Rollup merge of #88775 - pnkfelix:revert-anon-union-parsing, r=davidtwco

Revert anon union parsing

Revert PR #84571 and #85515, which implemented anonymous union parsing in a manner that broke the context-sensitivity for the `union` keyword and thus broke stable Rust code.

Fix #88583.

21 files changed, 50 insertions, 595 deletions

diff --git a/compiler/rustc_ast/src/ast.rs b/compiler/rustc_ast/src/ast.rs
index b92c5fa0727..c27ab810a4c 100644
--- a/compiler/rustc_ast/src/ast.rs
+++ b/compiler/rustc_ast/src/ast.rs
@@ -1902,10 +1902,6 @@ pub enum TyKind {
     Never,
     /// A tuple (`(A, B, C, D,...)`).
     Tup(Vec<P<Ty>>),
-    /// An anonymous struct type i.e. `struct { foo: Type }`
-    AnonymousStruct(Vec<FieldDef>, bool),
-    /// An anonymous union type i.e. `union { bar: Type }`
-    AnonymousUnion(Vec<FieldDef>, bool),
     /// A path (`module::module::...::Type`), optionally
     /// "qualified", e.g., `<Vec<T> as SomeTrait>::SomeType`.
     ///
diff --git a/compiler/rustc_ast/src/mut_visit.rs b/compiler/rustc_ast/src/mut_visit.rs
index 2ec941cbb24..ba86036577a 100644
--- a/compiler/rustc_ast/src/mut_visit.rs
+++ b/compiler/rustc_ast/src/mut_visit.rs
@@ -484,9 +484,6 @@ pub fn noop_visit_ty<T: MutVisitor>(ty: &mut P<Ty>, vis: &mut T) {
             visit_vec(bounds, |bound| vis.visit_param_bound(bound));
         }
         TyKind::MacCall(mac) => vis.visit_mac_call(mac),
-        TyKind::AnonymousStruct(fields, ..) | TyKind::AnonymousUnion(fields, ..) => {
-            fields.flat_map_in_place(|field| vis.flat_map_field_def(field));
-        }
     }
     vis.visit_span(span);
     visit_lazy_tts(tokens, vis);
diff --git a/compiler/rustc_ast/src/visit.rs b/compiler/rustc_ast/src/visit.rs
index c30f711b397..b38031042e0 100644
--- a/compiler/rustc_ast/src/visit.rs
+++ b/compiler/rustc_ast/src/visit.rs
@@ -407,9 +407,6 @@ pub fn walk_ty<'a, V: Visitor<'a>>(visitor: &mut V, typ: &'a Ty) {
         TyKind::Typeof(ref expression) => visitor.visit_anon_const(expression),
         TyKind::Infer | TyKind::ImplicitSelf | TyKind::Err => {}
         TyKind::MacCall(ref mac) => visitor.visit_mac_call(mac),
-        TyKind::AnonymousStruct(ref fields, ..) | TyKind::AnonymousUnion(ref fields, ..) => {
-            walk_list!(visitor, visit_field_def, fields)
-        }
         TyKind::Never | TyKind::CVarArgs => {}
     }
 }
diff --git a/compiler/rustc_ast_lowering/src/item.rs b/compiler/rustc_ast_lowering/src/item.rs
index b7497c713f3..a77e3e1997f 100644
--- a/compiler/rustc_ast_lowering/src/item.rs
+++ b/compiler/rustc_ast_lowering/src/item.rs
@@ -748,10 +748,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         }
     }
 
-    pub(super) fn lower_field_def(
-        &mut self,
-        (index, f): (usize, &FieldDef),
-    ) -> hir::FieldDef<'hir> {
+    fn lower_field_def(&mut self, (index, f): (usize, &FieldDef)) -> hir::FieldDef<'hir> {
         let ty = if let TyKind::Path(ref qself, ref path) = f.ty.kind {
             let t = self.lower_path_ty(
                 &f.ty,
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index 8d731d7a578..4cf54b07dbe 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -1301,15 +1301,6 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         let kind = match t.kind {
             TyKind::Infer => hir::TyKind::Infer,
             TyKind::Err => hir::TyKind::Err,
-            // FIXME(unnamed_fields): IMPLEMENTATION IN PROGRESS
-            TyKind::AnonymousStruct(ref _fields, _recovered) => {
-                self.sess.struct_span_err(t.span, "anonymous structs are unimplemented").emit();
-                hir::TyKind::Err
-            }
-            TyKind::AnonymousUnion(ref _fields, _recovered) => {
-                self.sess.struct_span_err(t.span, "anonymous unions are unimplemented").emit();
-                hir::TyKind::Err
-            }
             TyKind::Slice(ref ty) => hir::TyKind::Slice(self.lower_ty(ty, itctx)),
             TyKind::Ptr(ref mt) => hir::TyKind::Ptr(self.lower_mt(mt, itctx)),
             TyKind::Rptr(ref region, ref mt) => {
diff --git a/compiler/rustc_ast_passes/src/ast_validation.rs b/compiler/rustc_ast_passes/src/ast_validation.rs
index 11153284cad..24108f779c8 100644
--- a/compiler/rustc_ast_passes/src/ast_validation.rs
+++ b/compiler/rustc_ast_passes/src/ast_validation.rs
@@ -193,11 +193,6 @@ impl<'a> AstValidator<'a> {
                     }
                 }
             }
-            TyKind::AnonymousStruct(ref fields, ..) | TyKind::AnonymousUnion(ref fields, ..) => {
-                self.with_banned_assoc_ty_bound(|this| {
-                    walk_list!(this, visit_struct_field_def, fields)
-                });
-            }
             _ => visit::walk_ty(self, t),
         }
     }
@@ -205,7 +200,6 @@ impl<'a> AstValidator<'a> {
     fn visit_struct_field_def(&mut self, field: &'a FieldDef) {
         if let Some(ident) = field.ident {
             if ident.name == kw::Underscore {
-                self.check_anonymous_field(field);
                 self.visit_vis(&field.vis);
                 self.visit_ident(ident);
                 self.visit_ty_common(&field.ty);
@@ -251,66 +245,6 @@ impl<'a> AstValidator<'a> {
         err.emit();
     }
 
