Add StaticForeignItem and use it on ForeignItemKind
diff --git a/compiler/rustc_ast/src/ast.rs b/compiler/rustc_ast/src/ast.rs
index af246e3..f24e2a2 100644
--- a/compiler/rustc_ast/src/ast.rs
+++ b/compiler/rustc_ast/src/ast.rs
@@ -3126,6 +3126,35 @@
     pub expr: Option<P<Expr>>,
 }
 
+/// A static item in `extern` block.
+// This struct is identical to StaticItem for now but it's going to have a safety attribute.
+#[derive(Clone, Encodable, Decodable, Debug)]
+pub struct StaticForeignItem {
+    pub ty: P<Ty>,
+    pub mutability: Mutability,
+    pub expr: Option<P<Expr>>,
+}
+
+impl From<StaticItem> for StaticForeignItem {
+    fn from(static_item: StaticItem) -> StaticForeignItem {
+        StaticForeignItem {
+            ty: static_item.ty,
+            mutability: static_item.mutability,
+            expr: static_item.expr,
+        }
+    }
+}
+
+impl From<StaticForeignItem> for StaticItem {
+    fn from(static_item: StaticForeignItem) -> StaticItem {
+        StaticItem {
+            ty: static_item.ty,
+            mutability: static_item.mutability,
+            expr: static_item.expr,
+        }
+    }
+}
+
 #[derive(Clone, Encodable, Decodable, Debug)]
 pub struct ConstItem {
     pub defaultness: Defaultness,
@@ -3329,7 +3358,7 @@
 #[derive(Clone, Encodable, Decodable, Debug)]
 pub enum ForeignItemKind {
     /// A foreign static item (`static FOO: u8`).
-    Static(P<Ty>, Mutability, Option<P<Expr>>),
+    Static(Box<StaticForeignItem>),
     /// An foreign function.
     Fn(Box<Fn>),
     /// An foreign type.
@@ -3341,8 +3370,8 @@
 impl From<ForeignItemKind> for ItemKind {
     fn from(foreign_item_kind: ForeignItemKind) -> ItemKind {
         match foreign_item_kind {
-            ForeignItemKind::Static(a, b, c) => {
-                ItemKind::Static(StaticItem { ty: a, mutability: b, expr: c }.into())
+            ForeignItemKind::Static(box static_foreign_item) => {
+                ItemKind::Static(Box::new(static_foreign_item.into()))
             }
             ForeignItemKind::Fn(fn_kind) => ItemKind::Fn(fn_kind),
             ForeignItemKind::TyAlias(ty_alias_kind) => ItemKind::TyAlias(ty_alias_kind),
@@ -3356,8 +3385,8 @@
 
     fn try_from(item_kind: ItemKind) -> Result<ForeignItemKind, ItemKind> {
         Ok(match item_kind {
-            ItemKind::Static(box StaticItem { ty: a, mutability: b, expr: c }) => {
-                ForeignItemKind::Static(a, b, c)
+            ItemKind::Static(box static_item) => {
+                ForeignItemKind::Static(Box::new(static_item.into()))
             }
             ItemKind::Fn(fn_kind) => ForeignItemKind::Fn(fn_kind),
             ItemKind::TyAlias(ty_alias_kind) => ForeignItemKind::TyAlias(ty_alias_kind),
@@ -3382,8 +3411,8 @@
     static_assert_size!(Expr, 72);
     static_assert_size!(ExprKind, 40);
     static_assert_size!(Fn, 160);
-    static_assert_size!(ForeignItem, 96);
-    static_assert_size!(ForeignItemKind, 24);
+    static_assert_size!(ForeignItem, 88);
+    static_assert_size!(ForeignItemKind, 16);
     static_assert_size!(GenericArg, 24);
     static_assert_size!(GenericBound, 88);
     static_assert_size!(Generics, 40);
diff --git a/compiler/rustc_ast/src/mut_visit.rs b/compiler/rustc_ast/src/mut_visit.rs
index fc44560..4d28ef5 100644
--- a/compiler/rustc_ast/src/mut_visit.rs
+++ b/compiler/rustc_ast/src/mut_visit.rs
@@ -1261,7 +1261,7 @@
 impl NoopVisitItemKind for ForeignItemKind {
     fn noop_visit(&mut self, visitor: &mut impl MutVisitor) {
         match self {
-            ForeignItemKind::Static(ty, _, expr) => {
