Wrong type name while reporting error

[achanda]

This piece of code gives the following error

use std::path::Path;

pub struct Foo {
    id: i32,
    path: Path
}

impl Foo {
    pub fn new() -> Foo {
        Foo{id: 42, path: Path::new()}
    }
}

fn main() {
    let b = Foo::new();
}

$ rustc test.rs
error[E0277]: the trait bound `[u8]: std::marker::Sized` is not satisfied in `Foo`
 --> test.rs:9:21
  |
9 |     pub fn new() -> Foo {
  |                     ^^^ `[u8]` does not have a constant size known at compile-time
  |
  = help: within `Foo`, the trait `std::marker::Sized` is not implemented for `[u8]`
  = note: required because it appears within the type `Foo`
  = note: the return type of a function must have a statically known size

error[E0061]: this function takes 1 parameter but 0 parameters were supplied
  --> test.rs:10:27
   |
10 |         Foo{id: 42, path: Path::new()}
   |                           ^^^^^^^^^^^ expected 1 parameter

error[E0308]: mismatched types
  --> test.rs:10:27
   |
10 |         Foo{id: 42, path: Path::new()}
   |                           ^^^^^^^^^^^ expected struct `std::path::Path`, found reference
   |
   = note: expected type `std::path::Path`
              found type `&std::path::Path`

error[E0277]: the trait bound `[u8]: std::marker::Sized` is not satisfied in `Foo`
  --> test.rs:10:9
   |
10 |         Foo{id: 42, path: Path::new()}
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `[u8]` does not have a constant size known at compile-time
   |
   = help: within `Foo`, the trait `std::marker::Sized` is not implemented for `[u8]`
   = note: required because it appears within the type `Foo`
   = note: structs must have a statically known size to be initialized

error[E0277]: the trait bound `[u8]: std::marker::Sized` is not satisfied in `Foo`
  --> test.rs:15:9
   |
15 |     let b = Foo::new();
   |         ^ `[u8]` does not have a constant size known at compile-time
   |
   = help: within `Foo`, the trait `std::marker::Sized` is not implemented for `[u8]`
   = note: required because it appears within the type `Foo`
   = note: all local variables must have a statically known size

error: aborting due to previous error(s)

This is a bit confusing since the span points to Foo but the message says [u8]. The ergonomics will be nicer if the message said Foo. It will be easier to debug that way.

Meta:

$ rustc --version
rustc 1.19.0-nightly (76242aebb 2017-06-06)

[Mark-Simulacrum]

The message does say " = help: within Foo, the trait std::marker::Sized is not implemented for [u8]" but really, there is no [u8] within Foo, just Path, which is internally (on unix, IIRC) [u8]

[estebank]

CC #23286

[estebank]

Current output still mentions [u8] in the main message, but clarifies things a bit:

error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
 --> src/main.rs:9:21
  |
9 |     pub fn new() -> Foo {
  |                     ^^^ doesn't have a size known at compile-time
  |
  = help: within `Foo`, the trait `std::marker::Sized` is not implemented for `[u8]`
  = note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
  = note: required because it appears within the type `Foo`
  = note: the return type of a function must have a statically known size

error[E0061]: this function takes 1 parameter but 0 parameters were supplied
  --> src/main.rs:10:27
   |
10 |         Foo{id: 42, path: Path::new()}
   |                           ^^^^^^^^^^^ expected 1 parameter

error[E0308]: mismatched types
  --> src/main.rs:10:27
   |
10 |         Foo{id: 42, path: Path::new()}
   |                           ^^^^^^^^^^^ expected struct `std::path::Path`, found reference
   |
   = note: expected type `std::path::Path`
              found type `&std::path::Path`

error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
  --> src/main.rs:10:9
   |
10 |         Foo{id: 42, path: Path::new()}
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
   |
   = help: within `Foo`, the trait `std::marker::Sized` is not implemented for `[u8]`
   = note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
   = note: required because it appears within the type `Foo`
   = note: structs must have a statically known size to be initialized

error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
  --> src/main.rs:15:9
   |
15 |     let b = Foo::new();
   |         ^ doesn't have a size known at compile-time
   |
   = help: within `Foo`, the trait `std::marker::Sized` is not implemented for `[u8]`
   = note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
   = note: required because it appears within the type `Foo`
   = note: all local variables must have a statically known size
   = help: unsized locals are gated as an unstable feature

error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
  --> src/main.rs:15:13
   |
15 |     let b = Foo::new();
   |             ^^^^^^^^ doesn't have a size known at compile-time
   |
   = help: within `Foo`, the trait `std::marker::Sized` is not implemented for `[u8]`
   = note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
   = note: required because it appears within the type `Foo`
   = note: the return type of a function must have a statically known size