Check structs/enums/unions without loading their HIR

Author: oli-obk

compiler/rustc_hir_analysis/src/check/check.rs

@@ -37,8 +37,8 @@ use {rustc_attr_data_structures as attrs, rustc_hir as hir};
 use super::compare_impl_item::check_type_bounds;
 use super::*;
 use crate::check::wfcheck::{
-    check_associated_item, check_trait_item, check_variances_for_type_defn, check_where_clauses,
-    enter_wf_checking_ctxt,
+    check_associated_item, check_trait_item, check_type_defn, check_variances_for_type_defn,
+    check_where_clauses, enter_wf_checking_ctxt,
 };
 
 fn add_abi_diag_help<T: EmissionGuarantee>(abi: ExternAbi, diag: &mut Diag<'_, T>) {
@@ -89,7 +89,7 @@ pub fn check_custom_abi(tcx: TyCtxt<'_>, def_id: LocalDefId, fn_sig: FnSig<'_>,
     }
 }
 
-fn check_struct(tcx: TyCtxt<'_>, def_id: LocalDefId) {
+fn check_struct(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Result<(), ErrorGuaranteed> {
     let def = tcx.adt_def(def_id);
     let span = tcx.def_span(def_id);
     def.destructor(tcx); // force the destructor to be evaluated
@@ -100,15 +100,17 @@ fn check_struct(tcx: TyCtxt<'_>, def_id: LocalDefId) {
 
     check_transparent(tcx, def);
     check_packed(tcx, span, def);
+    check_type_defn(tcx, def_id, false)
 }
 
-fn check_union(tcx: TyCtxt<'_>, def_id: LocalDefId) {
+fn check_union(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Result<(), ErrorGuaranteed> {
     let def = tcx.adt_def(def_id);
     let span = tcx.def_span(def_id);
     def.destructor(tcx); // force the destructor to be evaluated
     check_transparent(tcx, def);
     check_union_fields(tcx, span, def_id);
     check_packed(tcx, span, def);
+    check_type_defn(tcx, def_id, true)
 }
 
 fn allowed_union_or_unsafe_field<'tcx>(
@@ -785,6 +787,9 @@ pub(crate) fn check_item_type(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Result<(),
             crate::collect::check_enum_variant_types(tcx, def_id.to_def_id());
             check_enum(tcx, def_id);
             check_variances_for_type_defn(tcx, def_id);
+            res = res.and(check_type_defn(tcx, def_id, true));
+            // enums are fully handled by the type based check and have no hir wfcheck logic
+            return res;
         }
         DefKind::Fn => {
             tcx.ensure_ok().generics_of(def_id);
@@ -873,12 +878,14 @@ pub(crate) fn check_item_type(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Result<(),
             if let Some((_, ctor_def_id)) = adt.ctor {
                 crate::collect::check_ctor(tcx, ctor_def_id.expect_local());
             }
-            match def_kind {
+            res = res.and(match def_kind {
                 DefKind::Struct => check_struct(tcx, def_id),
                 DefKind::Union => check_union(tcx, def_id),
                 _ => unreachable!(),
-            }
+            });
             check_variances_for_type_defn(tcx, def_id);
+            // structs and enums are fully handled by the type based check and have no hir wfcheck logic
+            return res;
         }
         DefKind::OpaqueTy => {
             check_opaque_precise_captures(tcx, def_id);

