Rustc suggests creating a Box<Box<Box<(...)File>>> when std::io::Write isn't imported

[C34A]

Given the following code:
play.rust-lang.org: https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=320bd0fa60b7736e04ac82df5a77c760
It isn't able to run in the online thing, but the rest of the code is at https://github.com/C34A/vm1/blob/files/src/main.rs

let mut output_file = fs::File::create(newfilename).expect("failed to create output file");
output_file.write_all(&binary).expect("failed to write to output file!");

The current output is:

error[E0599]: no method named `write_all` found for struct `File` in the current scope
    --> src/main.rs:76:41
     |
76   | ...                   output_file.write_all(&binary).expect("failed to write to output file!");
     |                                   ^^^^^^^^^ method not found in `File`
     | 
    ::: /home/theo/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/io/mod.rs:1438:8
     |
1438 |     fn write_all(&mut self, mut buf: &[u8]) -> Result<()> {
     |        ---------
     |        |
     |        the method is available for `Box<File>` here
     |        the method is available for `Box<&mut File>` here
     |        the method is available for `Box<&File>` here
     |
help: consider wrapping the receiver expression with the appropriate type
     |
76   |                             Box::new(output_file).write_all(&binary).expect("failed to write to output file!");
     |                             ^^^^^^^^^           ^
help: consider wrapping the receiver expression with the appropriate type
     |
76   |                             Box::new(&mut output_file).write_all(&binary).expect("failed to write to output file!");
     |                             ^^^^^^^^^^^^^            ^
help: consider wrapping the receiver expression with the appropriate type
     |
76   |                             Box::new(&output_file).write_all(&binary).expect("failed to write to output file!");

Boxing output_file results in:

1438 |     fn write_all(&mut self, mut buf: &[u8]) -> Result<()> {
     |        ---------
     |        |
     |        the method is available for `Box<Box<File>>` here
     |        the method is available for `Box<&mut Box<File>>` here

... and so on.

The issue is that I don't have std::io::Write imported. I'm not sure exactly what the best output would be.

I am using a recent 1.53 nightly build:

rustc 1.53.0-nightly (42816d61e 2021-04-24)
binary: rustc
commit-hash: 42816d61ead7e46d462df997958ccfd514f8c21c
commit-date: 2021-04-24
host: x86_64-unknown-linux-gnu
release: 1.53.0-nightly
LLVM version: 12.0.0

[5225225]

This might be the same issue as #84272 which was fixed a few days after that nightly.

Try removing rustfmt to allow rustup to upgrade past that and see if it works correctly after that.

[C34A]

Yep, I think you're right. With the nightly from 2021-04-30 this seems to be fixed.