-    fn check_anonymous_field(&self, field: &FieldDef) {
-        let FieldDef { ty, .. } = field;
-        match &ty.kind {
-            TyKind::AnonymousStruct(..) | TyKind::AnonymousUnion(..) => {
-                // We already checked for `kw::Underscore` before calling this function,
-                // so skip the check
-            }
-            TyKind::Path(..) => {
-                // If the anonymous field contains a Path as type, we can't determine
-                // if the path is a valid struct or union, so skip the check
-            }
-            _ => {
-                let msg = "unnamed fields can only have struct or union types";
-                let label = "not a struct or union";
-                self.err_handler()
-                    .struct_span_err(field.span, msg)
-                    .span_label(ty.span, label)
-                    .emit();
-            }
-        }
-    }
-
-    fn deny_anonymous_struct(&self, ty: &Ty) {
-        match &ty.kind {
-            TyKind::AnonymousStruct(..) => {
-                self.err_handler()
-                    .struct_span_err(
-                        ty.span,
-                        "anonymous structs are not allowed outside of unnamed struct or union fields",
-                    )
-                    .span_label(ty.span, "anonymous struct declared here")
-                    .emit();
-            }
-            TyKind::AnonymousUnion(..) => {
-                self.err_handler()
-                    .struct_span_err(
-                        ty.span,
-                        "anonymous unions are not allowed outside of unnamed struct or union fields",
-                    )
-                    .span_label(ty.span, "anonymous union declared here")
-                    .emit();
-            }
-            _ => {}
-        }
-    }
-
-    fn deny_anonymous_field(&self, field: &FieldDef) {
-        if let Some(ident) = field.ident {
-            if ident.name == kw::Underscore {
-                self.err_handler()
-                    .struct_span_err(
-                        field.span,
-                        "anonymous fields are not allowed outside of structs or unions",
-                    )
-                    .span_label(ident.span, "anonymous field declared here")
-                    .emit()
-            }
-        }
-    }
-
     fn check_decl_no_pat(decl: &FnDecl, mut report_err: impl FnMut(Span, Option<Ident>, bool)) {
         for Param { pat, .. } in &decl.inputs {
             match pat.kind {
@@ -1081,7 +1015,6 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
 
     fn visit_ty(&mut self, ty: &'a Ty) {
         self.visit_ty_common(ty);
-        self.deny_anonymous_struct(ty);
         self.walk_ty(ty)
     }
 
@@ -1096,7 +1029,6 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
     }
 
     fn visit_field_def(&mut self, s: &'a FieldDef) {
-        self.deny_anonymous_field(s);
         visit::walk_field_def(self, s)
     }
 
diff --git a/compiler/rustc_ast_passes/src/feature_gate.rs b/compiler/rustc_ast_passes/src/feature_gate.rs
index 1defb65ed87..30bc4edd7e6 100644
--- a/compiler/rustc_ast_passes/src/feature_gate.rs
+++ b/compiler/rustc_ast_passes/src/feature_gate.rs
@@ -668,7 +668,6 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session) {
         // involved, so we only emit errors where there are no other parsing errors.
         gate_all!(destructuring_assignment, "destructuring assignments are unstable");
     }
-    gate_all!(unnamed_fields, "unnamed fields are not yet fully implemented");
 
