borrowck: defer opaque type errors

7 files changed, 70 insertions, 47 deletions

diff --git a/compiler/rustc_borrowck/src/diagnostics/mod.rs b/compiler/rustc_borrowck/src/diagnostics/mod.rs
index 34bed375cb9..b67dba3af96 100644
--- a/compiler/rustc_borrowck/src/diagnostics/mod.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mod.rs
@@ -51,7 +51,7 @@ mod conflict_errors;
 mod explain_borrow;
 mod move_errors;
 mod mutability_errors;
-mod opaque_suggestions;
+mod opaque_types;
 mod region_errors;
 
 pub(crate) use bound_region_errors::{ToUniverseInfo, UniverseInfo};
diff --git a/compiler/rustc_borrowck/src/diagnostics/opaque_suggestions.rs b/compiler/rustc_borrowck/src/diagnostics/opaque_types.rs
index 7192a889adc..83fe4a9f98f 100644
--- a/compiler/rustc_borrowck/src/diagnostics/opaque_suggestions.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/opaque_types.rs
@@ -18,9 +18,28 @@ use rustc_trait_selection::errors::impl_trait_overcapture_suggestion;
 use crate::MirBorrowckCtxt;
 use crate::borrow_set::BorrowData;
 use crate::consumers::RegionInferenceContext;
+use crate::region_infer::opaque_types::DeferredOpaqueTypeError;
 use crate::type_check::Locations;
 
 impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
+    pub(crate) fn report_opaque_type_errors(&mut self, errors: Vec<DeferredOpaqueTypeError<'tcx>>) {
+        if errors.is_empty() {
+            return;
+        }
+        let mut guar = None;
+        for error in errors {
+            guar = Some(match error {
+                DeferredOpaqueTypeError::InvalidOpaqueTypeArgs(err) => err.report(self.infcx),
+                DeferredOpaqueTypeError::LifetimeMismatchOpaqueParam(err) => {
+                    self.infcx.dcx().emit_err(err)
+                }
+            });
+        }
+        let guar = guar.unwrap();
+        self.root_cx.set_tainted_by_errors(guar);
+        self.infcx.set_tainted_by_errors(guar);
+    }
+
     /// Try to note when an opaque is involved in a borrowck error and that
     /// opaque captures lifetimes due to edition 2024.
     // FIXME: This code is otherwise somewhat general, and could easily be adapted
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
index b130cf8ed27..2b74f1a48f7 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
@@ -92,9 +92,6 @@ impl<'tcx> RegionErrors<'tcx> {
     ) -> impl Iterator<Item = (RegionErrorKind<'tcx>, ErrorGuaranteed)> {
         self.0.into_iter()
     }
-    pub(crate) fn has_errors(&self) -> Option<ErrorGuaranteed> {
-        self.0.get(0).map(|x| x.1)
-    }
 }
 
 impl std::fmt::Debug for RegionErrors<'_> {
diff --git a/compiler/rustc_borrowck/src/lib.rs b/compiler/rustc_borrowck/src/lib.rs
index 752ff8e6f58..d76d6a04e6e 100644
--- a/compiler/rustc_borrowck/src/lib.rs
+++ b/compiler/rustc_borrowck/src/lib.rs
@@ -375,7 +375,7 @@ fn do_mir_borrowck<'tcx>(
         polonius_context,
     );
 
-    regioncx.infer_opaque_types(root_cx, &infcx, opaque_type_values);
+    let opaque_type_errors = regioncx.infer_opaque_types(root_cx, &infcx, opaque_type_values);
 
     // Dump MIR results into a file, if that is enabled. This lets us
     // write unit-tests, as well as helping with debugging.
@@ -471,7 +471,11 @@ fn do_mir_borrowck<'tcx>(
     };
 
     // Compute and report region errors, if any.
-    mbcx.report_region_errors(nll_errors);
+    if nll_errors.is_empty() {
+        mbcx.report_opaque_type_errors(opaque_type_errors);
+    } else {
+        mbcx.report_region_errors(nll_errors);
+    }
 
     let (mut flow_analysis, flow_entry_states) =
         get_flow_results(tcx, body, &move_data, &borrow_set, &regioncx);
diff --git a/compiler/rustc_borrowck/src/nll.rs b/compiler/rustc_borrowck/src/nll.rs
index ca6092e70d2..8608a8a3a66 100644
--- a/compiler/rustc_borrowck/src/nll.rs
+++ b/compiler/rustc_borrowck/src/nll.rs
@@ -148,11 +148,6 @@ pub(crate) fn compute_regions<'tcx>(
     let (closure_region_requirements, nll_errors) =
         regioncx.solve(infcx, body, polonius_output.clone());
 
-    if let Some(guar) = nll_errors.has_errors() {
-        // Suppress unhelpful extra errors in `infer_opaque_types`.
-        infcx.set_tainted_by_errors(guar);
-    }
-
     NllOutput {
         regioncx,
         polonius_input: polonius_facts.map(Box::new),
diff --git a/compiler/rustc_borrowck/src/region_infer/mod.rs b/compiler/rustc_borrowck/src/region_infer/mod.rs
index f1320048533..f4dc9627b35 100644
--- a/compiler/rustc_borrowck/src/region_infer/mod.rs
+++ b/compiler/rustc_borrowck/src/region_infer/mod.rs
@@ -44,7 +44,7 @@ use crate::{
 
 mod dump_mir;
 mod graphviz;
-mod opaque_types;
+pub(crate) mod opaque_types;
 mod reverse_sccs;
 
 pub(crate) mod values;
diff --git a/compiler/rustc_borrowck/src/region_infer/opaque_types.rs b/compiler/rustc_borrowck/src/region_infer/opaque_types.rs
index 6270e6d9a60..23c4554aa15 100644
--- a/compiler/rustc_borrowck/src/region_infer/opaque_types.rs
+++ b/compiler/rustc_borrowck/src/region_infer/opaque_types.rs
@@ -6,7 +6,9 @@ use rustc_middle::ty::{
     TypeVisitableExt, fold_regions,
 };
 use rustc_span::Span;
-use rustc_trait_selection::opaque_types::check_opaque_type_parameter_valid;
+use rustc_trait_selection::opaque_types::{
+    InvalidOpaqueTypeArgs, check_opaque_type_parameter_valid,
+};
 use tracing::{debug, instrument};
 
 use super::RegionInferenceContext;
@@ -14,6 +16,11 @@ use crate::BorrowCheckRootCtxt;
 use crate::session_diagnostics::LifetimeMismatchOpaqueParam;
 use crate::universal_regions::RegionClassification;
 
+pub(crate) enum DeferredOpaqueTypeError<'tcx> {
+    InvalidOpaqueTypeArgs(InvalidOpaqueTypeArgs<'tcx>),
+    LifetimeMismatchOpaqueParam(LifetimeMismatchOpaqueParam<'tcx>),
+}
+
 impl<'tcx> RegionInferenceContext<'tcx> {
     /// Resolve any opaque types that were encountered while borrow checking
     /// this item. This is then used to get the type in the `type_of` query.
@@ -58,13 +65,14 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     ///
     /// [rustc-dev-guide chapter]:
     /// https://rustc-dev-guide.rust-lang.org/opaque-types-region-infer-restrictions.html
-    #[instrument(level = "debug", skip(self, root_cx, infcx), ret)]
+    #[instrument(level = "debug", skip(self, root_cx, infcx))]
     pub(crate) fn infer_opaque_types(
         &self,
         root_cx: &mut BorrowCheckRootCtxt<'tcx>,
         infcx: &InferCtxt<'tcx>,
         opaque_ty_decls: FxIndexMap<OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>>,
-    ) {
+    ) -> Vec<DeferredOpaqueTypeError<'tcx>> {
+        let mut errors = Vec::new();
         let mut decls_modulo_regions: FxIndexMap<OpaqueTypeKey<'tcx>, (OpaqueTypeKey<'tcx>, Span)> =
             FxIndexMap::default();
 