+            ForeignItemKind::Static(box StaticForeignItem { ty, mutability: _, expr }) => {
                 visitor.visit_ty(ty);
                 visit_opt(expr, |expr| visitor.visit_expr(expr));
             }
diff --git a/compiler/rustc_ast/src/visit.rs b/compiler/rustc_ast/src/visit.rs
index a0ada9a..1d8fd63 100644
--- a/compiler/rustc_ast/src/visit.rs
+++ b/compiler/rustc_ast/src/visit.rs
@@ -642,7 +642,7 @@
     ) -> V::Result {
         let &Item { id, span, ident, ref vis, .. } = item;
         match self {
-            ForeignItemKind::Static(ty, _, expr) => {
+            ForeignItemKind::Static(box StaticForeignItem { ty, mutability: _, expr }) => {
                 try_visit!(visitor.visit_ty(ty));
                 visit_opt!(visitor, visit_expr, expr);
             }
diff --git a/compiler/rustc_ast_lowering/src/item.rs b/compiler/rustc_ast_lowering/src/item.rs
index dcce54d..ccbc44b 100644
--- a/compiler/rustc_ast_lowering/src/item.rs
+++ b/compiler/rustc_ast_lowering/src/item.rs
@@ -662,10 +662,10 @@
 
                     hir::ForeignItemKind::Fn(fn_dec, fn_args, generics)
                 }
-                ForeignItemKind::Static(t, m, _) => {
-                    let ty =
-                        self.lower_ty(t, ImplTraitContext::Disallowed(ImplTraitPosition::StaticTy));
-                    hir::ForeignItemKind::Static(ty, *m)
+                ForeignItemKind::Static(box StaticForeignItem { ty, mutability, expr: _ }) => {
+                    let ty = self
+                        .lower_ty(ty, ImplTraitContext::Disallowed(ImplTraitPosition::StaticTy));
+                    hir::ForeignItemKind::Static(ty, *mutability)
                 }
                 ForeignItemKind::TyAlias(..) => hir::ForeignItemKind::Type,
                 ForeignItemKind::MacCall(_) => panic!("macro shouldn't exist here"),
diff --git a/compiler/rustc_ast_passes/src/ast_validation.rs b/compiler/rustc_ast_passes/src/ast_validation.rs
index 1fb4102..1eefad2 100644
--- a/compiler/rustc_ast_passes/src/ast_validation.rs
+++ b/compiler/rustc_ast_passes/src/ast_validation.rs
@@ -1185,8 +1185,8 @@
                 self.check_foreign_ty_genericless(generics, where_clauses);
                 self.check_foreign_item_ascii_only(fi.ident);
             }
-            ForeignItemKind::Static(_, _, body) => {
-                self.check_foreign_kind_bodyless(fi.ident, "static", body.as_ref().map(|b| b.span));
+            ForeignItemKind::Static(box StaticForeignItem { ty: _, mutability: _, expr }) => {
+                self.check_foreign_kind_bodyless(fi.ident, "static", expr.as_ref().map(|b| b.span));
                 self.check_foreign_item_ascii_only(fi.ident);
             }
             ForeignItemKind::MacCall(..) => {}
diff --git a/compiler/rustc_ast_pretty/src/pprust/state/item.rs b/compiler/rustc_ast_pretty/src/pprust/state/item.rs
index 10886aa..b90182c 100644
--- a/compiler/rustc_ast_pretty/src/pprust/state/item.rs
+++ b/compiler/rustc_ast_pretty/src/pprust/state/item.rs
@@ -30,15 +30,17 @@
             ast::ForeignItemKind::Fn(box ast::Fn { defaultness, sig, generics, body }) => {
                 self.print_fn_full(sig, ident, generics, vis, *defaultness, body.as_deref(), attrs);
             }
-            ast::ForeignItemKind::Static(ty, mutbl, body) => self.print_item_const(
-                ident,
-                Some(*mutbl),
-                &ast::Generics::default(),
-                ty,
-                body.as_deref(),
-                vis,
-                ast::Defaultness::Final,
