
                             }
                             sym::suggestion => {
                                 if !sess.features_untracked().deprecated_suggestion {
-                                    let mut diag = sess.struct_span_err(
-                                        mi.span,
-                                        "suggestions on deprecated items are unstable",
-                                    );
-                                    if sess.is_nightly_build() {
-                                        diag.help("add `#![feature(deprecated_suggestion)]` to the crate root");
-                                    }
-                                    diag.note("see #94785 for more details").emit();
+                                    sess.emit_err(session_diagnostics::DeprecatedItemSuggestion {
+                                        span: mi.span,
+                                        is_nightly: sess.is_nightly_build().then_some(()),
+                                        details: (),
+                                    });
                                 }
 
                                 if !get(mi, &mut suggestion) {
@@ -911,7 +904,7 @@ where
                                 &sess.parse_sess,
                                 lit.span,
                                 AttrError::UnsupportedLiteral(
-                                    "item in `deprecated` must be a key/value pair",
+                                    UnsupportedLiteralReason::DeprecatedKvPair,
                                     false,
                                 ),
                             );
@@ -929,7 +922,7 @@ where
             }
 
             if note.is_none() {
-                struct_span_err!(diagnostic, attr.span, E0543, "missing 'note'").emit();
+                sess.emit_err(session_diagnostics::MissingNote { span: attr.span });
                 continue;
             }
         }
@@ -999,19 +992,9 @@ pub fn parse_repr_attr(sess: &Session, attr: &Attribute) -> Vec<ReprAttr> {
                     sym::simd => Some(ReprSimd),
                     sym::transparent => Some(ReprTransparent),
                     sym::align => {
-                        let mut err = struct_span_err!(
-                            diagnostic,
-                            item.span(),
-                            E0589,
-                            "invalid `repr(align)` attribute: `align` needs an argument"
-                        );
-                        err.span_suggestion(
-                            item.span(),
-                            "supply an argument here",
-                            "align(...)",
-                            Applicability::HasPlaceholders,
-                        );
-                        err.emit();
+                        sess.emit_err(session_diagnostics::InvalidReprAlignNeedArg {
+                            span: item.span(),
+                        });
                         recognised = true;
                         None
                     }
@@ -1040,109 +1023,64 @@ pub fn parse_repr_attr(sess: &Session, attr: &Attribute) -> Vec<ReprAttr> {
                     || int_type_of_word(name).is_some()
                 {
                     recognised = true;
-                    struct_span_err!(
-                                diagnostic,
-                                item.span(),
-                                E0552,
-                                "invalid representation hint: `{}` does not take a parenthesized argument list",
-                                name.to_ident_string(),
-                            ).emit();
+                    sess.emit_err(session_diagnostics::InvalidReprHintNoParen {
+                        span: item.span(),
+                        name: name.to_ident_string(),
+                    });
                 }
                 if let Some(literal_error) = literal_error {
-                    struct_span_err!(
-                        diagnostic,
-                        item.span(),
-                        E0589,
-                        "invalid `repr({})` attribute: {}",
-                        name.to_ident_string(),
-                        literal_error
-                    )
-                    .emit();
+                    sess.emit_err(session_diagnostics::InvalidReprGeneric {
+                        span: item.span(),
+                        repr_arg: name.to_ident_string(),
+                        error_part: literal_error,
+                    });
                 }
             } else if let Some(meta_item) = item.meta_item() {
                 if let MetaItemKind::NameValue(ref value) = meta_item.kind {
                     if meta_item.has_name(sym::align) || meta_item.has_name(sym::packed) {
                         let name = meta_item.name_or_empty().to_ident_string();
                         recognised = true;
-                        let mut err = struct_span_err!(
-                            diagnostic,
-                            item.span(),
-                            E0693,
-                            "incorrect `repr({})` attribute format",
-                            name,
-                        );
-                        match value.kind {
-                            ast::LitKind::Int(int, ast::LitIntType::Unsuffixed) => {
-                                err.span_suggestion(
-                                    item.span(),
-                                    "use parentheses instead",
-                                    format!("{}({})", name, int),
-                                    Applicability::MachineApplicable,
-                                );
-                            }
-                            ast::LitKind::Str(s, _) => {
-                                err.span_suggestion(
-                                    item.span(),
-                                    "use parentheses instead",
