Description
Hey folks, this just bit me so and took a bit to figure out, so I'd thought I'd file an issue for this admittedly niche issue.
Given the following code: playground
trait Foo {
fn get(&self);
}
struct Bar<T>(T);
struct Inner();
impl Foo for Inner {
fn get(&self) { }
}
fn main() {
let thing = Bar(Inner);
thing.0.get();
}The current output is:
error[E0599]: no method named `get` found for fn item `fn() -> Inner {Inner}` in the current scope
--> src/main.rs:16:13
|
16 | thing.0.get();
| ^^^ method not found in `fn() -> Inner {Inner}`
|
= note: `thing.0` is a function, perhaps you wish to call it
= help: items from traits can only be used if the trait is implemented and in scope
note: `Foo` defines an item `get`, perhaps you need to implement it
--> src/main.rs:2:1
|
2 | trait Foo {
| ^^^^^^^^^
error: aborting due to previous error
For more information about this error, try `rustc --explain E0599`.
error: could not compile `playground`
To learn more, run the command again with --verbose.
Ideally the output should look like:
error[E0599]: no method named `get` found for fn item `fn() -> Inner {Inner}` in the current scope
--> src/main.rs:16:13
|
16 | thing.0.get();
| ^^^ method not found in `fn() -> Inner {Inner}`
|
= note: `thing.0` is a function, perhaps you wish to call it
= note: `Inner` is a tuple struct with zero fields, perhaps you wish to initialize it instead: `Bar(Inner())`
= help: items from traits can only be used if the trait is implemented and in scope
note: `Foo` defines an item `get`, perhaps you need to implement it
--> src/main.rs:2:1
|
2 | trait Foo {
| ^^^^^^^^^
error: aborting due to previous error
For more information about this error, try `rustc --explain E0599`.
error: could not compile `playground`
To learn more, run the command again with --verbose.
This was an extremely confusing error message for me, as I suddenly had a fn() -> Inner type out of no where in my code! Of course, this was a simplified issue, but it's not immediately obvious that 1. a unit struct is actually a function returning its own type, and 2. the problem was due to the fact that a unit struct is not the same as a zero-member tuple struct.
This was extracted out of a much more complex error message, where the only hint to the actual problem was that the unit struct "constructor" didn't satisfy the trait bound, which pointed to a construction issue.
Not quite sure whether or not it's possible to actually implement a suggestion as written, but perhaps even a check between Inner vs Inner() might be a good note to have?