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.

9 files changed, 27 insertions, 454 deletions

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)
             }