-                                    format!("{}({})", name, s),
-                                    Applicability::MachineApplicable,
-                                );
-                            }
-                            _ => {}
-                        }
-                        err.emit();
-                    } else {
-                        if matches!(
-                            meta_item.name_or_empty(),
-                            sym::C | sym::simd | sym::transparent
-                        ) || int_type_of_word(meta_item.name_or_empty()).is_some()
-                        {
-                            recognised = true;
-                            struct_span_err!(
-                                diagnostic,
-                                meta_item.span,
-                                E0552,
-                                "invalid representation hint: `{}` does not take a value",
-                                meta_item.name_or_empty().to_ident_string(),
-                            )
-                            .emit();
-                        }
+                        sess.emit_err(session_diagnostics::IncorrectReprFormatGeneric {
+                            span: item.span(),
+                            repr_arg: &name,
+                            cause: IncorrectReprFormatGenericCause::from_lit_kind(
+                                item.span(),
+                                &value.kind,
+                                &name,
+                            ),
+                        });
+                    } else if matches!(
+                        meta_item.name_or_empty(),
+                        sym::C | sym::simd | sym::transparent
+                    ) || int_type_of_word(meta_item.name_or_empty()).is_some()
+                    {
+                        recognised = true;
+                        sess.emit_err(session_diagnostics::InvalidReprHintNoValue {
+                            span: meta_item.span,
+                            name: meta_item.name_or_empty().to_ident_string(),
+                        });
                     }
                 } else if let MetaItemKind::List(_) = meta_item.kind {
                     if meta_item.has_name(sym::align) {
                         recognised = true;
-                        struct_span_err!(
-                            diagnostic,
-                            meta_item.span,
-                            E0693,
-                            "incorrect `repr(align)` attribute format: \
-                                 `align` takes exactly one argument in parentheses"
-                        )
-                        .emit();
+                        sess.emit_err(session_diagnostics::IncorrectReprFormatAlignOneArg {
+                            span: meta_item.span,
+                        });
                     } else if meta_item.has_name(sym::packed) {
                         recognised = true;
-                        struct_span_err!(
-                            diagnostic,
-                            meta_item.span,
-                            E0552,
-                            "incorrect `repr(packed)` attribute format: \
-                                 `packed` takes exactly one parenthesized argument, \
-                                 or no parentheses at all"
-                        )
-                        .emit();
+                        sess.emit_err(session_diagnostics::IncorrectReprFormatPackedOneOrZeroArg {
+                            span: meta_item.span,
+                        });
                     } else if matches!(
                         meta_item.name_or_empty(),
                         sym::C | sym::simd | sym::transparent
                     ) || int_type_of_word(meta_item.name_or_empty()).is_some()
                     {
                         recognised = true;
-                        struct_span_err!(
-                                diagnostic,
-                                meta_item.span,
-                                E0552,
-                                "invalid representation hint: `{}` does not take a parenthesized argument list",
-                                meta_item.name_or_empty().to_ident_string(),
-                            ).emit();
+                        sess.emit_err(session_diagnostics::InvalidReprHintNoParen {
+                            span: meta_item.span,
+                            name: meta_item.name_or_empty().to_ident_string(),
+                        });
                     }
                 }
             }
@@ -1239,10 +1177,10 @@ fn allow_unstable<'a>(
     let list = attrs
         .filter_map(move |attr| {
             attr.meta_item_list().or_else(|| {
-                sess.diagnostic().span_err(
-                    attr.span,
-                    &format!("`{}` expects a list of feature names", symbol.to_ident_string()),
-                );
+                sess.emit_err(session_diagnostics::ExpectsFeatureList {
+                    span: attr.span,
+                    name: symbol.to_ident_string(),
+                });
                 None
             })
         })
@@ -1251,10 +1189,10 @@ fn allow_unstable<'a>(
     list.into_iter().filter_map(move |it| {
         let name = it.ident().map(|ident| ident.name);
         if name.is_none() {
-            sess.diagnostic().span_err(
-                it.span(),
-                &format!("`{}` expects feature names", symbol.to_ident_string()),
-            );
+            sess.emit_err(session_diagnostics::ExpectsFeatures {
+                span: it.span(),
+                name: symbol.to_ident_string(),
+            });
         }
         name
     })
diff --git a/compiler/rustc_attr/src/lib.rs b/compiler/rustc_attr/src/lib.rs
index c3f9f0cf3..4580ffcc6 100644
--- a/compiler/rustc_attr/src/lib.rs
+++ b/compiler/rustc_attr/src/lib.rs
@@ -5,12 +5,14 @@
 //! to this crate.
