Check representation of unnamed fields

12 files changed, 309 insertions, 30 deletions

diff --git a/compiler/rustc_hir_analysis/messages.ftl b/compiler/rustc_hir_analysis/messages.ftl
index 662d859e993..cf1a42c9285 100644
--- a/compiler/rustc_hir_analysis/messages.ftl
+++ b/compiler/rustc_hir_analysis/messages.ftl
@@ -439,6 +439,17 @@ hir_analysis_typeof_reserved_keyword_used =
 hir_analysis_unconstrained_opaque_type = unconstrained opaque type
     .note = `{$name}` must be used in combination with a concrete type within the same {$what}
 
+hir_analysis_unnamed_fields_repr_field_defined = unnamed field defined here
+
+hir_analysis_unnamed_fields_repr_field_missing_repr_c =
+    named type of unnamed field must have `#[repr(C)]` representation
+    .label = unnamed field defined here
+    .field_ty_label = `{$field_ty}` defined here
+
+hir_analysis_unnamed_fields_repr_missing_repr_c =
+    {$adt_kind} with unnamed fields must have `#[repr(C)]` representation
+    .label = {$adt_kind} `{$adt_name}` defined here
+
 hir_analysis_unrecognized_atomic_operation =
     unrecognized atomic operation function: `{$op}`
     .label = unrecognized atomic operation
diff --git a/compiler/rustc_hir_analysis/src/check/check.rs b/compiler/rustc_hir_analysis/src/check/check.rs
index 7250dc81faf..3cbd67a482c 100644
--- a/compiler/rustc_hir_analysis/src/check/check.rs
+++ b/compiler/rustc_hir_analysis/src/check/check.rs
@@ -80,6 +80,7 @@ fn check_struct(tcx: TyCtxt<'_>, def_id: LocalDefId) {
 
     check_transparent(tcx, def);
     check_packed(tcx, span, def);
+    check_unnamed_fields(tcx, def);
 }
 
 fn check_union(tcx: TyCtxt<'_>, def_id: LocalDefId) {
@@ -89,6 +90,54 @@ fn check_union(tcx: TyCtxt<'_>, def_id: LocalDefId) {
     check_transparent(tcx, def);
     check_union_fields(tcx, span, def_id);
     check_packed(tcx, span, def);
+    check_unnamed_fields(tcx, def);
+}
+
+/// Check the representation of adts with unnamed fields.
+fn check_unnamed_fields(tcx: TyCtxt<'_>, def: ty::AdtDef<'_>) {
+    if def.is_enum() {
+        return;
+    }
+    let variant = def.non_enum_variant();
+    if !variant.has_unnamed_fields() {
+        return;
+    }
+    if !def.is_anonymous() {
+        let adt_kind = def.descr();
+        let span = tcx.def_span(def.did());
+        let unnamed_fields = variant
+            .fields
+            .iter()
+            .filter(|f| f.is_unnamed())
+            .map(|f| {
+                let span = tcx.def_span(f.did);
+                errors::UnnamedFieldsReprFieldDefined { span }
+            })
+            .collect::<Vec<_>>();
+        debug_assert_ne!(unnamed_fields.len(), 0, "expect unnamed fields in this adt");
+        let adt_name = tcx.item_name(def.did());
+        if !def.repr().c() {
+            tcx.dcx().emit_err(errors::UnnamedFieldsRepr::MissingReprC {
+                span,
+                adt_kind,
+                adt_name,
+                unnamed_fields,
+            });
+        }
+    }
+    for field in variant.fields.iter().filter(|f| f.is_unnamed()) {
+        let field_ty = tcx.type_of(field.did).instantiate_identity();
+        if let Some(adt) = field_ty.ty_adt_def()
+            && !adt.is_anonymous()
+            && !adt.repr().c()
+        {
+            tcx.dcx().emit_err(errors::UnnamedFieldsRepr::FieldMissingReprC {
+                span: tcx.def_span(field.did),
+                field_ty_span: tcx.def_span(adt.did()),
+                field_ty,
+            });
+        }
+    }
 }
 
