diff --git a/Cargo.lock b/Cargo.lock
index 92dd45cf52019..f5ce875ccd428 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -4355,6 +4355,7 @@ name = "rustc_pattern_analysis"
 version = "0.0.0"
 dependencies = [
  "derivative",
+ "rustc-hash",
  "rustc_apfloat",
  "rustc_arena",
  "rustc_data_structures",
diff --git a/compiler/rustc_abi/src/lib.rs b/compiler/rustc_abi/src/lib.rs
index ea194e10defd6..c45a4a410f964 100644
--- a/compiler/rustc_abi/src/lib.rs
+++ b/compiler/rustc_abi/src/lib.rs
@@ -49,7 +49,14 @@ bitflags! {
                                  | ReprFlags::IS_LINEAR.bits();
     }
 }
-rustc_data_structures::external_bitflags_debug! { ReprFlags }
+
+// This is the same as `rustc_data_structures::external_bitflags_debug` but without the
+// `rustc_data_structures` to make it build on stable.
+impl std::fmt::Debug for ReprFlags {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        bitflags::parser::to_writer(self, f)
+    }
+}
 
 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
 #[cfg_attr(feature = "nightly", derive(Encodable_Generic, Decodable_Generic, HashStable_Generic))]
diff --git a/compiler/rustc_ast/src/ast.rs b/compiler/rustc_ast/src/ast.rs
index 21077c312bdc8..d0d98eb3d62d1 100644
--- a/compiler/rustc_ast/src/ast.rs
+++ b/compiler/rustc_ast/src/ast.rs
@@ -625,7 +625,8 @@ impl Pat {
             | PatKind::Range(..)
             | PatKind::Ident(..)
             | PatKind::Path(..)
-            | PatKind::MacCall(_) => {}
+            | PatKind::MacCall(_)
+            | PatKind::Err(_) => {}
         }
     }
 
@@ -809,6 +810,9 @@ pub enum PatKind {
 
     /// A macro pattern; pre-expansion.
     MacCall(P<MacCall>),
+
+    /// Placeholder for a pattern that wasn't syntactically well formed in some way.
+    Err(ErrorGuaranteed),
 }
 
 /// Whether the `..` is present in a struct fields pattern.
diff --git a/compiler/rustc_ast/src/mut_visit.rs b/compiler/rustc_ast/src/mut_visit.rs
index 450555d0cb56d..90677151d2506 100644
--- a/compiler/rustc_ast/src/mut_visit.rs
+++ b/compiler/rustc_ast/src/mut_visit.rs
@@ -1267,7 +1267,7 @@ pub fn noop_visit_pat<T: MutVisitor>(pat: &mut P<Pat>, vis: &mut T) {
     let Pat { id, kind, span, tokens } = pat.deref_mut();
     vis.visit_id(id);
     match kind {
-        PatKind::Wild | PatKind::Rest | PatKind::Never => {}
+        PatKind::Wild | PatKind::Rest | PatKind::Never | PatKind::Err(_) => {}
         PatKind::Ident(_binding_mode, ident, sub) => {
             vis.visit_ident(ident);
             visit_opt(sub, |sub| vis.visit_pat(sub));
diff --git a/compiler/rustc_ast/src/util/literal.rs b/compiler/rustc_ast/src/util/literal.rs
index 92b9adf1db751..fbae496458813 100644
--- a/compiler/rustc_ast/src/util/literal.rs
+++ b/compiler/rustc_ast/src/util/literal.rs
@@ -8,7 +8,6 @@ use rustc_lexer::unescape::{
 };
 use rustc_span::symbol::{kw, sym, Symbol};
 use rustc_span::Span;
-use std::ops::Range;
 use std::{ascii, fmt, str};
 
 // Escapes a string, represented as a symbol. Reuses the original symbol,
@@ -39,7 +38,6 @@ pub enum LitError {
     InvalidFloatSuffix,
     NonDecimalFloat(u32),
     IntTooLarge(u32),
-    NulInCStr(Range<usize>),
 }
 
 impl LitKind {
@@ -156,10 +154,7 @@ impl LitKind {
                 let s = symbol.as_str();
                 let mut buf = Vec::with_capacity(s.len());
                 let mut error = Ok(());
-                unescape_c_string(s, Mode::CStr, &mut |span, c| match c {
-                    Ok(CStrUnit::Byte(0) | CStrUnit::Char('\0')) => {
-                        error = Err(LitError::NulInCStr(span));
-                    }
+                unescape_c_string(s, Mode::CStr, &mut |_span, c| match c {
                     Ok(CStrUnit::Byte(b)) => buf.push(b),
                     Ok(CStrUnit::Char(c)) => {
                         buf.extend_from_slice(c.encode_utf8(&mut [0; 4]).as_bytes())
@@ -179,10 +174,7 @@ impl LitKind {
                 // can convert the symbol directly to a `Lrc<u8>` on success.
                 let s = symbol.as_str();
                 let mut error = Ok(());
-                unescape_c_string(s, Mode::RawCStr, &mut |span, c| match c {
-                    Ok(CStrUnit::Byte(0) | CStrUnit::Char('\0')) => {
-                        error = Err(LitError::NulInCStr(span));
-                    }
+                unescape_c_string(s, Mode::RawCStr, &mut |_, c| match c {
                     Ok(_) => {}
                     Err(err) => {
                         if err.is_fatal() {
diff --git a/compiler/rustc_ast/src/visit.rs b/compiler/rustc_ast/src/visit.rs
index 3617df931e2a2..89f50d3a0a7b8 100644
--- a/compiler/rustc_ast/src/visit.rs
+++ b/compiler/rustc_ast/src/visit.rs
@@ -568,7 +568,7 @@ pub fn walk_pat<'a, V: Visitor<'a>>(visitor: &mut V, pattern: &'a Pat) {
             walk_list!(visitor, visit_expr, lower_bound);
             walk_list!(visitor, visit_expr, upper_bound);
         }
-        PatKind::Wild | PatKind::Rest | PatKind::Never => {}
+        PatKind::Wild | PatKind::Rest | PatKind::Never | PatKind::Err(_) => {}
         PatKind::Tuple(elems) | PatKind::Slice(elems) | PatKind::Or(elems) => {
             walk_list!(visitor, visit_pat, elems);
         }
diff --git a/compiler/rustc_ast_lowering/src/pat.rs b/compiler/rustc_ast_lowering/src/pat.rs
index 1c405fac7e40a..0af141ff99a27 100644
--- a/compiler/rustc_ast_lowering/src/pat.rs
+++ b/compiler/rustc_ast_lowering/src/pat.rs
@@ -109,6 +109,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     // return inner to be processed in next loop
                     PatKind::Paren(inner) => pattern = inner,
                     PatKind::MacCall(_) => panic!("{:?} shouldn't exist here", pattern.span),
+                    PatKind::Err(guar) => break hir::PatKind::Err(*guar),
                 }
             };
 
diff --git a/compiler/rustc_ast_pretty/src/pprust/state.rs b/compiler/rustc_ast_pretty/src/pprust/state.rs
index f4b424259deef..c2fd4558fd76e 100644
--- a/compiler/rustc_ast_pretty/src/pprust/state.rs
+++ b/compiler/rustc_ast_pretty/src/pprust/state.rs
@@ -1519,6 +1519,11 @@ impl<'a> State<'a> {
                 self.pclose();
             }
             PatKind::MacCall(m) => self.print_mac(m),
+            PatKind::Err(_) => {
+                self.popen();
+                self.word("/*ERROR*/");
+                self.pclose();
+            }
         }
         self.ann.post(self, AnnNode::Pat(pat))
     }
diff --git a/compiler/rustc_expand/messages.ftl b/compiler/rustc_expand/messages.ftl
index 475dd348e7b63..3e3b481430043 100644
--- a/compiler/rustc_expand/messages.ftl
+++ b/compiler/rustc_expand/messages.ftl
@@ -16,6 +16,9 @@ expand_attributes_wrong_form =
 expand_cannot_be_name_of_macro =
     `{$trait_ident}` cannot be a name of {$macro_type} macro
 
+expand_collapse_debuginfo_illegal =
+    illegal value for attribute #[collapse_debuginfo(no|external|yes)]
+
 expand_count_repetition_misplaced =
     `count` can not be placed inside the inner-most repetition
 
diff --git a/compiler/rustc_expand/src/base.rs b/compiler/rustc_expand/src/base.rs
index 0a1c44303970a..edc9c5a9130a6 100644
--- a/compiler/rustc_expand/src/base.rs
+++ b/compiler/rustc_expand/src/base.rs
@@ -1,5 +1,6 @@
 #![deny(rustc::untranslatable_diagnostic)]
 
+use crate::base::ast::NestedMetaItem;
 use crate::errors;
 use crate::expand::{self, AstFragment, Invocation};
 use crate::module::DirOwnership;
@@ -19,6 +20,7 @@ use rustc_feature::Features;
 use rustc_lint_defs::builtin::PROC_MACRO_BACK_COMPAT;
 use rustc_lint_defs::{BufferedEarlyLint, BuiltinLintDiagnostics, RegisteredTools};
 use rustc_parse::{parser, MACRO_ARGUMENTS};
+use rustc_session::config::CollapseMacroDebuginfo;
 use rustc_session::errors::report_lit_error;
 use rustc_session::{parse::ParseSess, Limit, Session};
 use rustc_span::def_id::{CrateNum, DefId, LocalDefId};
@@ -761,6 +763,55 @@ impl SyntaxExtension {
         }
     }
 
