Perform more validation on CoercePointee

compiler/rustc_builtin_macros/messages.ftl

@@ -95,10 +95,6 @@ builtin_macros_cfg_accessible_literal_path = `cfg_accessible` path cannot be a l
 builtin_macros_cfg_accessible_multiple_paths = multiple `cfg_accessible` paths are specified
 builtin_macros_cfg_accessible_unspecified_path = `cfg_accessible` path is not specified
 
-builtin_macros_coerce_pointee_requires_maybe_sized = `derive(CoercePointee)` requires `{$name}` to be marked `?Sized`
-
-builtin_macros_coerce_pointee_requires_one_field = `CoercePointee` can only be derived on `struct`s with at least one field
-
 builtin_macros_coerce_pointee_requires_one_generic = `CoercePointee` can only be derived on `struct`s that are generic over at least one type
 
 builtin_macros_coerce_pointee_requires_one_pointee = exactly one generic type parameter must be marked as `#[pointee]` to derive `CoercePointee` traits

compiler/rustc_builtin_macros/src/deriving/coerce_pointee.rs

@@ -3,11 +3,11 @@ use ast::ptr::P;
 use rustc_ast::mut_visit::MutVisitor;
 use rustc_ast::visit::BoundKind;
 use rustc_ast::{
-    self as ast, GenericArg, GenericBound, GenericParamKind, ItemKind, MetaItem,
-    TraitBoundModifiers, VariantData, WherePredicate,
+    self as ast, GenericArg, GenericBound, GenericParamKind, Generics, ItemKind, MetaItem,
+    TraitBoundModifiers, TyAlias, WherePredicate,
 };
-use rustc_attr_parsing as attr;
 use rustc_data_structures::flat_map_in_place::FlatMapInPlace;
+use rustc_errors::E0802;
 use rustc_expand::base::{Annotatable, ExtCtxt};
 use rustc_macros::Diagnostic;
 use rustc_span::{Ident, Span, Symbol, sym};
@@ -30,25 +30,8 @@ pub(crate) fn expand_deriving_coerce_pointee(
     item.visit_with(&mut DetectNonGenericPointeeAttr { cx });
 
     let (name_ident, generics) = if let Annotatable::Item(aitem) = item
-        && let ItemKind::Struct(struct_data, g) = &aitem.kind
+        && let ItemKind::Struct(_struct_data, g) = &aitem.kind
     {
-        let is_transparent = aitem.attrs.iter().any(|attr| {
-            attr::find_repr_attrs(cx.sess, attr)
-                .into_iter()
-                .any(|r| matches!(r, attr::ReprTransparent))
-        });
-        if !is_transparent {
-            cx.dcx().emit_err(RequireTransparent { span });
-            return;
-        }
-        if !matches!(
-            struct_data,
-            VariantData::Struct { fields, recovered: _ } | VariantData::Tuple(fields, _)
-                if !fields.is_empty())
-        {
-            cx.dcx().emit_err(RequireOneField { span });
-            return;
-        }
         (aitem.ident, g)
     } else {
         cx.dcx().emit_err(RequireTransparent { span });
@@ -88,8 +71,7 @@ pub(crate) fn expand_deriving_coerce_pointee(
     } else {
         let mut pointees = type_params
             .iter()
-            .filter_map(|&(idx, span, is_pointee)| is_pointee.then_some((idx, span)))
-            .fuse();
+            .filter_map(|&(idx, span, is_pointee)| is_pointee.then_some((idx, span)));
         match (pointees.next(), pointees.next()) {
             (Some((idx, _span)), None) => idx,
             (None, _) => {
@@ -102,6 +84,7 @@ pub(crate) fn expand_deriving_coerce_pointee(
             }
         }
     };
+    let pointee_ty_ident = generics.params[pointee_param_idx].ident;
 