 /// Check that the fields of the `union` do not need dropping.
diff --git a/compiler/rustc_hir_analysis/src/collect.rs b/compiler/rustc_hir_analysis/src/collect.rs
index 15ddbd84b2c..45938eacd65 100644
--- a/compiler/rustc_hir_analysis/src/collect.rs
+++ b/compiler/rustc_hir_analysis/src/collect.rs
@@ -997,7 +997,11 @@ fn adt_def(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::AdtDef<'_> {
     };
 
     let is_anonymous = item.ident.name == kw::Empty;
-    let repr = tcx.repr_options_of_def(def_id.to_def_id());
+    let repr = if is_anonymous {
+        tcx.adt_def(tcx.local_parent(def_id)).repr()
+    } else {
+        tcx.repr_options_of_def(def_id.to_def_id())
+    };
     let (kind, variants) = match &item.kind {
         ItemKind::Enum(def, _) => {
             let mut distance_from_explicit = 0;
diff --git a/compiler/rustc_hir_analysis/src/errors.rs b/compiler/rustc_hir_analysis/src/errors.rs
index 1e172f1d9f0..f7fa3263eaa 100644
--- a/compiler/rustc_hir_analysis/src/errors.rs
+++ b/compiler/rustc_hir_analysis/src/errors.rs
@@ -1571,3 +1571,33 @@ pub(crate) enum UnusedGenericParameterHelp {
     #[help(hir_analysis_unused_generic_parameter_ty_alias_help)]
     TyAlias { param_name: Ident },
 }
+
+#[derive(Diagnostic)]
+pub enum UnnamedFieldsRepr<'a> {
+    #[diag(hir_analysis_unnamed_fields_repr_missing_repr_c)]
+    MissingReprC {
+        #[primary_span]
+        #[label]
+        span: Span,
+        adt_kind: &'static str,
+        adt_name: Symbol,
+        #[subdiagnostic]
+        unnamed_fields: Vec<UnnamedFieldsReprFieldDefined>,
+    },
+    #[diag(hir_analysis_unnamed_fields_repr_field_missing_repr_c)]
+    FieldMissingReprC {
+        #[primary_span]
+        #[label]
+        span: Span,
+        #[label(hir_analysis_field_ty_label)]
+        field_ty_span: Span,
+        field_ty: Ty<'a>,
+    },
+}
+
+#[derive(Subdiagnostic)]
+#[note(hir_analysis_unnamed_fields_repr_field_defined)]
+pub struct UnnamedFieldsReprFieldDefined {
+    #[primary_span]
+    pub span: Span,
+}
diff --git a/compiler/rustc_resolve/src/def_collector.rs b/compiler/rustc_resolve/src/def_collector.rs
index 08b1c88873e..45aea585f97 100644
--- a/compiler/rustc_resolve/src/def_collector.rs
+++ b/compiler/rustc_resolve/src/def_collector.rs
@@ -80,6 +80,22 @@ impl<'a, 'b, 'tcx> DefCollector<'a, 'b, 'tcx> {
             let name = field.ident.map_or_else(|| sym::integer(index(self)), |ident| ident.name);
             let def = self.create_def(field.id, name, DefKind::Field, field.span);
             self.with_parent(def, |this| visit::walk_field_def(this, field));
+            self.visit_anon_adt(&field.ty);
+        }
+    }
+
+    fn visit_anon_adt(&mut self, ty: &'a Ty) {
+        let def_kind = match &ty.kind {
+            TyKind::AnonStruct(..) => DefKind::Struct,
+            TyKind::AnonUnion(..) => DefKind::Union,
+            _ => return,
+        };
+        match &ty.kind {
+            TyKind::AnonStruct(node_id, _) | TyKind::AnonUnion(node_id, _) => {
+                let def_id = self.create_def(*node_id, kw::Empty, def_kind, ty.span);
+                self.with_parent(def_id, |this| visit::walk_ty(this, ty));
+            }
+            _ => {}
         }
     }
 
@@ -326,19 +342,8 @@ impl<'a, 'b, 'tcx> visit::Visitor<'a> for DefCollector<'a, 'b, 'tcx> {
     fn visit_ty(&mut self, ty: &'a Ty) {
         match &ty.kind {
             TyKind::MacCall(..) => self.visit_macro_invoc(ty.id),
-            TyKind::AnonStruct(node_id, fields) | TyKind::AnonUnion(node_id, fields) => {
-                let def_kind = match &ty.kind {
-                    TyKind::AnonStruct(..) => DefKind::Struct,
-                    TyKind::AnonUnion(..) => DefKind::Union,
-                    _ => unreachable!(),
-                };
-                let def_id = self.create_def(*node_id, kw::Empty, def_kind, ty.span);
-                self.with_parent(def_id, |this| {
-                    for f in fields {
-                        this.visit_field_def(f);
-                    }
-                });
-            }
+            // Anonymous structs or unions are visited later after defined.
+            TyKind::AnonStruct(..) | TyKind::AnonUnion(..) => {}
             _ => visit::walk_ty(self, ty),
         }
     }
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index 43ab476056a..60453f5ab9c 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -2216,11 +2216,9 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
             // if all of its fields are `Copy` and `Clone`
             ty::Adt(adt, args) if adt.is_anonymous() => {
                 // (*) binder moved here
-                Where(
-                    obligation
-                        .predicate
-                        .rebind(adt.non_enum_variant().fields.iter().map(|f| f.ty(self.tcx(), args)).collect()),
-                )
+                Where(obligation.predicate.rebind(
+                    adt.non_enum_variant().fields.iter().map(|f| f.ty(self.tcx(), args)).collect(),
+                ))
             }
 