+    fn collapse_debuginfo_by_name(sess: &Session, attr: &Attribute) -> CollapseMacroDebuginfo {
+        use crate::errors::CollapseMacroDebuginfoIllegal;
+        // #[collapse_debuginfo] without enum value (#[collapse_debuginfo(no/external/yes)])
+        // considered as `yes`
+        attr.meta_item_list().map_or(CollapseMacroDebuginfo::Yes, |l| {
+            let [NestedMetaItem::MetaItem(item)] = &l[..] else {
+                sess.dcx().emit_err(CollapseMacroDebuginfoIllegal { span: attr.span });
+                return CollapseMacroDebuginfo::Unspecified;
+            };
+            if !item.is_word() {
+                sess.dcx().emit_err(CollapseMacroDebuginfoIllegal { span: item.span });
+                CollapseMacroDebuginfo::Unspecified
+            } else {
+                match item.name_or_empty() {
+                    sym::no => CollapseMacroDebuginfo::No,
+                    sym::external => CollapseMacroDebuginfo::External,
+                    sym::yes => CollapseMacroDebuginfo::Yes,
+                    _ => {
+                        sess.dcx().emit_err(CollapseMacroDebuginfoIllegal { span: item.span });
+                        CollapseMacroDebuginfo::Unspecified
+                    }
+                }
+            }
+        })
+    }
+
+    /// if-ext - if macro from different crate (related to callsite code)
+    /// | cmd \ attr    | no  | (unspecified) | external | yes |
+    /// | no            | no  | no            | no       | no  |
+    /// | (unspecified) | no  | no            | if-ext   | yes |
+    /// | external      | no  | if-ext        | if-ext   | yes |
+    /// | yes           | yes | yes           | yes      | yes |
+    fn get_collapse_debuginfo(sess: &Session, attrs: &[ast::Attribute], is_local: bool) -> bool {
+        let collapse_debuginfo_attr = attr::find_by_name(attrs, sym::collapse_debuginfo)
+            .map(|v| Self::collapse_debuginfo_by_name(sess, v))
+            .unwrap_or(CollapseMacroDebuginfo::Unspecified);
+        let flag = sess.opts.unstable_opts.collapse_macro_debuginfo;
+        let attr = collapse_debuginfo_attr;
+        let ext = !is_local;
+        #[rustfmt::skip]
+        let collapse_table = [
+            [false, false, false, false],
+            [false, false, ext,   true],
+            [false, ext,   ext,   true],
+            [true,  true,  true,  true],
+        ];
+        collapse_table[flag as usize][attr as usize]
+    }
+
     /// Constructs a syntax extension with the given properties
     /// and other properties converted from attributes.
     pub fn new(
@@ -772,6 +823,7 @@ impl SyntaxExtension {
         edition: Edition,
         name: Symbol,
         attrs: &[ast::Attribute],
+        is_local: bool,
     ) -> SyntaxExtension {
         let allow_internal_unstable =
             attr::allow_internal_unstable(sess, attrs).collect::<Vec<Symbol>>();
@@ -780,8 +832,8 @@ impl SyntaxExtension {
         let local_inner_macros = attr::find_by_name(attrs, sym::macro_export)
             .and_then(|macro_export| macro_export.meta_item_list())
             .is_some_and(|l| attr::list_contains_name(&l, sym::local_inner_macros));
-        let collapse_debuginfo = attr::contains_name(attrs, sym::collapse_debuginfo);
-        tracing::debug!(?local_inner_macros, ?collapse_debuginfo, ?allow_internal_unsafe);
+        let collapse_debuginfo = Self::get_collapse_debuginfo(sess, attrs, is_local);
+        tracing::debug!(?name, ?local_inner_macros, ?collapse_debuginfo, ?allow_internal_unsafe);
 
         let (builtin_name, helper_attrs) = attr::find_by_name(attrs, sym::rustc_builtin_macro)
             .map(|attr| {
diff --git a/compiler/rustc_expand/src/errors.rs b/compiler/rustc_expand/src/errors.rs
index 2b43fae6852a1..4a1c00f0104fd 100644
--- a/compiler/rustc_expand/src/errors.rs
+++ b/compiler/rustc_expand/src/errors.rs
@@ -58,6 +58,13 @@ pub(crate) struct ResolveRelativePath {
     pub path: String,
 }
 
+#[derive(Diagnostic)]
+#[diag(expand_collapse_debuginfo_illegal)]
+pub(crate) struct CollapseMacroDebuginfoIllegal {
+    #[primary_span]
+    pub span: Span,
+}
+
 #[derive(Diagnostic)]
 #[diag(expand_macro_const_stability)]
 pub(crate) struct MacroConstStability {
diff --git a/compiler/rustc_expand/src/mbe/macro_rules.rs b/compiler/rustc_expand/src/mbe/macro_rules.rs
index 363b52aef8a78..1a39708ed8ed8 100644
--- a/compiler/rustc_expand/src/mbe/macro_rules.rs
+++ b/compiler/rustc_expand/src/mbe/macro_rules.rs
@@ -367,6 +367,7 @@ pub fn compile_declarative_macro(
             edition,
             def.ident.name,
             &def.attrs,
+            def.id != DUMMY_NODE_ID,
         )
     };
     let dummy_syn_ext = || (mk_syn_ext(Box::new(macro_rules_dummy_expander)), Vec::new());
diff --git a/compiler/rustc_feature/src/builtin_attrs.rs b/compiler/rustc_feature/src/builtin_attrs.rs
index 4442b67df6e28..68b6f69854dd6 100644
--- a/compiler/rustc_feature/src/builtin_attrs.rs
+++ b/compiler/rustc_feature/src/builtin_attrs.rs
@@ -469,7 +469,7 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
 
     // `#[collapse_debuginfo]`
     gated!(
-        collapse_debuginfo, Normal, template!(Word), WarnFollowing,
+        collapse_debuginfo, Normal, template!(Word, List: "no|external|yes"), ErrorFollowing,
         experimental!(collapse_debuginfo)
     ),
 
diff --git a/compiler/rustc_hir/src/hir.rs b/compiler/rustc_hir/src/hir.rs
index 6b347f7035a3b..6d5917c7b99f2 100644
--- a/compiler/rustc_hir/src/hir.rs
+++ b/compiler/rustc_hir/src/hir.rs
@@ -1015,7 +1015,7 @@ impl<'hir> Pat<'hir> {
 
         use PatKind::*;
         match self.kind {
-            Wild | Never | Lit(_) | Range(..) | Binding(.., None) | Path(_) => true,
+            Wild | Never | Lit(_) | Range(..) | Binding(.., None) | Path(_) | Err(_) => true,
             Box(s) | Ref(s, _) | Binding(.., Some(s)) => s.walk_short_(it),
             Struct(_, fields, _) => fields.iter().all(|field| field.pat.walk_short_(it)),
             TupleStruct(_, s, _) | Tuple(s, _) | Or(s) => s.iter().all(|p| p.walk_short_(it)),
@@ -1042,7 +1042,7 @@ impl<'hir> Pat<'hir> {
 
         use PatKind::*;
         match self.kind {
-            Wild | Never | Lit(_) | Range(..) | Binding(.., None) | Path(_) => {}
+            Wild | Never | Lit(_) | Range(..) | Binding(.., None) | Path(_) | Err(_) => {}
             Box(s) | Ref(s, _) | Binding(.., Some(s)) => s.walk_(it),
             Struct(_, fields, _) => fields.iter().for_each(|field| field.pat.walk_(it)),
             TupleStruct(_, s, _) | Tuple(s, _) | Or(s) => s.iter().for_each(|p| p.walk_(it)),
@@ -1205,6 +1205,9 @@ pub enum PatKind<'hir> {
     /// PatKind::Slice([Binding(a), Binding(b)], Some(Wild), [Binding(c), Binding(d)])
     /// ```
     Slice(&'hir [Pat<'hir>], Option<&'hir Pat<'hir>>, &'hir [Pat<'hir>]),
+
+    /// A placeholder for a pattern that wasn't well formed in some way.
+    Err(ErrorGuaranteed),
 }
 
 /// A statement.
diff --git a/compiler/rustc_hir/src/intravisit.rs b/compiler/rustc_hir/src/intravisit.rs
index adc090258093a..116de6fb04d99 100644
--- a/compiler/rustc_hir/src/intravisit.rs
+++ b/compiler/rustc_hir/src/intravisit.rs
@@ -655,7 +655,7 @@ pub fn walk_pat<'v, V: Visitor<'v>>(visitor: &mut V, pattern: &'v Pat<'v>) {
             walk_list!(visitor, visit_expr, lower_bound);
             walk_list!(visitor, visit_expr, upper_bound);
         }
-        PatKind::Never | PatKind::Wild => (),
+        PatKind::Never | PatKind::Wild | PatKind::Err(_) => (),
         PatKind::Slice(prepatterns, ref slice_pattern, postpatterns) => {
             walk_list!(visitor, visit_pat, prepatterns);
             walk_list!(visitor, visit_pat, slice_pattern);
diff --git a/compiler/rustc_hir_analysis/src/check/region.rs b/compiler/rustc_hir_analysis/src/check/region.rs
index 5d5a4789734a7..1c0a1a6951398 100644
--- a/compiler/rustc_hir_analysis/src/check/region.rs
+++ b/compiler/rustc_hir_analysis/src/check/region.rs
@@ -681,7 +681,8 @@ fn resolve_local<'tcx>(
             | PatKind::Never
             | PatKind::Path(_)
             | PatKind::Lit(_)
-            | PatKind::Range(_, _, _) => false,
+            | PatKind::Range(_, _, _)
+            | PatKind::Err(_) => false,
         }
     }
 
diff --git a/compiler/rustc_hir_pretty/src/lib.rs b/compiler/rustc_hir_pretty/src/lib.rs
index d36e0892d19d9..e76303bc6dfa1 100644
--- a/compiler/rustc_hir_pretty/src/lib.rs
+++ b/compiler/rustc_hir_pretty/src/lib.rs
@@ -1838,6 +1838,11 @@ impl<'a> State<'a> {
                 self.commasep(Inconsistent, after, |s, p| s.print_pat(p));
                 self.word("]");
             }
+            PatKind::Err(_) => {
+                self.popen();
+                self.word("/*ERROR*/");
+                self.pclose();
+            }
         }
         self.ann.post(self, AnnNode::Pat(pat))
     }
diff --git a/compiler/rustc_hir_typeck/src/closure.rs b/compiler/rustc_hir_typeck/src/closure.rs
index 57fdfa4ecb6ea..d11198d7fd4e7 100644
--- a/compiler/rustc_hir_typeck/src/closure.rs
+++ b/compiler/rustc_hir_typeck/src/closure.rs
@@ -68,12 +68,58 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         debug!(?bound_sig, ?liberated_sig);
 