     // All uses of `gate_all!` below this point were added in #65742,
     // and subsequently disabled (with the non-early gating readded).
diff --git a/compiler/rustc_ast_pretty/src/pprust/state.rs b/compiler/rustc_ast_pretty/src/pprust/state.rs
index 3cf04be160c..c24882086e1 100644
--- a/compiler/rustc_ast_pretty/src/pprust/state.rs
+++ b/compiler/rustc_ast_pretty/src/pprust/state.rs
@@ -985,14 +985,6 @@ impl<'a> State<'a> {
                 }
                 self.pclose();
             }
-            ast::TyKind::AnonymousStruct(ref fields, ..) => {
-                self.head("struct");
-                self.print_record_struct_body(&fields, ty.span);
-            }
-            ast::TyKind::AnonymousUnion(ref fields, ..) => {
-                self.head("union");
-                self.print_record_struct_body(&fields, ty.span);
-            }
             ast::TyKind::Paren(ref typ) => {
                 self.popen();
                 self.print_type(typ);
@@ -1413,7 +1405,12 @@ impl<'a> State<'a> {
         }
     }
 
-    crate fn print_record_struct_body(&mut self, fields: &[ast::FieldDef], span: rustc_span::Span) {
+    crate fn print_record_struct_body(
+        &mut self,
+        fields: &Vec<ast::FieldDef>,
+        span: rustc_span::Span,
+    ) {
+        self.nbsp();
         self.bopen();
         self.hardbreak_if_not_bol();
 
@@ -1462,7 +1459,6 @@ impl<'a> State<'a> {
             }
             ast::VariantData::Struct(ref fields, ..) => {
                 self.print_where_clause(&generics.where_clause);
-                self.nbsp();
                 self.print_record_struct_body(fields, span);
             }
         }
diff --git a/compiler/rustc_feature/src/active.rs b/compiler/rustc_feature/src/active.rs
index 366ed715434..efa93c18636 100644
--- a/compiler/rustc_feature/src/active.rs
+++ b/compiler/rustc_feature/src/active.rs
@@ -638,9 +638,6 @@ declare_features! (
     /// Allows specifying the as-needed link modifier
     (active, native_link_modifiers_as_needed, "1.53.0", Some(81490), None),
 
-    /// Allows unnamed fields of struct and union type
-    (incomplete, unnamed_fields, "1.53.0", Some(49804), None),
-
     /// Allows qualified paths in struct expressions, struct patterns and tuple struct patterns.
     (active, more_qualified_paths, "1.54.0", Some(86935), None),
 
diff --git a/compiler/rustc_parse/src/parser/item.rs b/compiler/rustc_parse/src/parser/item.rs
index 04a7948e8c9..0e2222bf840 100644
--- a/compiler/rustc_parse/src/parser/item.rs
+++ b/compiler/rustc_parse/src/parser/item.rs
@@ -1247,7 +1247,7 @@ impl<'a> Parser<'a> {
         Ok((class_name, ItemKind::Union(vdata, generics)))
     }
 