             ty::Adt(..) | ty::Alias(..) | ty::Param(..) | ty::Placeholder(..) => {
diff --git a/tests/mir-opt/unnamed-fields/field_access.bar.SimplifyCfg-initial.after.mir b/tests/mir-opt/unnamed-fields/field_access.bar.SimplifyCfg-initial.after.mir
index 2a57b272f9b..8edc7b5df88 100644
--- a/tests/mir-opt/unnamed-fields/field_access.bar.SimplifyCfg-initial.after.mir
+++ b/tests/mir-opt/unnamed-fields/field_access.bar.SimplifyCfg-initial.after.mir
@@ -26,7 +26,7 @@ fn bar(_1: Bar) -> () {
         StorageDead(_2);
         StorageLive(_4);
         StorageLive(_5);
-        _5 = ((_1.1: Bar::_::{anon_adt#0}).0: i8);
+        _5 = ((_1.1: Bar::{anon_adt#0}).0: i8);
         _4 = access::<i8>(move _5) -> [return: bb2, unwind: bb5];
     }
 
@@ -35,7 +35,7 @@ fn bar(_1: Bar) -> () {
         StorageDead(_4);
         StorageLive(_6);
         StorageLive(_7);
-        _7 = ((_1.1: Bar::_::{anon_adt#0}).1: bool);
+        _7 = ((_1.1: Bar::{anon_adt#0}).1: bool);
         _6 = access::<bool>(move _7) -> [return: bb3, unwind: bb5];
     }
 
@@ -44,7 +44,7 @@ fn bar(_1: Bar) -> () {
         StorageDead(_6);
         StorageLive(_8);
         StorageLive(_9);
-        _9 = (((_1.2: Bar::_::{anon_adt#0}).0: Bar::_::{anon_adt#0}::_::{anon_adt#0}).0: [u8; 1]);
+        _9 = (((_1.2: Bar::{anon_adt#1}).0: Bar::{anon_adt#1}::{anon_adt#0}).0: [u8; 1]);
         _8 = access::<[u8; 1]>(move _9) -> [return: bb4, unwind: bb5];
     }
 
diff --git a/tests/mir-opt/unnamed-fields/field_access.foo.SimplifyCfg-initial.after.mir b/tests/mir-opt/unnamed-fields/field_access.foo.SimplifyCfg-initial.after.mir
index 8b10a6f13ce..d48a969f06e 100644
--- a/tests/mir-opt/unnamed-fields/field_access.foo.SimplifyCfg-initial.after.mir
+++ b/tests/mir-opt/unnamed-fields/field_access.foo.SimplifyCfg-initial.after.mir
@@ -24,7 +24,7 @@ fn foo(_1: Foo) -> () {
         StorageDead(_2);
         StorageLive(_4);
         StorageLive(_5);
-        _5 = ((_1.1: Foo::_::{anon_adt#0}).0: i8);
+        _5 = ((_1.1: Foo::{anon_adt#0}).0: i8);
         _4 = access::<i8>(move _5) -> [return: bb2, unwind: bb5];
     }
 
@@ -33,7 +33,7 @@ fn foo(_1: Foo) -> () {
         StorageDead(_4);
         StorageLive(_6);
         StorageLive(_7);
-        _7 = ((_1.1: Foo::_::{anon_adt#0}).1: bool);
+        _7 = ((_1.1: Foo::{anon_adt#0}).1: bool);
         _6 = access::<bool>(move _7) -> [return: bb3, unwind: bb5];
     }
 