+        let parent_args =
+            GenericArgs::identity_for_item(tcx, tcx.typeck_root_def_id(expr_def_id.to_def_id()));
+
+        let tupled_upvars_ty = self.next_root_ty_var(TypeVariableOrigin {
+            kind: TypeVariableOriginKind::ClosureSynthetic,
+            span: expr_span,
+        });
+
         // FIXME: We could probably actually just unify this further --
         // instead of having a `FnSig` and a `Option<CoroutineTypes>`,
         // we can have a `ClosureSignature { Coroutine { .. }, Closure { .. } }`,
         // similar to how `ty::GenSig` is a distinct data structure.
-        let coroutine_types = match closure.kind {
-            hir::ClosureKind::Closure => None,
+        let (closure_ty, coroutine_types) = match closure.kind {
+            hir::ClosureKind::Closure => {
+                // Tuple up the arguments and insert the resulting function type into
+                // the `closures` table.
+                let sig = bound_sig.map_bound(|sig| {
+                    tcx.mk_fn_sig(
+                        [Ty::new_tup(tcx, sig.inputs())],
+                        sig.output(),
+                        sig.c_variadic,
+                        sig.unsafety,
+                        sig.abi,
+                    )
+                });
+
+                debug!(?sig, ?expected_kind);
+
+                let closure_kind_ty = match expected_kind {
+                    Some(kind) => Ty::from_closure_kind(tcx, kind),
+
+                    // Create a type variable (for now) to represent the closure kind.
+                    // It will be unified during the upvar inference phase (`upvar.rs`)
+                    None => self.next_root_ty_var(TypeVariableOrigin {
+                        // FIXME(eddyb) distinguish closure kind inference variables from the rest.
+                        kind: TypeVariableOriginKind::ClosureSynthetic,
+                        span: expr_span,
+                    }),
+                };
+
+                let closure_args = ty::ClosureArgs::new(
+                    tcx,
+                    ty::ClosureArgsParts {
+                        parent_args,
+                        closure_kind_ty,
+                        closure_sig_as_fn_ptr_ty: Ty::new_fn_ptr(tcx, sig),
+                        tupled_upvars_ty,
+                    },
+                );
+
+                (Ty::new_closure(tcx, expr_def_id.to_def_id(), closure_args.args), None)
+            }
             hir::ClosureKind::Coroutine(kind) => {
                 let yield_ty = match kind {
                     hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Gen, _)
@@ -119,74 +165,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 // Resume type defaults to `()` if the coroutine has no argument.
                 let resume_ty = liberated_sig.inputs().get(0).copied().unwrap_or(tcx.types.unit);
 
-                Some(CoroutineTypes { resume_ty, yield_ty })
-            }
-        };
-
-        check_fn(
-            &mut FnCtxt::new(self, self.param_env, closure.def_id),
-            liberated_sig,
-            coroutine_types,
-            closure.fn_decl,
-            expr_def_id,
-            body,
-            // Closure "rust-call" ABI doesn't support unsized params
-            false,
-        );
-
-        let parent_args =
-            GenericArgs::identity_for_item(tcx, tcx.typeck_root_def_id(expr_def_id.to_def_id()));
-
-        let tupled_upvars_ty = self.next_root_ty_var(TypeVariableOrigin {
-            kind: TypeVariableOriginKind::ClosureSynthetic,
-            span: expr_span,
-        });
-
-        match closure.kind {
-            hir::ClosureKind::Closure => {
-                assert_eq!(coroutine_types, None);
-                // Tuple up the arguments and insert the resulting function type into
-                // the `closures` table.
-                let sig = bound_sig.map_bound(|sig| {
-                    tcx.mk_fn_sig(
-                        [Ty::new_tup(tcx, sig.inputs())],
-                        sig.output(),
-                        sig.c_variadic,
-                        sig.unsafety,
-                        sig.abi,
-                    )
-                });
-
-                debug!(?sig, ?expected_kind);
-
-                let closure_kind_ty = match expected_kind {
-                    Some(kind) => Ty::from_closure_kind(tcx, kind),
-
-                    // Create a type variable (for now) to represent the closure kind.
-                    // It will be unified during the upvar inference phase (`upvar.rs`)
-                    None => self.next_root_ty_var(TypeVariableOrigin {
-                        // FIXME(eddyb) distinguish closure kind inference variables from the rest.
-                        kind: TypeVariableOriginKind::ClosureSynthetic,
-                        span: expr_span,
-                    }),
-                };
-
-                let closure_args = ty::ClosureArgs::new(
-                    tcx,
-                    ty::ClosureArgsParts {
-                        parent_args,
-                        closure_kind_ty,
-                        closure_sig_as_fn_ptr_ty: Ty::new_fn_ptr(tcx, sig),
-                        tupled_upvars_ty,
-                    },
-                );
-
-                Ty::new_closure(tcx, expr_def_id.to_def_id(), closure_args.args)
-            }
-            hir::ClosureKind::Coroutine(_) => {
-                let Some(CoroutineTypes { resume_ty, yield_ty }) = coroutine_types else {
-                    bug!("expected coroutine to have yield/resume types");
-                };
                 let interior = self.next_ty_var(TypeVariableOrigin {
                     kind: TypeVariableOriginKind::MiscVariable,
                     span: body.value.span,
@@ -209,9 +187,25 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     },
                 );
 
-                Ty::new_coroutine(tcx, expr_def_id.to_def_id(), coroutine_args.args)
+                (
+                    Ty::new_coroutine(tcx, expr_def_id.to_def_id(), coroutine_args.args),
+                    Some(CoroutineTypes { resume_ty, yield_ty }),
+                )
             }
-        }
+        };
+
+        check_fn(
+            &mut FnCtxt::new(self, self.param_env, closure.def_id),
+            liberated_sig,
+            coroutine_types,
+            closure.fn_decl,
+            expr_def_id,
+            body,
+            // Closure "rust-call" ABI doesn't support unsized params
+            false,
+        );
+
+        closure_ty
     }
 
     /// Given the expected type, figures out what it can about this closure we
@@ -683,10 +677,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     })
                 }
                 // All `gen {}` and `async gen {}` must return unit.
-                hir::ClosureKind::Coroutine(
-                    hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Gen, _)
-                    | hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::AsyncGen, _),
-                ) => self.tcx.types.unit,
+                hir::ClosureKind::Coroutine(hir::CoroutineKind::Desugared(
+                    hir::CoroutineDesugaring::Gen | hir::CoroutineDesugaring::AsyncGen,
+                    _,
+                )) => self.tcx.types.unit,
 
                 // For async blocks, we just fall back to `_` here.
                 // For closures/coroutines, we know nothing about the return
diff --git a/compiler/rustc_hir_typeck/src/expr_use_visitor.rs b/compiler/rustc_hir_typeck/src/expr_use_visitor.rs
index ed3dd1e39dfc9..3ecf6c5e428be 100644
--- a/compiler/rustc_hir_typeck/src/expr_use_visitor.rs
+++ b/compiler/rustc_hir_typeck/src/expr_use_visitor.rs
@@ -458,11 +458,15 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
                             needs_to_be_read = true;
                         }
                     }
-                    PatKind::Or(_) | PatKind::Box(_) | PatKind::Ref(..) | PatKind::Wild => {
+                    PatKind::Or(_)
+                    | PatKind::Box(_)
+                    | PatKind::Ref(..)
+                    | PatKind::Wild
+                    | PatKind::Err(_) => {
                         // If the PatKind is Or, Box, or Ref, the decision is made later
                         // as these patterns contains subpatterns
-                        // If the PatKind is Wild, the decision is made based on the other patterns being
-                        // examined
+                        // If the PatKind is Wild or Err, the decision is made based on the other patterns
+                        // being examined
                     }
                 }
             })?
diff --git a/compiler/rustc_hir_typeck/src/mem_categorization.rs b/compiler/rustc_hir_typeck/src/mem_categorization.rs
index ce3a4b4c80ce7..1ce0240f7b830 100644
--- a/compiler/rustc_hir_typeck/src/mem_categorization.rs
+++ b/compiler/rustc_hir_typeck/src/mem_categorization.rs
@@ -767,7 +767,8 @@ impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx> {
             | PatKind::Lit(..)
             | PatKind::Range(..)
             | PatKind::Never
-            | PatKind::Wild => {
+            | PatKind::Wild
+            | PatKind::Err(_) => {
                 // always ok
             }
         }
diff --git a/compiler/rustc_hir_typeck/src/pat.rs b/compiler/rustc_hir_typeck/src/pat.rs
index 95813cb68a664..fe8c36dbe069d 100644
--- a/compiler/rustc_hir_typeck/src/pat.rs
+++ b/compiler/rustc_hir_typeck/src/pat.rs
@@ -177,7 +177,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             PatInfo { binding_mode: def_bm, top_info: ti, decl_origin: pat_info.decl_origin };
 
         let ty = match pat.kind {
-            PatKind::Wild => expected,
+            PatKind::Wild | PatKind::Err(_) => expected,
             // FIXME(never_patterns): check the type is uninhabited. If that is not possible within
             // typeck, do that in a later phase.
             PatKind::Never => expected,
@@ -325,6 +325,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             PatKind::Ref(..) => AdjustMode::Reset,
             // A `_` pattern works with any expected type, so there's no need to do anything.
             PatKind::Wild
+            // A malformed pattern doesn't have an expected type, so let's just accept any type.
+            | PatKind::Err(_)
             // Bindings also work with whatever the expected type is,
             // and moreover if we peel references off, that will give us the wrong binding type.
             // Also, we can have a subpattern `binding @ pat`.
@@ -754,7 +756,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         | PatKind::Box(..)
                         | PatKind::Ref(..)
                         | PatKind::Lit(..)
-                        | PatKind::Range(..) => break 'block None,
+                        | PatKind::Range(..)
+                        | PatKind::Err(_) => break 'block None,
                     },
 