 
 #![feature(let_chains)]
-#![feature(let_else)]
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 
 #[macro_use]
 extern crate rustc_macros;
 
 mod builtin;
+mod session_diagnostics;
 
 pub use builtin::*;
 pub use IntType::*;
diff --git a/compiler/rustc_attr/src/session_diagnostics.rs b/compiler/rustc_attr/src/session_diagnostics.rs
new file mode 100644
index 000000000..edccfa1c8
--- /dev/null
+++ b/compiler/rustc_attr/src/session_diagnostics.rs
@@ -0,0 +1,393 @@
+use std::num::IntErrorKind;
+
+use rustc_ast as ast;
+use rustc_errors::{
+    error_code, fluent, Applicability, DiagnosticBuilder, ErrorGuaranteed, Handler, IntoDiagnostic,
+};
+use rustc_macros::Diagnostic;
+use rustc_span::{Span, Symbol};
+
+use crate::UnsupportedLiteralReason;
+
+#[derive(Diagnostic)]
+#[diag(attr_expected_one_cfg_pattern, code = "E0536")]
+pub(crate) struct ExpectedOneCfgPattern {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_invalid_predicate, code = "E0537")]
+pub(crate) struct InvalidPredicate {
+    #[primary_span]
+    pub span: Span,
+
+    pub predicate: String,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_multiple_item, code = "E0538")]
+pub(crate) struct MultipleItem {
+    #[primary_span]
+    pub span: Span,
+
+    pub item: String,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_incorrect_meta_item, code = "E0539")]
+pub(crate) struct IncorrectMetaItem {
+    #[primary_span]
+    pub span: Span,
+}
+
+// Error code: E0541
+pub(crate) struct UnknownMetaItem<'a> {
+    pub span: Span,
+    pub item: String,
+    pub expected: &'a [&'a str],
+}
+
+// Manual implementation to be able to format `expected` items correctly.
+impl<'a> IntoDiagnostic<'a> for UnknownMetaItem<'_> {
+    fn into_diagnostic(self, handler: &'a Handler) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
+        let expected = self.expected.iter().map(|name| format!("`{}`", name)).collect::<Vec<_>>();
+        let mut diag = handler.struct_span_err_with_code(
+            self.span,
+            fluent::attr_unknown_meta_item,
+            error_code!(E0541),
+        );
+        diag.set_arg("item", self.item);
+        diag.set_arg("expected", expected.join(", "));
+        diag.span_label(self.span, fluent::label);
+        diag
+    }
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_missing_since, code = "E0542")]
+pub(crate) struct MissingSince {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_missing_note, code = "E0543")]
+pub(crate) struct MissingNote {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_multiple_stability_levels, code = "E0544")]
+pub(crate) struct MultipleStabilityLevels {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_invalid_issue_string, code = "E0545")]
+pub(crate) struct InvalidIssueString {
+    #[primary_span]
+    pub span: Span,
+
+    #[subdiagnostic]
+    pub cause: Option<InvalidIssueStringCause>,
+}
+
+// The error kinds of `IntErrorKind` are duplicated here in order to allow the messages to be
+// translatable.