-            ),
+            ast::ForeignItemKind::Static(box ast::StaticForeignItem { ty, mutability, expr }) => {
+                self.print_item_const(
+                    ident,
+                    Some(*mutability),
+                    &ast::Generics::default(),
+                    ty,
+                    expr.as_deref(),
+                    vis,
+                    ast::Defaultness::Final,
+                )
+            }
             ast::ForeignItemKind::TyAlias(box ast::TyAlias {
                 defaultness,
                 generics,
diff --git a/compiler/rustc_parse/src/parser/item.rs b/compiler/rustc_parse/src/parser/item.rs
index ed51710..848277c 100644
--- a/compiler/rustc_parse/src/parser/item.rs
+++ b/compiler/rustc_parse/src/parser/item.rs
@@ -1191,7 +1191,11 @@
                                 ident_span: ident.span,
                                 const_span,
                             });
-                            ForeignItemKind::Static(ty, Mutability::Not, expr)
+                            ForeignItemKind::Static(Box::new(StaticForeignItem {
+                                ty,
+                                mutability: Mutability::Not,
+                                expr,
+                            }))
                         }
                         _ => return self.error_bad_item_kind(span, &kind, "`extern` blocks"),
                     },
diff --git a/compiler/rustc_resolve/src/def_collector.rs b/compiler/rustc_resolve/src/def_collector.rs
index d4d999f..a27a6bc 100644
--- a/compiler/rustc_resolve/src/def_collector.rs
+++ b/compiler/rustc_resolve/src/def_collector.rs
@@ -209,7 +209,7 @@
 
     fn visit_foreign_item(&mut self, fi: &'a ForeignItem) {
         let def_kind = match fi.kind {
-            ForeignItemKind::Static(_, mutability, _) => {
+            ForeignItemKind::Static(box StaticForeignItem { ty: _, mutability, expr: _ }) => {
                 DefKind::Static { mutability, nested: false }
             }
             ForeignItemKind::Fn(_) => DefKind::Fn,
diff --git a/src/tools/clippy/clippy_utils/src/ast_utils.rs b/src/tools/clippy/clippy_utils/src/ast_utils.rs
index 0395eb1..529d201 100644
--- a/src/tools/clippy/clippy_utils/src/ast_utils.rs
+++ b/src/tools/clippy/clippy_utils/src/ast_utils.rs
@@ -446,7 +446,18 @@
 pub fn eq_foreign_item_kind(l: &ForeignItemKind, r: &ForeignItemKind) -> bool {
     use ForeignItemKind::*;
     match (l, r) {
-        (Static(lt, lm, le), Static(rt, rm, re)) => lm == rm && eq_ty(lt, rt) && eq_expr_opt(le, re),
+        (
+            Static(box StaticForeignItem {
+                ty: lt,
+                mutability: lm,
+                expr: le,
+            }),
+            Static(box StaticForeignItem {
+                ty: rt,
+                mutability: rm,
+                expr: re,
+            }),
+        ) => lm == rm && eq_ty(lt, rt) && eq_expr_opt(le, re),
         (
             Fn(box ast::Fn {
                 defaultness: ld,
diff --git a/src/tools/rustfmt/src/items.rs b/src/tools/rustfmt/src/items.rs
index f6f51fb..e196d18 100644
--- a/src/tools/rustfmt/src/items.rs
+++ b/src/tools/rustfmt/src/items.rs
@@ -3325,11 +3325,11 @@
                     .map(|(s, _, _)| format!("{};", s))
                 }
             }
-            ast::ForeignItemKind::Static(ref ty, mutability, _) => {
+            ast::ForeignItemKind::Static(ref static_foreign_item) => {
                 // FIXME(#21): we're dropping potential comments in between the
                 // function kw here.