     // Create the type of `self`.
     let path = cx.path_all(span, false, vec![name_ident], self_params.clone());
@@ -110,6 +93,67 @@ pub(crate) fn expand_deriving_coerce_pointee(
     // Declare helper function that adds implementation blocks.
     // FIXME(dingxiangfei2009): Investigate the set of attributes on target struct to be propagated to impls
     let attrs = thin_vec![cx.attr_word(sym::automatically_derived, span),];
+    // # Validity assertion
+    // This will be checked later in `rustc_hir_analysis::coherence::builtins`.
+    {
+        let trait_path =
+            cx.path_all(span, true, path!(span, core::marker::CoercePointeeValidated), vec![]);
+        let trait_ref = cx.trait_ref(trait_path);
+        let pointee_assoc_item = cx.assoc_item(
+            span,
+            Ident::new(sym::Pointee, span),
+            thin_vec![],
+            ast::AssocItemKind::Type(Box::new(TyAlias {
+                defaultness: ast::Defaultness::Final,
+                generics: ast::Generics::default(),
+                where_clauses: ast::TyAliasWhereClauses::default(),
+                bounds: vec![],
+                ty: Some(
+                    cx.ty(span, ast::TyKind::Path(None, cx.path_ident(span, pointee_ty_ident))),
+                ),
+            })),
+        );
+        push(Annotatable::Item(
+            cx.item(
+                span,
+                Ident::empty(),
+                attrs.clone(),
+                ast::ItemKind::Impl(Box::new(ast::Impl {
+                    safety: ast::Safety::Default,
+                    polarity: ast::ImplPolarity::Positive,
+                    defaultness: ast::Defaultness::Final,
+                    constness: ast::Const::No,
+                    generics: Generics {
+                        params: generics
+                            .params
+                            .iter()
+                            .map(|p| match &p.kind {
+                                GenericParamKind::Lifetime => {
+                                    cx.lifetime_param(p.span(), p.ident, p.bounds.clone())
+                                }
+                                GenericParamKind::Type { default: _ } => {
+                                    cx.typaram(p.span(), p.ident, p.bounds.clone(), None)
+                                }
+                                GenericParamKind::Const { ty, kw_span: _, default: _ } => cx
+                                    .const_param(
+                                        p.span(),
+                                        p.ident,
+                                        p.bounds.clone(),
+                                        ty.clone(),
+                                        None,
+                                    ),
+                            })
+                            .collect(),
+                        where_clause: generics.where_clause.clone(),
+                        span: generics.span,
+                    },
+                    of_trait: Some(trait_ref),
+                    self_ty: self_type.clone(),
+                    items: thin_vec![pointee_assoc_item],
+                })),
+            ),
+        ));
+    }
     let mut add_impl_block = |generics, trait_symbol, trait_args| {
         let mut parts = path!(span, core::ops);
         parts.push(Ident::new(trait_symbol, span));
@@ -144,7 +188,6 @@ pub(crate) fn expand_deriving_coerce_pointee(
     //
     // Find the `#[pointee]` parameter and add an `Unsize<__S>` bound to it.
     let mut impl_generics = generics.clone();
-    let pointee_ty_ident = generics.params[pointee_param_idx].ident;
     let mut self_bounds;
     {
         let pointee = &mut impl_generics.params[pointee_param_idx];
@@ -155,10 +198,7 @@ pub(crate) fn expand_deriving_coerce_pointee(
                 pointee_ty_ident.name,
             )
         {
-            cx.dcx().emit_err(RequiresMaybeSized {
-                span: pointee_ty_ident.span,
-                name: pointee_ty_ident,
-            });
+            cx.dcx().span_delayed_bug(pointee_ty_ident.span, "?Sized should be checked");
             return;
         }
         let arg = GenericArg::Type(s_ty.clone());
@@ -430,46 +470,31 @@ impl<'a, 'b> rustc_ast::visit::Visitor<'a> for AlwaysErrorOnGenericParam<'a, 'b>
 }
 
 #[derive(Diagnostic)]
-#[diag(builtin_macros_coerce_pointee_requires_transparent)]
+#[diag(builtin_macros_coerce_pointee_requires_transparent, code = E0802)]
 struct RequireTransparent {
     #[primary_span]
     span: Span,
 }
 
 #[derive(Diagnostic)]
-#[diag(builtin_macros_coerce_pointee_requires_one_field)]
-struct RequireOneField {
-    #[primary_span]
-    span: Span,
-}
-
-#[derive(Diagnostic)]
-#[diag(builtin_macros_coerce_pointee_requires_one_generic)]
+#[diag(builtin_macros_coerce_pointee_requires_one_generic, code = E0802)]
 struct RequireOneGeneric {
     #[primary_span]
     span: Span,
 }
 
 #[derive(Diagnostic)]
-#[diag(builtin_macros_coerce_pointee_requires_one_pointee)]
+#[diag(builtin_macros_coerce_pointee_requires_one_pointee, code = E0802)]
 struct RequireOnePointee {
     #[primary_span]
     span: Span,
 }
 
 #[derive(Diagnostic)]
-#[diag(builtin_macros_coerce_pointee_too_many_pointees)]
+#[diag(builtin_macros_coerce_pointee_too_many_pointees, code = E0802)]
 struct TooManyPointees {
     #[primary_span]
     one: Span,
     #[label]
     another: Span,
 }
-
-#[derive(Diagnostic)]
-#[diag(builtin_macros_coerce_pointee_requires_maybe_sized)]
-struct RequiresMaybeSized {
-    #[primary_span]
-    span: Span,
-    name: Ident,
-}

compiler/rustc_codegen_cranelift/example/mini_core.rs

@@ -29,6 +29,13 @@ pub trait Unsize<T: ?Sized> {}
 #[lang = "coerce_unsized"]
 pub trait CoerceUnsized<T> {}
 
