move maybe sized check into coherence

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

@@ -4,7 +4,7 @@ use rustc_ast::mut_visit::MutVisitor;
 use rustc_ast::visit::BoundKind;
 use rustc_ast::{
     self as ast, GenericArg, GenericBound, GenericParamKind, Generics, ItemKind, MetaItem,
-    TraitBoundModifiers, TyAlias, VariantData, WherePredicate,
+    TraitBoundModifiers, TyAlias, WherePredicate,
 };
 use rustc_data_structures::flat_map_in_place::FlatMapInPlace;
 use rustc_errors::E0802;
@@ -30,16 +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
     {
-        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 });
@@ -206,10 +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());
@@ -487,13 +476,6 @@ struct RequireTransparent {
     span: Span,
 }
 
-#[derive(Diagnostic)]
-#[diag(builtin_macros_coerce_pointee_requires_one_field, code = E0802)]
-struct RequireOneField {
-    #[primary_span]
-    span: Span,
-}
-
 #[derive(Diagnostic)]
 #[diag(builtin_macros_coerce_pointee_requires_one_generic, code = E0802)]
 struct RequireOneGeneric {
@@ -516,11 +498,3 @@ struct TooManyPointees {
     #[label]
     another: Span,
 }
-
-#[derive(Diagnostic)]
-#[diag(builtin_macros_coerce_pointee_requires_maybe_sized, code = E0802)]
-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;
 

compiler/rustc_hir_analysis/messages.ftl

@@ -85,6 +85,8 @@ hir_analysis_cmse_output_stack_spill =
     .note1 = functions with the `"{$abi_name}"` ABI must pass their result via the available return registers
     .note2 = the result must either be a (transparently wrapped) i64, u64 or f64, or be at most 4 bytes in size
 
+hir_analysis_coerce_pointee_missing_maybe_sized = `derive(CoercePointee)` requires the `#[pointee]` to be `?Sized`
+
 hir_analysis_coerce_pointee_multiple_derive = `derive(CoercePointee)` is derived multiple times
     .label = another derivation originates from here
 

compiler/rustc_hir_analysis/src/coherence/builtin.rs

@@ -328,12 +328,19 @@ fn visit_implementation_of_dispatch_from_dyn(checker: &Checker<'_>) -> Result<()
                 .collect::<Vec<_>>();
 
             if coerced_fields.is_empty() {
-                // `CoercePointeeValidated` will report a more specific error
-                res = Err(tcx.dcx().emit_err(errors::DispatchFromDynSingle {
-                    span,
-                    trait_name: "DispatchFromDyn",
-                    note: true,
-                }));
+                if coerce_pointee_data.is_some() {
+                    // `CoercePointeeValidated` will report a more specific error
+                    res = Err(tcx.dcx().span_delayed_bug(
+                        span,
+                        "a more specific error from CoercePointee is expected",
+                    ))
+                } else {
+                    res = Err(tcx.dcx().emit_err(errors::DispatchFromDynSingle {
+                        span,
+                        trait_name: "DispatchFromDyn",
+                        note: true,
+                    }));
+                }
             } else if coerced_fields.len() > 1 {
                 if coerce_pointee_data.is_some() {
                     let spans =
@@ -405,6 +412,9 @@ fn visit_implementation_of_dispatch_from_dyn(checker: &Checker<'_>) -> Result<()
             }
             res
         }
+        (&Adt(def, _), _) if tcx.coerce_pointee_data(()).contains_key(&def.did()) => {
+            Err(tcx.dcx().span_delayed_bug(span, "a specific error for CoercePointee is expected"))
+        }
         _ => Err(tcx
             .dcx()
             .emit_err(errors::CoerceUnsizedMay { span, trait_name: "DispatchFromDyn" })),
@@ -898,23 +908,44 @@ fn visit_implementation_of_coerce_pointee_validity(
     checker: &Checker<'_>,
 ) -> Result<(), ErrorGuaranteed> {
     let tcx = checker.tcx;
-    let self_ty = tcx.impl_trait_ref(checker.impl_def_id).unwrap().instantiate_identity().self_ty();
-    let span = tcx.def_span(checker.impl_def_id);
-    if !tcx.is_builtin_derived(checker.impl_def_id.into()) {
+    let impl_did = checker.impl_def_id;
+    let self_ty = tcx.impl_trait_ref(impl_did).unwrap().instantiate_identity().self_ty();
+    let span = tcx.def_span(impl_did);
+    if !tcx.is_builtin_derived(impl_did.into()) {
         return Err(tcx.dcx().emit_err(errors::CoercePointeeNoUserValidityAssertion { span }));
     }
-    let ty::Adt(def, _args) = self_ty.kind() else {
+    let ty::Adt(def, args) = self_ty.kind() else {
         return Err(tcx.dcx().emit_err(errors::CoercePointeeNotConcreteType { span }));
     };
     let did = def.did();
     let Some(info) = tcx.coerce_pointee_data(()).get(&did) else {
         return Err(tcx.dcx().emit_err(errors::CoercePointeeNoUserValidityAssertion { span }));
     };
-    if let &ty::CoercePointeeInfo::Duplicated { impls } = info {
-        return Err(tcx.dcx().emit_err(errors::CoercePointeePointeeMultipleDerive {
-            spans: impls.iter().copied().map(|did| tcx.def_span(did)).collect(),
-        }));
-    }
+    let pointee_idx = match info {
+        &ty::CoercePointeeInfo::Validated { pointee_index_in_args, .. } => pointee_index_in_args,
+        ty::CoercePointeeInfo::PointeeUnnormalized { ty, .. } => {
+            return Err(tcx.dcx().emit_err(errors::CoercePointeePointeeNotGenericPointee {
+                span,
+                got: ty.to_string(),
+            }));
+        }
+        ty::CoercePointeeInfo::PointeeIsConst { konst, .. } => {
+            return Err(tcx.dcx().emit_err(errors::CoercePointeePointeeNotGenericPointee {
+                span,
+                got: konst.to_string(),
+            }));
+        }
+        ty::CoercePointeeInfo::Duplicated { impls } => {
+            return Err(tcx.dcx().emit_err(errors::CoercePointeePointeeMultipleDerive {
+                spans: impls.iter().copied().map(|did| tcx.def_span(did)).collect(),
+            }));
+        }
+        ty::CoercePointeeInfo::PointeeNotFound { ty, .. } => {
+            return Err(tcx
+                .dcx()
+                .emit_err(errors::CoercePointeeNoPointee { span, ty: ty.to_string() }));
+        }
+    };
     // Now get a more precise span of the `struct`.
     let span = tcx.def_span(did);
     if !def.is_struct() {
@@ -926,8 +957,28 @@ fn visit_implementation_of_coerce_pointee_validity(
         return Err(tcx.dcx().emit_err(errors::CoercePointeeNotTransparent { span }));
     }
     if def.all_fields().next().is_none() {
-        return Err(tcx.dcx().emit_err(errors::CoercePointeeNoField { span }));
+        return Err(tcx.dcx().span_delayed_bug(
+            span,
+            "a specific error from CoercePointee is expected in CoerceUnsized coherence check",
+        ));
     }
+
+    let infcx = tcx.infer_ctxt().build(TypingMode::non_body_analysis());
+    let param_env = tcx.param_env(impl_did);
+    let ocx = ObligationCtxt::new(&infcx);
+    let cause = ObligationCause::misc(span, impl_did);
+    let pointee_ty = args.type_at(pointee_idx);
+    let obligation = Obligation::new(
+        tcx,
+        cause,
+        param_env,
+        ty::TraitRef::new(tcx, tcx.require_lang_item(LangItem::Sized, None), [pointee_ty]),
+    );
+    ocx.register_obligation(obligation);
+    if ocx.select_all_or_error().is_empty() {
+        return Err(tcx.dcx().emit_err(errors::CoercePointeePointeeMissingMaybeSized { span }));
+    }
+
     Ok(())
 }
 
@@ -937,24 +988,16 @@ fn try_extract_coerce_pointee_data<'tcx>(
     info: &ty::CoercePointeeInfo<'tcx>,
 ) -> Result<(usize, DefId), ErrorGuaranteed> {
     match info {
-        ty::CoercePointeeInfo::PointeeUnnormalized { ty, .. } => Err(tcx
-            .dcx()
-            .emit_err(errors::CoercePointeePointeeNotGenericPointee { span, got: ty.to_string() })),
-        ty::CoercePointeeInfo::PointeeIsConst { konst, .. } => {
-            Err(tcx.dcx().emit_err(errors::CoercePointeePointeeNotGenericPointee {
-                span,
-                got: konst.to_string(),
-            }))
-        }
-        ty::CoercePointeeInfo::Validated { pointee_index_in_args, impl_def_id } => {
-            Ok((*pointee_index_in_args, *impl_def_id))
-        }
-        ty::CoercePointeeInfo::Duplicated { .. } => Err(tcx
-            .dcx()
-            .span_delayed_bug(span, "a special error for duplicated CoercePointee is expected")),
-        ty::CoercePointeeInfo::PointeeNotFound { ty, .. } => {
-            Err(tcx.dcx().emit_err(errors::CoercePointeeNoPointee { span, ty: ty.to_string() }))
+        &ty::CoercePointeeInfo::Validated { pointee_index_in_args, impl_def_id } => {
+            Ok((pointee_index_in_args, impl_def_id))
         }
+        ty::CoercePointeeInfo::PointeeUnnormalized { .. }
+        | ty::CoercePointeeInfo::PointeeIsConst { .. }
+        | ty::CoercePointeeInfo::PointeeNotFound { .. }
+        | ty::CoercePointeeInfo::Duplicated { .. } => Err(tcx.dcx().span_delayed_bug(
+            span,
+            "a more specific error for malformed CoercePointee is expected",
+        )),
     }
 }
 

compiler/rustc_hir_analysis/src/errors.rs

@@ -1247,6 +1247,13 @@ pub(crate) struct CoercePointeePointeeMultipleDerive {
     pub spans: Vec<Span>,
 }
 
+#[derive(Diagnostic)]
+#[diag(hir_analysis_coerce_pointee_missing_maybe_sized, code = E0802)]
+pub(crate) struct CoercePointeePointeeMissingMaybeSized {
+    #[primary_span]
+    pub span: Span,
+}
+
 #[derive(Diagnostic)]
 #[diag(hir_analysis_inherent_ty_outside_relevant, code = E0390)]
 #[help]