Auto merge of #105102 - compiler-errors:copy-impl-considering-regions, r=lcnr

Check ADT fields for copy implementations considering regions

Fixes #88901
r? `@ghost`

compiler/rustc_trait_selection/src/traits/misc.rs

@@ -1,29 +1,36 @@
 //! Miscellaneous type-system utilities that are too small to deserve their own modules.
 
-use crate::infer::InferCtxtExt as _;
 use crate::traits::{self, ObligationCause};
 
+use rustc_data_structures::fx::FxIndexSet;
 use rustc_hir as hir;
-use rustc_infer::infer::TyCtxtInferExt;
+use rustc_infer::infer::{RegionResolutionError, TyCtxtInferExt};
+use rustc_infer::{infer::outlives::env::OutlivesEnvironment, traits::FulfillmentError};
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitable};
 
-use crate::traits::error_reporting::TypeErrCtxtExt;
+use super::outlives_bounds::InferCtxtExt;
 
-#[derive(Clone)]
 pub enum CopyImplementationError<'tcx> {
-    InfrigingFields(Vec<(&'tcx ty::FieldDef, Ty<'tcx>)>),
+    InfrigingFields(Vec<(&'tcx ty::FieldDef, Ty<'tcx>, InfringingFieldsReason<'tcx>)>),
     NotAnAdt,
     HasDestructor,
 }
 
-pub fn can_type_implement_copy<'tcx>(
+pub enum InfringingFieldsReason<'tcx> {
+    Fulfill(Vec<FulfillmentError<'tcx>>),
+    Regions(Vec<RegionResolutionError<'tcx>>),
+}
+
+/// Checks that the fields of the type (an ADT) all implement copy.
+///
+/// If fields don't implement copy, return an error containing a list of
+/// those violating fields. If it's not an ADT, returns `Err(NotAnAdt)`.
+pub fn type_allowed_to_implement_copy<'tcx>(
     tcx: TyCtxt<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
     self_type: Ty<'tcx>,
     parent_cause: ObligationCause<'tcx>,
 ) -> Result<(), CopyImplementationError<'tcx>> {
-    // FIXME: (@jroesch) float this code up
-    let infcx = tcx.infer_ctxt().build();
     let (adt, substs) = match self_type.kind() {
         // These types used to have a builtin impl.
         // Now libcore provides that impl.
@@ -42,42 +49,82 @@ pub fn can_type_implement_copy<'tcx>(
         _ => return Err(CopyImplementationError::NotAnAdt),
     };
 
+    let copy_def_id = tcx.require_lang_item(hir::LangItem::Copy, Some(parent_cause.span));
+
     let mut infringing = Vec::new();
     for variant in adt.variants() {
         for field in &variant.fields {
-            let ty = field.ty(tcx, substs);
-            if ty.references_error() {
+            // Do this per-field to get better error messages.
+            let infcx = tcx.infer_ctxt().build();
+            let ocx = traits::ObligationCtxt::new(&infcx);
+
+            let unnormalized_ty = field.ty(tcx, substs);
+            if unnormalized_ty.references_error() {
                 continue;
             }
-            let span = tcx.def_span(field.did);
+
+            let field_span = tcx.def_span(field.did);
+            let field_ty_span = match tcx.hir().get_if_local(field.did) {
+                Some(hir::Node::Field(field_def)) => field_def.ty.span,
+                _ => field_span,
+            };
+
             // FIXME(compiler-errors): This gives us better spans for bad
             // projection types like in issue-50480.
             // If the ADT has substs, point to the cause we are given.
             // If it does not, then this field probably doesn't normalize
             // to begin with, and point to the bad field's span instead.
-            let cause = if field
+            let normalization_cause = if field
                 .ty(tcx, traits::InternalSubsts::identity_for_item(tcx, adt.did()))
                 .has_non_region_param()
             {
                 parent_cause.clone()
             } else {
-                ObligationCause::dummy_with_span(span)
-            };
-            match traits::fully_normalize(&infcx, cause, param_env, ty) {
-                Ok(ty) => {
-                    if !infcx.type_is_copy_modulo_regions(param_env, ty, span) {
-                        infringing.push((field, ty));
-                    }
-                }
-                Err(errors) => {
-                    infcx.err_ctxt().report_fulfillment_errors(&errors, None);
-                }
+                ObligationCause::dummy_with_span(field_ty_span)
             };
+            let ty = ocx.normalize(&normalization_cause, param_env, unnormalized_ty);
+            let normalization_errors = ocx.select_where_possible();
+            if !normalization_errors.is_empty() {
+                tcx.sess.delay_span_bug(field_span, format!("couldn't normalize struct field `{unnormalized_ty}` when checking Copy implementation"));
+                continue;
+            }
+
+            ocx.register_bound(
+                ObligationCause::dummy_with_span(field_ty_span),
+                param_env,
+                ty,
+                copy_def_id,
+            );
+            let errors = ocx.select_all_or_error();
+            if !errors.is_empty() {
+                infringing.push((field, ty, InfringingFieldsReason::Fulfill(errors)));
+            }
+
+            // Check regions assuming the self type of the impl is WF
+            let outlives_env = OutlivesEnvironment::with_bounds(
+                param_env,
+                Some(&infcx),
+                infcx.implied_bounds_tys(
+                    param_env,
+                    parent_cause.body_id,
+                    FxIndexSet::from_iter([self_type]),
+                ),
+            );
+            infcx.process_registered_region_obligations(
+                outlives_env.region_bound_pairs(),
+                param_env,
+            );
+            let errors = infcx.resolve_regions(&outlives_env);
+            if !errors.is_empty() {
+                infringing.push((field, ty, InfringingFieldsReason::Regions(errors)));
+            }
         }
     }
+
     if !infringing.is_empty() {
         return Err(CopyImplementationError::InfrigingFields(infringing));
     }
+
     if adt.has_dtor(tcx) {
         return Err(CopyImplementationError::HasDestructor);
     }