                     // Don't provide suggestions in other cases
diff --git a/compiler/rustc_interface/src/tests.rs b/compiler/rustc_interface/src/tests.rs
index 588139a303c52..555c822ad6d68 100644
--- a/compiler/rustc_interface/src/tests.rs
+++ b/compiler/rustc_interface/src/tests.rs
@@ -4,10 +4,10 @@ use rustc_data_structures::profiling::TimePassesFormat;
 use rustc_errors::{emitter::HumanReadableErrorType, registry, ColorConfig};
 use rustc_session::config::{
     build_configuration, build_session_options, rustc_optgroups, BranchProtection, CFGuard, Cfg,
-    DebugInfo, DumpMonoStatsFormat, ErrorOutputType, ExternEntry, ExternLocation, Externs,
-    FunctionReturn, InliningThreshold, Input, InstrumentCoverage, InstrumentXRay,
-    LinkSelfContained, LinkerPluginLto, LocationDetail, LtoCli, NextSolverConfig, OomStrategy,
-    Options, OutFileName, OutputType, OutputTypes, PAuthKey, PacRet, Passes, Polonius,
+    CollapseMacroDebuginfo, DebugInfo, DumpMonoStatsFormat, ErrorOutputType, ExternEntry,
+    ExternLocation, Externs, FunctionReturn, InliningThreshold, Input, InstrumentCoverage,
+    InstrumentXRay, LinkSelfContained, LinkerPluginLto, LocationDetail, LtoCli, NextSolverConfig,
+    OomStrategy, Options, OutFileName, OutputType, OutputTypes, PAuthKey, PacRet, Passes, Polonius,
     ProcMacroExecutionStrategy, Strip, SwitchWithOptPath, SymbolManglingVersion, WasiExecModel,
 };
 use rustc_session::lint::Level;
@@ -742,6 +742,7 @@ fn test_unstable_options_tracking_hash() {
         })
     );
     tracked!(codegen_backend, Some("abc".to_string()));
+    tracked!(collapse_macro_debuginfo, CollapseMacroDebuginfo::Yes);
     tracked!(crate_attr, vec!["abc".to_string()]);
     tracked!(cross_crate_inline_threshold, InliningThreshold::Always);
     tracked!(debug_info_for_profiling, true);
diff --git a/compiler/rustc_lexer/src/unescape.rs b/compiler/rustc_lexer/src/unescape.rs
index abec12f52a6e6..0a632c4d12ad5 100644
--- a/compiler/rustc_lexer/src/unescape.rs
+++ b/compiler/rustc_lexer/src/unescape.rs
@@ -59,6 +59,9 @@ pub enum EscapeError {
     /// Non-ascii character in byte literal, byte string literal, or raw byte string literal.
     NonAsciiCharInByte,
 
+    // `\0` in a C string literal.
+    NulInCStr,
+
     /// After a line ending with '\', the next line contains whitespace
     /// characters that are not skipped.
     UnskippedWhitespaceWarning,
@@ -122,10 +125,20 @@ where
 {
     match mode {
         CStr => {
-            unescape_non_raw_common(src, mode, callback);
+            unescape_non_raw_common(src, mode, &mut |r, mut result| {
+                if let Ok(CStrUnit::Byte(0) | CStrUnit::Char('\0')) = result {
+                    result = Err(EscapeError::NulInCStr);
+                }
+                callback(r, result)
+            });
         }
         RawCStr => {
-            check_raw_common(src, mode, &mut |r, result| callback(r, result.map(CStrUnit::Char)));
+            check_raw_common(src, mode, &mut |r, mut result| {
+                if let Ok('\0') = result {
+                    result = Err(EscapeError::NulInCStr);
+                }
+                callback(r, result.map(CStrUnit::Char))
+            });
         }
         Char | Byte | Str | RawStr | ByteStr | RawByteStr => unreachable!(),
     }
diff --git a/compiler/rustc_lint/src/unused.rs b/compiler/rustc_lint/src/unused.rs
index 0f4528d1d5c2b..39decf1faabf1 100644
--- a/compiler/rustc_lint/src/unused.rs
+++ b/compiler/rustc_lint/src/unused.rs
@@ -1166,7 +1166,7 @@ impl EarlyLintPass for UnusedParens {
             // Do not lint on `(..)` as that will result in the other arms being useless.
             Paren(_)
             // The other cases do not contain sub-patterns.
-            | Wild | Never | Rest | Lit(..) | MacCall(..) | Range(..) | Ident(.., None) | Path(..) => {},
+            | Wild | Never | Rest | Lit(..) | MacCall(..) | Range(..) | Ident(.., None) | Path(..) | Err(_) => {},
             // These are list-like patterns; parens can always be removed.
             TupleStruct(_, _, ps) | Tuple(ps) | Slice(ps) | Or(ps) => for p in ps {
                 self.check_unused_parens_pat(cx, p, false, false, keep_space);
diff --git a/compiler/rustc_metadata/src/rmeta/decoder.rs b/compiler/rustc_metadata/src/rmeta/decoder.rs
index 49e849964be47..20e3ae3ba9492 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder.rs
@@ -1027,6 +1027,7 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
             self.root.edition,
             Symbol::intern(name),
             &attrs,
+            false,
         )
     }
 
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index ad9296a4cc88a..a5d9e0fcf44cd 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -2535,8 +2535,7 @@ impl<'tcx> TyCtxt<'tcx> {
         if self.sess.opts.unstable_opts.debug_macros || !span.from_expansion() {
             return span;
         }
-        let collapse_debuginfo_enabled = self.features().collapse_debuginfo;
-        hygiene::walk_chain_collapsed(span, upto, collapse_debuginfo_enabled)
+        hygiene::walk_chain_collapsed(span, upto, self.features().collapse_debuginfo)
     }
 
     #[inline]
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index 6c9000c45f61b..4028de27cae14 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -1013,7 +1013,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                                 .extend(
                                     // Group the return ty with its def id, if we had one.
                                     entry.return_ty.map(|ty| {
-                                        (tcx.require_lang_item(LangItem::FnOnce, None), ty)
+                                        (tcx.require_lang_item(LangItem::FnOnceOutput, None), ty)
                                     }),
                                 );
                         }
diff --git a/compiler/rustc_mir_build/src/thir/pattern/mod.rs b/compiler/rustc_mir_build/src/thir/pattern/mod.rs
index c4987634b78b3..ff7e985bdfdcc 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/mod.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/mod.rs
@@ -345,6 +345,8 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
             }
 
             hir::PatKind::Or(pats) => PatKind::Or { pats: self.lower_patterns(pats) },
+
+            hir::PatKind::Err(guar) => PatKind::Error(guar),
         };
 
         Box::new(Pat { span, ty, kind })
diff --git a/compiler/rustc_parse/messages.ftl b/compiler/rustc_parse/messages.ftl
index d515e86a18296..fb19bb996f922 100644
--- a/compiler/rustc_parse/messages.ftl
+++ b/compiler/rustc_parse/messages.ftl
@@ -616,6 +616,8 @@ parse_note_mut_pattern_usage = `mut` may be followed by `variable` and `variable
 
 parse_note_pattern_alternatives_use_single_vert = alternatives in or-patterns are separated with `|`, not `||`
 
+parse_nul_in_c_str = null characters in C string literals are not supported
+
 parse_or_pattern_not_allowed_in_fn_parameters = top-level or-patterns are not allowed in function parameters
 parse_or_pattern_not_allowed_in_let_binding = top-level or-patterns are not allowed in `let` bindings
 parse_out_of_range_hex_escape = out of range hex escape
diff --git a/compiler/rustc_parse/src/errors.rs b/compiler/rustc_parse/src/errors.rs
index 34b34a1bad6c9..7dc711d96109d 100644
--- a/compiler/rustc_parse/src/errors.rs
+++ b/compiler/rustc_parse/src/errors.rs
@@ -2163,6 +2163,11 @@ pub enum UnescapeError {
         #[subdiagnostic]
         suggestion: MoreThanOneCharSugg,
     },
+    #[diag(parse_nul_in_c_str)]
+    NulInCStr {
+        #[primary_span]
+        span: Span,
+    },
 }
 
 #[derive(Subdiagnostic)]
diff --git a/compiler/rustc_parse/src/lexer/unescape_error_reporting.rs b/compiler/rustc_parse/src/lexer/unescape_error_reporting.rs
index fbc77f2878081..3238f8e23bb0a 100644
--- a/compiler/rustc_parse/src/lexer/unescape_error_reporting.rs
+++ b/compiler/rustc_parse/src/lexer/unescape_error_reporting.rs
@@ -262,6 +262,9 @@ pub(crate) fn emit_unescape_error(
         EscapeError::LoneSlash => {
             dcx.emit_err(UnescapeError::LoneSlash(err_span));
         }
+        EscapeError::NulInCStr => {
+            dcx.emit_err(UnescapeError::NulInCStr { span: err_span });
+        }
         EscapeError::UnskippedWhitespaceWarning => {
             let (c, char_span) = last_char();
             dcx.emit_warn(UnescapeError::UnskippedWhitespace {
diff --git a/compiler/rustc_passes/src/hir_stats.rs b/compiler/rustc_passes/src/hir_stats.rs
index ff29fc5929c76..528a52f42255e 100644
--- a/compiler/rustc_passes/src/hir_stats.rs
+++ b/compiler/rustc_passes/src/hir_stats.rs
@@ -303,7 +303,8 @@ impl<'v> hir_visit::Visitor<'v> for StatCollector<'v> {
                 Ref,
                 Lit,
                 Range,
-                Slice
+                Slice,
+                Err
             ]
         );
         hir_visit::walk_pat(self, p)
@@ -576,7 +577,8 @@ impl<'v> ast_visit::Visitor<'v> for StatCollector<'v> {
                 Rest,
                 Never,
                 Paren,
-                MacCall
+                MacCall,
+                Err
             ]
         );
         ast_visit::walk_pat(self, p)
diff --git a/compiler/rustc_pattern_analysis/Cargo.toml b/compiler/rustc_pattern_analysis/Cargo.toml
index 7cc585bea3af7..1d0e1cb7e6a57 100644
--- a/compiler/rustc_pattern_analysis/Cargo.toml
+++ b/compiler/rustc_pattern_analysis/Cargo.toml
@@ -6,6 +6,7 @@ edition = "2021"
 [dependencies]
 # tidy-alphabetical-start
 derivative = "2.2.0"
+rustc-hash = "1.1.0"
 rustc_apfloat = "0.2.0"
 rustc_arena = { path = "../rustc_arena", optional = true }
 rustc_data_structures = { path = "../rustc_data_structures", optional = true }
diff --git a/compiler/rustc_pattern_analysis/src/constructor.rs b/compiler/rustc_pattern_analysis/src/constructor.rs
index c1042d5b66eca..76098505b7944 100644
--- a/compiler/rustc_pattern_analysis/src/constructor.rs
+++ b/compiler/rustc_pattern_analysis/src/constructor.rs
@@ -155,13 +155,13 @@ use std::iter::once;
 use smallvec::SmallVec;
 
 use rustc_apfloat::ieee::{DoubleS, IeeeFloat, SingleS};
-use rustc_index::bit_set::{BitSet, GrowableBitSet};
-use rustc_index::IndexVec;
+use rustc_index::bit_set::GrowableBitSet;
 
 use self::Constructor::*;
 use self::MaybeInfiniteInt::*;
 use self::SliceKind::*;
 