@@ -42,7 +42,7 @@ fn foo(_1: Foo) -> () {
         StorageDead(_6);
         StorageLive(_8);
         StorageLive(_9);
-        _9 = (((_1.2: Foo::_::{anon_adt#0}).0: Foo::_::{anon_adt#0}::_::{anon_adt#0}).0: [u8; 1]);
+        _9 = (((_1.2: Foo::{anon_adt#1}).0: Foo::{anon_adt#1}::{anon_adt#0}).0: [u8; 1]);
         _8 = access::<[u8; 1]>(move _9) -> [return: bb4, unwind: bb5];
     }
 
diff --git a/tests/ui/feature-gates/feature-gate-unnamed_fields.rs b/tests/ui/feature-gates/feature-gate-unnamed_fields.rs
index 6ee8de89564..302a9bbeb45 100644
--- a/tests/ui/feature-gates/feature-gate-unnamed_fields.rs
+++ b/tests/ui/feature-gates/feature-gate-unnamed_fields.rs
@@ -1,3 +1,4 @@
+#[repr(C)]
 struct Foo {
     foo: u8,
     _: union { //~ ERROR unnamed fields are not yet fully implemented [E0658]
@@ -7,6 +8,7 @@ struct Foo {
     }
 }
 
+#[repr(C)]
 union Bar {
     foobar: u8,
     _: struct { //~ ERROR unnamed fields are not yet fully implemented [E0658]
@@ -16,7 +18,10 @@ union Bar {
     }
 }
 
