[libcxx-commits] [libcxx] [libc++] Uniformly require complete types in vector member functions (PR #211110)

[Louis Dionne via libcxx-commits]

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@@ -0,0 +1,30 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// <vector>
+
+// This test ensures that we diagnose when an incomplete type is used in one of
+// vector's methods. The Standard requires that to be the case, and we want to
+// uniformly produce an error for that. Note that producing the same diagnostic
+// in all cases is difficult, but we at least want to fail to fight back against
+// Hyrum's law.
+
+#include <vector>
+
+struct Incomplete;
+
+void f(std::vector<Incomplete>& v) {
+  (void)v.empty();  // expected-error@*:* {{}}
+  (void)v.size();   // expected-error@*:* {{}}
+  (void)v.begin();  // expected-error@*:* {{}}
+  (void)v.end();    // expected-error@*:* {{}}
+  (void)v.cbegin(); // expected-error@*:* {{}}
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ldionne wrote:

Another question is which methods should we test here. Some methods like `push_back(T const&)` clearly already imply a complete `T`, so I don't think there's a point in testing those. I'm not sure where we should draw the line.

https://github.com/llvm/llvm-project/pull/211110