+use crate::index;
 use crate::usefulness::PlaceCtxt;
 use crate::TypeCx;
 
@@ -804,7 +804,10 @@ pub enum ConstructorSet<Cx: TypeCx> {
     Struct { empty: bool },
     /// This type has the following list of constructors. If `variants` is empty and
     /// `non_exhaustive` is false, don't use this; use `NoConstructors` instead.
-    Variants { variants: IndexVec<Cx::VariantIdx, VariantVisibility>, non_exhaustive: bool },
+    Variants {
+        variants: index::IdxContainer<Cx::VariantIdx, VariantVisibility>,
+        non_exhaustive: bool,
+    },
     /// The type is `&T`.
     Ref,
     /// The type is a union.
@@ -904,7 +907,7 @@ impl<Cx: TypeCx> ConstructorSet<Cx> {
                 }
             }
             ConstructorSet::Variants { variants, non_exhaustive } => {
-                let mut seen_set: BitSet<_> = BitSet::new_empty(variants.len());
+                let mut seen_set = index::IdxSet::new_empty(variants.len());
                 for idx in seen.iter().map(|c| c.as_variant().unwrap()) {
                     seen_set.insert(idx);
                 }
diff --git a/compiler/rustc_pattern_analysis/src/lib.rs b/compiler/rustc_pattern_analysis/src/lib.rs
index 0bc432fa6f0ad..21fa8e68d82e8 100644
--- a/compiler/rustc_pattern_analysis/src/lib.rs
+++ b/compiler/rustc_pattern_analysis/src/lib.rs
@@ -21,7 +21,45 @@ rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
 
 use std::fmt;
 
-use rustc_index::Idx;
+#[cfg(feature = "rustc")]
+pub mod index {
+    // Faster version when the indices of variants are `0..variants.len()`.
+    pub use rustc_index::bit_set::BitSet as IdxSet;
+    pub use rustc_index::Idx;
+    pub use rustc_index::IndexVec as IdxContainer;
+}
+#[cfg(not(feature = "rustc"))]
+pub mod index {
+    // Slower version when the indices of variants are something else.
+    pub trait Idx: Copy + PartialEq + Eq + std::hash::Hash {}
+    impl<T: Copy + PartialEq + Eq + std::hash::Hash> Idx for T {}
+
+    #[derive(Debug)]
+    pub struct IdxContainer<K, V>(pub rustc_hash::FxHashMap<K, V>);
+    impl<K: Idx, V> IdxContainer<K, V> {
+        pub fn len(&self) -> usize {
+            self.0.len()
+        }
+        pub fn iter_enumerated(&self) -> impl Iterator<Item = (K, &V)> {
+            self.0.iter().map(|(k, v)| (*k, v))
+        }
+    }
+
+    #[derive(Debug)]
+    pub struct IdxSet<T>(pub rustc_hash::FxHashSet<T>);
+    impl<T: Idx> IdxSet<T> {
+        pub fn new_empty(_len: usize) -> Self {
+            Self(Default::default())
+        }
+        pub fn contains(&self, elem: T) -> bool {
+            self.0.contains(&elem)
+        }
+        pub fn insert(&mut self, elem: T) {
+            self.0.insert(elem);
+        }
+    }
+}
+
 #[cfg(feature = "rustc")]
 use rustc_middle::ty::Ty;
 #[cfg(feature = "rustc")]
@@ -48,7 +86,7 @@ pub trait TypeCx: Sized + fmt::Debug {
     /// Errors that can abort analysis.
     type Error: fmt::Debug;
     /// The index of an enum variant.
-    type VariantIdx: Clone + Idx;
+    type VariantIdx: Clone + index::Idx + fmt::Debug;
     /// A string literal
     type StrLit: Clone + PartialEq + fmt::Debug;
     /// Extra data to store in a match arm.
diff --git a/compiler/rustc_session/messages.ftl b/compiler/rustc_session/messages.ftl
index 53bdef6dfa0fb..af8c962a2ed6a 100644
--- a/compiler/rustc_session/messages.ftl
+++ b/compiler/rustc_session/messages.ftl
@@ -75,8 +75,6 @@ session_not_circumvent_feature = `-Zunleash-the-miri-inside-of-you` may not be u
 
 session_not_supported = not supported
 
-session_nul_in_c_str = null characters in C string literals are not supported
-
 session_octal_float_literal_not_supported = octal float literal is not supported
 
 session_optimization_fuel_exhausted = optimization-fuel-exhausted: {$msg}
diff --git a/compiler/rustc_session/src/config.rs b/compiler/rustc_session/src/config.rs
index ac15c3b407b27..e751ff13a34ca 100644
--- a/compiler/rustc_session/src/config.rs
+++ b/compiler/rustc_session/src/config.rs
@@ -3190,12 +3190,12 @@ pub enum WasiExecModel {
 /// how the hash should be calculated when adding a new command-line argument.
 pub(crate) mod dep_tracking {
     use super::{
-        BranchProtection, CFGuard, CFProtection, CrateType, DebugInfo, DebugInfoCompression,
-        ErrorOutputType, FunctionReturn, InliningThreshold, InstrumentCoverage, InstrumentXRay,
-        LinkerPluginLto, LocationDetail, LtoCli, NextSolverConfig, OomStrategy, OptLevel,
-        OutFileName, OutputType, OutputTypes, Polonius, RemapPathScopeComponents, ResolveDocLinks,
-        SourceFileHashAlgorithm, SplitDwarfKind, SwitchWithOptPath, SymbolManglingVersion,
-        WasiExecModel,
+        BranchProtection, CFGuard, CFProtection, CollapseMacroDebuginfo, CrateType, DebugInfo,
+        DebugInfoCompression, ErrorOutputType, FunctionReturn, InliningThreshold,
+        InstrumentCoverage, InstrumentXRay, LinkerPluginLto, LocationDetail, LtoCli,
+        NextSolverConfig, OomStrategy, OptLevel, OutFileName, OutputType, OutputTypes, Polonius,
+        RemapPathScopeComponents, ResolveDocLinks, SourceFileHashAlgorithm, SplitDwarfKind,
+        SwitchWithOptPath, SymbolManglingVersion, WasiExecModel,
     };
     use crate::lint;
     use crate::utils::NativeLib;
@@ -3274,6 +3274,7 @@ pub(crate) mod dep_tracking {
         LtoCli,
         DebugInfo,
         DebugInfoCompression,
+        CollapseMacroDebuginfo,
         UnstableFeatures,
         NativeLib,
         SanitizerSet,
@@ -3437,6 +3438,25 @@ pub enum ProcMacroExecutionStrategy {
     CrossThread,
 }
 
+/// How to perform collapse macros debug info
+/// if-ext - if macro from different crate (related to callsite code)
+/// | cmd \ attr    | no  | (unspecified) | external | yes |
+/// | no            | no  | no            | no       | no  |
+/// | (unspecified) | no  | no            | if-ext   | yes |
+/// | external      | no  | if-ext        | if-ext   | yes |
+/// | yes           | yes | yes           | yes      | yes |
+#[derive(Clone, Copy, PartialEq, Hash, Debug)]
+pub enum CollapseMacroDebuginfo {
+    /// Don't collapse debuginfo for the macro
+    No = 0,
+    /// Unspecified value
+    Unspecified = 1,
+    /// Collapse debuginfo if the macro comes from a different crate
+    External = 2,
+    /// Collapse debuginfo for the macro
+    Yes = 3,
+}
+
 /// Which format to use for `-Z dump-mono-stats`
 #[derive(Clone, Copy, PartialEq, Hash, Debug)]
 pub enum DumpMonoStatsFormat {
diff --git a/compiler/rustc_session/src/errors.rs b/compiler/rustc_session/src/errors.rs
index 21a206798af18..e19f0fd84de56 100644
--- a/compiler/rustc_session/src/errors.rs
+++ b/compiler/rustc_session/src/errors.rs
@@ -6,7 +6,7 @@ use rustc_errors::{
     error_code, DiagCtxt, DiagnosticBuilder, DiagnosticMessage, IntoDiagnostic, Level, MultiSpan,
 };
 use rustc_macros::Diagnostic;
-use rustc_span::{BytePos, Span, Symbol};
+use rustc_span::{Span, Symbol};
 use rustc_target::spec::{SplitDebuginfo, StackProtector, TargetTriple};
 
 use crate::parse::ParseSess;
@@ -346,13 +346,6 @@ pub(crate) struct BinaryFloatLiteralNotSupported {
     pub span: Span,
 }
 
