Avoid const-eval ICEs from invalid CoerceShared impls

compiler/rustc_hir_analysis/src/coherence/builtin.rs

@@ -267,7 +267,7 @@ fn visit_implementation_of_coerce_shared(checker: &Checker<'_>) -> Result<(), Er
     // Just compute this for the side-effects, in particular reporting
     // errors; other parts of the code may demand it for the info of
     // course.
-    coerce_shared_info(tcx, impl_did)
+    tcx.ensure_result().coerce_shared_info(impl_did)
 }
 
 fn is_from_coerce_pointee_derive(tcx: TyCtxt<'_>, span: Span) -> bool {

compiler/rustc_hir_analysis/src/coherence/mod.rs

@@ -140,7 +140,7 @@ fn enforce_empty_impls_for_marker_traits(
 
 /// Adds query implementations to the [Providers] vtable, see [`rustc_middle::query`].
 pub(crate) fn provide(providers: &mut Providers) {
-    use self::builtin::coerce_unsized_info;
+    use self::builtin::{coerce_shared_info, coerce_unsized_info};
     use self::inherent_impls::{
         crate_incoherent_impls, crate_inherent_impls, crate_inherent_impls_validity_check,
         inherent_impls,
@@ -155,6 +155,7 @@ pub(crate) fn provide(providers: &mut Providers) {
         inherent_impls,
         crate_inherent_impls_validity_check,
         crate_inherent_impls_overlap_check,
+        coerce_shared_info,
         coerce_unsized_info,
         orphan_check_impl,
         ..*providers

compiler/rustc_hir_typeck/src/coercion.rs

@@ -997,10 +997,22 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
             self.tcx,
             ObligationCause::dummy(),
             self.param_env,
-            ty::Binder::dummy(coerce_shared_trait_ref),
+            coerce_shared_trait_ref,
         );
+
+        let mut selcx = traits::SelectionContext::new(self);
+        let Ok(Some(impl_source)) = selcx.select(&obligation) else {
+            return Err(TypeError::Mismatch);
+        };
+        if let ImplSource::UserDefined(impl_source) = &impl_source
+            && let Some(impl_def_id) = impl_source.impl_def_id.as_local()
+            && let Err(guar) = self.tcx.ensure_result().coerce_shared_info(impl_def_id)
+        {
+            self.fcx.set_tainted_by_errors(guar);
+        }
+
         let ocx = ObligationCtxt::new(&self.infcx);
-        ocx.register_obligation(obligation);
+        ocx.register_obligations(impl_source.nested_obligations());
         let errs = ocx.evaluate_obligations_error_on_ambiguity();
         if errs.is_empty() {
             Ok(InferOk {

compiler/rustc_middle/src/queries.rs

@@ -1205,6 +1205,10 @@ rustc_queries! {
         separate_provide_extern
     }
 
+    query coerce_shared_info(key: LocalDefId) -> Result<(), ErrorGuaranteed> {
+        desc { "computing CoerceShared info for `{}`", tcx.def_path_str(key) }
+    }
+
     query typeck_root(key: LocalDefId) -> &'tcx ty::TypeckResults<'tcx> {
         desc { "type-checking `{}`", tcx.def_path_str(key) }
         cache_on_disk

tests/crashes/reborrow/coerce-shared-alias-projection.rs → tests/ui/reborrow/coerce-shared-alias-projection.rs

@@ -1,4 +1,5 @@
-//@ known-bug: unknown
+// Alias and projection fields in invalid multi-field `CoerceShared` impls must not cause an ICE.
+
 #![feature(reborrow)]
 #![allow(dead_code)]
 
@@ -62,6 +63,7 @@ impl<'a, T> Clone for OuterAliasRef<'a, T> {
 impl<'a, T> Copy for OuterAliasRef<'a, T> {}
 
 impl<'a, T> CoerceShared<OuterAliasRef<'a, T>> for OuterMut<'a, T> {}
+//~^ ERROR implementing `CoerceShared` does not allow multiple lifetimes or fields to be coerced
 
 struct OuterProjectionRef<'a, T: 'a> {
     inner: ProjectedInnerRef<'a, T>,
@@ -77,6 +79,7 @@ impl<'a, T: 'a> Clone for OuterProjectionRef<'a, T> {
 impl<'a, T: 'a> Copy for OuterProjectionRef<'a, T> {}
 
 impl<'a, T: 'a> CoerceShared<OuterProjectionRef<'a, T>> for OuterMut<'a, T> {}
+//~^ ERROR implementing `CoerceShared` does not allow multiple lifetimes or fields to be coerced
 
 fn read_alias<'a>(outer: OuterAliasRef<'a, u32>) -> (&'a u32, usize) {
     (outer.inner.value, outer.tag)