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -19,9 +19,8 @@ use rustc_middle::query::Providers;
 use rustc_middle::traits::solve::NoSolution;
 use rustc_middle::ty::trait_def::TraitSpecializationKind;
 use rustc_middle::ty::{
-    self, AdtKind, GenericArgKind, GenericArgs, GenericParamDefKind, Ty, TyCtxt, TypeFlags,
-    TypeFoldable, TypeSuperVisitable, TypeVisitable, TypeVisitableExt, TypeVisitor, TypingMode,
-    Upcast,
+    self, GenericArgKind, GenericArgs, GenericParamDefKind, Ty, TyCtxt, TypeFlags, TypeFoldable,
+    TypeSuperVisitable, TypeVisitable, TypeVisitableExt, TypeVisitor, TypingMode, Upcast,
 };
 use rustc_middle::{bug, span_bug};
 use rustc_session::parse::feature_err;
@@ -289,9 +288,6 @@ pub(super) fn check_item<'tcx>(
         }
         hir::ItemKind::Fn { sig, .. } => check_item_fn(tcx, def_id, sig.decl),
         hir::ItemKind::Const(_, _, ty, _) => check_const_item(tcx, def_id, ty.span),
-        hir::ItemKind::Struct(..) => check_type_defn(tcx, item, false),
-        hir::ItemKind::Union(..) => check_type_defn(tcx, item, true),
-        hir::ItemKind::Enum(..) => check_type_defn(tcx, item, true),
         // Note: do not add new entries to this match. Instead add all new logic in `check_item_type`
         _ => span_bug!(item.span, "should have been handled by the type based wf check: {item:?}"),
     }
@@ -989,15 +985,15 @@ pub(crate) fn check_associated_item(
 }
 
 /// In a type definition, we check that to ensure that the types of the fields are well-formed.
-fn check_type_defn<'tcx>(
+pub(crate) fn check_type_defn<'tcx>(
     tcx: TyCtxt<'tcx>,
-    item: &hir::Item<'tcx>,
+    item: LocalDefId,
     all_sized: bool,
 ) -> Result<(), ErrorGuaranteed> {
-    let _ = tcx.representability(item.owner_id.def_id);
-    let adt_def = tcx.adt_def(item.owner_id);
+    let _ = tcx.representability(item);
+    let adt_def = tcx.adt_def(item);
 
-    enter_wf_checking_ctxt(tcx, item.owner_id.def_id, |wfcx| {
+    enter_wf_checking_ctxt(tcx, item, |wfcx| {
         let variants = adt_def.variants();
         let packed = adt_def.repr().packed();
 
@@ -1068,15 +1064,7 @@ fn check_type_defn<'tcx>(
                         hir_ty.span,
                         wfcx.body_def_id,
                         ObligationCauseCode::FieldSized {
-                            adt_kind: match &item.kind {
-                                ItemKind::Struct(..) => AdtKind::Struct,
-                                ItemKind::Union(..) => AdtKind::Union,
-                                ItemKind::Enum(..) => AdtKind::Enum,
-                                kind => span_bug!(
-                                    item.span,
-                                    "should be wfchecking an ADT, got {kind:?}"
-                                ),
-                            },
+                            adt_kind: adt_def.adt_kind(),
                             span: hir_ty.span,
                             last,
                         },
@@ -1099,7 +1087,7 @@ fn check_type_defn<'tcx>(
             }
         }
 
-        check_where_clauses(wfcx, item.owner_id.def_id);
+        check_where_clauses(wfcx, item);
         Ok(())
     })
 }

tests/ui/generic-associated-types/static-lifetime-tip-with-default-type.stderr

@@ -82,14 +82,6 @@ help: consider adding an explicit lifetime bound
 LL | struct Far<T: 'static
    |             +++++++++
 
-error[E0392]: lifetime parameter `'a` is never used
-  --> $DIR/static-lifetime-tip-with-default-type.rs:22:10
-   |
-LL | struct S<'a, K: 'a = i32>(&'static K);
-   |          ^^ unused lifetime parameter
-   |
-   = help: consider removing `'a`, referring to it in a field, or using a marker such as `PhantomData`
-
 error[E0310]: the parameter type `K` may not live long enough
   --> $DIR/static-lifetime-tip-with-default-type.rs:22:27
    |
@@ -104,6 +96,14 @@ help: consider adding an explicit lifetime bound
 LL | struct S<'a, K: 'a + 'static = i32>(&'static K);
    |                    +++++++++
 
+error[E0392]: lifetime parameter `'a` is never used
+  --> $DIR/static-lifetime-tip-with-default-type.rs:22:10
+   |
+LL | struct S<'a, K: 'a = i32>(&'static K);
+   |          ^^ unused lifetime parameter
+   |
+   = help: consider removing `'a`, referring to it in a field, or using a marker such as `PhantomData`
+
 error: aborting due to 8 previous errors
 
 Some errors have detailed explanations: E0310, E0392.

tests/ui/lifetimes/issue-64173-unused-lifetimes.stderr

@@ -7,6 +7,12 @@ LL |     beta: [(); foo::<&'a ()>()],
    = note: lifetime parameters may not be used in const expressions
    = help: add `#![feature(generic_const_exprs)]` to allow generic const expressions
 
+error: generic `Self` types are currently not permitted in anonymous constants
+  --> $DIR/issue-64173-unused-lifetimes.rs:4:28
+   |
+LL |     array: [(); size_of::<&Self>()],
+   |                            ^^^^
+
 error[E0392]: lifetime parameter `'s` is never used
   --> $DIR/issue-64173-unused-lifetimes.rs:3:12
    |
@@ -15,12 +21,6 @@ LL | struct Foo<'s> {
    |
    = help: consider removing `'s`, referring to it in a field, or using a marker such as `PhantomData`
 
-error: generic `Self` types are currently not permitted in anonymous constants
-  --> $DIR/issue-64173-unused-lifetimes.rs:4:28
-   |
-LL |     array: [(); size_of::<&Self>()],
-   |                            ^^^^
-
 error[E0392]: lifetime parameter `'a` is never used
   --> $DIR/issue-64173-unused-lifetimes.rs:15:12
    |

tests/ui/regions/region-bounds-on-objects-and-type-parameters.stderr

@@ -4,14 +4,6 @@ error[E0226]: only a single explicit lifetime bound is permitted
 LL |     z: Box<dyn Is<'a>+'b+'c>,
    |                          ^^
 
-error[E0392]: lifetime parameter `'c` is never used
-  --> $DIR/region-bounds-on-objects-and-type-parameters.rs:11:18
-   |
-LL | struct Foo<'a,'b,'c> {
-   |                  ^^ unused lifetime parameter
-   |
-   = help: consider removing `'c`, referring to it in a field, or using a marker such as `PhantomData`
-
 error[E0478]: lifetime bound not satisfied
   --> $DIR/region-bounds-on-objects-and-type-parameters.rs:21:8
    |
@@ -29,6 +21,14 @@ note: but lifetime parameter must outlive the lifetime `'a` as defined here
 LL | struct Foo<'a,'b,'c> {
    |            ^^
 
+error[E0392]: lifetime parameter `'c` is never used
+  --> $DIR/region-bounds-on-objects-and-type-parameters.rs:11:18
+   |
+LL | struct Foo<'a,'b,'c> {
+   |                  ^^ unused lifetime parameter
+   |
+   = help: consider removing `'c`, referring to it in a field, or using a marker such as `PhantomData`
+
 error: aborting due to 3 previous errors
 
 Some errors have detailed explanations: E0226, E0392, E0478.

tests/ui/traits/issue-105231.stderr

@@ -1,14 +1,3 @@
-error: type parameter `T` is only used recursively
-  --> $DIR/issue-105231.rs:1:15
-   |
-LL | struct A<T>(B<T>);
-   |          -    ^
-   |          |
-   |          type parameter must be used non-recursively in the definition
-   |
-   = help: consider removing `T`, referring to it in a field, or using a marker such as `PhantomData`
-   = note: all type parameters must be used in a non-recursive way in order to constrain their variance
-
 error[E0072]: recursive types `A` and `B` have infinite size
   --> $DIR/issue-105231.rs:1:1
    |
@@ -26,6 +15,17 @@ LL |
 LL ~ struct B<T>(Box<A<A<T>>>);
    |
 
+error: type parameter `T` is only used recursively
+  --> $DIR/issue-105231.rs:1:15
+   |
+LL | struct A<T>(B<T>);
+   |          -    ^
+   |          |
+   |          type parameter must be used non-recursively in the definition
+   |
+   = help: consider removing `T`, referring to it in a field, or using a marker such as `PhantomData`
+   = note: all type parameters must be used in a non-recursive way in order to constrain their variance
+
 error: type parameter `T` is only used recursively
   --> $DIR/issue-105231.rs:4:17
    |