-#[derive(Diagnostic)]
-#[diag(session_nul_in_c_str)]
-pub(crate) struct NulInCStr {
-    #[primary_span]
-    pub span: Span,
-}
-
 pub fn report_lit_error(sess: &ParseSess, err: LitError, lit: token::Lit, span: Span) {
     // Checks if `s` looks like i32 or u1234 etc.
     fn looks_like_width_suffix(first_chars: &[char], s: &str) -> bool {
@@ -432,12 +425,6 @@ pub fn report_lit_error(sess: &ParseSess, err: LitError, lit: token::Lit, span:
             };
             dcx.emit_err(IntLiteralTooLarge { span, limit });
         }
-        LitError::NulInCStr(range) => {
-            let lo = BytePos(span.lo().0 + range.start as u32 + 2);
-            let hi = BytePos(span.lo().0 + range.end as u32 + 2);
-            let span = span.with_lo(lo).with_hi(hi);
-            dcx.emit_err(NulInCStr { span });
-        }
     }
 }
 
diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs
index f4bf79f93f287..6c91929fcbe49 100644
--- a/compiler/rustc_session/src/options.rs
+++ b/compiler/rustc_session/src/options.rs
@@ -388,6 +388,7 @@ mod desc {
     pub const parse_cfprotection: &str = "`none`|`no`|`n` (default), `branch`, `return`, or `full`|`yes`|`y` (equivalent to `branch` and `return`)";
     pub const parse_debuginfo: &str = "either an integer (0, 1, 2), `none`, `line-directives-only`, `line-tables-only`, `limited`, or `full`";
     pub const parse_debuginfo_compression: &str = "one of `none`, `zlib`, or `zstd`";
+    pub const parse_collapse_macro_debuginfo: &str = "one of `no`, `external`, or `yes`";
     pub const parse_strip: &str = "either `none`, `debuginfo`, or `symbols`";
     pub const parse_linker_flavor: &str = ::rustc_target::spec::LinkerFlavorCli::one_of();
     pub const parse_optimization_fuel: &str = "crate=integer";
@@ -1302,6 +1303,19 @@ mod parse {
         true
     }
 
+    pub(crate) fn parse_collapse_macro_debuginfo(
+        slot: &mut CollapseMacroDebuginfo,
+        v: Option<&str>,
+    ) -> bool {
+        *slot = match v {
+            Some("no") => CollapseMacroDebuginfo::No,
+            Some("external") => CollapseMacroDebuginfo::External,
+            Some("yes") => CollapseMacroDebuginfo::Yes,
+            _ => return false,
+        };
+        true
+    }
+
     pub(crate) fn parse_proc_macro_execution_strategy(
         slot: &mut ProcMacroExecutionStrategy,
         v: Option<&str>,
@@ -1534,6 +1548,9 @@ options! {
         "instrument control-flow architecture protection"),
     codegen_backend: Option<String> = (None, parse_opt_string, [TRACKED],
         "the backend to use"),
+    collapse_macro_debuginfo: CollapseMacroDebuginfo = (CollapseMacroDebuginfo::Unspecified,
+        parse_collapse_macro_debuginfo, [TRACKED],
+        "set option to collapse debuginfo for macros"),
     combine_cgu: bool = (false, parse_bool, [TRACKED],
         "combine CGUs into a single one"),
     crate_attr: Vec<String> = (Vec::new(), parse_string_push, [TRACKED],
diff --git a/compiler/rustc_span/src/hygiene.rs b/compiler/rustc_span/src/hygiene.rs
index d03965b539c84..21623fdc1d234 100644
--- a/compiler/rustc_span/src/hygiene.rs
+++ b/compiler/rustc_span/src/hygiene.rs
@@ -464,12 +464,15 @@ impl HygieneData {
         &self,
         mut span: Span,
         to: Span,
-        collapse_debuginfo_enabled: bool,
+        collapse_debuginfo_feature_enabled: bool,
     ) -> Span {
         let orig_span = span;
         let mut ret_span = span;
 
-        debug!("walk_chain_collapsed({:?}, {:?})", span, to);
+        debug!(
+            "walk_chain_collapsed({:?}, {:?}), feature_enable={}",
+            span, to, collapse_debuginfo_feature_enabled,
+        );
         debug!("walk_chain_collapsed: span ctxt = {:?}", span.ctxt());
         while !span.eq_ctxt(to) && span.from_expansion() {
             let outer_expn = self.outer_expn(span.ctxt());
@@ -477,7 +480,7 @@ impl HygieneData {
             let expn_data = self.expn_data(outer_expn);
             debug!("walk_chain_collapsed({:?}): expn_data={:?}", span, expn_data);
             span = expn_data.call_site;
-            if !collapse_debuginfo_enabled || expn_data.collapse_debuginfo {
+            if !collapse_debuginfo_feature_enabled || expn_data.collapse_debuginfo {
                 ret_span = span;
             }
         }
@@ -601,8 +604,14 @@ pub fn walk_chain(span: Span, to: SyntaxContext) -> Span {
     HygieneData::with(|data| data.walk_chain(span, to))
 }
 
-pub fn walk_chain_collapsed(span: Span, to: Span, collapse_debuginfo_enabled: bool) -> Span {
-    HygieneData::with(|hdata| hdata.walk_chain_collapsed(span, to, collapse_debuginfo_enabled))
+pub fn walk_chain_collapsed(
+    span: Span,
+    to: Span,
+    collapse_debuginfo_feature_enabled: bool,
+) -> Span {
+    HygieneData::with(|hdata| {
+        hdata.walk_chain_collapsed(span, to, collapse_debuginfo_feature_enabled)
+    })
 }
 
 pub fn update_dollar_crate_names(mut get_name: impl FnMut(SyntaxContext) -> Symbol) {
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index 72b62a795fc50..44795022cbab3 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -749,6 +749,7 @@ symbols! {
         extern_in_paths,
         extern_prelude,
         extern_types,
+        external,
         external_doc,
         f,
         f16c_target_feature,
@@ -1811,6 +1812,7 @@ symbols! {
         xmm_reg,
         yeet_desugar_details,
         yeet_expr,
+        yes,
         yield_expr,
         ymm_reg,
         zmm_reg,
diff --git a/library/alloc/src/vec/in_place_collect.rs b/library/alloc/src/vec/in_place_collect.rs
index 0a2280545dac3..ec5f32539f2c2 100644
--- a/library/alloc/src/vec/in_place_collect.rs
+++ b/library/alloc/src/vec/in_place_collect.rs
@@ -9,7 +9,7 @@
 //! or [`BinaryHeap<T>`], the adapters guarantee to consume enough items per step to make room
 //! for the results (represented by [`InPlaceIterable`]), provide transitive access to `source`
 //! (via [`SourceIter`]) and thus the underlying allocation.
-//! And finally there are alignment and size constriants to consider, this is currently ensured via
+//! And finally there are alignment and size constraints to consider, this is currently ensured via
 //! const eval instead of trait bounds in the specialized [`SpecFromIter`] implementation.
 //!
 //! [`BinaryHeap<T>`]: crate::collections::BinaryHeap
diff --git a/src/librustdoc/clean/utils.rs b/src/librustdoc/clean/utils.rs
index 437517598ac49..b2b20c95a7e6a 100644
--- a/src/librustdoc/clean/utils.rs
+++ b/src/librustdoc/clean/utils.rs
@@ -312,7 +312,9 @@ pub(crate) fn name_from_pat(p: &hir::Pat<'_>) -> Symbol {
 
     Symbol::intern(&match p.kind {
         // FIXME(never_patterns): does this make sense?
-        PatKind::Wild | PatKind::Never | PatKind::Struct(..) => return kw::Underscore,
+        PatKind::Wild | PatKind::Err(_) | PatKind::Never | PatKind::Struct(..) => {
+            return kw::Underscore;
+        }
         PatKind::Binding(_, _, ident, _) => return ident.name,
         PatKind::TupleStruct(ref p, ..) | PatKind::Path(ref p) => qpath_to_string(p),
         PatKind::Or(pats) => {
diff --git a/src/tools/clippy/clippy_lints/src/equatable_if_let.rs b/src/tools/clippy/clippy_lints/src/equatable_if_let.rs
index 3c43529425265..4e728d61b853a 100644
--- a/src/tools/clippy/clippy_lints/src/equatable_if_let.rs
+++ b/src/tools/clippy/clippy_lints/src/equatable_if_let.rs
@@ -51,7 +51,8 @@ fn unary_pattern(pat: &Pat<'_>) -> bool {
         | PatKind::Binding(..)
         | PatKind::Wild
         | PatKind::Never
-        | PatKind::Or(_) => false,
+        | PatKind::Or(_)
+        | PatKind::Err(_) => false,
         PatKind::Struct(_, a, etc) => !etc && a.iter().all(|x| unary_pattern(x.pat)),
         PatKind::Tuple(a, etc) | PatKind::TupleStruct(_, a, etc) => etc.as_opt_usize().is_none() && array_rec(a),
         PatKind::Ref(x, _) | PatKind::Box(x) => unary_pattern(x),
diff --git a/src/tools/clippy/clippy_lints/src/matches/match_same_arms.rs b/src/tools/clippy/clippy_lints/src/matches/match_same_arms.rs
index c823d07e2bd3d..5ca161e93096d 100644
--- a/src/tools/clippy/clippy_lints/src/matches/match_same_arms.rs
+++ b/src/tools/clippy/clippy_lints/src/matches/match_same_arms.rs
@@ -11,7 +11,7 @@ use rustc_hir::{Arm, Expr, ExprKind, HirId, HirIdMap, HirIdMapEntry, HirIdSet, P
 use rustc_lint::builtin::NON_EXHAUSTIVE_OMITTED_PATTERNS;
 use rustc_lint::LateContext;
 use rustc_middle::ty;
-use rustc_span::Symbol;
+use rustc_span::{ErrorGuaranteed, Symbol};
 
 use super::MATCH_SAME_ARMS;
 
@@ -167,6 +167,8 @@ enum NormalizedPat<'a> {
     /// contains everything afterwards. Note that either side, or both sides, may contain zero
     /// patterns.
     Slice(&'a [Self], Option<&'a [Self]>),
+    /// A placeholder for a pattern that wasn't well formed in some way.
+    Err(ErrorGuaranteed),
 }
 
