Sema: better error when coercing error sets

1 files changed, 19 insertions, 0 deletions

diff --git a/test/cases/compile_errors/nested_error_set_mismatch.zig b/test/cases/compile_errors/nested_error_set_mismatch.zig
new file mode 100644
index 0000000000..c0d68a5e53
--- /dev/null
+++ b/test/cases/compile_errors/nested_error_set_mismatch.zig
@@ -0,0 +1,19 @@
+const NextError = error{NextError};
+const OtherError = error{OutOfMemory};
+
+export fn entry() void {
+    const a: ?NextError!i32 = foo();
+    _ = a;
+}
+
+fn foo() ?OtherError!i32 {
+    return null;
+}
+
+// error
+// backend=llvm
+// target=native
+//
+// :4:1: error: expected type '?error{NextError}!i32', found '?error{OutOfMemory}!i32'
+// :4:1: note: optional type child 'error{OutOfMemory}!i32' cannot cast into optional type child 'error{NextError}!i32'
+// :4:1: note: 'error.OutOfMemory' not a member of destination error set