From 3e3e70d529d8c7d7c4d7bc4fefc9f109393b9245 Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Wed, 17 Apr 2024 14:19:43 +0200
Subject: Merging upstream version 1.69.0+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 compiler/rustc_expand/src/base.rs             | 62 ++++++++++++----------
 compiler/rustc_expand/src/build.rs            | 74 +++++++++++++++++----------
 compiler/rustc_expand/src/config.rs           | 13 +++--
 compiler/rustc_expand/src/errors.rs           | 43 +++++++++++++---
 compiler/rustc_expand/src/lib.rs              |  5 ++
 compiler/rustc_expand/src/mbe/macro_parser.rs |  2 +-
 compiler/rustc_expand/src/mbe/macro_rules.rs  | 30 +++++++----
 compiler/rustc_expand/src/mbe/metavar_expr.rs | 12 ++---
 compiler/rustc_expand/src/mbe/transcribe.rs   |  2 +-
 compiler/rustc_expand/src/module.rs           |  4 +-
 compiler/rustc_expand/src/parse/tests.rs      |  5 +-
 compiler/rustc_expand/src/proc_macro.rs       | 14 ++---
 compiler/rustc_expand/src/tests.rs            | 20 +++++---
 13 files changed, 184 insertions(+), 102 deletions(-)

(limited to 'compiler/rustc_expand/src')

diff --git a/compiler/rustc_expand/src/base.rs b/compiler/rustc_expand/src/base.rs
index 951d59246..22bc90f5c 100644
--- a/compiler/rustc_expand/src/base.rs
+++ b/compiler/rustc_expand/src/base.rs
@@ -1,15 +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::errors;
 use crate::expand::{self, AstFragment, Invocation};
 use crate::module::DirOwnership;
 
 use rustc_ast::attr::MarkedAttrs;
+use rustc_ast::mut_visit::DummyAstNode;
 use rustc_ast::ptr::P;
 use rustc_ast::token::{self, Nonterminal};
 use rustc_ast::tokenstream::TokenStream;
@@ -33,10 +29,11 @@ use rustc_span::source_map::SourceMap;
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::{BytePos, FileName, Span, DUMMY_SP};
 use smallvec::{smallvec, SmallVec};
-
+use std::default::Default;
 use std::iter;
 use std::path::{Path, PathBuf};
 use std::rc::Rc;
+use thin_vec::ThinVec;
 
 pub(crate) use rustc_span::hygiene::MacroKind;
 
@@ -558,7 +555,7 @@ impl DummyResult {
     pub fn raw_expr(sp: Span, is_error: bool) -> P<ast::Expr> {
         P(ast::Expr {
             id: ast::DUMMY_NODE_ID,
-            kind: if is_error { ast::ExprKind::Err } else { ast::ExprKind::Tup(Vec::new()) },
+            kind: if is_error { ast::ExprKind::Err } else { ast::ExprKind::Tup(ThinVec::new()) },
             span: sp,
             attrs: ast::AttrVec::new(),
             tokens: None,
@@ -574,7 +571,7 @@ impl DummyResult {
     pub fn raw_ty(sp: Span, is_error: bool) -> P<ast::Ty> {
         P(ast::Ty {
             id: ast::DUMMY_NODE_ID,
-            kind: if is_error { ast::TyKind::Err } else { ast::TyKind::Tup(Vec::new()) },
+            kind: if is_error { ast::TyKind::Err } else { ast::TyKind::Tup(ThinVec::new()) },
             span: sp,
             tokens: None,
         })
@@ -645,6 +642,10 @@ impl MacResult for DummyResult {
     fn make_variants(self: Box<DummyResult>) -> Option<SmallVec<[ast::Variant; 1]>> {
         Some(SmallVec::new())
     }
+
+    fn make_crate(self: Box<DummyResult>) -> Option<ast::Crate> {
+        Some(DummyAstNode::dummy())
+    }
 }
 
 /// A syntax extension kind.
@@ -796,13 +797,13 @@ 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.emit_err(MacroConstStability {
+            sess.emit_err(errors::MacroConstStability {
                 span: sp,
                 head_span: sess.source_map().guess_head_span(span),
             });
         }
         if let Some((_, sp)) = body_stability {
-            sess.emit_err(MacroBodyStability {
+            sess.emit_err(errors::MacroBodyStability {
                 span: sp,
                 head_span: sess.source_map().guess_head_span(span),
             });
@@ -1142,8 +1143,8 @@ impl<'a> ExtCtxt<'a> {
         self.sess.parse_sess.span_diagnostic.span_bug(sp, msg);
     }
     pub fn trace_macros_diag(&mut self) {
-        for (sp, notes) in self.expansions.iter() {
-            let mut db = self.sess.parse_sess.span_diagnostic.span_note_diag(*sp, "trace_macro");
+        for (span, notes) in self.expansions.iter() {
+            let mut db = self.sess.parse_sess.create_note(errors::TraceMacro { span: *span });
             for note in notes {
                 db.note(note);
             }
@@ -1197,7 +1198,7 @@ pub fn resolve_path(
                 .expect("attempting to resolve a file path in an external file"),
             FileName::DocTest(path, _) => path,
             other => {
-                return Err(ResolveRelativePath {
+                return Err(errors::ResolveRelativePath {
                     span,
                     path: parse_sess.source_map().filename_for_diagnostics(&other).to_string(),
                 }
@@ -1279,7 +1280,7 @@ pub fn expr_to_string(
 /// done as rarely as possible).
 pub fn check_zero_tts(cx: &ExtCtxt<'_>, span: Span, tts: TokenStream, name: &str) {
     if !tts.is_empty() {
-        cx.emit_err(TakesNoArguments { span, name });
+        cx.emit_err(errors::TakesNoArguments { span, name });
     }
 }
 