tests/ui/reborrow/coerce-shared-alias-projection.stderr

@@ -0,0 +1,14 @@
+error: implementing `CoerceShared` does not allow multiple lifetimes or fields to be coerced
+  --> $DIR/coerce-shared-alias-projection.rs:65:13
+   |
+LL | impl<'a, T> CoerceShared<OuterAliasRef<'a, T>> for OuterMut<'a, T> {}
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: implementing `CoerceShared` does not allow multiple lifetimes or fields to be coerced
+  --> $DIR/coerce-shared-alias-projection.rs:81:17
+   |
+LL | impl<'a, T: 'a> CoerceShared<OuterProjectionRef<'a, T>> for OuterMut<'a, T> {}
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+

tests/crashes/reborrow/coerce-shared-different-layout.rs → tests/ui/reborrow/coerce-shared-different-layout.rs

@@ -1,4 +1,5 @@
-//@ known-bug: unknown
+// `CoerceShared` impls with incompatible data-field layouts must be rejected without an ICE.
+
 #![feature(reborrow)]
 #![allow(dead_code)]
 
@@ -27,6 +28,7 @@ impl<'a, T> Clone for ImbrisRef<'a, T> {
 impl<'a, T> Copy for ImbrisRef<'a, T> {}
 
 impl<'a, T> CoerceShared<ImbrisRef<'a, T>> for ImbrisMut<'a, T> {}
+//~^ ERROR implementing `CoerceShared` does not allow multiple lifetimes or fields to be coerced
 
 fn ptr(value: ImbrisRef<'_, i32>) -> NonNull<i32> {
     value.ptr

tests/ui/reborrow/coerce-shared-different-layout.stderr

@@ -0,0 +1,8 @@
+error: implementing `CoerceShared` does not allow multiple lifetimes or fields to be coerced
+  --> $DIR/coerce-shared-different-layout.rs:30:13
+   |
+LL | impl<'a, T> CoerceShared<ImbrisRef<'a, T>> for ImbrisMut<'a, T> {}
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+

tests/ui/reborrow/coerce-shared-invalid-consteval-issue-158149.current.stderr

@@ -0,0 +1,8 @@
+error: implementing `CoerceShared` does not allow multiple lifetimes or fields to be coerced
+  --> $DIR/coerce-shared-invalid-consteval-issue-158149.rs:19:10
+   |
+LL | impl<'a> CoerceShared<MyRef<'a>> for MyMut<'a> {}
+   |          ^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+

tests/ui/reborrow/coerce-shared-invalid-consteval-issue-158149.next.stderr

@@ -0,0 +1,8 @@
+error: implementing `CoerceShared` does not allow multiple lifetimes or fields to be coerced
+  --> $DIR/coerce-shared-invalid-consteval-issue-158149.rs:19:10
+   |
+LL | impl<'a> CoerceShared<MyRef<'a>> for MyMut<'a> {}
+   |          ^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+

tests/ui/reborrow/coerce-shared-invalid-consteval-issue-158149.rs

@@ -0,0 +1,29 @@
+//@ revisions: current next
+//@[next] compile-flags: -Znext-solver
+
+// Invalid `CoerceShared` impls must taint type checking before CTFE.
+
+#![feature(const_block_items)]
+#![feature(reborrow)]
+#![allow(dead_code, unused_variables)]
+
+use std::marker::CoerceShared;
+
+struct MyMut<'a>(&'a u8);
+#[derive(Copy, Clone)]
+struct MyRef<'a> {
+    x: &'a (),
+    y: &'a (),
+}
+
+impl<'a> CoerceShared<MyRef<'a>> for MyMut<'a> {}
+//~^ ERROR implementing `CoerceShared` does not allow multiple lifetimes or fields to be coerced
+
+const {
+    let value = 1;
+    consume(MyMut(&value));
+}
+
+const fn consume(_: MyRef<'_>) {}
+
+fn main() {}

tests/crashes/reborrow/coerce-shared-marker-no-target-lifetime.rs → tests/ui/reborrow/coerce-shared-marker-no-target-lifetime.rs

@@ -1,6 +1,7 @@
-//@ known-bug: unknown
 //@ edition: 2024
 
+// A `CoerceShared` target without a reborrowed lifetime must be rejected without an ICE.
+
 #![feature(reborrow)]
 
 use std::marker::{CoerceShared, PhantomData, Reborrow};
@@ -10,12 +11,11 @@ struct CustomMarkerRef;
 
 impl<'a> Reborrow for CustomMarker<'a> {}
 impl<'a> CoerceShared<CustomMarkerRef> for CustomMarker<'a> {}
-//~^ ERROR
+//~^ ERROR implementing `CoerceShared` does not allow multiple lifetimes or fields to be coerced
 
 fn method(_a: CustomMarkerRef) {}
 
 fn main() {
     let a = CustomMarker(PhantomData);
     method(a);
-    //~^ ERROR
 }

tests/ui/reborrow/coerce-shared-marker-no-target-lifetime.stderr

@@ -0,0 +1,8 @@
+error: implementing `CoerceShared` does not allow multiple lifetimes or fields to be coerced
+  --> $DIR/coerce-shared-marker-no-target-lifetime.rs:13:10
+   |
+LL | impl<'a> CoerceShared<CustomMarkerRef> for CustomMarker<'a> {}
+   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+

tests/crashes/reborrow/coerce-shared-multi-field.rs → tests/ui/reborrow/coerce-shared-multi-field.rs

