Compilation error when calling `Utf8Path::try_from` on an `std::path::Path`

[Nicholas Bishop]

Calling Utf8Path::try_from on an std::path::Path fails with "the size for values of type [u8] cannot be known at compilation time".

Example code:

use camino::Utf8Path;
use std::path::Path;

fn main() {
    let path1 = Path::new("/test");
    // This works:
    let path2 = Utf8Path::from_path(path1).unwrap();
    // But this fails with "the size for values of type `[u8]` cannot be known at compilation time"
    let path3 = Utf8Path::try_from(path1).unwrap();
}

Full error output:

$ cargo build
   Compiling camino-test v0.1.0 (/home/nicholasbishop/tmp/camino-test)
error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
   --> src/main.rs:9:17
    |
9   |     let path3 = Utf8Path::try_from(path1).unwrap();
    |                 ^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
    |
    = help: within `Utf8Path`, the trait `Sized` is not implemented for `[u8]`
note: required because it appears within the type `Utf8Path`
   --> /home/nicholasbishop/.cargo/registry/src/index.crates.io-6f17d22bba15001f/camino-1.1.6/src/lib.rs:545:12
    |
545 | pub struct Utf8Path(Path);
    |            ^^^^^^^^
note: required by a bound in `try_from`
   --> /home/nicholasbishop/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/convert/mod.rs:638:23
    |
638 | pub trait TryFrom<T>: Sized {
    |                       ^^^^^ required by this bound in `TryFrom::try_from`
...
645 |     fn try_from(value: T) -> Result<Self, Self::Error>;
    |        -------- required by a bound in this associated function

error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
   --> src/main.rs:9:17
    |
9   |     let path3 = Utf8Path::try_from(path1).unwrap();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
    |
    = help: within `Utf8Path`, the trait `Sized` is not implemented for `[u8]`
    = help: the trait `TryFrom<&'a Path>` is implemented for `&'a Utf8Path`
note: required because it appears within the type `Utf8Path`
   --> /home/nicholasbishop/.cargo/registry/src/index.crates.io-6f17d22bba15001f/camino-1.1.6/src/lib.rs:545:12
    |
545 | pub struct Utf8Path(Path);
    |            ^^^^^^^^
    = note: required for `Utf8Path` to implement `TryFrom<_>`

error[E0277]: the trait bound `Utf8Path: From<&Path>` is not satisfied
 --> src/main.rs:9:36
  |
9 |     let path3 = Utf8Path::try_from(path1).unwrap();
  |                 ------------------ ^^^^^ the trait `From<&Path>` is not implemented for `Utf8Path`
  |                 |
  |                 required by a bound introduced by this call
  |
  = help: the trait `From<&'a str>` is implemented for `&'a Utf8Path`
  = note: required for `&Path` to implement `Into<Utf8Path>`
  = note: required for `Utf8Path` to implement `TryFrom<&Path>`

error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
   --> src/main.rs:9:36
    |
9   |     let path3 = Utf8Path::try_from(path1).unwrap();
    |                 ------------------ ^^^^^ doesn't have a size known at compile-time
    |                 |
    |                 required by a bound introduced by this call
    |
    = help: within `Utf8Path`, the trait `Sized` is not implemented for `[u8]`
    = help: the trait `TryFrom<&'a Path>` is implemented for `&'a Utf8Path`
note: required because it appears within the type `Utf8Path`
   --> /home/nicholasbishop/.cargo/registry/src/index.crates.io-6f17d22bba15001f/camino-1.1.6/src/lib.rs:545:12
    |
545 | pub struct Utf8Path(Path);
    |            ^^^^^^^^
    = note: required for `&Path` to implement `Into<Utf8Path>`
    = note: required for `Utf8Path` to implement `TryFrom<&Path>`

error[E0599]: the method `unwrap` exists for enum `Result<Utf8Path, Infallible>`, but its trait bounds were not satisfied
   --> src/main.rs:9:43
    |
9   |     let path3 = Utf8Path::try_from(path1).unwrap();
    |                                           ^^^^^^ method cannot be called on `Result<Utf8Path, Infallible>` due to unsatisfied trait bounds
    |
   ::: /home/nicholasbishop/.cargo/registry/src/index.crates.io-6f17d22bba15001f/camino-1.1.6/src/lib.rs:545:1
    |
545 | pub struct Utf8Path(Path);
    | ------------------- doesn't satisfy `Utf8Path: Sized`
    |
    = note: the following trait bounds were not satisfied:
            `Utf8Path: Sized`

error[E0277]: the trait bound `Utf8Path: From<&Path>` is not satisfied
 --> src/main.rs:9:17
  |
9 |     let path3 = Utf8Path::try_from(path1).unwrap();
  |                 ^^^^^^^^^^^^^^^^^^ the trait `From<&Path>` is not implemented for `Utf8Path`
  |
  = help: the trait `From<&'a str>` is implemented for `&'a Utf8Path`
  = note: required for `&Path` to implement `Into<Utf8Path>`
  = note: required for `Utf8Path` to implement `TryFrom<&Path>`

Some errors have detailed explanations: E0277, E0599.
For more information about an error, try `rustc --explain E0277`.

[Rain]

That's how Rust works—you have to say <& Utf8Path>::try_from.

[Nicholas Bishop]

Ah, thank you :) I hadn't encountered that syntax before.