Issue 1 is that the FileMode default arguments in the D1 version of the documentation are screwed up. Instead of seeing symbolic constants you see things like "Filemode mode=cast(FileMode)1". It's ok in the D2 version of the doc, so maybe the D1 documentation just needs to be re-generated. Second, the FileMode enum really needs a doc comment added. It doesn't have one currently (in either D1 or D2) so the only way to figure out what the possible values are is from the documentation from the constructor of one particular class way down near the end of the doc page.
I just added a pull request (https://github.com/D-Programming-Language/phobos/pull/417) to the Phobos repo to address the second issue. However, bear in mind that D2 std.streams will be revamped or rewritten, so I don't know if the pull will be accepted (besides my english is not good). And, with respect to the first one is a bug in the doc generator, when documenting parameters that are enums with default int arguments. I don't have the issue number at the moment but I will look for it and mark this as a duplicated or just add the link. Marking as both D1 and D2 because the doc gen bug is present in both versions.
https://github.com/D-Programming-Language/phobos/pull/2119
Commits pushed to master at https://github.com/D-Programming-Language/phobos https://github.com/D-Programming-Language/phobos/commit/941e2e31f54625a195748f244fe2fe8d3883b77d Fix Issue 1726 - Document FileMode in std.stream. https://github.com/D-Programming-Language/phobos/commit/86c83142e4df0e4a557097290a2487972fbcb732 Merge pull request #2119 from AndrejMitrovic/Fix1726 Issue 1726 - Document FileMode in std.stream.