t.Fatalf("error copying %s: %v", file, err)
		}
	}

	// Change MultFn from a concrete function to a parameterized function.
	if err := convertMultToGeneric(filepath.Join(dir, "mult.pkg", "mult.go")); err != nil {
		t.Fatalf("error editing mult.go: %v", err)
	}

	// Same as TestPGODevirtualize except for MultFn, which we cannot