-    pub(super) fn parse_record_struct_body(
+    fn parse_record_struct_body(
         &mut self,
         adt_ty: &str,
     ) -> PResult<'a, (Vec<FieldDef>, /* recovered */ bool)> {
@@ -1481,28 +1481,22 @@ impl<'a> Parser<'a> {
     fn parse_field_ident(&mut self, adt_ty: &str, lo: Span) -> PResult<'a, Ident> {
         let (ident, is_raw) = self.ident_or_err()?;
         if !is_raw && ident.is_reserved() {
-            if ident.name == kw::Underscore {
-                self.sess.gated_spans.gate(sym::unnamed_fields, lo);
+            let err = if self.check_fn_front_matter(false) {
+                // We use `parse_fn` to get a span for the function
+                if let Err(mut db) = self.parse_fn(&mut Vec::new(), |_| true, lo) {
+                    db.delay_as_bug();
+                }
+                let mut err = self.struct_span_err(
+                    lo.to(self.prev_token.span),
+                    &format!("functions are not allowed in {} definitions", adt_ty),
+                );
+                err.help("unlike in C++, Java, and C#, functions are declared in `impl` blocks");
+                err.help("see https://doc.rust-lang.org/book/ch05-03-method-syntax.html for more information");
+                err
             } else {
-                let err = if self.check_fn_front_matter(false) {
-                    // We use `parse_fn` to get a span for the function
-                    if let Err(mut db) = self.parse_fn(&mut Vec::new(), |_| true, lo) {
-                        db.delay_as_bug();
-                    }
-                    let mut err = self.struct_span_err(
-                        lo.to(self.prev_token.span),
-                        &format!("functions are not allowed in {} definitions", adt_ty),
-                    );
-                    err.help(
-                        "unlike in C++, Java, and C#, functions are declared in `impl` blocks",
-                    );
-                    err.help("see https://doc.rust-lang.org/book/ch05-03-method-syntax.html for more information");
-                    err
-                } else {
-                    self.expected_ident_found()
-                };
-                return Err(err);
-            }
+                self.expected_ident_found()
+            };
+            return Err(err);
         }
         self.bump();
         Ok(ident)
diff --git a/compiler/rustc_parse/src/parser/ty.rs b/compiler/rustc_parse/src/parser/ty.rs
index 299fc916ac9..98400372c36 100644
--- a/compiler/rustc_parse/src/parser/ty.rs
+++ b/compiler/rustc_parse/src/parser/ty.rs
@@ -226,19 +226,6 @@ impl<'a> Parser<'a> {
             }
         } else if self.eat_keyword(kw::Impl) {
             self.parse_impl_ty(&mut impl_dyn_multi)?
-        } else if self.token.is_keyword(kw::Union)
-            && self.look_ahead(1, |t| t == &token::OpenDelim(token::Brace))
-        {
-            self.bump();
-            let (fields, recovered) = self.parse_record_struct_body("union")?;
-            let span = lo.to(self.prev_token.span);
-            self.sess.gated_spans.gate(sym::unnamed_fields, span);
-            TyKind::AnonymousUnion(fields, recovered)
-        } else if self.eat_keyword(kw::Struct) {
-            let (fields, recovered) = self.parse_record_struct_body("struct")?;
-            let span = lo.to(self.prev_token.span);
-            self.sess.gated_spans.gate(sym::unnamed_fields, span);
-            TyKind::AnonymousStruct(fields, recovered)
         } else if self.is_explicit_dyn_type() {
             self.parse_dyn_ty(&mut impl_dyn_multi)?
         } else if self.eat_lt() {
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index 1df5b8cd2cc..4b416f29f26 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -1359,7 +1359,6 @@ symbols! {
         unix,
         unlikely,
         unmarked_api,
-        unnamed_fields,
         unpin,
         unreachable,
         unreachable_code,
diff --git a/src/test/pretty/anonymous-types.rs b/src/test/pretty/anonymous-types.rs
deleted file mode 100644
index 5ff452e8e43..00000000000
--- a/src/test/pretty/anonymous-types.rs
+++ /dev/null
@@ -1,24 +0,0 @@
-// Test for issue 85480
-// Pretty print anonymous struct and union types
-
-// pp-exact
-// pretty-compare-only
-
-struct Foo {
-    _: union {
-           _: struct {
-                  a: u8,
-                  b: u16,
-              },
-           c: u32,
-       },
-    d: u64,
-    e: f32,
-}
-
-type A =
- struct {
-     field: u8,
- };
-
-fn main() { }
diff --git a/src/test/ui/feature-gates/feature-gate-unnamed_fields.rs b/src/test/ui/feature-gates/feature-gate-unnamed_fields.rs
deleted file mode 100644
index bd815dbcc92..00000000000
--- a/src/test/ui/feature-gates/feature-gate-unnamed_fields.rs
+++ /dev/null
@@ -1,27 +0,0 @@
-struct Foo {
-    foo: u8,
-    _: union { //~ ERROR unnamed fields are not yet fully implemented [E0658]
-    //~^ ERROR unnamed fields are not yet fully implemented [E0658]
-    //~| ERROR anonymous unions are unimplemented
-        bar: u8,
-        baz: u16
-    }
-}
-
-union Bar {
-    foobar: u8,
-    _: struct { //~ ERROR unnamed fields are not yet fully implemented [E0658]
-    //~^ ERROR unnamed fields are not yet fully implemented [E0658]
-    //~| ERROR anonymous structs are unimplemented
-    //~| ERROR unions may not contain fields that need dropping [E0740]
-        foobaz: u8,
-        barbaz: u16
-    }
-}
-
-struct S;
-struct Baz {
-    _: S //~ ERROR unnamed fields are not yet fully implemented [E0658]
-}
-
-fn main(){}
diff --git a/src/test/ui/feature-gates/feature-gate-unnamed_fields.stderr b/src/test/ui/feature-gates/feature-gate-unnamed_fields.stderr
deleted file mode 100644
index 4f3ab85c987..00000000000
--- a/src/test/ui/feature-gates/feature-gate-unnamed_fields.stderr
+++ /dev/null
@@ -1,111 +0,0 @@
-error[E0658]: unnamed fields are not yet fully implemented
-  --> $DIR/feature-gate-unnamed_fields.rs:3:5
-   |
-LL |     _: union {
-   |     ^
-   |
-   = note: see issue #49804 <https://github.com/rust-lang/rust/issues/49804> for more information
-   = help: add `#![feature(unnamed_fields)]` to the crate attributes to enable
-
-error[E0658]: unnamed fields are not yet fully implemented
