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Diagnostics: help text for missing left-hand side in arbitrary self type #64252

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yoshuawuyts opened this issue Sep 7, 2019 · 1 comment · Fixed by #64959
Closed

Diagnostics: help text for missing left-hand side in arbitrary self type #64252

yoshuawuyts opened this issue Sep 7, 2019 · 1 comment · Fixed by #64959
Labels
A-diagnostics Area: Messages for errors, warnings, and lints A-suggestion-diagnostics Area: Suggestions generated by the compiler applied by `cargo fix`. C-enhancement Category: An issue proposing an enhancement or a PR with one. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

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@yoshuawuyts
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Forgetting to include the left-hand side of an arbitrary self type can give some confusing errors. This was reported by someone trying to implement a future manually, and the diagnostics threw them off.

I realize diagnostics for arbitrary self types are an open issue, but figured I'd include this variant as to not overlook it. Thanks!

Link to playground

Code

pub fn hello(Box<Self>) {}

Expected

error: expected one of `:` or `@`, found `<`
 --> src/lib.rs:1:17
  |
1 | pub fn hello(Box<Self>) {}
  |              ^ expected one of `:` or `@` here
  |
help: if this is a `self` type, give it a parameter name
  |
1 | pub fn hello(self: Box<Self>) {}
  |              ^^^^^^^^^^^^^^^

error: aborting due to previous error

Current

error: expected one of `:` or `@`, found `<`
 --> src/lib.rs:1:17
  |
1 | pub fn hello(Box<Self>) {}
  |                 ^ expected one of `:` or `@` here

error: aborting due to previous error
@Centril
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Centril commented Sep 7, 2019

The output with:

impl Foo for Baz {
    pub fn hello(Box<Self>) {}
}

is:

error: expected one of `:` or `@`, found `<`
 --> src/lib.rs:2:21
  |
2 |     pub fn hello(Box<Self>) {}
  |                     ^ expected one of `:` or `@` here
  |
  = note: anonymous parameters are removed in the 2018 edition (see RFC 1685)
help: if this was a parameter name, give it a type
  |
2 |     pub fn hello(Box: TypeName<Self>) {}
  |                  ^^^^^^^^^^^^^
help: if this is a type, explicitly ignore the parameter name
  |
2 |     pub fn hello(_: Box<Self>) {}
  |                  ^^^^^^

error: aborting due to previous error

@Centril Centril self-assigned this Sep 7, 2019
@Centril Centril added A-diagnostics Area: Messages for errors, warnings, and lints A-suggestion-diagnostics Area: Suggestions generated by the compiler applied by `cargo fix`. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. C-enhancement Category: An issue proposing an enhancement or a PR with one. labels Sep 7, 2019
@Centril Centril removed their assignment Sep 30, 2019
Centril added a commit to Centril/rust that referenced this issue Oct 1, 2019
syntax: cleanup param, method, and misc parsing

Do some misc cleanup of the parser:
- Method and parameter parsing is refactored.
- A parser for `const | mut` is introduced that rust-lang#64588 can reuse.
- Some other misc parsing.

Next up in a different PR:
- ~Implementing rust-lang#64252 -- maybe some other time...
- Heavily restructuring up `item.rs` which is a mess (hopefully, no promises ^^).

r? @petrochenkov
Centril added a commit to Centril/rust that referenced this issue Oct 1, 2019
syntax: cleanup param, method, and misc parsing

Do some misc cleanup of the parser:
- Method and parameter parsing is refactored.
- A parser for `const | mut` is introduced that rust-lang#64588 can reuse.
- Some other misc parsing.

Next up in a different PR:
- ~Implementing rust-lang#64252 -- maybe some other time...
- Heavily restructuring up `item.rs` which is a mess (hopefully, no promises ^^).

r? @petrochenkov
Centril added a commit to Centril/rust that referenced this issue Oct 1, 2019
syntax: cleanup param, method, and misc parsing

Do some misc cleanup of the parser:
- Method and parameter parsing is refactored.
- A parser for `const | mut` is introduced that rust-lang#64588 can reuse.
- Some other misc parsing.

Next up in a different PR:
- ~Implementing rust-lang#64252 -- maybe some other time...
- Heavily restructuring up `item.rs` which is a mess (hopefully, no promises ^^).

r? @petrochenkov
Centril added a commit to Centril/rust that referenced this issue Oct 1, 2019
syntax: cleanup param, method, and misc parsing

Do some misc cleanup of the parser:
- Method and parameter parsing is refactored.
- A parser for `const | mut` is introduced that rust-lang#64588 can reuse.
- Some other misc parsing.