                 let vis = format_visibility(context, &self.vis);
-                let mut_str = format_mutability(mutability);
+                let mut_str = format_mutability(static_foreign_item.mutability);
                 let prefix = format!(
                     "{}static {}{}:",
                     vis,
@@ -3340,7 +3340,7 @@
                 rewrite_assign_rhs(
                     context,
                     prefix,
-                    &**ty,
+                    &static_foreign_item.ty,
                     &RhsAssignKind::Ty,
                     shape.sub_width(1)?,
                 )
diff --git a/tests/ui/stats/hir-stats.stderr b/tests/ui/stats/hir-stats.stderr
index dc24833..1a67c94 100644
--- a/tests/ui/stats/hir-stats.stderr
+++ b/tests/ui/stats/hir-stats.stderr
@@ -11,15 +11,15 @@
 ast-stats-1 - Normal                    32 ( 0.5%)             1
 ast-stats-1 - DocComment                32 ( 0.5%)             1
 ast-stats-1 Local                     80 ( 1.2%)             1            80
-ast-stats-1 Arm                       96 ( 1.4%)             2            48
-ast-stats-1 ForeignItem               96 ( 1.4%)             1            96
-ast-stats-1 - Fn                        96 ( 1.4%)             1
+ast-stats-1 ForeignItem               88 ( 1.3%)             1            88
+ast-stats-1 - Fn                        88 ( 1.3%)             1
+ast-stats-1 Arm                       96 ( 1.5%)             2            48
 ast-stats-1 FnDecl                   120 ( 1.8%)             5            24
 ast-stats-1 FieldDef                 160 ( 2.4%)             2            80
 ast-stats-1 Stmt                     160 ( 2.4%)             5            32
 ast-stats-1 - Let                       32 ( 0.5%)             1
 ast-stats-1 - MacCall                   32 ( 0.5%)             1
-ast-stats-1 - Expr                      96 ( 1.4%)             3
+ast-stats-1 - Expr                      96 ( 1.5%)             3
 ast-stats-1 Param                    160 ( 2.4%)             4            40
 ast-stats-1 Block                    192 ( 2.9%)             6            32
 ast-stats-1 Variant                  208 ( 3.1%)             2           104
@@ -28,7 +28,7 @@
 ast-stats-1 AssocItem                352 ( 5.3%)             4            88
 ast-stats-1 - Type                     176 ( 2.7%)             2
 ast-stats-1 - Fn                       176 ( 2.7%)             2
-ast-stats-1 GenericParam             480 ( 7.2%)             5            96
+ast-stats-1 GenericParam             480 ( 7.3%)             5            96
 ast-stats-1 Pat                      504 ( 7.6%)             7            72
 ast-stats-1 - Struct                    72 ( 1.1%)             1
 ast-stats-1 - Wild                      72 ( 1.1%)             1
@@ -53,7 +53,7 @@
 ast-stats-1 - Fn                       272 ( 4.1%)             2
 ast-stats-1 - Use                      408 ( 6.2%)             3
 ast-stats-1 ----------------------------------------------------------------
-ast-stats-1 Total                  6_624
+ast-stats-1 Total                  6_616
 ast-stats-1
 ast-stats-2 POST EXPANSION AST STATS
 ast-stats-2 Name                Accumulated Size         Count     Item Size
@@ -65,9 +65,9 @@
 ast-stats-2 WherePredicate            56 ( 0.8%)             1            56
 ast-stats-2 - BoundPredicate            56 ( 0.8%)             1
 ast-stats-2 Local                     80 ( 1.1%)             1            80
+ast-stats-2 ForeignItem               88 ( 1.2%)             1            88
+ast-stats-2 - Fn                        88 ( 1.2%)             1
 ast-stats-2 Arm                       96 ( 1.3%)             2            48
-ast-stats-2 ForeignItem               96 ( 1.3%)             1            96
-ast-stats-2 - Fn                        96 ( 1.3%)             1
 ast-stats-2 InlineAsm                120 ( 1.7%)             1           120
 ast-stats-2 FnDecl                   120 ( 1.7%)             5            24
 ast-stats-2 Attribute                128 ( 1.8%)             4            32
@@ -86,7 +86,7 @@
 ast-stats-2 AssocItem                352 ( 4.9%)             4            88
 ast-stats-2 - Type                     176 ( 2.4%)             2
 ast-stats-2 - Fn                       176 ( 2.4%)             2
-ast-stats-2 GenericParam             480 ( 6.6%)             5            96
+ast-stats-2 GenericParam             480 ( 6.7%)             5            96
 ast-stats-2 Pat                      504 ( 7.0%)             7            72
 ast-stats-2 - Struct                    72 ( 1.0%)             1
 ast-stats-2 - Wild                      72 ( 1.0%)             1
@@ -113,7 +113,7 @@
 ast-stats-2 - Fn                       272 ( 3.8%)             2
 ast-stats-2 - Use                      544 ( 7.5%)             4
 ast-stats-2 ----------------------------------------------------------------
-ast-stats-2 Total                  7_224
+ast-stats-2 Total                  7_216
 ast-stats-2
 hir-stats HIR STATS
 hir-stats Name                Accumulated Size         Count     Item Size