-  --> $DIR/feature-gate-unnamed_fields.rs:3:8
-   |
-LL |       _: union {
-   |  ________^
-LL | |
-LL | |
-LL | |         bar: u8,
-LL | |         baz: u16
-LL | |     }
-   | |_____^
-   |
-   = note: see issue #49804 <https://github.com/rust-lang/rust/issues/49804> for more information
-   = help: add `#![feature(unnamed_fields)]` to the crate attributes to enable
-
-error[E0658]: unnamed fields are not yet fully implemented
-  --> $DIR/feature-gate-unnamed_fields.rs:13:5
-   |
-LL |     _: struct {
-   |     ^
-   |
-   = note: see issue #49804 <https://github.com/rust-lang/rust/issues/49804> for more information
-   = help: add `#![feature(unnamed_fields)]` to the crate attributes to enable
-
-error[E0658]: unnamed fields are not yet fully implemented
-  --> $DIR/feature-gate-unnamed_fields.rs:13:8
-   |
-LL |       _: struct {
-   |  ________^
-LL | |
-LL | |
-LL | |
-LL | |         foobaz: u8,
-LL | |         barbaz: u16
-LL | |     }
-   | |_____^
-   |
-   = note: see issue #49804 <https://github.com/rust-lang/rust/issues/49804> for more information
-   = help: add `#![feature(unnamed_fields)]` to the crate attributes to enable
-
-error[E0658]: unnamed fields are not yet fully implemented
-  --> $DIR/feature-gate-unnamed_fields.rs:24:5
-   |
-LL |     _: S
-   |     ^
-   |
-   = note: see issue #49804 <https://github.com/rust-lang/rust/issues/49804> for more information
-   = help: add `#![feature(unnamed_fields)]` to the crate attributes to enable
-
-error: anonymous unions are unimplemented
-  --> $DIR/feature-gate-unnamed_fields.rs:3:8
-   |
-LL |       _: union {
-   |  ________^
-LL | |
-LL | |
-LL | |         bar: u8,
-LL | |         baz: u16
-LL | |     }
-   | |_____^
-
-error: anonymous structs are unimplemented
-  --> $DIR/feature-gate-unnamed_fields.rs:13:8
-   |
-LL |       _: struct {
-   |  ________^
-LL | |
-LL | |
-LL | |
-LL | |         foobaz: u8,
-LL | |         barbaz: u16
-LL | |     }
-   | |_____^
-
-error[E0740]: unions may not contain fields that need dropping
-  --> $DIR/feature-gate-unnamed_fields.rs:13:5
-   |
-LL | /     _: struct {
-LL | |
-LL | |
-LL | |
-LL | |         foobaz: u8,
-LL | |         barbaz: u16
-LL | |     }
-   | |_____^
-   |
-note: `std::mem::ManuallyDrop` can be used to wrap the type
-  --> $DIR/feature-gate-unnamed_fields.rs:13:5
-   |
-LL | /     _: struct {
-LL | |
-LL | |
-LL | |
-LL | |         foobaz: u8,
-LL | |         barbaz: u16
-LL | |     }
-   | |_____^
-
-error: aborting due to 8 previous errors
-
-Some errors have detailed explanations: E0658, E0740.
-For more information about an error, try `rustc --explain E0658`.
diff --git a/src/test/ui/parser/issue-88583-union-as-ident.rs b/src/test/ui/parser/issue-88583-union-as-ident.rs
new file mode 100644
index 00000000000..b3d66d46b1d
--- /dev/null
+++ b/src/test/ui/parser/issue-88583-union-as-ident.rs
@@ -0,0 +1,15 @@
+// check-pass
+
+#![allow(non_camel_case_types)]
+
+struct union;
+
+impl union {
+    pub fn new() -> Self {
+        union { }
+    }
+}
+
+fn main() {
+    let _u = union::new();
+}
diff --git a/src/test/ui/unnamed_fields/restrict_anonymous.rs b/src/test/ui/unnamed_fields/restrict_anonymous.rs
deleted file mode 100644
index 99637d11053..00000000000
--- a/src/test/ui/unnamed_fields/restrict_anonymous.rs
+++ /dev/null
@@ -1,52 +0,0 @@
-#![allow(incomplete_features)]
-#![feature(unnamed_fields)]
-
-fn f() -> struct { field: u8 } {} //~ ERROR anonymous structs are not allowed outside of unnamed struct or union fields
-//~^ ERROR anonymous structs are unimplemented
-
-fn f2(a: struct { field: u8 } ) {} //~ ERROR anonymous structs are not allowed outside of unnamed struct or union fields
-//~^ ERROR anonymous structs are unimplemented
-
-union G {
-    field: struct { field: u8 } //~ ERROR anonymous structs are not allowed outside of unnamed struct or union fields
-    //~^ ERROR anonymous structs are unimplemented
-}
-//~| ERROR unions may not contain fields that need dropping [E0740]
-
-struct H { _: u8 } // Should error after hir checks
-
-struct I(struct { field: u8 }, u8); //~ ERROR anonymous structs are not allowed outside of unnamed struct or union fields
-//~^ ERROR anonymous structs are unimplemented
-
-enum J {
-    K(struct { field: u8 }), //~ ERROR anonymous structs are not allowed outside of unnamed struct or union fields
-    //~^ ERROR anonymous structs are unimplemented
-    L {
-        _ : struct { field: u8 } //~ ERROR anonymous structs are not allowed outside of unnamed struct or union fields
-        //~^ ERROR anonymous fields are not allowed outside of structs or unions
-        //~| ERROR anonymous structs are unimplemented
-    },
-    M {
-        _ : u8 //~ ERROR anonymous fields are not allowed outside of structs or unions
-    }
-}
-
-static M: union { field: u8 } = 0; //~ ERROR anonymous unions are not allowed outside of unnamed struct or union fields
-//~^ ERROR anonymous unions are unimplemented
-
-type N = union { field: u8 }; //~ ERROR anonymous unions are not allowed outside of unnamed struct or union fields
-//~^ ERROR anonymous unions are unimplemented
-
-fn main() {
-    const O: struct { field: u8 } = 0; //~ ERROR anonymous structs are not allowed outside of unnamed struct or union fields
-    //~^ ERROR anonymous structs are unimplemented
-
-    let p: [struct { field: u8 }; 1]; //~ ERROR anonymous structs are not allowed outside of unnamed struct or union fields
-    //~^ ERROR anonymous structs are unimplemented
-
-    let q: (struct { field: u8 }, u8); //~ ERROR anonymous structs are not allowed outside of unnamed struct or union fields
-    //~^ ERROR anonymous structs are unimplemented
-
-    let cl = || -> struct { field: u8 } {}; //~ ERROR anonymous structs are not allowed outside of unnamed struct or union fields
-    //~^ ERROR anonymous structs are unimplemented
-}
diff --git a/src/test/ui/unnamed_fields/restrict_anonymous.stderr b/src/test/ui/unnamed_fields/restrict_anonymous.stderr
deleted file mode 100644
index efcf544fde4..00000000000
--- a/src/test/ui/unnamed_fields/restrict_anonymous.stderr
+++ /dev/null
@@ -1,175 +0,0 @@
-error: anonymous structs are not allowed outside of unnamed struct or union fields
-  --> $DIR/restrict_anonymous.rs:4:11