+#[derive(Subdiagnostic)]
+pub(crate) enum InvalidIssueStringCause {
+    #[label(must_not_be_zero)]
+    MustNotBeZero {
+        #[primary_span]
+        span: Span,
+    },
+
+    #[label(empty)]
+    Empty {
+        #[primary_span]
+        span: Span,
+    },
+
+    #[label(invalid_digit)]
+    InvalidDigit {
+        #[primary_span]
+        span: Span,
+    },
+
+    #[label(pos_overflow)]
+    PosOverflow {
+        #[primary_span]
+        span: Span,
+    },
+
+    #[label(neg_overflow)]
+    NegOverflow {
+        #[primary_span]
+        span: Span,
+    },
+}
+
+impl InvalidIssueStringCause {
+    pub fn from_int_error_kind(span: Span, kind: &IntErrorKind) -> Option<Self> {
+        match kind {
+            IntErrorKind::Empty => Some(Self::Empty { span }),
+            IntErrorKind::InvalidDigit => Some(Self::InvalidDigit { span }),
+            IntErrorKind::PosOverflow => Some(Self::PosOverflow { span }),
+            IntErrorKind::NegOverflow => Some(Self::NegOverflow { span }),
+            IntErrorKind::Zero => Some(Self::MustNotBeZero { span }),
+            _ => None,
+        }
+    }
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_missing_feature, code = "E0546")]
+pub(crate) struct MissingFeature {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_non_ident_feature, code = "E0546")]
+pub(crate) struct NonIdentFeature {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_missing_issue, code = "E0547")]
+pub(crate) struct MissingIssue {
+    #[primary_span]
+    pub span: Span,
+}
+
+// FIXME: This diagnostic is identical to `IncorrectMetaItem`, barring the error code. Consider
+// changing this to `IncorrectMetaItem`. See #51489.
+#[derive(Diagnostic)]
+#[diag(attr_incorrect_meta_item, code = "E0551")]
+pub(crate) struct IncorrectMetaItem2 {
+    #[primary_span]
+    pub span: Span,
+}
+
+// FIXME: Why is this the same error code as `InvalidReprHintNoParen` and `InvalidReprHintNoValue`?
+// It is more similar to `IncorrectReprFormatGeneric`.
+#[derive(Diagnostic)]
+#[diag(attr_incorrect_repr_format_packed_one_or_zero_arg, code = "E0552")]
+pub(crate) struct IncorrectReprFormatPackedOneOrZeroArg {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_invalid_repr_hint_no_paren, code = "E0552")]
+pub(crate) struct InvalidReprHintNoParen {
+    #[primary_span]
+    pub span: Span,
+
+    pub name: String,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_invalid_repr_hint_no_value, code = "E0552")]
+pub(crate) struct InvalidReprHintNoValue {
+    #[primary_span]
+    pub span: Span,
+
+    pub name: String,
+}
+
+// Error code: E0565
+pub(crate) struct UnsupportedLiteral {
+    pub span: Span,
+    pub reason: UnsupportedLiteralReason,
+    pub is_bytestr: bool,
+    pub start_point_span: Span,
+}
+
+impl<'a> IntoDiagnostic<'a> for UnsupportedLiteral {
+    fn into_diagnostic(self, handler: &'a Handler) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
+        let mut diag = handler.struct_span_err_with_code(
+            self.span,
+            match self.reason {
+                UnsupportedLiteralReason::Generic => fluent::attr_unsupported_literal_generic,
+                UnsupportedLiteralReason::CfgString => fluent::attr_unsupported_literal_cfg_string,
+                UnsupportedLiteralReason::DeprecatedString => {
+                    fluent::attr_unsupported_literal_deprecated_string
+                }
+                UnsupportedLiteralReason::DeprecatedKvPair => {
+                    fluent::attr_unsupported_literal_deprecated_kv_pair
+                }
+            },
+            error_code!(E0565),
+        );
+        if self.is_bytestr {
+            diag.span_suggestion(
+                self.start_point_span,
+                fluent::attr_unsupported_literal_suggestion,
+                "",
+                Applicability::MaybeIncorrect,
+            );
+        }
+        diag
+    }
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_invalid_repr_align_need_arg, code = "E0589")]
+pub(crate) struct InvalidReprAlignNeedArg {
+    #[primary_span]
+    #[suggestion(code = "align(...)", applicability = "has-placeholders")]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_invalid_repr_generic, code = "E0589")]
+pub(crate) struct InvalidReprGeneric<'a> {
+    #[primary_span]
+    pub span: Span,
+
+    pub repr_arg: String,
+    pub error_part: &'a str,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_incorrect_repr_format_align_one_arg, code = "E0693")]
+pub(crate) struct IncorrectReprFormatAlignOneArg {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_incorrect_repr_format_generic, code = "E0693")]
+pub(crate) struct IncorrectReprFormatGeneric<'a> {
+    #[primary_span]
+    pub span: Span,
+
+    pub repr_arg: &'a str,
+
+    #[subdiagnostic]
+    pub cause: Option<IncorrectReprFormatGenericCause<'a>>,
+}
+
+#[derive(Subdiagnostic)]
+pub(crate) enum IncorrectReprFormatGenericCause<'a> {
+    #[suggestion(suggestion, code = "{name}({int})", applicability = "machine-applicable")]
+    Int {
+        #[primary_span]
+        span: Span,
+
+        #[skip_arg]
+        name: &'a str,
+
+        #[skip_arg]
+        int: u128,
+    },
+
+    #[suggestion(suggestion, code = "{name}({symbol})", applicability = "machine-applicable")]
+    Symbol {
+        #[primary_span]
+        span: Span,
+
+        #[skip_arg]
+        name: &'a str,
+
+        #[skip_arg]
+        symbol: Symbol,
+    },
+}
+
+impl<'a> IncorrectReprFormatGenericCause<'a> {
+    pub fn from_lit_kind(span: Span, kind: &ast::LitKind, name: &'a str) -> Option<Self> {
+        match kind {
+            ast::LitKind::Int(int, ast::LitIntType::Unsuffixed) => {
+                Some(Self::Int { span, name, int: *int })
+            }
+            ast::LitKind::Str(symbol, _) => Some(Self::Symbol { span, name, symbol: *symbol }),
+            _ => None,
+        }
+    }
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_rustc_promotable_pairing, code = "E0717")]
+pub(crate) struct RustcPromotablePairing {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_rustc_allowed_unstable_pairing, code = "E0789")]
+pub(crate) struct RustcAllowedUnstablePairing {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_cfg_predicate_identifier)]
+pub(crate) struct CfgPredicateIdentifier {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_deprecated_item_suggestion)]
+pub(crate) struct DeprecatedItemSuggestion {
+    #[primary_span]
+    pub span: Span,
+
+    #[help]
+    pub is_nightly: Option<()>,
+
+    #[note]
+    pub details: (),
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_expected_single_version_literal)]
+pub(crate) struct ExpectedSingleVersionLiteral {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_expected_version_literal)]
+pub(crate) struct ExpectedVersionLiteral {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_expects_feature_list)]
+pub(crate) struct ExpectsFeatureList {
+    #[primary_span]
+    pub span: Span,
+
+    pub name: String,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_expects_features)]
+pub(crate) struct ExpectsFeatures {
+    #[primary_span]
+    pub span: Span,
+
+    pub name: String,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_soft_no_args)]
+pub(crate) struct SoftNoArgs {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_unknown_version_literal)]
+pub(crate) struct UnknownVersionLiteral {
+    #[primary_span]
+    pub span: Span,
+}