Merge pull request #11010 from mitchellh/peer-errors

stage2: peer resolve error sets and error unions 

1 files changed, 17 insertions, 0 deletions

diff --git a/src/type.zig b/src/type.zig
index dbb5eb4ba3..96b8a78dea 100644
--- a/src/type.zig
+++ b/src/type.zig
@@ -4216,6 +4216,23 @@ pub const Type = extern union {
         };
     }
 
+    /// Merge lhs with rhs.
+    /// Asserts that lhs and rhs are both error sets and are resolved.
+    pub fn errorSetMerge(lhs: Type, arena: Allocator, rhs: Type) !Type {
+        const lhs_names = lhs.errorSetNames();
+        const rhs_names = rhs.errorSetNames();
+        var names: Module.ErrorSet.NameMap = .{};
+        try names.ensureUnusedCapacity(arena, lhs_names.len);
+        for (lhs_names) |name| {
+            names.putAssumeCapacityNoClobber(name, {});
+        }
+        for (rhs_names) |name| {
+            try names.put(arena, name, {});
+        }
+
+        return try Tag.error_set_merged.create(arena, names);
+    }
+
     pub fn enumFields(ty: Type) Module.EnumFull.NameMap {
         return switch (ty.tag()) {
             .enum_full, .enum_nonexhaustive => ty.cast(Payload.EnumFull).?.data.fields,