-   |
-LL | fn f() -> struct { field: u8 } {}
-   |           ^^^^^^^^^^^^^^^^^^^^ anonymous struct declared here
-
-error: anonymous structs are not allowed outside of unnamed struct or union fields
-  --> $DIR/restrict_anonymous.rs:7:10
-   |
-LL | fn f2(a: struct { field: u8 } ) {}
-   |          ^^^^^^^^^^^^^^^^^^^^ anonymous struct declared here
-
-error: anonymous structs are not allowed outside of unnamed struct or union fields
-  --> $DIR/restrict_anonymous.rs:11:12
-   |
-LL |     field: struct { field: u8 }
-   |            ^^^^^^^^^^^^^^^^^^^^ anonymous struct declared here
-
-error: anonymous structs are not allowed outside of unnamed struct or union fields
-  --> $DIR/restrict_anonymous.rs:18:10
-   |
-LL | struct I(struct { field: u8 }, u8);
-   |          ^^^^^^^^^^^^^^^^^^^^ anonymous struct declared here
-
-error: anonymous structs are not allowed outside of unnamed struct or union fields
-  --> $DIR/restrict_anonymous.rs:22:7
-   |
-LL |     K(struct { field: u8 }),
-   |       ^^^^^^^^^^^^^^^^^^^^ anonymous struct declared here
-
-error: anonymous fields are not allowed outside of structs or unions
-  --> $DIR/restrict_anonymous.rs:25:9
-   |
-LL |         _ : struct { field: u8 }
-   |         -^^^^^^^^^^^^^^^^^^^^^^^
-   |         |
-   |         anonymous field declared here
-
-error: anonymous structs are not allowed outside of unnamed struct or union fields
-  --> $DIR/restrict_anonymous.rs:25:13
-   |
-LL |         _ : struct { field: u8 }
-   |             ^^^^^^^^^^^^^^^^^^^^ anonymous struct declared here
-
-error: anonymous fields are not allowed outside of structs or unions
-  --> $DIR/restrict_anonymous.rs:30:9
-   |
-LL |         _ : u8
-   |         -^^^^^
-   |         |
-   |         anonymous field declared here
-
-error: anonymous unions are not allowed outside of unnamed struct or union fields
-  --> $DIR/restrict_anonymous.rs:34:11
-   |
-LL | static M: union { field: u8 } = 0;
-   |           ^^^^^^^^^^^^^^^^^^^ anonymous union declared here
-
-error: anonymous unions are not allowed outside of unnamed struct or union fields
-  --> $DIR/restrict_anonymous.rs:37:10
-   |
-LL | type N = union { field: u8 };
-   |          ^^^^^^^^^^^^^^^^^^^ anonymous union declared here
-
-error: anonymous structs are not allowed outside of unnamed struct or union fields
-  --> $DIR/restrict_anonymous.rs:41:14
-   |
-LL |     const O: struct { field: u8 } = 0;
-   |              ^^^^^^^^^^^^^^^^^^^^ anonymous struct declared here
-
-error: anonymous structs are not allowed outside of unnamed struct or union fields
-  --> $DIR/restrict_anonymous.rs:44:13
-   |
-LL |     let p: [struct { field: u8 }; 1];
-   |             ^^^^^^^^^^^^^^^^^^^^ anonymous struct declared here
-
-error: anonymous structs are not allowed outside of unnamed struct or union fields
-  --> $DIR/restrict_anonymous.rs:47:13
-   |
-LL |     let q: (struct { field: u8 }, u8);
-   |             ^^^^^^^^^^^^^^^^^^^^ anonymous struct declared here
-
-error: anonymous structs are not allowed outside of unnamed struct or union fields
-  --> $DIR/restrict_anonymous.rs:50:20
-   |
-LL |     let cl = || -> struct { field: u8 } {};
-   |                    ^^^^^^^^^^^^^^^^^^^^ anonymous struct declared here
-
-error: anonymous structs are unimplemented
-  --> $DIR/restrict_anonymous.rs:4:11
-   |
-LL | fn f() -> struct { field: u8 } {}
-   |           ^^^^^^^^^^^^^^^^^^^^
-
-error: anonymous structs are unimplemented
-  --> $DIR/restrict_anonymous.rs:7:10
-   |
-LL | fn f2(a: struct { field: u8 } ) {}
-   |          ^^^^^^^^^^^^^^^^^^^^
-
-error: anonymous structs are unimplemented
-  --> $DIR/restrict_anonymous.rs:11:12
-   |
-LL |     field: struct { field: u8 }
-   |            ^^^^^^^^^^^^^^^^^^^^
-
-error: anonymous structs are unimplemented
-  --> $DIR/restrict_anonymous.rs:18:10
-   |
-LL | struct I(struct { field: u8 }, u8);
-   |          ^^^^^^^^^^^^^^^^^^^^
-
-error: anonymous structs are unimplemented
-  --> $DIR/restrict_anonymous.rs:22:7
-   |
-LL |     K(struct { field: u8 }),
-   |       ^^^^^^^^^^^^^^^^^^^^
-
-error: anonymous structs are unimplemented
-  --> $DIR/restrict_anonymous.rs:25:13
-   |
-LL |         _ : struct { field: u8 }
-   |             ^^^^^^^^^^^^^^^^^^^^
-
-error: anonymous unions are unimplemented
-  --> $DIR/restrict_anonymous.rs:34:11
-   |
-LL | static M: union { field: u8 } = 0;
-   |           ^^^^^^^^^^^^^^^^^^^
-
-error: anonymous unions are unimplemented
-  --> $DIR/restrict_anonymous.rs:37:10
-   |
-LL | type N = union { field: u8 };
-   |          ^^^^^^^^^^^^^^^^^^^
-
-error: anonymous structs are unimplemented
-  --> $DIR/restrict_anonymous.rs:44:13
-   |
-LL |     let p: [struct { field: u8 }; 1];
-   |             ^^^^^^^^^^^^^^^^^^^^
-
-error: anonymous structs are unimplemented
-  --> $DIR/restrict_anonymous.rs:47:13
-   |
-LL |     let q: (struct { field: u8 }, u8);
-   |             ^^^^^^^^^^^^^^^^^^^^
-
-error: anonymous structs are unimplemented
-  --> $DIR/restrict_anonymous.rs:50:20
-   |
-LL |     let cl = || -> struct { field: u8 } {};
-   |                    ^^^^^^^^^^^^^^^^^^^^
-
-error: anonymous structs are unimplemented
-  --> $DIR/restrict_anonymous.rs:41:14
-   |
-LL |     const O: struct { field: u8 } = 0;
-   |              ^^^^^^^^^^^^^^^^^^^^
-
-error[E0740]: unions may not contain fields that need dropping
-  --> $DIR/restrict_anonymous.rs:11:5
-   |
-LL |     field: struct { field: u8 }
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-note: `std::mem::ManuallyDrop` can be used to wrap the type
-  --> $DIR/restrict_anonymous.rs:11:5
-   |
-LL |     field: struct { field: u8 }
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-error: aborting due to 27 previous errors
-
-For more information about this error, try `rustc --explain E0740`.
diff --git a/src/tools/rustfmt/src/items.rs b/src/tools/rustfmt/src/items.rs
index 2483d0570d9..14041539b9d 100644
--- a/src/tools/rustfmt/src/items.rs
+++ b/src/tools/rustfmt/src/items.rs
@@ -6,7 +6,7 @@ use std::cmp::{max, min, Ordering};
 use regex::Regex;
 use rustc_ast::visit;
 use rustc_ast::{ast, ptr};
-use rustc_span::{symbol, BytePos, Span};
+use rustc_span::{symbol, BytePos, Span, DUMMY_SP};
 
