Do not create trait object type if missing associated types

2 files changed, 20 insertions, 11 deletions

diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs
index cab04ee0987..321a8aba7f7 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs
@@ -219,11 +219,13 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             def_ids.retain(|def_id| !tcx.generics_require_sized_self(def_id));
         }
 
-        self.complain_about_missing_assoc_tys(
+        if let Err(guar) = self.check_for_required_assoc_tys(
             associated_types,
             potential_assoc_types,
             hir_trait_bounds,
-        );
+        ) {
+            return Ty::new_error(tcx, guar);
+        }
 
         // De-duplicate auto traits so that, e.g., `dyn Trait + Send + Send` is the same as
         // `dyn Trait + Send`.
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
index 0b58b807090..ff449a858d6 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
@@ -714,14 +714,14 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
     /// reasonable suggestion on how to write it. For the case of multiple associated types in the
     /// same trait bound have the same name (as they come from different supertraits), we instead
     /// emit a generic note suggesting using a `where` clause to constraint instead.
-    pub(crate) fn complain_about_missing_assoc_tys(
+    pub(crate) fn check_for_required_assoc_tys(
         &self,
         associated_types: FxIndexMap<Span, FxIndexSet<DefId>>,
         potential_assoc_types: Vec<usize>,
         trait_bounds: &[hir::PolyTraitRef<'_>],
-    ) {
+    ) -> Result<(), ErrorGuaranteed> {
         if associated_types.values().all(|v| v.is_empty()) {
-            return;
+            return Ok(());
         }
 
         let tcx = self.tcx();
@@ -739,7 +739,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         // Account for things like `dyn Foo + 'a`, like in tests `issue-22434.rs` and
         // `issue-22560.rs`.
         let mut trait_bound_spans: Vec<Span> = vec![];
-        let mut dyn_compatibility_violations = false;
+        let mut dyn_compatibility_violations = Ok(());
         for (span, items) in &associated_types {
             if !items.is_empty() {
                 trait_bound_spans.push(*span);
@@ -752,13 +752,20 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 let violations =
                     dyn_compatibility_violations_for_assoc_item(tcx, trait_def_id, *assoc_item);
                 if !violations.is_empty() {
-                    report_dyn_incompatibility(tcx, *span, None, trait_def_id, &violations).emit();
-                    dyn_compatibility_violations = true;
+                    dyn_compatibility_violations = Err(report_dyn_incompatibility(
+                        tcx,
+                        *span,
+                        None,
+                        trait_def_id,
+                        &violations,
+                    )
+                    .emit());
                 }
             }
         }
-        if dyn_compatibility_violations {
-            return;
+
+        if let Err(guar) = dyn_compatibility_violations {
+            return Err(guar);
         }
 
         // related to issue #91997, turbofishes added only when in an expr or pat
@@ -965,7 +972,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             }
         }
 
-        err.emit();
+        Err(err.emit())
     }
 
     /// On ambiguous associated type, look for an associated function whose name matches the