+#[lang = "coerce_pointee_validated"]
+pub trait CoercePointeeValidated {
+    /* compiler built-in */
+    #[lang = "coerce_pointee_validated_pointee"]
+    type Pointee: ?Sized;
+}
+
 impl<'a, 'b: 'a, T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<&'a U> for &'b T {}
 impl<'a, T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<&'a mut U> for &'a mut T {}
 impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<*const U> for *const T {}

compiler/rustc_codegen_gcc/example/mini_core.rs

@@ -1,6 +1,14 @@
 #![feature(
-    no_core, lang_items, intrinsics, unboxed_closures, extern_types,
-    decl_macro, rustc_attrs, transparent_unions, auto_traits, freeze_impls,
+    no_core,
+    lang_items,
+    intrinsics,
+    unboxed_closures,
+    extern_types,
+    decl_macro,
+    rustc_attrs,
+    transparent_unions,
+    auto_traits,
+    freeze_impls,
     thread_local
 )]
 #![no_core]
@@ -26,6 +34,13 @@ pub trait Unsize<T: ?Sized> {}
 #[lang = "coerce_unsized"]
 pub trait CoerceUnsized<T> {}
 
+#[lang = "coerce_pointee_validated"]
+pub trait CoercePointeeValidated {
+    /* compiler built-in */
+    #[lang = "coerce_pointee_validated_pointee"]
+    type Pointee: ?Sized;
+}
+
 impl<'a, 'b: 'a, T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<&'a U> for &'b T {}
 impl<'a, T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<&'a mut U> for &'a mut T {}
 impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<*const U> for *const T {}
@@ -35,13 +50,13 @@ impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<*mut U> for *mut T {}
 pub trait DispatchFromDyn<T> {}
 
 // &T -> &U
-impl<'a, T: ?Sized+Unsize<U>, U: ?Sized> DispatchFromDyn<&'a U> for &'a T {}
+impl<'a, T: ?Sized + Unsize<U>, U: ?Sized> DispatchFromDyn<&'a U> for &'a T {}
 // &mut T -> &mut U
-impl<'a, T: ?Sized+Unsize<U>, U: ?Sized> DispatchFromDyn<&'a mut U> for &'a mut T {}
+impl<'a, T: ?Sized + Unsize<U>, U: ?Sized> DispatchFromDyn<&'a mut U> for &'a mut T {}
 // *const T -> *const U
-impl<T: ?Sized+Unsize<U>, U: ?Sized> DispatchFromDyn<*const U> for *const T {}
+impl<T: ?Sized + Unsize<U>, U: ?Sized> DispatchFromDyn<*const U> for *const T {}
 // *mut T -> *mut U
-impl<T: ?Sized+Unsize<U>, U: ?Sized> DispatchFromDyn<*mut U> for *mut T {}
+impl<T: ?Sized + Unsize<U>, U: ?Sized> DispatchFromDyn<*mut U> for *mut T {}
 impl<T: ?Sized + Unsize<U>, U: ?Sized> DispatchFromDyn<Box<U, ()>> for Box<T, ()> {}
 
 #[lang = "legacy_receiver"]
@@ -289,7 +304,6 @@ impl PartialEq for u32 {
     }
 }
 
-
 impl PartialEq for u64 {
     fn eq(&self, other: &u64) -> bool {
         (*self) == (*other)
@@ -476,7 +490,11 @@ fn panic_in_cleanup() -> ! {
 #[track_caller]
 fn panic_bounds_check(index: usize, len: usize) -> ! {
     unsafe {
-        libc::printf("index out of bounds: the len is %d but the index is %d\n\0" as *const str as *const i8, len, index);
+        libc::printf(
+            "index out of bounds: the len is %d but the index is %d\n\0" as *const str as *const i8,
+            len,
+            index,
+        );
         intrinsics::abort();
     }
 }
@@ -504,8 +522,7 @@ pub trait Deref {
     fn deref(&self) -> &Self::Target;
 }
 
-pub trait Allocator {
-}
+pub trait Allocator {}
 
 impl Allocator for () {}
 
@@ -699,19 +716,27 @@ pub struct VaList<'a>(&'a mut VaListImpl);
 
 #[rustc_builtin_macro]
 #[rustc_macro_transparency = "semitransparent"]
-pub macro stringify($($t:tt)*) { /* compiler built-in */ }
+pub macro stringify($($t:tt)*) {
+    /* compiler built-in */
+}
 
 #[rustc_builtin_macro]
 #[rustc_macro_transparency = "semitransparent"]
-pub macro file() { /* compiler built-in */ }
+pub macro file() {
+    /* compiler built-in */
+}
 
 #[rustc_builtin_macro]
 #[rustc_macro_transparency = "semitransparent"]
-pub macro line() { /* compiler built-in */ }
+pub macro line() {
+    /* compiler built-in */
+}
 
 #[rustc_builtin_macro]
 #[rustc_macro_transparency = "semitransparent"]
-pub macro cfg() { /* compiler built-in */ }
+pub macro cfg() {
+    /* compiler built-in */
+}
 
 pub static A_STATIC: u8 = 42;