[SYCL][E2E] Add a test showing pre-existing swizzle-related bugs (#16352

)

sycl/test/basic_tests/vectors/swizzle.cpp

@@ -0,0 +1,41 @@
+// RUN: %clangxx -fsycl %s -o %t_default.out
+// RUN: %t_default.out
+
+// FIXME: Everything should compile cleanly.
+// RUN: %clangxx -fsycl -fsycl-device-only -DCHECK_ERRORS -fsyntax-only -Xclang -verify -Xclang -verify-ignore-unexpected=note,error %s
+
+#include <sycl/vector.hpp>
+
+int main() {
+  sycl::vec<int, 4> v{1, 2, 3, 4};
+  auto sw = v.swizzle<1, 2>();
+  assert(sw.lo()[0] == 2);
+  assert(sw.hi()[0] == 3);
+
+  // FIXME: Should be "4":
+  assert((sw + sw).lo()[0] == 2);
+
+  // FIXME: The below should compile.
+#if CHECK_ERRORS
+  // expected-error-re@+1 {{no template named 'swizzle' in {{.*}}}}
+  assert(sw.swizzle<0>()[0] == 2);
+  // expected-error-re@+1 {{no template named 'swizzle' in {{.*}}}}
+  assert(sw.swizzle<1>()[0] == 3);
+
+  {
+    // expected-error-re@+1 {{no template named 'swizzle' in {{.*}}}}
+    auto tmp = sw.swizzle<1, 0>();
+    assert(tmp[0] == 3);
+    assert(tmp[1] == 2);
+  }
+
+  {
+    // expected-error-re@+1 {{no template named 'swizzle' in {{.*}}}}
+    auto tmp = (sw + sw).swizzle<1, 0>();
+    assert(tmp[0] == 6);
+    assert(tmp[1] == 4);
+  }
+#endif
+
+  return 0;
+}