Deduplicate the error printing code for hidden type mismatches

Author: oli-obk

Diff for: compiler/rustc_borrowck/src/region_infer/opaque_types.rs

@@ -128,17 +128,10 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             if let Some(prev) = result.get_mut(&opaque_type_key.def_id) {
                 if prev.ty != ty {
                     if !ty.references_error() {
-                        let mut err = infcx.tcx.sess.struct_span_err(
-                            concrete_type.span,
-                            "concrete type differs from previous defining opaque type use",
+                        prev.report_mismatch(
+                            &OpaqueHiddenType { ty, span: concrete_type.span },
+                            infcx.tcx,
                         );
-                        err.span_label(prev.span, format!("expected `{}`, got `{}`", prev.ty, ty));
-                        if prev.span == concrete_type.span {
-                            err.span_label(prev.span, "this expression supplies two conflicting concrete types for the same opaque type");
-                        } else {
-                            err.span_note(prev.span, "previous use here");
-                        }
-                        err.emit();
                     }
                     prev.ty = infcx.tcx.ty_error();
                 }

Diff for: compiler/rustc_middle/src/ty/mod.rs

@@ -1112,6 +1112,26 @@ pub struct OpaqueHiddenType<'tcx> {
     pub ty: Ty<'tcx>,
 }
 
+impl<'tcx> OpaqueHiddenType<'tcx> {
+    pub fn report_mismatch(&self, other: &Self, tcx: TyCtxt<'tcx>) {
+        // Found different concrete types for the opaque type.
+        let mut err = tcx.sess.struct_span_err(
+            other.span,
+            "concrete type differs from previous defining opaque type use",
+        );
+        err.span_label(other.span, format!("expected `{}`, got `{}`", self.ty, other.ty));
+        if self.span == other.span {
+            err.span_label(
+                self.span,
+                "this expression supplies two conflicting concrete types for the same opaque type",
+            );
+        } else {
+            err.span_note(self.span, "previous use here");
+        }
+        err.emit();
+    }
+}
+
 rustc_index::newtype_index! {
     /// "Universes" are used during type- and trait-checking in the
     /// presence of `for<..>` binders to control what sets of names are

Diff for: compiler/rustc_typeck/src/collect/type_of.rs

@@ -601,21 +601,7 @@ fn find_opaque_ty_constraints(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Ty<'_> {
 
                 if let Some(prev) = self.found {
                     if concrete_type.ty != prev.ty && !(concrete_type, prev).references_error() {
-                        // Found different concrete types for the opaque type.
-                        let mut err = self.tcx.sess.struct_span_err(
-                            concrete_type.span,
-                            "concrete type differs from previous defining opaque type use",
-                        );
-                        err.span_label(
-                            concrete_type.span,
-                            format!("expected `{}`, got `{}`", prev.ty, concrete_type.ty),
-                        );
-                        if prev.span == concrete_type.span {
-                            err.span_label(prev.span, "this expression supplies two conflicting concrete types for the same opaque type");
-                        } else {
-                            err.span_note(prev.span, "previous use here");
-                        }
-                        err.emit();
+                        prev.report_mismatch(&concrete_type, self.tcx);
                     }
                 } else {
                     self.found = Some(concrete_type);