Next up in a different PR:
- ~Implementing rust-lang#64252 -- maybe some other time...
- Heavily restructuring up `item.rs` which is a mess (hopefully, no promises ^^).

r? @petrochenkov
tmandry added a commit to tmandry/rust that referenced this issue Oct 1, 2019
syntax: cleanup param, method, and misc parsing

Do some misc cleanup of the parser:
- Method and parameter parsing is refactored.
- A parser for `const | mut` is introduced that rust-lang#64588 can reuse.
- Some other misc parsing.

Next up in a different PR:
- ~Implementing rust-lang#64252 -- maybe some other time...
- Heavily restructuring up `item.rs` which is a mess (hopefully, no promises ^^).

r? @petrochenkov
tmandry added a commit to tmandry/rust that referenced this issue Oct 1, 2019
syntax: cleanup param, method, and misc parsing

Do some misc cleanup of the parser:
- Method and parameter parsing is refactored.
- A parser for `const | mut` is introduced that rust-lang#64588 can reuse.
- Some other misc parsing.

Next up in a different PR:
- ~Implementing rust-lang#64252 -- maybe some other time...
- Heavily restructuring up `item.rs` which is a mess (hopefully, no promises ^^).

r? @petrochenkov
Centril added a commit to Centril/rust that referenced this issue Oct 1, 2019
syntax: cleanup param, method, and misc parsing

Do some misc cleanup of the parser:
- Method and parameter parsing is refactored.
- A parser for `const | mut` is introduced that rust-lang#64588 can reuse.
- Some other misc parsing.

Next up in a different PR:
- ~Implementing rust-lang#64252 -- maybe some other time...
- Heavily restructuring up `item.rs` which is a mess (hopefully, no promises ^^).

r? @petrochenkov
Centril added a commit to Centril/rust that referenced this issue Oct 1, 2019
syntax: cleanup param, method, and misc parsing

Do some misc cleanup of the parser:
- Method and parameter parsing is refactored.
- A parser for `const | mut` is introduced that rust-lang#64588 can reuse.
- Some other misc parsing.

Next up in a different PR:
- ~Implementing rust-lang#64252 -- maybe some other time...
- Heavily restructuring up `item.rs` which is a mess (hopefully, no promises ^^).

r? @petrochenkov
Manishearth added a commit to Manishearth/rust that referenced this issue Oct 2, 2019
…p, r=Centril,estebank

syntax: improve parameter without type suggestions

Fixes rust-lang#64252.

This PR improves the suggestions provided when function parameters
do not have types:

- A new suggestion is added for arbitrary self types, which suggests
adding `self: ` before the type.

- Existing suggestions are now provided when a `<` is found where a `:`
was expected (previously only `,` and `)` or trait items), this gives
suggestions in the case where the unnamed parameter type is generic
in a free function.

- The suggestion that a type name be provided (e.g. `fn foo(HashMap<u32>)`
-> `fn foo(HashMap: TypeName<u32>)`) will no longer occur when a `<` was
found instead of `:`.

- The ident will not be used for recovery when a `<` was found instead
of `:`.

r? @Centril
cc @estebank @yoshuawuyts
Centril added a commit to Centril/rust that referenced this issue Oct 2, 2019
…p, r=Centril,estebank

syntax: improve parameter without type suggestions

Fixes rust-lang#64252.

This PR improves the suggestions provided when function parameters
do not have types:

- A new suggestion is added for arbitrary self types, which suggests
adding `self: ` before the type.

- Existing suggestions are now provided when a `<` is found where a `:`
was expected (previously only `,` and `)` or trait items), this gives
suggestions in the case where the unnamed parameter type is generic
in a free function.

- The suggestion that a type name be provided (e.g. `fn foo(HashMap<u32>)`
-> `fn foo(HashMap: TypeName<u32>)`) will no longer occur when a `<` was
found instead of `:`.

- The ident will not be used for recovery when a `<` was found instead
of `:`.

r? @Centril
cc @estebank @yoshuawuyts
@bors bors closed this as completed in faf2e80 Oct 3, 2019
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Labels
A-diagnostics Area: Messages for errors, warnings, and lints A-suggestion-diagnostics Area: Suggestions generated by the compiler applied by `cargo fix`. C-enhancement Category: An issue proposing an enhancement or a PR with one. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.
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