[libc++] Add a few basic tests for C++ / Swift interoperation

libcxx/test/libcxx/vendor/apple/swift-interop.sh.cpp

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+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// This test requires access to the Swift compiler, which we assume is only available on Apple
+// platforms for now.
+// REQUIRES: buildhost=darwin
+
+// std::string basic test
+// RUN: swiftc -cxx-interoperability-mode=default %S/swift-interop/string/main.swift -o %t.string.exe \
+// RUN:   -Xcc -nostdinc++ -Xcc -nostdlib++ -Xcc -isystem -Xcc "%{include-dir}"
+// RUN: %{exec} %t.string.exe
+
+// std::vector test with a modulemap
+// RUN: swiftc -cxx-interoperability-mode=default %S/swift-interop/vector/main.swift -o %t.vector.exe \
+// RUN:   -Xcc -nostdinc++ -Xcc -nostdlib++ -Xcc -isystem -Xcc "%{include-dir}" -Xcc -I -Xcc %S/swift-interop/vector
+// RUN: %{exec} %t.vector.exe

libcxx/test/libcxx/vendor/apple/swift-interop/string/main.swift

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+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+import CxxStdlib
+
+let s: std.string = "abc123"
+
+for char in s { print(char) }

libcxx/test/libcxx/vendor/apple/swift-interop/vector/header.h

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+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include <vector>
+
+using VectorOfInt = std::vector<int>;
+
+inline VectorOfInt getStdVector() { return {1, 2, 3}; }

libcxx/test/libcxx/vendor/apple/swift-interop/vector/main.swift

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+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+import MyCxxDep // no explicit import of CxxStdlib
+
+let vec = getStdVector()
+
+for it in vec { print(it) }

libcxx/test/libcxx/vendor/apple/swift-interop/vector/module.modulemap

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+module MyCxxDep {
+    header "header.h"
+    export *
+}