Suggest deref when coercing mutable ty::Ref to ty::RawPtr
#71676
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.
Comments
Alexendoo
added
A-diagnostics
Dylan-DPC-zz
pushed a commit
to Dylan-DPC-zz/rust
that referenced
this issue
May 2, 2020
Suggest deref when coercing `ty::Ref` to `ty::RawPtr` with arbitrary mutability Fixes rust-lang#71676 1. Implement dereference suggestion when coercing `ty::Ref` to `ty::RawPtr` with arbitrary mutability. 2. Extract the dereference steps into `deref_steps()`, which removes all the `use` and `pub` noise introduced by last PR rust-lang#71540, and makes the code more readable. 3. Use the `remove_prefix()` closure which makes the prefix removal more readable. 4. Introduce `Applicability` as a return value of `check_ref` to suggest `Applicability::Unspecified` suggestion. **Special**: I found it is not possible to genereate `Applicability::MachineApplicable` suggestion for situation like this: ```rust use std::ops::Deref; use std::ops::DerefMut; struct Bar(u8); struct Foo(Bar); struct Emm(Foo); impl Deref for Bar{ type Target = u8; fn deref(&self) -> &Self::Target { &self.0 } } impl Deref for Foo { type Target = Bar; fn deref(&self) -> &Self::Target { &self.0 } } impl Deref for Emm { type Target = Foo; fn deref(&self) -> &Self::Target { &self.0 } } impl DerefMut for Bar{ fn deref_mut(&mut self) -> &mut Self::Target { &mut self.0 } } impl DerefMut for Foo { fn deref_mut(&mut self) -> &mut Self::Target { &mut self.0 } } impl DerefMut for Emm { fn deref_mut(&mut self) -> &mut Self::Target { &mut self.0 } } fn main() { let a = Emm(Foo(Bar(0))); let _: *mut u8 = &a; //~ ERROR mismatched types } ``` We may suggest `&mut ***a` here, but the `a` is not declared as mutable variable. And also when processing HIR, it's not possible to check if `a` is declared as a mutable variable (currently we do borrow checking with MIR). So we cannot ensure that suggestion when coercing immutable reference to mutable pointer is always machine applicable. Therefore I added a `Applicability` return value in `check_ref()`. And move the `immutable reference -> mutable pointer` situation into a sperate test file without `run-rustfix`. (It seems that `run-rustfix` will also adopt `Applicability::Unspecified` suggestion, which is strange)
Dylan-DPC-zz
pushed a commit
to Dylan-DPC-zz/rust
that referenced
this issue
May 3, 2020
Suggest deref when coercing `ty::Ref` to `ty::RawPtr` with arbitrary mutability Fixes rust-lang#71676 1. Implement dereference suggestion when coercing `ty::Ref` to `ty::RawPtr` with arbitrary mutability. 2. Extract the dereference steps into `deref_steps()`, which removes all the `use` and `pub` noise introduced by last PR rust-lang#71540, and makes the code more readable. 3. Use the `remove_prefix()` closure which makes the prefix removal more readable. 4. Introduce `Applicability` as a return value of `check_ref` to suggest `Applicability::Unspecified` suggestion. **Special**: I found it is not possible to genereate `Applicability::MachineApplicable` suggestion for situation like this: ```rust use std::ops::Deref; use std::ops::DerefMut; struct Bar(u8); struct Foo(Bar); struct Emm(Foo); impl Deref for Bar{ type Target = u8; fn deref(&self) -> &Self::Target { &self.0 } } impl Deref for Foo { type Target = Bar; fn deref(&self) -> &Self::Target { &self.0 } } impl Deref for Emm { type Target = Foo; fn deref(&self) -> &Self::Target { &self.0 } } impl DerefMut for Bar{ fn deref_mut(&mut self) -> &mut Self::Target { &mut self.0 } } impl DerefMut for Foo { fn deref_mut(&mut self) -> &mut Self::Target { &mut self.0 } } impl DerefMut for Emm { fn deref_mut(&mut self) -> &mut Self::Target { &mut self.0 } } fn main() { let a = Emm(Foo(Bar(0))); let _: *mut u8 = &a; //~ ERROR mismatched types } ``` We may suggest `&mut ***a` here, but the `a` is not declared as mutable variable. And also when processing HIR, it's not possible to check if `a` is declared as a mutable variable (currently we do borrow checking with MIR). So we cannot ensure that suggestion when coercing immutable reference to mutable pointer is always machine applicable. Therefore I added a `Applicability` return value in `check_ref()`. And move the `immutable reference -> mutable pointer` situation into a sperate test file without `run-rustfix`. (It seems that `run-rustfix` will also adopt `Applicability::Unspecified` suggestion, which is strange)
Dylan-DPC-zz
pushed a commit
to Dylan-DPC-zz/rust
that referenced
this issue
May 3, 2020
Suggest deref when coercing `ty::Ref` to `ty::RawPtr` with arbitrary mutability Fixes rust-lang#71676 1. Implement dereference suggestion when coercing `ty::Ref` to `ty::RawPtr` with arbitrary mutability. 2. Extract the dereference steps into `deref_steps()`, which removes all the `use` and `pub` noise introduced by last PR rust-lang#71540, and makes the code more readable. 3. Use the `remove_prefix()` closure which makes the prefix removal more readable. 4. Introduce `Applicability` as a return value of `check_ref` to suggest `Applicability::Unspecified` suggestion. **Special**: I found it is not possible to genereate `Applicability::MachineApplicable` suggestion for situation like this: ```rust use std::ops::Deref; use std::ops::DerefMut; struct Bar(u8); struct Foo(Bar); struct Emm(Foo); impl Deref for Bar{ type Target = u8; fn deref(&self) -> &Self::Target { &self.0 } } impl Deref for Foo { type Target = Bar; fn deref(&self) -> &Self::Target { &self.0 } } impl Deref for Emm { type Target = Foo; fn deref(&self) -> &Self::Target { &self.0 } } impl DerefMut for Bar{ fn deref_mut(&mut self) -> &mut Self::Target { &mut self.0 } } impl DerefMut for Foo { fn deref_mut(&mut self) -> &mut Self::Target { &mut self.0 } } impl DerefMut for Emm { fn deref_mut(&mut self) -> &mut Self::Target { &mut self.0 } } fn main() { let a = Emm(Foo(Bar(0))); let _: *mut u8 = &a; //~ ERROR mismatched types } ``` We may suggest `&mut ***a` here, but the `a` is not declared as mutable variable. And also when processing HIR, it's not possible to check if `a` is declared as a mutable variable (currently we do borrow checking with MIR). So we cannot ensure that suggestion when coercing immutable reference to mutable pointer is always machine applicable. Therefore I added a `Applicability` return value in `check_ref()`. And move the `immutable reference -> mutable pointer` situation into a sperate test file without `run-rustfix`. (It seems that `run-rustfix` will also adopt `Applicability::Unspecified` suggestion, which is strange)
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
This is a missing part of #71540. I think we should be able to suggest
&mut ***ahere.The text was updated successfully, but these errors were encountered: