Include type of missing trait methods in error #24626
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A-diagnostics
Area: Messages for errors, warnings, and lints
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jdm
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estebank
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Sep 10, 2016
For a given file `foo.rs`:
```rust
use std::str::FromStr;
struct A {}
trait X<T> {
type Foo;
const BAR: u32 = 128;
fn foo() -> T;
fn bar();
fn bay<
'lifetime, TypeParameterA
>( a : usize,
b: u8 );
}
impl std::fmt::Display for A {
}
impl FromStr for A{}
impl X<usize> for A {
}
```
Provide the following output:
```bash
error: main function not found
error[E0046]: not all trait items implemented, missing: `fmt`
--> file2.rs:18:1
|
18 | impl std::fmt::Display for A {
| ^ missing `fmt` in implementation
|
= note: fn fmt(&Self, &mut std::fmt::Formatter<'_>) -> std::result::Result<(), std::fmt::Error>;
error[E0046]: not all trait items implemented, missing: `Err`, `from_str`
--> file2.rs:20:1
|
20 | impl FromStr for A{}
| ^^^^^^^^^^^^^^^^^^^^ missing `Err`, `from_str` in implementation
|
= note: type Err;
= note: fn from_str(&str) -> std::result::Result<Self, <Self as std::str::FromStr>::Err>;
error[E0046]: not all trait items implemented, missing: `Foo`, `foo`, `bar`, `bay`
--> file2.rs:22:1
|
22 | impl X<usize> for A {
| ^ missing `Foo`, `foo`, `bar`, `bay` in implementation
|
= note: type Foo;
= note: fn foo() -> T;
= note: fn bar();
= note: fn bay<'lifetime, TypeParameterA>(a: usize, b: u8);
error: aborting due to 3 previous errors
```
Fixes rust-lang#24626
estebank
added a commit
to estebank/rust
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Oct 1, 2016
For a given file `foo.rs`:
```rust
use std::str::FromStr;
struct A {}
trait X<T> {
type Foo;
const BAR: u32 = 128;
fn foo() -> T;
fn bar();
fn bay<
'lifetime, TypeParameterA
>( a : usize,
b: u8 );
}
impl std::fmt::Display for A {
}
impl FromStr for A{}
impl X<usize> for A {
}
```
Provide the following output:
```bash
error: main function not found
error[E0046]: not all trait items implemented, missing: `fmt`
--> foo.rs:18:1
|
18 | impl std::fmt::Display for A {
| ^ missing `fmt` in implementation
|
= note: fn fmt(&Self, &mut std::fmt::Formatter<'_>) -> std::result::Result<(), std::fmt::Error>;
error[E0046]: not all trait items implemented, missing: `Err`, `from_str`
--> foo.rs:20:1
|
20 | impl FromStr for A{}
| ^^^^^^^^^^^^^^^^^^^^ missing `Err`, `from_str` in implementation
|
= note: type Err;
= note: fn from_str(&str) -> std::result::Result<Self, <Self as std::str::FromStr>::Err>;
error[E0046]: not all trait items implemented, missing: `Foo`, `foo`, `bar`, `bay`
--> foo.rs:22:1
|
22 | impl X<usize> for A {
| ^ missing `Foo`, `foo`, `bar`, `bay` in implementation
|
= note: type Foo;
= note: fn foo() -> T;
= note: fn bar();
= note: fn bay<'lifetime, TypeParameterA>(a: usize, b: u8);
error: aborting due to 3 previous errors
```
Fixes rust-lang#24626
For a given file `foo.rs`:
```rust
struct A {}
impl std::fmt::Display for A {
fn fmt() -> () {}
}
```
provide the expected method signature:
```bash
error: main function not found
error[E0186]: method `fmt` has a `&self` declaration in the trait, but not in the impl
--> foo.rs:4:5
|
4 | fn fmt() -> () {}
| ^^^^^^^^^^^^^^^^^ expected `&self` in impl
|
= note: Expected signature: fn fmt(&Self, &mut std::fmt::Formatter<'_>) -> std::result::Result<(), std::fmt::Error>;
= note: Found signature: fn fmt();
error: aborting due to previous error
```
Fixes rust-lang#28011
eddyb
added a commit
to eddyb/rust
that referenced
this issue
Nov 9, 2016
…-back, r=nikomatsakis Include type of missing trait methods in error Provide either a span pointing to the original definition of missing trait items, or a message with the inferred definitions. Fixes rust-lang#24626. Follow up to PR rust-lang#36371. If PR rust-lang#37369 lands, missing trait items that present a multiline span will be able to show the entirety of the item definition on the error itself, instead of just the first line.
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Feature request (improved diagnostics):
This is what the error currently looks like:
In order to implement the missing method I need to double check the type in the documentation, even though I already know what the function needs to do. It would be really convenient if the compiler could print out the required type for me.
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