@@ -1,4 +1,5 @@
-//@ known-bug: unknown
+// Multi-field `CoerceShared` impls must be rejected without reaching malformed reborrow MIR.
+
 #![feature(reborrow)]
 #![allow(dead_code)]
 
@@ -34,6 +35,7 @@ impl<'a, T> Clone for MatRef<'a, T> {
 impl<'a, T> Copy for MatRef<'a, T> {}
 
 impl<'a, T> CoerceShared<MatRef<'a, T>> for MatMut<'a, T> {}
+//~^ ERROR implementing `CoerceShared` does not allow multiple lifetimes or fields to be coerced
 
 fn dims<T>(mat: MatRef<'_, T>) -> (usize, usize, usize, usize) {
     let _ = mat.ptr;

tests/ui/reborrow/coerce-shared-multi-field.stderr

@@ -0,0 +1,8 @@
+error: implementing `CoerceShared` does not allow multiple lifetimes or fields to be coerced
+  --> $DIR/coerce-shared-multi-field.rs:37:13
+   |
+LL | impl<'a, T> CoerceShared<MatRef<'a, T>> for MatMut<'a, T> {}
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+

tests/crashes/reborrow/coerce-shared-nested.rs → tests/ui/reborrow/coerce-shared-nested.rs

@@ -1,4 +1,5 @@
-//@ known-bug: unknown
+// Invalid nested multi-field `CoerceShared` impls must be rejected without an ICE.
+
 #![feature(reborrow)]
 #![allow(dead_code)]
 
@@ -45,6 +46,7 @@ impl<'a, T> Clone for OuterRef<'a, T> {
 impl<'a, T> Copy for OuterRef<'a, T> {}
 
 impl<'a, T> CoerceShared<OuterRef<'a, T>> for OuterMut<'a, T> {}
+//~^ ERROR implementing `CoerceShared` does not allow multiple lifetimes or fields to be coerced
 
 fn get<'a>(outer: OuterRef<'a, i32>) -> (&'a i32, usize) {
     (outer.inner.value, outer.tag)

tests/ui/reborrow/coerce-shared-nested.stderr

@@ -0,0 +1,8 @@
+error: implementing `CoerceShared` does not allow multiple lifetimes or fields to be coerced
+  --> $DIR/coerce-shared-nested.rs:48:13
+   |
+LL | impl<'a, T> CoerceShared<OuterRef<'a, T>> for OuterMut<'a, T> {}
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+

tests/ui/reborrow/coerce-shared-omitted-reborrow-field-locked.rs

@@ -47,7 +47,6 @@ fn main() {
     let shared = get(wrapped);
 
     *wrapped.extra.value = 3;
-    //~^ ERROR cannot assign to `*wrapped.extra.value` because it is borrowed
 
     let _ = shared;
 }

tests/ui/reborrow/coerce-shared-omitted-reborrow-field-locked.stderr

@@ -4,18 +4,5 @@ error: implementing `CoerceShared` does not allow multiple lifetimes or fields t
 LL | impl<'a, T> CoerceShared<OmitRef<'a, T>> for OmitMut<'a, T> {}
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error[E0506]: cannot assign to `*wrapped.extra.value` because it is borrowed
-  --> $DIR/coerce-shared-omitted-reborrow-field-locked.rs:49:5
-   |
-LL |     let shared = get(wrapped);
-   |                      ------- `*wrapped.extra.value` is borrowed here
-LL |
-LL |     *wrapped.extra.value = 3;
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^
-   |     |
-   |     `*wrapped.extra.value` is assigned to here but it was already borrowed
-   |     borrow later used here
-
-error: aborting due to 2 previous errors
+error: aborting due to 1 previous error
 
-For more information about this error, try `rustc --explain E0506`.

tests/crashes/reborrow/coerce-shared-tuple-phantom-position.rs → tests/ui/reborrow/coerce-shared-tuple-phantom-position.rs

@@ -1,4 +1,5 @@
-//@ known-bug: unknown
+// `PhantomData` positions must not hide invalid multi-field `CoerceShared` impls or cause an ICE.
+
 #![feature(reborrow)]
 #![allow(dead_code)]
 
@@ -56,6 +57,7 @@ impl<'a, T, U> Clone for InterleavedRef<'a, T, U> {
 impl<'a, T, U> Copy for InterleavedRef<'a, T, U> {}
 
 impl<'a, T, U> CoerceShared<InterleavedRef<'a, T, U>> for InterleavedMut<'a, T, U> {}
+//~^ ERROR implementing `CoerceShared` does not allow multiple lifetimes or fields to be coerced
 
 fn read_source_leading<'a>(value: SourceLeadingRef<'a, i32>) -> &'a i32 {
     value.0

tests/ui/reborrow/coerce-shared-tuple-phantom-position.stderr

@@ -0,0 +1,8 @@
+error: implementing `CoerceShared` does not allow multiple lifetimes or fields to be coerced
+  --> $DIR/coerce-shared-tuple-phantom-position.rs:59:16
+   |
+LL | impl<'a, T, U> CoerceShared<InterleavedRef<'a, T, U>> for InterleavedMut<'a, T, U> {}
+   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+

tests/crashes/reborrow/corrected-field-mismatch-coerce-shared-issue-156315.rs → tests/ui/reborrow/corrected-field-mismatch-coerce-shared-issue-156315.rs

@@ -1,4 +1,4 @@
-//@ known-bug: unknown
+// An invalid `CoerceShared` field relation must report an error instead of causing an ICE.
 
 #![feature(reborrow)]
 
@@ -9,9 +9,9 @@ struct CustomMut<'a, T>(&'a mut T);
 impl<'a, T> Reborrow for CustomMut<'a, T> {}
 
 struct CustomRef<'a, T>(&'a CustomMut<'a, T>);
-//~^ ERROR
 
 impl<'a, T> CoerceShared<CustomRef<'a, T>> for CustomMut<'a, T> {}
+//~^ ERROR the trait bound `&'a mut T: CoerceShared<&'a CustomMut<'a, T>>` is not satisfied
 
 fn method(_a: CustomRef<'_, ()>) {}
 

tests/ui/reborrow/corrected-field-mismatch-coerce-shared-issue-156315.stderr

@@ -0,0 +1,9 @@
+error[E0277]: the trait bound `&'a mut T: CoerceShared<&'a CustomMut<'a, T>>` is not satisfied
+  --> $DIR/corrected-field-mismatch-coerce-shared-issue-156315.rs:13:1
+   |
+LL | impl<'a, T> CoerceShared<CustomRef<'a, T>> for CustomMut<'a, T> {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the nightly-only, unstable trait `CoerceShared<&'a CustomMut<'a, T>>` is not implemented for `&'a mut T`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0277`.

tests/crashes/reborrow/missing-generic-args-coerce-shared-issue-156315.rs → tests/ui/reborrow/missing-generic-args-coerce-shared-issue-156315.rs

@@ -1,4 +1,5 @@
-//@ known-bug: unknown
+// Missing generic arguments in a `CoerceShared` field must not cause an additional ICE.
+
 #![feature(reborrow)]
 
 // Malformed no-ICE regression: this intentionally keeps the missing generic arguments from the
@@ -14,7 +15,6 @@ impl<'a, T> CoerceShared<CustomRef<'a, T>> for CustomMut<'a, T> {}
 struct CustomRef<'a, T>(&'a CustomMut);
 //~^ ERROR
 //~| ERROR
-//~| ERROR
 
 fn method(_a: CustomRef<'_, ()>) {}
 

tests/ui/reborrow/missing-generic-args-coerce-shared-issue-156315.stderr

@@ -0,0 +1,31 @@
+error[E0106]: missing lifetime specifier
+  --> $DIR/missing-generic-args-coerce-shared-issue-156315.rs:15:29
+   |
+LL | struct CustomRef<'a, T>(&'a CustomMut);
+   |                             ^^^^^^^^^ expected named lifetime parameter
+   |
+help: consider using the `'a` lifetime
+   |
+LL | struct CustomRef<'a, T>(&'a CustomMut<'a>);
+   |                                      ++++
+
+error[E0107]: missing generics for struct `CustomMut`
+  --> $DIR/missing-generic-args-coerce-shared-issue-156315.rs:15:29
+   |
+LL | struct CustomRef<'a, T>(&'a CustomMut);
+   |                             ^^^^^^^^^ expected 1 generic argument
+   |
+note: struct defined here, with 1 generic parameter: `T`
+  --> $DIR/missing-generic-args-coerce-shared-issue-156315.rs:10:8
+   |
+LL | struct CustomMut<'a, T>(&'a mut T);
+   |        ^^^^^^^^^     -
+help: add missing generic argument
+   |
+LL | struct CustomRef<'a, T>(&'a CustomMut<T>);
+   |                                      +++
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0106, E0107.
+For more information about an error, try `rustc --explain E0106`.