@@ -124,8 +132,15 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             });
             debug!(?concrete_type);
 
-            let ty =
-                infcx.infer_opaque_definition_from_instantiation(opaque_type_key, concrete_type);
+            let ty = match infcx
+                .infer_opaque_definition_from_instantiation(opaque_type_key, concrete_type)
+            {
+                Ok(ty) => ty,
+                Err(err) => {
+                    errors.push(DeferredOpaqueTypeError::InvalidOpaqueTypeArgs(err));
+                    continue;
+                }
+            };
 
             // Sometimes, when the hidden type is an inference variable, it can happen that
             // the hidden type becomes the opaque type itself. In this case, this was an opaque
@@ -149,25 +164,27 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             // non-region parameters. This is necessary because within the new solver we perform
             // various query operations modulo regions, and thus could unsoundly select some impls
             // that don't hold.
-            if !ty.references_error()
-                && let Some((prev_decl_key, prev_span)) = decls_modulo_regions.insert(
-                    infcx.tcx.erase_regions(opaque_type_key),
-                    (opaque_type_key, concrete_type.span),
-                )
-                && let Some((arg1, arg2)) = std::iter::zip(
-                    prev_decl_key.iter_captured_args(infcx.tcx).map(|(_, arg)| arg),
-                    opaque_type_key.iter_captured_args(infcx.tcx).map(|(_, arg)| arg),
-                )
-                .find(|(arg1, arg2)| arg1 != arg2)
+            if let Some((prev_decl_key, prev_span)) = decls_modulo_regions.insert(
+                infcx.tcx.erase_regions(opaque_type_key),
+                (opaque_type_key, concrete_type.span),
+            ) && let Some((arg1, arg2)) = std::iter::zip(
+                prev_decl_key.iter_captured_args(infcx.tcx).map(|(_, arg)| arg),
+                opaque_type_key.iter_captured_args(infcx.tcx).map(|(_, arg)| arg),
+            )
+            .find(|(arg1, arg2)| arg1 != arg2)
             {
-                infcx.dcx().emit_err(LifetimeMismatchOpaqueParam {
-                    arg: arg1,
-                    prev: arg2,
-                    span: prev_span,
-                    prev_span: concrete_type.span,
-                });
+                errors.push(DeferredOpaqueTypeError::LifetimeMismatchOpaqueParam(
+                    LifetimeMismatchOpaqueParam {
+                        arg: arg1,
+                        prev: arg2,
+                        span: prev_span,
+                        prev_span: concrete_type.span,
+                    },
+                ));
             }
         }
+
+        errors
     }
 
     /// Map the regions in the type to named regions. This is similar to what
@@ -260,19 +277,13 @@ impl<'tcx> InferCtxt<'tcx> {
         &self,
         opaque_type_key: OpaqueTypeKey<'tcx>,
         instantiated_ty: OpaqueHiddenType<'tcx>,
-    ) -> Ty<'tcx> {
-        if let Some(e) = self.tainted_by_errors() {
-            return Ty::new_error(self.tcx, e);
-        }
-
-        if let Err(err) = check_opaque_type_parameter_valid(
+    ) -> Result<Ty<'tcx>, InvalidOpaqueTypeArgs<'tcx>> {
+        check_opaque_type_parameter_valid(
             self,
             opaque_type_key,
             instantiated_ty.span,
             DefiningScopeKind::MirBorrowck,
-        ) {
-            return Ty::new_error(self.tcx, err.report(self));
-        }
+        )?;
 
         let definition_ty = instantiated_ty
             .remap_generic_params_to_declaration_params(
@@ -282,10 +293,7 @@ impl<'tcx> InferCtxt<'tcx> {
             )
             .ty;
 
-        if let Err(e) = definition_ty.error_reported() {
-            return Ty::new_error(self.tcx, e);
-        }
-
-        definition_ty
+        definition_ty.error_reported()?;
+        Ok(definition_ty)
     }
 }