Sema: add missing peer type resolution for error unions

Closes #14077

1 files changed, 19 insertions, 0 deletions

diff --git a/src/Sema.zig b/src/Sema.zig
index 2dba678931..ddcdecb6b4 100644
--- a/src/Sema.zig
+++ b/src/Sema.zig
@@ -29761,6 +29761,25 @@ fn resolvePeerTypes(
                     continue;
                 }
             },
+            .ErrorSet => {
+                chosen = candidate;
+                chosen_i = candidate_i + 1;
+                if (err_set_ty) |chosen_set_ty| {
+                    if (.ok == try sema.coerceInMemoryAllowedErrorSets(block, chosen_set_ty, chosen_ty, src, src)) {
+                        continue;
+                    }
+                    if (.ok == try sema.coerceInMemoryAllowedErrorSets(block, chosen_ty, chosen_set_ty, src, src)) {
+                        err_set_ty = chosen_ty;
+                        continue;
+                    }
+
+                    err_set_ty = try chosen_set_ty.errorSetMerge(sema.arena, chosen_ty);
+                    continue;
+                } else {
+                    err_set_ty = chosen_ty;
+                    continue;
+                }
+            },
             else => {},
         }