OpenOptions: create() and create_new() are flip flopped

[JesterOrNot]

I tried this code:

OpenOptions::new()
        .write(true)
        .create(true)
        .open(&args.target)

and it creates a file even if it already exists

OpenOptions::new()
        .write(true)
        .create_new(true)
        .open(&args.target)

This code creates a file only if the file does not exist

But look at the docs
For create()

For create_new()

I expected to see this happen: explanation
The functions to match their docs
Instead, this happened: explanation
They each do what the other is described to do

Meta

rustc --version --verbose:

rustc 1.41.0 (5e1a79984 2020-01-27)
binary: rustc
commit-hash: 5e1a799842ba6ed4a57e91f7ab9435947482f7d8
commit-date: 2020-01-27
host: x86_64-unknown-linux-gnu
release: 1.41.0
LLVM version: 9.0

Backtrace

gitpod /workspace/nushell $ RUST_BACKTRACE=1 cargo build
   Compiling nu v0.9.1 (/workspace/nushell)
    Finished dev [unoptimized + debuginfo] target(s) in 26.35s

[jumbatm]

This appears to be a doc issue, not a library bug.

In RFC 1252 expand_open_options, it says create should open an existing file, or create a new file if it does not already exist, and create_new should open a new file, failing if it doesn't exist, which is consistent with the observed behaviour. I believe the current wording is a bit ambiguous, though.

cc @pitdicker

@rustbot modify labels to +T-doc