@@ -1307,14 +1308,14 @@ pub fn get_single_str_from_tts(
 ) -> Option<Symbol> {
     let mut p = cx.new_parser_from_tts(tts);
     if p.token == token::Eof {
-        cx.emit_err(OnlyOneArgument { span, name });
+        cx.emit_err(errors::OnlyOneArgument { span, name });
         return None;
     }
     let ret = parse_expr(&mut p)?;
     let _ = p.eat(&token::Comma);
 
     if p.token != token::Eof {
-        cx.emit_err(OnlyOneArgument { span, name });
+        cx.emit_err(errors::OnlyOneArgument { span, name });
     }
     expr_to_string(cx, ret, "argument must be a string literal").map(|(s, _)| s)
 }
@@ -1336,7 +1337,7 @@ pub fn get_exprs_from_tts(cx: &mut ExtCtxt<'_>, tts: TokenStream) -> Option<Vec<
             continue;
         }
         if p.token != token::Eof {
-            cx.emit_err(ExpectedCommaInList { span: p.token.span });
+            cx.emit_err(errors::ExpectedCommaInList { span: p.token.span });
             return None;
         }
     }
@@ -1353,51 +1354,58 @@ pub fn parse_macro_name_and_helper_attrs(
     // `#[proc_macro_derive(Foo, attributes(A, ..))]`
     let list = attr.meta_item_list()?;
     if list.len() != 1 && list.len() != 2 {
-        diag.emit_err(AttrNoArguments { span: attr.span });
+        diag.emit_err(errors::AttrNoArguments { span: attr.span });
         return None;
     }
     let Some(trait_attr) = list[0].meta_item() else {
-        diag.emit_err(NotAMetaItem {span: list[0].span()});
+        diag.emit_err(errors::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.emit_err(OnlyOneWord { span: trait_attr.span });
+            diag.emit_err(errors::OnlyOneWord { span: trait_attr.span });
             return None;
         }
     };
 
     if !trait_ident.name.can_be_raw() {
-        diag.emit_err(CannotBeNameOfMacro { span: trait_attr.span, trait_ident, macro_type });
+        diag.emit_err(errors::CannotBeNameOfMacro {
+            span: trait_attr.span,
+            trait_ident,
+            macro_type,
+        });
     }
 
     let attributes_attr = list.get(1);
     let proc_attrs: Vec<_> = if let Some(attr) = attributes_attr {
         if !attr.has_name(sym::attributes) {
-            diag.emit_err(ArgumentNotAttributes { span: attr.span() });
+            diag.emit_err(errors::ArgumentNotAttributes { span: attr.span() });
         }
         attr.meta_item_list()
             .unwrap_or_else(|| {
-                diag.emit_err(AttributesWrongForm { span: attr.span() });
+                diag.emit_err(errors::AttributesWrongForm { span: attr.span() });
                 &[]
             })
             .iter()
             .filter_map(|attr| {
                 let Some(attr) = attr.meta_item() else {
-                    diag.emit_err(AttributeMetaItem { span: attr.span() });
+                    diag.emit_err(errors::AttributeMetaItem { span: attr.span() });
                     return None;
                 };
 
                 let ident = match attr.ident() {
                     Some(ident) if attr.is_word() => ident,
                     _ => {
-                        diag.emit_err(AttributeSingleWord { span: attr.span });
+                        diag.emit_err(errors::AttributeSingleWord { span: attr.span });
                         return None;
                     }
                 };
                 if !ident.name.can_be_raw() {
-                    diag.emit_err(HelperAttributeNameInvalid { span: attr.span, name: ident });
+                    diag.emit_err(errors::HelperAttributeNameInvalid {
+                        span: attr.span,
+                        name: ident,
+                    });
                 }
 
                 Some(ident.name)
diff --git a/compiler/rustc_expand/src/build.rs b/compiler/rustc_expand/src/build.rs
index 9b16e79d4..8a78c3296 100644
--- a/compiler/rustc_expand/src/build.rs
+++ b/compiler/rustc_expand/src/build.rs
@@ -5,7 +5,7 @@ use rustc_ast::{attr, token, util::literal};
 use rustc_span::source_map::Spanned;
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::Span;
-use thin_vec::ThinVec;
+use thin_vec::{thin_vec, ThinVec};
 
 impl<'a> ExtCtxt<'a> {
     pub fn path(&self, span: Span, strs: Vec<Ident>) -> ast::Path {
@@ -125,16 +125,20 @@ impl<'a> ExtCtxt<'a> {
 
     pub fn poly_trait_ref(&self, span: Span, path: ast::Path) -> ast::PolyTraitRef {
         ast::PolyTraitRef {
-            bound_generic_params: Vec::new(),
+            bound_generic_params: ThinVec::new(),
             trait_ref: self.trait_ref(path),
             span,
         }
     }
 
-    pub fn trait_bound(&self, path: ast::Path) -> ast::GenericBound {
+    pub fn trait_bound(&self, path: ast::Path, is_const: bool) -> ast::GenericBound {
         ast::GenericBound::Trait(
             self.poly_trait_ref(path.span, path),
-            ast::TraitBoundModifier::None,
+            if is_const {
+                ast::TraitBoundModifier::MaybeConst
+            } else {
+                ast::TraitBoundModifier::None
+            },
         )
     }
 
@@ -217,14 +221,14 @@ impl<'a> ExtCtxt<'a> {
     pub fn block_expr(&self, expr: P<ast::Expr>) -> P<ast::Block> {
         self.block(
             expr.span,
-            vec![ast::Stmt {
+            thin_vec![ast::Stmt {
                 id: ast::DUMMY_NODE_ID,
                 span: expr.span,
                 kind: ast::StmtKind::Expr(expr),
             }],
         )
     }
-    pub fn block(&self, span: Span, stmts: Vec<ast::Stmt>) -> P<ast::Block> {
+    pub fn block(&self, span: Span, stmts: ThinVec<ast::Stmt>) -> P<ast::Block> {
         P(ast::Block {
             stmts,
             id: ast::DUMMY_NODE_ID,
@@ -272,22 +276,31 @@ impl<'a> ExtCtxt<'a> {
         self.expr(sp, ast::ExprKind::AddrOf(ast::BorrowKind::Ref, ast::Mutability::Not, e))
     }
 
+    pub fn expr_paren(&self, sp: Span, e: P<ast::Expr>) -> P<ast::Expr> {
+        self.expr(sp, ast::ExprKind::Paren(e))
+    }
+
     pub fn expr_call(
         &self,
         span: Span,
         expr: P<ast::Expr>,
-        args: Vec<P<ast::Expr>>,
+        args: ThinVec<P<ast::Expr>>,
     ) -> P<ast::Expr> {
         self.expr(span, ast::ExprKind::Call(expr, args))
     }
-    pub fn expr_call_ident(&self, span: Span, id: Ident, args: Vec<P<ast::Expr>>) -> P<ast::Expr> {
+    pub fn expr_call_ident(
+        &self,
+        span: Span,
+        id: Ident,
+        args: ThinVec<P<ast::Expr>>,
+    ) -> P<ast::Expr> {
         self.expr(span, ast::ExprKind::Call(self.expr_ident(span, id), args))
     }
     pub fn expr_call_global(
         &self,
         sp: Span,
         fn_path: Vec<Ident>,
-        args: Vec<P<ast::Expr>>,
+        args: ThinVec<P<ast::Expr>>,
     ) -> P<ast::Expr> {
         let pathexpr = self.expr_path(self.path_global(sp, fn_path));
         self.expr_call(sp, pathexpr, args)
@@ -310,7 +323,7 @@ impl<'a> ExtCtxt<'a> {
         &self,
         span: Span,
         path: ast::Path,
-        fields: Vec<ast::ExprField>,
+        fields: ThinVec<ast::ExprField>,
     ) -> P<ast::Expr> {
         self.expr(
             span,
@@ -326,7 +339,7 @@ impl<'a> ExtCtxt<'a> {
         &self,
         span: Span,
         id: Ident,
-        fields: Vec<ast::ExprField>,
+        fields: ThinVec<ast::ExprField>,
     ) -> P<ast::Expr> {
         self.expr_struct(span, self.path_ident(span, id), fields)
     }
@@ -364,12 +377,12 @@ impl<'a> ExtCtxt<'a> {
     }
 
     /// `[expr1, expr2, ...]`
-    pub fn expr_array(&self, sp: Span, exprs: Vec<P<ast::Expr>>) -> P<ast::Expr> {
+    pub fn expr_array(&self, sp: Span, exprs: ThinVec<P<ast::Expr>>) -> P<ast::Expr> {
         self.expr(sp, ast::ExprKind::Array(exprs))
     }
 
     /// `&[expr1, expr2, ...]`
-    pub fn expr_array_ref(&self, sp: Span, exprs: Vec<P<ast::Expr>>) -> P<ast::Expr> {
+    pub fn expr_array_ref(&self, sp: Span, exprs: ThinVec<P<ast::Expr>>) -> P<ast::Expr> {
         self.expr_addr_of(sp, self.expr_array(sp, exprs))
     }
 
@@ -379,14 +392,14 @@ impl<'a> ExtCtxt<'a> {
 
     pub fn expr_some(&self, sp: Span, expr: P<ast::Expr>) -> P<ast::Expr> {
         let some = self.std_path(&[sym::option, sym::Option, sym::Some]);
-        self.expr_call_global(sp, some, vec![expr])
+        self.expr_call_global(sp, some, thin_vec![expr])
     }
 
     pub fn expr_none(&self, sp: Span) -> P<ast::Expr> {
         let none = self.std_path(&[sym::option, sym::Option, sym::None]);
         self.expr_path(self.path_global(sp, none))
     }
-    pub fn expr_tuple(&self, sp: Span, exprs: Vec<P<ast::Expr>>) -> P<ast::Expr> {
+    pub fn expr_tuple(&self, sp: Span, exprs: ThinVec<P<ast::Expr>>) -> P<ast::Expr> {
         self.expr(sp, ast::ExprKind::Tup(exprs))
     }
 
@@ -394,7 +407,7 @@ impl<'a> ExtCtxt<'a> {
         self.expr_call_global(
             span,
             [sym::std, sym::rt, sym::begin_panic].iter().map(|s| Ident::new(*s, span)).collect(),
-            vec![self.expr_str(span, msg)],
+            thin_vec![self.expr_str(span, msg)],
         )
     }
 
@@ -404,7 +417,7 @@ impl<'a> ExtCtxt<'a> {
 
     pub fn expr_ok(&self, sp: Span, expr: P<ast::Expr>) -> P<ast::Expr> {
         let ok = self.std_path(&[sym::result, sym::Result, sym::Ok]);
-        self.expr_call_global(sp, ok, vec![expr])
+        self.expr_call_global(sp, ok, thin_vec![expr])
     }
 
     pub fn expr_try(&self, sp: Span, head: P<ast::Expr>) -> P<ast::Expr> {
@@ -418,12 +431,12 @@ impl<'a> ExtCtxt<'a> {
         let binding_expr = self.expr_ident(sp, binding_variable);
 
         // `Ok(__try_var)` pattern
-        let ok_pat = self.pat_tuple_struct(sp, ok_path, vec![binding_pat.clone()]);
+        let ok_pat = self.pat_tuple_struct(sp, ok_path, thin_vec![binding_pat.clone()]);
 
         // `Err(__try_var)` (pattern and expression respectively)
-        let err_pat = self.pat_tuple_struct(sp, err_path.clone(), vec![binding_pat]);
+        let err_pat = self.pat_tuple_struct(sp, err_path.clone(), thin_vec![binding_pat]);
         let err_inner_expr =
-            self.expr_call(sp, self.expr_path(err_path), vec![binding_expr.clone()]);
+            self.expr_call(sp, self.expr_path(err_path), thin_vec![binding_expr.clone()]);
         // `return Err(__try_var)`
         let err_expr = self.expr(sp, ast::ExprKind::Ret(Some(err_inner_expr)));
 
@@ -433,7 +446,7 @@ impl<'a> ExtCtxt<'a> {
         let err_arm = self.arm(sp, err_pat, err_expr);
 
         // `match head { Ok() => ..., Err() => ... }`
-        self.expr_match(sp, head, vec![ok_arm, err_arm])
+        self.expr_match(sp, head, thin_vec![ok_arm, err_arm])
     }
 
     pub fn pat(&self, span: Span, kind: PatKind) -> P<ast::Pat> {
@@ -465,7 +478,7 @@ impl<'a> ExtCtxt<'a> {
         &self,
         span: Span,
         path: ast::Path,
-        subpats: Vec<P<ast::Pat>>,
+        subpats: ThinVec<P<ast::Pat>>,
     ) -> P<ast::Pat> {
         self.pat(span, PatKind::TupleStruct(None, path, subpats))
     }
@@ -473,18 +486,18 @@ impl<'a> ExtCtxt<'a> {
         &self,
         span: Span,
         path: ast::Path,
-        field_pats: Vec<ast::PatField>,
+        field_pats: ThinVec<ast::PatField>,
     ) -> P<ast::Pat> {
         self.pat(span, PatKind::Struct(None, path, field_pats, false))
     }
-    pub fn pat_tuple(&self, span: Span, pats: Vec<P<ast::Pat>>) -> P<ast::Pat> {
+    pub fn pat_tuple(&self, span: Span, pats: ThinVec<P<ast::Pat>>) -> P<ast::Pat> {
         self.pat(span, PatKind::Tuple(pats))
     }
 
     pub fn pat_some(&self, span: Span, pat: P<ast::Pat>) -> P<ast::Pat> {
         let some = self.std_path(&[sym::option, sym::Option, sym::Some]);
         let path = self.path_global(span, some);
-        self.pat_tuple_struct(span, path, vec![pat])
+        self.pat_tuple_struct(span, path, thin_vec![pat])
     }
 
     pub fn arm(&self, span: Span, pat: P<ast::Pat>, expr: P<ast::Expr>) -> ast::Arm {
@@ -503,7 +516,7 @@ impl<'a> ExtCtxt<'a> {
         self.arm(span, self.pat_wild(span), self.expr_unreachable(span))
     }
 
-    pub fn expr_match(&self, span: Span, arg: P<ast::Expr>, arms: Vec<ast::Arm>) -> P<Expr> {
+    pub fn expr_match(&self, span: Span, arg: P<ast::Expr>, arms: ThinVec<ast::Arm>) -> P<Expr> {
         self.expr(span, ast::ExprKind::Match(arg, arms))
     }
 
@@ -554,7 +567,12 @@ impl<'a> ExtCtxt<'a> {
         self.lambda(span, vec![ident], body)
     }
 
-    pub fn lambda_stmts_1(&self, span: Span, stmts: Vec<ast::Stmt>, ident: Ident) -> P<ast::Expr> {
+    pub fn lambda_stmts_1(
+        &self,
+        span: Span,
+        stmts: ThinVec<ast::Stmt>,
+        ident: Ident,
+    ) -> P<ast::Expr> {
         self.lambda1(span, self.expr_block(self.block(span, stmts)), ident)
     }
 
@@ -571,7 +589,7 @@ impl<'a> ExtCtxt<'a> {
     }
 
     // `self` is unused but keep it as method for the convenience use.
-    pub fn fn_decl(&self, inputs: Vec<ast::Param>, output: ast::FnRetTy) -> P<ast::FnDecl> {
+    pub fn fn_decl(&self, inputs: ThinVec<ast::Param>, output: ast::FnRetTy) -> P<ast::FnDecl> {
         P(ast::FnDecl { inputs, output })
     }
 
diff --git a/compiler/rustc_expand/src/config.rs b/compiler/rustc_expand/src/config.rs
index 1fcbdfd9b..01500c2c7 100644
--- a/compiler/rustc_expand/src/config.rs
+++ b/compiler/rustc_expand/src/config.rs
@@ -24,6 +24,7 @@ use rustc_session::Session;
 use rustc_span::edition::{Edition, ALL_EDITIONS};
 use rustc_span::symbol::{sym, Symbol};
 use rustc_span::{Span, DUMMY_SP};
+use thin_vec::ThinVec;
 
 /// A folder that strips out items that do not belong in the current configuration.
 pub struct StripUnconfigured<'a> {
@@ -206,7 +207,7 @@ pub fn features(
         None => {
             // The entire crate is unconfigured.
             krate.attrs = ast::AttrVec::new();
-            krate.items = Vec::new();
+            krate.items = ThinVec::new();
             Features::default()
         }
         Some(attrs) => {
@@ -238,12 +239,10 @@ macro_rules! configure {
 impl<'a> StripUnconfigured<'a> {
     pub fn configure<T: HasAttrs + HasTokens>(&self, mut node: T) -> Option<T> {
         self.process_cfg_attrs(&mut node);
-        if self.in_cfg(node.attrs()) {
+        self.in_cfg(node.attrs()).then(|| {
             self.try_configure_tokens(&mut node);
-            Some(node)
-        } else {
-            None
-        }
+            node
+        })
     }
 
     fn try_configure_tokens<T: HasTokens>(&self, node: &mut T) {
@@ -257,7 +256,7 @@ impl<'a> StripUnconfigured<'a> {
 
     fn configure_krate_attrs(&self, mut attrs: ast::AttrVec) -> Option<ast::AttrVec> {
         attrs.flat_map_in_place(|attr| self.process_cfg_attr(attr));
-        if self.in_cfg(&attrs) { Some(attrs) } else { None }
+        self.in_cfg(&attrs).then_some(attrs)
     }
 
     /// Performs cfg-expansion on `stream`, producing a new `AttrTokenStream`.
diff --git a/compiler/rustc_expand/src/errors.rs b/compiler/rustc_expand/src/errors.rs
index afe5169d3..e5102a952 100644
--- a/compiler/rustc_expand/src/errors.rs
+++ b/compiler/rustc_expand/src/errors.rs
@@ -65,7 +65,7 @@ pub(crate) struct MacroConstStability {
     #[primary_span]
     #[label]
     pub span: Span,
-    #[label(label2)]
+    #[label(expand_label2)]
     pub head_span: Span,
 }
 
@@ -75,7 +75,7 @@ pub(crate) struct MacroBodyStability {
     #[primary_span]
     #[label]
     pub span: Span,
-    #[label(label2)]
+    #[label(expand_label2)]
     pub head_span: Span,
 }
 
@@ -188,7 +188,7 @@ pub(crate) struct FeatureRemoved<'a> {
 }
 
 #[derive(Subdiagnostic)]
-#[note(reason)]
+#[note(expand_reason)]
 pub(crate) struct FeatureRemovedReason<'a> {
     pub reason: &'a str,
 }
@@ -223,12 +223,12 @@ pub(crate) struct MalformedFeatureAttribute {
 
 #[derive(Subdiagnostic)]
 pub(crate) enum MalformedFeatureAttributeHelp {
-    #[label(expected)]
+    #[label(expand_expected)]
     Label {
         #[primary_span]
         span: Span,
     },
-    #[suggestion(expected, code = "{suggestion}", applicability = "maybe-incorrect")]
+    #[suggestion(expand_expected, code = "{suggestion}", applicability = "maybe-incorrect")]
     Suggestion {
         #[primary_span]
         span: Span,
@@ -306,7 +306,7 @@ pub(crate) struct IncompleteParse<'a> {
     pub kind_name: &'a str,
 
     #[suggestion(
-        suggestion_add_semi,
+        expand_suggestion_add_semi,
         style = "verbose",
         code = ";",
         applicability = "maybe-incorrect"
@@ -340,7 +340,7 @@ pub(crate) struct ModuleInBlock {
 }
 
 #[derive(Subdiagnostic)]
-#[note(note)]
+#[note(expand_note)]
 pub(crate) struct ModuleInBlockName {
     #[primary_span]
     pub span: Span,
@@ -368,3 +368,32 @@ pub(crate) struct ModuleMultipleCandidates {
     pub default_path: String,
     pub secondary_path: String,
 }
+
+#[derive(Diagnostic)]
+#[diag(expand_trace_macro)]
+pub struct TraceMacro {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(expand_proc_macro_panicked)]
+pub(crate) struct ProcMacroPanicked {
+    #[primary_span]
+    pub span: Span,
+    #[subdiagnostic]
+    pub message: Option<ProcMacroPanickedHelp>,
+}
+
+#[derive(Subdiagnostic)]
+#[help(expand_help)]
+pub(crate) struct ProcMacroPanickedHelp {
+    pub message: String,
+}
+
+#[derive(Diagnostic)]
+#[diag(expand_proc_macro_derive_tokens)]
+pub struct ProcMacroDeriveTokens {
+    #[primary_span]
+    pub span: Span,
+}
diff --git a/compiler/rustc_expand/src/lib.rs b/compiler/rustc_expand/src/lib.rs
index 897268566..634e206e5 100644
--- a/compiler/rustc_expand/src/lib.rs
+++ b/compiler/rustc_expand/src/lib.rs
@@ -20,6 +20,9 @@ extern crate tracing;
 
 extern crate proc_macro as pm;
 
+use rustc_errors::{DiagnosticMessage, SubdiagnosticMessage};
+use rustc_macros::fluent_messages;
+
 mod placeholders;
 mod proc_macro_server;
 
@@ -60,3 +63,5 @@ mod tokenstream {
 mod mut_visit {
     mod tests;
 }
+
+fluent_messages! { "../locales/en-US.ftl" }
diff --git a/compiler/rustc_expand/src/mbe/macro_parser.rs b/compiler/rustc_expand/src/mbe/macro_parser.rs
index 2e199541b..283e68a68 100644
--- a/compiler/rustc_expand/src/mbe/macro_parser.rs
+++ b/compiler/rustc_expand/src/mbe/macro_parser.rs
@@ -503,7 +503,7 @@ impl TtParser {
                         mp.push_match(metavar_idx, seq_depth, MatchedSeq(vec![]));
                     }
 
-                    if op == KleeneOp::ZeroOrMore || op == KleeneOp::ZeroOrOne {
+                    if matches!(op, KleeneOp::ZeroOrMore | KleeneOp::ZeroOrOne) {
                         // Try zero matches of this sequence, by skipping over it.
                         self.cur_mps.push(MatcherPos {
                             idx: idx_first_after,
diff --git a/compiler/rustc_expand/src/mbe/macro_rules.rs b/compiler/rustc_expand/src/mbe/macro_rules.rs
index 4ebd75f01..5679cdcbb 100644
--- a/compiler/rustc_expand/src/mbe/macro_rules.rs
+++ b/compiler/rustc_expand/src/mbe/macro_rules.rs
@@ -10,13 +10,12 @@ use crate::mbe::transcribe::transcribe;
 
 use rustc_ast as ast;
 use rustc_ast::token::{self, Delimiter, NonterminalKind, Token, TokenKind, TokenKind::*};
-use rustc_ast::tokenstream::{DelimSpan, TokenStream};
+use rustc_ast::tokenstream::{DelimSpan, TokenStream, TokenTree};
 use rustc_ast::{NodeId, DUMMY_NODE_ID};
 use rustc_ast_pretty::pprust;
 use rustc_attr::{self as attr, TransparencyError};
 use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
 use rustc_errors::{Applicability, ErrorGuaranteed};
-use rustc_feature::Features;
 use rustc_lint_defs::builtin::{
     RUST_2021_INCOMPATIBLE_OR_PATTERNS, SEMICOLON_IN_EXPRESSIONS_FROM_MACROS,
 };
@@ -212,7 +211,6 @@ fn expand_macro<'cx>(
             };
             let arm_span = rhses[i].span();
 
-            let rhs_spans = rhs.tts.iter().map(|t| t.span()).collect::<Vec<_>>();
             // rhs has holes ( `$id` and `$(...)` that need filled)
             let mut tts = match transcribe(cx, &named_matches, &rhs, rhs_span, transparency) {
                 Ok(tts) => tts,
@@ -224,12 +222,25 @@ fn expand_macro<'cx>(
 
             // Replace all the tokens for the corresponding positions in the macro, to maintain
             // proper positions in error reporting, while maintaining the macro_backtrace.
-            if rhs_spans.len() == tts.len() {
+            if tts.len() == rhs.tts.len() {
                 tts = tts.map_enumerated(|i, tt| {
                     let mut tt = tt.clone();
-                    let mut sp = rhs_spans[i];
-                    sp = sp.with_ctxt(tt.span().ctxt());
-                    tt.set_span(sp);
+                    let rhs_tt = &rhs.tts[i];
+                    let ctxt = tt.span().ctxt();
+                    match (&mut tt, rhs_tt) {
+                        // preserve the delim spans if able
+                        (
+                            TokenTree::Delimited(target_sp, ..),
+                            mbe::TokenTree::Delimited(source_sp, ..),
+                        ) => {
+                            target_sp.open = source_sp.open.with_ctxt(ctxt);
+                            target_sp.close = source_sp.close.with_ctxt(ctxt);
+                        }
+                        _ => {
+                            let sp = rhs_tt.span().with_ctxt(ctxt);
+                            tt.set_span(sp);
+                        }
+                    }
                     tt
                 });
             }
@@ -367,7 +378,6 @@ pub(super) fn try_match_macro<'matcher, T: Tracker<'matcher>>(
 /// Converts a macro item into a syntax extension.
 pub fn compile_declarative_macro(
     sess: &Session,
-    features: &Features,
     def: &ast::Item,
     edition: Edition,
 ) -> (SyntaxExtension, Vec<(usize, Span)>) {
@@ -496,7 +506,7 @@ pub fn compile_declarative_macro(
                         true,
                         &sess.parse_sess,
                         def.id,
-                        features,
+                        sess.features_untracked(),
                         edition,
                     )
                     .pop()
@@ -520,7 +530,7 @@ pub fn compile_declarative_macro(
                         false,
                         &sess.parse_sess,
                         def.id,
-                        features,
+                        sess.features_untracked(),
                         edition,
                     )
                     .pop()
diff --git a/compiler/rustc_expand/src/mbe/metavar_expr.rs b/compiler/rustc_expand/src/mbe/metavar_expr.rs
index 99fe47454..de34df011 100644
--- a/compiler/rustc_expand/src/mbe/metavar_expr.rs
+++ b/compiler/rustc_expand/src/mbe/metavar_expr.rs
@@ -1,5 +1,5 @@
 use rustc_ast::token::{self, Delimiter};
-use rustc_ast::tokenstream::{CursorRef, TokenStream, TokenTree};
+use rustc_ast::tokenstream::{RefTokenTreeCursor, TokenStream, TokenTree};
 use rustc_ast::{LitIntType, LitKind};
 use rustc_ast_pretty::pprust;
 use rustc_errors::{Applicability, PResult};
@@ -72,7 +72,7 @@ impl MetaVarExpr {
 
 // Checks if there are any remaining tokens. For example, `${ignore(ident ... a b c ...)}`
 fn check_trailing_token<'sess>(
-    iter: &mut CursorRef<'_>,
+    iter: &mut RefTokenTreeCursor<'_>,
     sess: &'sess ParseSess,
 ) -> PResult<'sess, ()> {
     if let Some(tt) = iter.next() {
@@ -88,7 +88,7 @@ fn check_trailing_token<'sess>(
 
 /// Parse a meta-variable `count` expression: `count(ident[, depth])`
 fn parse_count<'sess>(
-    iter: &mut CursorRef<'_>,
+    iter: &mut RefTokenTreeCursor<'_>,
     sess: &'sess ParseSess,
     span: Span,
 ) -> PResult<'sess, MetaVarExpr> {
@@ -99,7 +99,7 @@ fn parse_count<'sess>(
 
 /// Parses the depth used by index(depth) and length(depth).
 fn parse_depth<'sess>(
-    iter: &mut CursorRef<'_>,
+    iter: &mut RefTokenTreeCursor<'_>,
     sess: &'sess ParseSess,
     span: Span,
 ) -> PResult<'sess, usize> {
@@ -126,7 +126,7 @@ fn parse_depth<'sess>(
 
 /// Parses an generic ident
 fn parse_ident<'sess>(
-    iter: &mut CursorRef<'_>,
+    iter: &mut RefTokenTreeCursor<'_>,
     sess: &'sess ParseSess,
     span: Span,
 ) -> PResult<'sess, Ident> {
@@ -152,7 +152,7 @@ fn parse_ident<'sess>(
 
 /// Tries to move the iterator forward returning `true` if there is a comma. If not, then the
 /// iterator is not modified and the result is `false`.
-fn try_eat_comma(iter: &mut CursorRef<'_>) -> bool {
+fn try_eat_comma(iter: &mut RefTokenTreeCursor<'_>) -> bool {
     if let Some(TokenTree::Token(token::Token { kind: token::Comma, .. }, _)) = iter.look_ahead(0) {
         let _ = iter.next();
         return true;
diff --git a/compiler/rustc_expand/src/mbe/transcribe.rs b/compiler/rustc_expand/src/mbe/transcribe.rs
index b79835be7..47a8b4bc4 100644
--- a/compiler/rustc_expand/src/mbe/transcribe.rs
+++ b/compiler/rustc_expand/src/mbe/transcribe.rs
@@ -282,7 +282,7 @@ pub(super) fn transcribe<'a>(
             }
 
             // There should be no meta-var declarations in the invocation of a macro.
-            mbe::TokenTree::MetaVarDecl(..) => panic!("unexpected `TokenTree::MetaVarDecl"),
+            mbe::TokenTree::MetaVarDecl(..) => panic!("unexpected `TokenTree::MetaVarDecl`"),
         }
     }
 }
diff --git a/compiler/rustc_expand/src/module.rs b/compiler/rustc_expand/src/module.rs
index 07f47a9c3..3779af19e 100644
--- a/compiler/rustc_expand/src/module.rs
+++ b/compiler/rustc_expand/src/module.rs
@@ -12,8 +12,8 @@ use rustc_session::Session;
 use rustc_span::symbol::{sym, Ident};
 use rustc_span::Span;
 use std::iter::once;
-
 use std::path::{self, Path, PathBuf};
+use thin_vec::ThinVec;
 