 #[derive(Clone, Copy)]
@@ -329,6 +331,7 @@ impl<'a> NormalizedPat<'a> {
                 arena.alloc_from_iter(front.iter().map(|pat| Self::from_pat(cx, arena, pat))),
                 wild_pat.map(|_| &*arena.alloc_from_iter(back.iter().map(|pat| Self::from_pat(cx, arena, pat)))),
             ),
+            PatKind::Err(guar) => Self::Err(guar),
         }
     }
 
diff --git a/src/tools/clippy/clippy_lints/src/unnested_or_patterns.rs b/src/tools/clippy/clippy_lints/src/unnested_or_patterns.rs
index 77adcdd0e6bfb..7246214f9bf87 100644
--- a/src/tools/clippy/clippy_lints/src/unnested_or_patterns.rs
+++ b/src/tools/clippy/clippy_lints/src/unnested_or_patterns.rs
@@ -226,7 +226,7 @@ fn transform_with_focus_on_idx(alternatives: &mut ThinVec<P<Pat>>, focus_idx: us
         // Therefore they are not some form of constructor `C`,
         // with which a pattern `C(p_0)` may be formed,
         // which we would want to join with other `C(p_j)`s.
-        Ident(.., None) | Lit(_) | Wild | Never | Path(..) | Range(..) | Rest | MacCall(_)
+        Ident(.., None) | Lit(_) | Wild | Err(_) | Never | Path(..) | Range(..) | Rest | MacCall(_)
         // Skip immutable refs, as grouping them saves few characters,
         // and almost always requires adding parens (increasing noisiness).
         // In the case of only two patterns, replacement adds net characters.
diff --git a/src/tools/clippy/clippy_lints/src/utils/author.rs b/src/tools/clippy/clippy_lints/src/utils/author.rs
index 8d38b87e1d794..b26ebe5cee321 100644
--- a/src/tools/clippy/clippy_lints/src/utils/author.rs
+++ b/src/tools/clippy/clippy_lints/src/utils/author.rs
@@ -710,6 +710,7 @@ impl<'a, 'tcx> PrintVisitor<'a, 'tcx> {
                 self.slice(start, |pat| self.pat(pat));
                 self.slice(end, |pat| self.pat(pat));
             },
+            PatKind::Err(_) => kind!("Err"),
         }
     }
 
diff --git a/src/tools/clippy/clippy_utils/src/hir_utils.rs b/src/tools/clippy/clippy_utils/src/hir_utils.rs
index 482eaed77d1d3..979b117db256a 100644
--- a/src/tools/clippy/clippy_utils/src/hir_utils.rs
+++ b/src/tools/clippy/clippy_utils/src/hir_utils.rs
@@ -1007,7 +1007,7 @@ impl<'a, 'tcx> SpanlessHash<'a, 'tcx> {
                 }
                 e.hash(&mut self.s);
             },
-            PatKind::Never | PatKind::Wild => {},
+            PatKind::Never | PatKind::Wild | PatKind::Err(_) => {},
         }
     }
 
diff --git a/src/tools/clippy/clippy_utils/src/lib.rs b/src/tools/clippy/clippy_utils/src/lib.rs
index cdf8528f48a27..2e54690d123cc 100644
--- a/src/tools/clippy/clippy_utils/src/lib.rs
+++ b/src/tools/clippy/clippy_utils/src/lib.rs
@@ -1733,6 +1733,7 @@ pub fn is_refutable(cx: &LateContext<'_>, pat: &Pat<'_>) -> bool {
                 },
             }
         },
+        PatKind::Err(_) => true,
     }
 }
 
diff --git a/src/tools/rust-analyzer/crates/parser/src/lexed_str.rs b/src/tools/rust-analyzer/crates/parser/src/lexed_str.rs
index f47ec49df1d9f..aa25f82ae1d8d 100644
--- a/src/tools/rust-analyzer/crates/parser/src/lexed_str.rs
+++ b/src/tools/rust-analyzer/crates/parser/src/lexed_str.rs
@@ -369,6 +369,7 @@ fn error_to_diagnostic_message(error: EscapeError, mode: Mode) -> &'static str {
             "non-ASCII character in byte string literal"
         }
         EscapeError::NonAsciiCharInByte => "non-ASCII character in raw byte string literal",
+        EscapeError::NulInCStr => "null character in C string literal",
         EscapeError::UnskippedWhitespaceWarning => "",
         EscapeError::MultipleSkippedLinesWarning => "",
     }
diff --git a/src/tools/rust-analyzer/crates/syntax/src/validation.rs b/src/tools/rust-analyzer/crates/syntax/src/validation.rs
index 6c6916c585f1f..69dffbf79f191 100644
--- a/src/tools/rust-analyzer/crates/syntax/src/validation.rs
+++ b/src/tools/rust-analyzer/crates/syntax/src/validation.rs
@@ -106,6 +106,9 @@ fn rustc_unescape_error_to_string(err: unescape::EscapeError) -> (&'static str,
         EE::NonAsciiCharInByte  => {
             "Byte literals must not contain non-ASCII characters"
         }
+        EE::NulInCStr  => {
+            "C strings literals must not contain null characters"
+        }
         EE::UnskippedWhitespaceWarning => "Whitespace after this escape is not skipped",
         EE::MultipleSkippedLinesWarning => "Multiple lines are skipped by this escape",
 
diff --git a/src/tools/rustfmt/src/patterns.rs b/src/tools/rustfmt/src/patterns.rs
index 0fa6edaa5d78b..7f57627943209 100644
--- a/src/tools/rustfmt/src/patterns.rs
+++ b/src/tools/rustfmt/src/patterns.rs
@@ -40,9 +40,11 @@ pub(crate) fn is_short_pattern(pat: &ast::Pat, pat_str: &str) -> bool {
 
 fn is_short_pattern_inner(pat: &ast::Pat) -> bool {
     match pat.kind {
-        ast::PatKind::Rest | ast::PatKind::Never | ast::PatKind::Wild | ast::PatKind::Lit(_) => {
-            true
-        }
+        ast::PatKind::Rest
+        | ast::PatKind::Never
+        | ast::PatKind::Wild
+        | ast::PatKind::Err(_)
+        | ast::PatKind::Lit(_) => true,
         ast::PatKind::Ident(_, _, ref pat) => pat.is_none(),
         ast::PatKind::Struct(..)
         | ast::PatKind::MacCall(..)
@@ -274,6 +276,7 @@ impl Rewrite for Pat {
             PatKind::Paren(ref pat) => pat
                 .rewrite(context, shape.offset_left(1)?.sub_width(1)?)
                 .map(|inner_pat| format!("({})", inner_pat)),
+            PatKind::Err(_) => None,
         }
     }
 }
diff --git a/tests/debuginfo/collapse-debuginfo-external-attr.rs b/tests/debuginfo/collapse-debuginfo-external-attr.rs
new file mode 100644
index 0000000000000..f36b0833ad519
--- /dev/null
+++ b/tests/debuginfo/collapse-debuginfo-external-attr.rs
@@ -0,0 +1,31 @@
+// ignore-lldb
+#![feature(collapse_debuginfo)]
+
+// Test that local macro debug info is not collapsed with #[collapse_debuginfo(external)]
+
+// compile-flags:-g
+
+// === GDB TESTS ===================================================================================
+
+// gdb-command:run
+// gdb-command:next
+// gdb-command:frame
+// gdb-check:[...]#one_callsite[...]
+// gdb-command:continue
+
+fn one() {
+    println!("one");
+}
+
+#[collapse_debuginfo(external)]
+macro_rules! outer {
+    () => {
+        one(); // #one_callsite
+    };
+}
+
+fn main() {
+    let ret = 0; // #break
+    outer!();
+    std::process::exit(ret);
+}
diff --git a/tests/debuginfo/collapse-debuginfo-external-flag-overriden-by-attr.rs b/tests/debuginfo/collapse-debuginfo-external-flag-overriden-by-attr.rs
new file mode 100644
index 0000000000000..e5cbc1a685d06
--- /dev/null
+++ b/tests/debuginfo/collapse-debuginfo-external-flag-overriden-by-attr.rs
@@ -0,0 +1,34 @@
+// ignore-lldb
+#![feature(collapse_debuginfo)]
+
+// Test that macro attribute #[collapse_debuginfo(no)]
+// overrides "collapse_macro_debuginfo=external" flag
+
+// compile-flags:-g -Z collapse_macro_debuginfo=external
+
+// === GDB TESTS ===================================================================================
+
+// gdb-command:run
+// gdb-command:next
+// gdb-command:frame
+// gdb-check:[...]#one_callsite[...]
+// gdb-command:next
+// gdb-command:frame
+// gdb-command:continue
+
+fn one() {
+    println!("one");
+}
+
+#[collapse_debuginfo(no)]
+macro_rules! outer {
+    () => {
+        one(); // #one_callsite
+    };
+}
+
+fn main() {
+    let ret = 0; // #break
+    outer!();
+    std::process::exit(ret);
+}
diff --git a/tests/debuginfo/collapse-debuginfo-external-flag.rs b/tests/debuginfo/collapse-debuginfo-external-flag.rs
new file mode 100644
index 0000000000000..9a0aef38ea6c1
--- /dev/null
+++ b/tests/debuginfo/collapse-debuginfo-external-flag.rs
@@ -0,0 +1,26 @@
+// ignore-lldb
+#![feature(collapse_debuginfo)]
+
+// Test that println macro debug info is collapsed with "collapse_macro_debuginfo=external" flag
+
+// compile-flags:-g -Z collapse_macro_debuginfo=external
+
+// === GDB TESTS ===================================================================================
+
+// gdb-command:run
+// gdb-command:next
+// gdb-command:frame
+// gdb-check:[...]#println_callsite[...]
+// gdb-command:continue
+
+macro_rules! outer {
+    () => {
+        println!("one"); // #println_callsite
+    };
+}
+
+fn main() {
+    let ret = 0; // #break
+    outer!();
+    std::process::exit(ret);
+}
diff --git a/tests/debuginfo/collapse-debuginfo-no-attr.rs b/tests/debuginfo/collapse-debuginfo-no-attr.rs
index 230c8795be365..d156c381a150e 100644
--- a/tests/debuginfo/collapse-debuginfo-no-attr.rs
+++ b/tests/debuginfo/collapse-debuginfo-no-attr.rs
@@ -4,7 +4,7 @@
 // Test that line numbers are not replaced with those of the outermost expansion site when the
 // `collapse_debuginfo` feature is active and the attribute is not provided.
 