 use crate::attr::filter_inline_attrs;
 use crate::comment::{
@@ -31,7 +31,12 @@ use crate::stmt::Stmt;
 use crate::utils::*;
 use crate::vertical::rewrite_with_alignment;
 use crate::visitor::FmtVisitor;
-use crate::DEFAULT_VISIBILITY;
+
+const DEFAULT_VISIBILITY: ast::Visibility = ast::Visibility {
+    kind: ast::VisibilityKind::Inherited,
+    span: DUMMY_SP,
+    tokens: None,
+};
 
 fn type_annotation_separator(config: &Config) -> &str {
     colon_spaces(config)
@@ -972,7 +977,7 @@ impl<'a> StructParts<'a> {
         format_header(context, self.prefix, self.ident, self.vis, offset)
     }
 
-    pub(crate) fn from_variant(variant: &'a ast::Variant) -> Self {
+    fn from_variant(variant: &'a ast::Variant) -> Self {
         StructParts {
             prefix: "",
             ident: variant.ident,
diff --git a/src/tools/rustfmt/src/lib.rs b/src/tools/rustfmt/src/lib.rs
index 206d2f78290..47a7b9d4dbe 100644
--- a/src/tools/rustfmt/src/lib.rs
+++ b/src/tools/rustfmt/src/lib.rs
@@ -32,7 +32,7 @@ use std::path::PathBuf;
 use std::rc::Rc;
 