 #[derive(Copy, Clone)]
 pub enum DirOwnership {
@@ -31,7 +31,7 @@ pub struct ModulePathSuccess {
 }
 
 pub(crate) struct ParsedExternalMod {
-    pub items: Vec<P<Item>>,
+    pub items: ThinVec<P<Item>>,
     pub spans: ModSpans,
     pub file_path: PathBuf,
     pub dir_path: PathBuf,
diff --git a/compiler/rustc_expand/src/parse/tests.rs b/compiler/rustc_expand/src/parse/tests.rs
index 0726d922c..8b37728b6 100644
--- a/compiler/rustc_expand/src/parse/tests.rs
+++ b/compiler/rustc_expand/src/parse/tests.rs
@@ -18,7 +18,10 @@ use rustc_span::{BytePos, FileName, Pos, Span};
 use std::path::PathBuf;
 
 fn sess() -> ParseSess {
-    ParseSess::new(FilePathMapping::empty())
+    ParseSess::new(
+        vec![crate::DEFAULT_LOCALE_RESOURCE, rustc_parse::DEFAULT_LOCALE_RESOURCE],
+        FilePathMapping::empty(),
+    )
 }
 
 /// Parses an item.
diff --git a/compiler/rustc_expand/src/proc_macro.rs b/compiler/rustc_expand/src/proc_macro.rs
index e9a691920..ddba14417 100644
--- a/compiler/rustc_expand/src/proc_macro.rs
+++ b/compiler/rustc_expand/src/proc_macro.rs
@@ -1,4 +1,5 @@
 use crate::base::{self, *};
+use crate::errors;
 use crate::proc_macro_server;
 
 use rustc_ast as ast;
@@ -60,11 +61,12 @@ impl base::BangProcMacro for BangProcMacro {
         let strategy = exec_strategy(ecx);
         let server = proc_macro_server::Rustc::new(ecx);
         self.client.run(&strategy, server, input, proc_macro_backtrace).map_err(|e| {
-            let mut err = ecx.struct_span_err(span, "proc macro panicked");
-            if let Some(s) = e.as_str() {
-                err.help(&format!("message: {}", s));
-            }
-            err.emit()
+            ecx.sess.emit_err(errors::ProcMacroPanicked {
+                span,
+                message: e
+                    .as_str()
+                    .map(|message| errors::ProcMacroPanickedHelp { message: message.into() }),
+            })
         })
     }
 }
@@ -174,7 +176,7 @@ impl MultiItemModifier for DeriveProcMacro {
 
         // fail if there have been errors emitted
         if ecx.sess.parse_sess.span_diagnostic.err_count() > error_count_before {
-            ecx.struct_span_err(span, "proc-macro derive produced unparseable tokens").emit();
+            ecx.sess.emit_err(errors::ProcMacroDeriveTokens { span });
         }
 
         ExpandResult::Ready(items)
diff --git a/compiler/rustc_expand/src/tests.rs b/compiler/rustc_expand/src/tests.rs
index 8f3bea29f..480d95b77 100644
--- a/compiler/rustc_expand/src/tests.rs
+++ b/compiler/rustc_expand/src/tests.rs
@@ -8,7 +8,7 @@ use rustc_span::{BytePos, Span};
 
 use rustc_data_structures::sync::Lrc;
 use rustc_errors::emitter::EmitterWriter;
-use rustc_errors::{Handler, MultiSpan, PResult};
+use rustc_errors::{Handler, MultiSpan, PResult, TerminalUrl};
 
 use std::io;
 use std::io::prelude::*;
@@ -34,18 +34,23 @@ where
 
 /// Maps a string to tts, using a made-up filename.
 pub(crate) fn string_to_stream(source_str: String) -> TokenStream {
-    let ps = ParseSess::new(FilePathMapping::empty());
+    let ps = ParseSess::new(
+        vec![crate::DEFAULT_LOCALE_RESOURCE, rustc_parse::DEFAULT_LOCALE_RESOURCE],
+        FilePathMapping::empty(),
+    );
     source_file_to_stream(
         &ps,
         ps.source_map().new_source_file(PathBuf::from("bogofile").into(), source_str),
         None,
     )
-    .0
 }
 
 /// Parses a string, returns a crate.
 pub(crate) fn string_to_crate(source_str: String) -> ast::Crate {
-    let ps = ParseSess::new(FilePathMapping::empty());
+    let ps = ParseSess::new(
+        vec![crate::DEFAULT_LOCALE_RESOURCE, rustc_parse::DEFAULT_LOCALE_RESOURCE],
+        FilePathMapping::empty(),
+    );
     with_error_checking_parse(source_str, &ps, |p| p.parse_crate_mod())
 }
 
@@ -127,8 +132,10 @@ fn test_harness(file_text: &str, span_labels: Vec<SpanLabel>, expected_output: &
     create_default_session_if_not_set_then(|_| {
         let output = Arc::new(Mutex::new(Vec::new()));
 
-        let fallback_bundle =
-            rustc_errors::fallback_fluent_bundle(rustc_errors::DEFAULT_LOCALE_RESOURCES, false);
+        let fallback_bundle = rustc_errors::fallback_fluent_bundle(
+            vec![crate::DEFAULT_LOCALE_RESOURCE, rustc_parse::DEFAULT_LOCALE_RESOURCE],
+            false,
+        );
         let source_map = Lrc::new(SourceMap::new(FilePathMapping::empty()));
         source_map.new_source_file(Path::new("test.rs").to_owned().into(), file_text.to_owned());
 
@@ -152,6 +159,7 @@ fn test_harness(file_text: &str, span_labels: Vec<SpanLabel>, expected_output: &
             None,
             false,
             false,
+            TerminalUrl::No,
         );
         let handler = Handler::with_emitter(true, None, Box::new(emitter));
         #[allow(rustc::untranslatable_diagnostic)]
-- 
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