-// compile-flags:-g
+// compile-flags:-g -Z collapse_macro_debuginfo=no
 
 // === GDB TESTS ===================================================================================
 
diff --git a/tests/debuginfo/collapse-debuginfo-with-yes-flag.rs b/tests/debuginfo/collapse-debuginfo-with-yes-flag.rs
new file mode 100644
index 0000000000000..76a97a325d7ef
--- /dev/null
+++ b/tests/debuginfo/collapse-debuginfo-with-yes-flag.rs
@@ -0,0 +1,57 @@
+// ignore-lldb
+#![feature(collapse_debuginfo)]
+
+// Test that line numbers are replaced with those of the outermost expansion site when the
+// `collapse_debuginfo` feature is active and the command line flag is provided.
+
+// compile-flags:-g -Z collapse_macro_debuginfo=yes
+
+// === GDB TESTS ===================================================================================
+
+// gdb-command:run
+// gdb-command:next
+// gdb-command:frame
+// gdb-check:[...]#loc1[...]
+// gdb-command:next
+// gdb-command:frame
+// gdb-check:[...]#loc2[...]
+// gdb-command:next
+// gdb-command:frame
+// gdb-check:[...]#loc3[...]
+// gdb-command:continue
+
+fn one() {
+    println!("one");
+}
+fn two() {
+    println!("two");
+}
+fn three() {
+    println!("three");
+}
+fn four() {
+    println!("four");
+}
+
+macro_rules! outer {
+    ($b:block) => {
+        one();
+        inner!();
+        $b
+    };
+}
+
+macro_rules! inner {
+    () => {
+        two();
+    };
+}
+
+fn main() {
+    let ret = 0; // #break
+    outer!({ // #loc1
+        three(); // #loc2
+        four(); // #loc3
+    });
+    std::process::exit(ret);
+}
diff --git a/tests/ui/closures/print/closure-print-generic-trim-off-verbose-2.stderr b/tests/ui/closures/print/closure-print-generic-trim-off-verbose-2.stderr
index 1a13255429f00..02d75ff1228d6 100644
--- a/tests/ui/closures/print/closure-print-generic-trim-off-verbose-2.stderr
+++ b/tests/ui/closures/print/closure-print-generic-trim-off-verbose-2.stderr
@@ -9,7 +9,7 @@ LL |         let c1 : () = c;
    |                  expected due to this
    |
    = note: expected unit type `()`
-                found closure `{mod1::f<T>::{closure#0} closure_args=(unavailable) args=[T, ?16t, extern "rust-call" fn(()), ?15t]}`
+                found closure `{mod1::f<T>::{closure#0} closure_args=(unavailable) args=[T, ?8t, extern "rust-call" fn(()), ?7t]}`
 help: use parentheses to call this closure
    |
 LL |         let c1 : () = c();
diff --git a/tests/ui/closures/print/closure-print-generic-verbose-2.stderr b/tests/ui/closures/print/closure-print-generic-verbose-2.stderr
index 8553817247d54..a536768898988 100644
--- a/tests/ui/closures/print/closure-print-generic-verbose-2.stderr
+++ b/tests/ui/closures/print/closure-print-generic-verbose-2.stderr
@@ -9,7 +9,7 @@ LL |         let c1 : () = c;
    |                  expected due to this
    |
    = note: expected unit type `()`
-                found closure `{f<T>::{closure#0} closure_args=(unavailable) args=[T, ?16t, extern "rust-call" fn(()), ?15t]}`
+                found closure `{f<T>::{closure#0} closure_args=(unavailable) args=[T, ?8t, extern "rust-call" fn(()), ?7t]}`
 help: use parentheses to call this closure
    |
 LL |         let c1 : () = c();
diff --git a/tests/ui/closures/print/closure-print-verbose.stderr b/tests/ui/closures/print/closure-print-verbose.stderr
index 3d0af5eb171c8..fca8f25792ac3 100644
--- a/tests/ui/closures/print/closure-print-verbose.stderr
+++ b/tests/ui/closures/print/closure-print-verbose.stderr
@@ -7,7 +7,7 @@ LL |     let foo: fn(u8) -> u8 = |v: u8| { a += v; a };
    |              expected due to this
    |
    = note: expected fn pointer `fn(u8) -> u8`
-                 found closure `{main::{closure#0} closure_args=(unavailable) args=[i8, extern "rust-call" fn((u8,)) -> u8, ?6t]}`
+                 found closure `{main::{closure#0} closure_args=(unavailable) args=[i8, extern "rust-call" fn((u8,)) -> u8, ?4t]}`
 note: closures can only be coerced to `fn` types if they do not capture any variables
   --> $DIR/closure-print-verbose.rs:10:39
    |
diff --git a/tests/ui/impl-trait/opaque-used-in-extraneous-argument.rs b/tests/ui/impl-trait/opaque-used-in-extraneous-argument.rs
new file mode 100644
index 0000000000000..529913479ef4b
--- /dev/null
+++ b/tests/ui/impl-trait/opaque-used-in-extraneous-argument.rs
@@ -0,0 +1,21 @@
+//! This is a regression test to avoid an ICE in diagnostics code.
+//! A typo in the compiler used to get the DefId of FnOnce, and
+//! use it where an associated item was expected.
+
+fn frob() -> impl Fn<P, Output = T> + '_ {}
+//~^ ERROR missing lifetime specifier
+//~| ERROR cannot find type `P`
+//~| ERROR cannot find type `T`
+//~| ERROR `Fn`-family traits' type parameters is subject to change
+
+fn open_parent<'path>() {
+    todo!()
+}
+
+fn main() {
+    let old_path = frob("hello");
+    //~^ ERROR function takes 0 arguments
+
+    open_parent(&old_path)
+    //~^ ERROR function takes 0 arguments
+}
diff --git a/tests/ui/impl-trait/opaque-used-in-extraneous-argument.stderr b/tests/ui/impl-trait/opaque-used-in-extraneous-argument.stderr
new file mode 100644
index 0000000000000..b54b9f908b2a4
--- /dev/null
+++ b/tests/ui/impl-trait/opaque-used-in-extraneous-argument.stderr
@@ -0,0 +1,78 @@
+error[E0106]: missing lifetime specifier
+  --> $DIR/opaque-used-in-extraneous-argument.rs:5:39
+   |
+LL | fn frob() -> impl Fn<P, Output = T> + '_ {}
+   |                                       ^^ expected named lifetime parameter
+   |
+   = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from
+help: consider using the `'static` lifetime, but this is uncommon unless you're returning a borrowed value from a `const` or a `static`, or if you will only have owned values
+   |
+LL | fn frob() -> impl Fn<P, Output = T> + 'static {}
+   |                                       ~~~~~~~
+
+error[E0412]: cannot find type `P` in this scope
+  --> $DIR/opaque-used-in-extraneous-argument.rs:5:22
+   |
+LL | fn frob() -> impl Fn<P, Output = T> + '_ {}
+   |                      ^ not found in this scope
+   |
+help: you might be missing a type parameter
+   |
+LL | fn frob<P>() -> impl Fn<P, Output = T> + '_ {}
+   |        +++
+
+error[E0412]: cannot find type `T` in this scope
+  --> $DIR/opaque-used-in-extraneous-argument.rs:5:34
+   |
+LL | fn frob() -> impl Fn<P, Output = T> + '_ {}
+   |                                  ^ not found in this scope
+   |
+help: you might be missing a type parameter
+   |
+LL | fn frob<T>() -> impl Fn<P, Output = T> + '_ {}
+   |        +++
+
+error[E0658]: the precise format of `Fn`-family traits' type parameters is subject to change
+  --> $DIR/opaque-used-in-extraneous-argument.rs:5:19
+   |
+LL | fn frob() -> impl Fn<P, Output = T> + '_ {}
+   |                   ^^^^^^^^^^^^^^^^^ help: use parenthetical notation instead: `Fn(P) -> T`
+   |
+   = note: see issue #29625 <https://github.com/rust-lang/rust/issues/29625> for more information
+   = help: add `#![feature(unboxed_closures)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+
+error[E0061]: this function takes 0 arguments but 1 argument was supplied
+  --> $DIR/opaque-used-in-extraneous-argument.rs:16:20
+   |
+LL |     let old_path = frob("hello");
+   |                    ^^^^ -------
+   |                         |
+   |                         unexpected argument of type `&'static str`
+   |                         help: remove the extra argument
+   |
+note: function defined here
+  --> $DIR/opaque-used-in-extraneous-argument.rs:5:4
+   |
+LL | fn frob() -> impl Fn<P, Output = T> + '_ {}
+   |    ^^^^
+
+error[E0061]: this function takes 0 arguments but 1 argument was supplied
+  --> $DIR/opaque-used-in-extraneous-argument.rs:19:5
+   |
+LL |     open_parent(&old_path)
+   |     ^^^^^^^^^^^ ---------
+   |                 |
+   |                 unexpected argument of type `&impl FnOnce<{type error}, Output = {type error}> + Fn<{type error}> + 'static`
+   |                 help: remove the extra argument
+   |
+note: function defined here
+  --> $DIR/opaque-used-in-extraneous-argument.rs:11:4
+   |
+LL | fn open_parent<'path>() {
+   |    ^^^^^^^^^^^
+
+error: aborting due to 6 previous errors
+
+Some errors have detailed explanations: E0061, E0106, E0412, E0658.
+For more information about an error, try `rustc --explain E0061`.
diff --git a/tests/ui/rfcs/rfc-3348-c-string-literals/no-nuls.rs b/tests/ui/rfcs/rfc-3348-c-string-literals/no-nuls.rs
index e20ca50b88f90..2f9ca09f3a5de 100644
Binary files a/tests/ui/rfcs/rfc-3348-c-string-literals/no-nuls.rs and b/tests/ui/rfcs/rfc-3348-c-string-literals/no-nuls.rs differ
diff --git a/tests/ui/rfcs/rfc-3348-c-string-literals/no-nuls.stderr b/tests/ui/rfcs/rfc-3348-c-string-literals/no-nuls.stderr
index ff9006f6f97f1..a05dea3ff07e6 100644
Binary files a/tests/ui/rfcs/rfc-3348-c-string-literals/no-nuls.stderr and b/tests/ui/rfcs/rfc-3348-c-string-literals/no-nuls.stderr differ