[llvm] [Support] Report EISDIR when opening a directory (PR #79880)

[Hubert Tong via llvm-commits]

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@@ -1296,6 +1296,39 @@ TEST_F(FileSystemTest, UTF8ToUTF16DirectoryIteration) {
 }
 #endif
 
+TEST_F(FileSystemTest, OpenDirectoryAsFileForRead) {
+  ASSERT_NO_ERROR(fs::create_directory(Twine(TestDirectory)));
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hubert-reinterpretcast wrote:

The use of `TestDirectory` here does not seem consistent with the other uses of the `TestDirectory` that is shared between tests.

https://github.com/llvm/llvm-project/blob/b667596e78d16c613ef0b6d2d16d1ea1c3493f78/llvm/unittests/Support/Path.cpp#L665-L667

It seems that `TestDirectory` is created (and removed) by the test harness.

It seems we don't need to create/remove a directory here?

https://github.com/llvm/llvm-project/pull/79880