Add test case for apparently-fixed crasher

#83011

Author: slavapestov

test/SILGen/typed_throws_async.swift

@@ -0,0 +1,15 @@
+// RUN: %target-swift-emit-silgen %s
+
+enum CustomError: Error {
+    case error
+}
+
+struct Test2<T> {
+    init(_: T) async throws(CustomError) {}
+}
+
+do {
+    _ = try await Test2(1)
+} catch {
+    print("\(error)")
+}