+#[repr(C)]
 struct S;
+
+#[repr(C)]
 struct Baz {
     _: S //~ ERROR unnamed fields are not yet fully implemented [E0658]
 }
diff --git a/tests/ui/feature-gates/feature-gate-unnamed_fields.stderr b/tests/ui/feature-gates/feature-gate-unnamed_fields.stderr
index 8fa342c08ae..bc9e95bab98 100644
--- a/tests/ui/feature-gates/feature-gate-unnamed_fields.stderr
+++ b/tests/ui/feature-gates/feature-gate-unnamed_fields.stderr
@@ -1,5 +1,5 @@
 error[E0658]: unnamed fields are not yet fully implemented
-  --> $DIR/feature-gate-unnamed_fields.rs:3:5
+  --> $DIR/feature-gate-unnamed_fields.rs:4:5
    |
 LL |     _: union {
    |     ^
@@ -9,7 +9,7 @@ LL |     _: union {
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error[E0658]: unnamed fields are not yet fully implemented
-  --> $DIR/feature-gate-unnamed_fields.rs:3:8
+  --> $DIR/feature-gate-unnamed_fields.rs:4:8
    |
 LL |       _: union {
    |  ________^
@@ -24,7 +24,7 @@ LL | |     }
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error[E0658]: unnamed fields are not yet fully implemented
-  --> $DIR/feature-gate-unnamed_fields.rs:12:5
+  --> $DIR/feature-gate-unnamed_fields.rs:14:5
    |
 LL |     _: struct {
    |     ^
@@ -34,7 +34,7 @@ LL |     _: struct {
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error[E0658]: unnamed fields are not yet fully implemented
-  --> $DIR/feature-gate-unnamed_fields.rs:12:8
+  --> $DIR/feature-gate-unnamed_fields.rs:14:8
    |
 LL |       _: struct {
    |  ________^
@@ -49,7 +49,7 @@ LL | |     }
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error[E0658]: unnamed fields are not yet fully implemented
-  --> $DIR/feature-gate-unnamed_fields.rs:21:5
+  --> $DIR/feature-gate-unnamed_fields.rs:26:5
    |
 LL |     _: S
    |     ^
diff --git a/tests/ui/union/unnamed-fields/repr_check.rs b/tests/ui/union/unnamed-fields/repr_check.rs
new file mode 100644
index 00000000000..b50b54b20af
--- /dev/null
+++ b/tests/ui/union/unnamed-fields/repr_check.rs
@@ -0,0 +1,69 @@
+#![allow(incomplete_features)]
+#![feature(unnamed_fields)]
+
+struct A { //~ ERROR struct with unnamed fields must have `#[repr(C)]` representation
+           //~^ NOTE struct `A` defined here
+    _: struct { //~ NOTE unnamed field defined here
+        a: i32,
+    },
+    _: struct { //~ NOTE unnamed field defined here
+        _: struct {
+            b: i32,
+        },
+    },
+}
+
+union B { //~ ERROR union with unnamed fields must have `#[repr(C)]` representation
+          //~^ NOTE union `B` defined here
+    _: union { //~ NOTE unnamed field defined here
+        a: i32,
+    },
+    _: union { //~ NOTE unnamed field defined here
+        _: union {
+            b: i32,
+        },
+    },
+}
+
+#[derive(Clone, Copy)]
+#[repr(C)]
+struct Foo {}
+
+#[derive(Clone, Copy)]
+struct Bar {}
+//~^ `Bar` defined here
+//~| `Bar` defined here
+//~| `Bar` defined here
+//~| `Bar` defined here
+
+struct C { //~ ERROR struct with unnamed fields must have `#[repr(C)]` representation
+           //~^ NOTE struct `C` defined here
+    _: Foo, //~ NOTE unnamed field defined here
+}
+
+union D { //~ ERROR union with unnamed fields must have `#[repr(C)]` representation
+          //~^ NOTE union `D` defined here
+    _: Foo, //~ NOTE unnamed field defined here
+}
+
+#[repr(C)]
+struct E {
+    _: Bar, //~ ERROR named type of unnamed field must have `#[repr(C)]` representation
+            //~^ NOTE unnamed field defined here
+    _: struct {
+        _: Bar, //~ ERROR named type of unnamed field must have `#[repr(C)]` representation
+                //~^ NOTE unnamed field defined here
+    },
+}
+
+#[repr(C)]
+union F {
+    _: Bar, //~ ERROR named type of unnamed field must have `#[repr(C)]` representation
+            //~^ NOTE unnamed field defined here
+    _: union {
+        _: Bar, //~ ERROR named type of unnamed field must have `#[repr(C)]` representation
+                //~^ NOTE unnamed field defined here
+    },
+}
+
+fn main() {}
diff --git a/tests/ui/union/unnamed-fields/repr_check.stderr b/tests/ui/union/unnamed-fields/repr_check.stderr
new file mode 100644
index 00000000000..ca6a1f3a780
--- /dev/null
+++ b/tests/ui/union/unnamed-fields/repr_check.stderr
@@ -0,0 +1,108 @@
+error: struct with unnamed fields must have `#[repr(C)]` representation
+  --> $DIR/repr_check.rs:4:1
+   |
+LL | struct A {
+   | ^^^^^^^^ struct `A` defined here
+   |
+note: unnamed field defined here
+  --> $DIR/repr_check.rs:6:5
+   |
+LL | /     _: struct {
+LL | |         a: i32,
+LL | |     },
+   | |_____^
+note: unnamed field defined here
+  --> $DIR/repr_check.rs:9:5
+   |
+LL | /     _: struct {
+LL | |         _: struct {
+LL | |             b: i32,
+LL | |         },
+LL | |     },
+   | |_____^
+
+error: union with unnamed fields must have `#[repr(C)]` representation
+  --> $DIR/repr_check.rs:16:1
+   |
+LL | union B {
+   | ^^^^^^^ union `B` defined here
+   |
+note: unnamed field defined here
+  --> $DIR/repr_check.rs:18:5
+   |
+LL | /     _: union {
+LL | |         a: i32,
+LL | |     },
+   | |_____^
+note: unnamed field defined here
+  --> $DIR/repr_check.rs:21:5
+   |
+LL | /     _: union {
+LL | |         _: union {
+LL | |             b: i32,
+LL | |         },
+LL | |     },
+   | |_____^
+
+error: struct with unnamed fields must have `#[repr(C)]` representation
+  --> $DIR/repr_check.rs:39:1
+   |
+LL | struct C {
+   | ^^^^^^^^ struct `C` defined here
+   |
+note: unnamed field defined here
+  --> $DIR/repr_check.rs:41:5
+   |
+LL |     _: Foo,
+   |     ^^^^^^
+
+error: union with unnamed fields must have `#[repr(C)]` representation
+  --> $DIR/repr_check.rs:44:1
+   |
+LL | union D {
+   | ^^^^^^^ union `D` defined here
+   |
+note: unnamed field defined here
+  --> $DIR/repr_check.rs:46:5
+   |
+LL |     _: Foo,
+   |     ^^^^^^
+
+error: named type of unnamed field must have `#[repr(C)]` representation
+  --> $DIR/repr_check.rs:51:5
+   |
+LL | struct Bar {}
+   | ---------- `Bar` defined here
+...
+LL |     _: Bar,
+   |     ^^^^^^ unnamed field defined here
+
+error: named type of unnamed field must have `#[repr(C)]` representation
+  --> $DIR/repr_check.rs:54:9
+   |
+LL | struct Bar {}
+   | ---------- `Bar` defined here
+...
+LL |         _: Bar,
+   |         ^^^^^^ unnamed field defined here
+
+error: named type of unnamed field must have `#[repr(C)]` representation
+  --> $DIR/repr_check.rs:61:5
+   |
+LL | struct Bar {}
+   | ---------- `Bar` defined here
+...
+LL |     _: Bar,
+   |     ^^^^^^ unnamed field defined here
+
+error: named type of unnamed field must have `#[repr(C)]` representation
+  --> $DIR/repr_check.rs:64:9
+   |
+LL | struct Bar {}
+   | ---------- `Bar` defined here
+...
+LL |         _: Bar,
+   |         ^^^^^^ unnamed field defined here
+
+error: aborting due to 8 previous errors
+