 use rustc_ast::ast;
-use rustc_span::{symbol, DUMMY_SP};
+use rustc_span::symbol;
 use thiserror::Error;
 
 use crate::comment::LineClasses;
@@ -96,11 +96,6 @@ mod types;
 mod vertical;
 pub(crate) mod visitor;
 
-const DEFAULT_VISIBILITY: ast::Visibility = ast::Visibility {
-    kind: ast::VisibilityKind::Inherited,
-    span: DUMMY_SP,
-    tokens: None,
-};
 /// The various errors that can occur during formatting. Note that not all of
 /// these can currently be propagated to clients.
 #[derive(Error, Debug)]
diff --git a/src/tools/rustfmt/src/types.rs b/src/tools/rustfmt/src/types.rs
index 640d127e860..76bf58e875b 100644
--- a/src/tools/rustfmt/src/types.rs
+++ b/src/tools/rustfmt/src/types.rs
@@ -1,15 +1,15 @@
 use std::iter::ExactSizeIterator;
 use std::ops::Deref;
 
-use rustc_ast::ast::{self, AttrVec, FnRetTy, Mutability};
-use rustc_span::{symbol::kw, symbol::Ident, BytePos, Pos, Span};
+use rustc_ast::ast::{self, FnRetTy, Mutability};
+use rustc_span::{symbol::kw, BytePos, Pos, Span};
 
+use crate::comment::{combine_strs_with_missing_comments, contains_comment};
 use crate::config::lists::*;
 use crate::config::{IndentStyle, TypeDensity, Version};
 use crate::expr::{
     format_expr, rewrite_assign_rhs, rewrite_call, rewrite_tuple, rewrite_unary_prefix, ExprType,
 };
-use crate::items::StructParts;
 use crate::lists::{
     definitive_tactic, itemize_list, write_list, ListFormatting, ListItem, Separator,
 };
@@ -24,11 +24,6 @@ use crate::utils::{
     colon_spaces, extra_offset, first_line_width, format_extern, format_mutability,
     last_line_extendable, last_line_width, mk_sp, rewrite_ident,
 };
-use crate::DEFAULT_VISIBILITY;
-use crate::{
-    comment::{combine_strs_with_missing_comments, contains_comment},
-    items::format_struct_struct,
-};
 
 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
 pub(crate) enum PathContext {
@@ -769,54 +764,6 @@ impl Rewrite for ast::Ty {
             ast::TyKind::Tup(ref items) => {
                 rewrite_tuple(context, items.iter(), self.span, shape, items.len() == 1)
             }
-            ast::TyKind::AnonymousStruct(ref fields, recovered) => {
-                let ident = Ident::new(
-                    kw::Struct,
-                    mk_sp(self.span.lo(), self.span.lo() + BytePos(6)),
-                );
-                let data = ast::VariantData::Struct(fields.clone(), recovered);
-                let variant = ast::Variant {
-                    attrs: AttrVec::new(),
-                    id: self.id,
-                    span: self.span,
-                    vis: DEFAULT_VISIBILITY,
-                    ident,
-                    data,
-                    disr_expr: None,
-                    is_placeholder: false,
-                };
-                format_struct_struct(
-                    &context,
-                    &StructParts::from_variant(&variant),
-                    fields,
-                    shape.indent,
-                    None,
-                )
-            }
-            ast::TyKind::AnonymousUnion(ref fields, recovered) => {
-                let ident = Ident::new(
-                    kw::Union,
-                    mk_sp(self.span.lo(), self.span.lo() + BytePos(5)),
-                );
-                let data = ast::VariantData::Struct(fields.clone(), recovered);
-                let variant = ast::Variant {
-                    attrs: AttrVec::new(),
-                    id: self.id,
-                    span: self.span,
-                    vis: DEFAULT_VISIBILITY,
-                    ident,
-                    data,
-                    disr_expr: None,
-                    is_placeholder: false,
-                };
-                format_struct_struct(
-                    &context,
-                    &StructParts::from_variant(&variant),
-                    fields,
-                    shape.indent,
-                    None,
-                )
-            }
             ast::TyKind::Path(ref q_self, ref path) => {
                 rewrite_path(context, PathContext::Type, q_self.as_ref(), path, shape)
             }