user0/rust
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Rollup merge of #120261 - estebank:issue-102629, r=wesleywiser

Browse source 
Provide structured suggestion to use trait objects in some cases of `if` arm type divergence

```
error[E0308]: `if` and `else` have incompatible types
  --> $DIR/suggest-box-on-divergent-if-else-arms.rs:15:9
   |
LL |       let _ = if true {
   |  _____________-
LL | |         Struct
   | |         ------ expected because of this
LL | |     } else {
LL | |         foo()
   | |         ^^^^^ expected `Struct`, found `Box<dyn Trait>`
LL | |     };
   | |_____- `if` and `else` have incompatible types
   |
   = note: expected struct `Struct`
              found struct `Box<dyn Trait>`
help: `Struct` implements `Trait` so you can box it to coerce to the trait object `Box<dyn Trait>`
   |
LL |         Box::new(Struct)
   |         +++++++++      +

error[E0308]: `if` and `else` have incompatible types
  --> $DIR/suggest-box-on-divergent-if-else-arms.rs:20:9
   |
LL |       let _ = if true {
   |  _____________-
LL | |         foo()
   | |         ----- expected because of this
LL | |     } else {
LL | |         Struct
   | |         ^^^^^^ expected `Box<dyn Trait>`, found `Struct`
LL | |     };
   | |_____- `if` and `else` have incompatible types
   |
   = note: expected struct `Box<dyn Trait>`
              found struct `Struct`
   = note: for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
help: store this in the heap by calling `Box::new`
   |
LL |         Box::new(Struct)
   |         +++++++++      +

error[E0308]: `if` and `else` have incompatible types
  --> $DIR/suggest-box-on-divergent-if-else-arms.rs:25:9
   |
LL |   fn bar() -> impl Trait {
   |               ---------- the found opaque type
...
LL |       let _ = if true {
   |  _____________-
LL | |         Struct
   | |         ------ expected because of this
LL | |     } else {
LL | |         bar()
   | |         ^^^^^ expected `Struct`, found opaque type
LL | |     };
   | |_____- `if` and `else` have incompatible types
   |
   = note:   expected struct `Struct`
           found opaque type `impl Trait`
help: `Struct` implements `Trait` so you can box both arms and coerce to the trait object `Box<dyn Trait>`
   |
LL ~         Box::new(Struct) as Box<dyn Trait>
LL |     } else {
LL ~         Box::new(bar())
   |

error[E0308]: `if` and `else` have incompatible types
  --> $DIR/suggest-box-on-divergent-if-else-arms.rs:30:9
   |
LL |   fn bar() -> impl Trait {
   |               ---------- the expected opaque type
...
LL |       let _ = if true {
   |  _____________-
LL | |         bar()
   | |         ----- expected because of this
LL | |     } else {
LL | |         Struct
   | |         ^^^^^^ expected opaque type, found `Struct`
LL | |     };
   | |_____- `if` and `else` have incompatible types
   |
   = note: expected opaque type `impl Trait`
                   found struct `Struct`
help: `Struct` implements `Trait` so you can box both arms and coerce to the trait object `Box<dyn Trait>`
   |
LL ~         Box::new(bar()) as Box<dyn Trait>
LL |     } else {
LL ~         Box::new(Struct)
   |
```

Partially address #102629.
This commit is contained in:
León Orell Valerian Liehr 2024-01-23 21:53:59 +01:00 • committed by GitHub
commit 3f2f8eee02
No known key found for this signature in database
GPG key ID: B5690EEEBB952194
5 changed files with 267 additions and 17 deletions
Download patch file Download diff file Expand all files Collapse all files

32
tests/ui/typeck/suggest-box-on-divergent-if-else-arms.fixed Normal file
View file

@ -0,0 +1,32 @@
// run-rustfix
trait Trait {}
struct Struct;
impl Trait for Struct {}
fn foo() -> Box<dyn Trait> {
Box::new(Struct)
}
fn bar() -> impl Trait {
Struct
}
fn main() {
let _ = if true {
Box::new(Struct)
} else {
foo() //~ ERROR E0308
};
let _ = if true {
foo()
} else {
Box::new(Struct) //~ ERROR E0308
};
let _ = if true {
Box::new(Struct) as Box<dyn Trait>
} else {
Box::new(bar()) //~ ERROR E0308
};
let _ = if true {
Box::new(bar()) as Box<dyn Trait>
} else {
Box::new(Struct) //~ ERROR E0308
};
}

32
tests/ui/typeck/suggest-box-on-divergent-if-else-arms.rs Normal file
View file

@ -0,0 +1,32 @@
// run-rustfix
trait Trait {}
struct Struct;
impl Trait for Struct {}
fn foo() -> Box<dyn Trait> {
Box::new(Struct)
}
fn bar() -> impl Trait {
Struct
}
fn main() {
let _ = if true {
Struct
} else {
foo() //~ ERROR E0308
};
let _ = if true {
foo()
} else {
Struct //~ ERROR E0308
};
let _ = if true {
Struct
} else {
bar() //~ ERROR E0308
};
let _ = if true {
bar()
} else {
Struct //~ ERROR E0308
};
}

94
tests/ui/typeck/suggest-box-on-divergent-if-else-arms.stderr Normal file
View file

@ -0,0 +1,94 @@
error[E0308]: `if` and `else` have incompatible types
--> $DIR/suggest-box-on-divergent-if-else-arms.rs:15:9
|
LL | let _ = if true {
| _____________-
LL | | Struct
| | ------ expected because of this
LL | | } else {
LL | | foo()
| | ^^^^^ expected `Struct`, found `Box<dyn Trait>`
LL | | };
| |_____- `if` and `else` have incompatible types
|
= note: expected struct `Struct`
found struct `Box<dyn Trait>`
help: `Struct` implements `Trait` so you can box it to coerce to the trait object `Box<dyn Trait>`
|
LL | Box::new(Struct)
| +++++++++ +
error[E0308]: `if` and `else` have incompatible types
--> $DIR/suggest-box-on-divergent-if-else-arms.rs:20:9
|
LL | let _ = if true {
| _____________-
LL | | foo()
| | ----- expected because of this
LL | | } else {
LL | | Struct
| | ^^^^^^ expected `Box<dyn Trait>`, found `Struct`
LL | | };
| |_____- `if` and `else` have incompatible types
|
= note: expected struct `Box<dyn Trait>`
found struct `Struct`
= note: for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
help: store this in the heap by calling `Box::new`
|
LL | Box::new(Struct)
| +++++++++ +
error[E0308]: `if` and `else` have incompatible types
--> $DIR/suggest-box-on-divergent-if-else-arms.rs:25:9
|
LL | fn bar() -> impl Trait {
| ---------- the found opaque type
...
LL | let _ = if true {
| _____________-
LL | | Struct
| | ------ expected because of this
LL | | } else {
LL | | bar()
| | ^^^^^ expected `Struct`, found opaque type
LL | | };
| |_____- `if` and `else` have incompatible types
|
= note: expected struct `Struct`
found opaque type `impl Trait`
help: `Struct` implements `Trait` so you can box both arms and coerce to the trait object `Box<dyn Trait>`
|
LL ~ Box::new(Struct) as Box<dyn Trait>
LL | } else {
LL ~ Box::new(bar())
|
error[E0308]: `if` and `else` have incompatible types
--> $DIR/suggest-box-on-divergent-if-else-arms.rs:30:9
|
LL | fn bar() -> impl Trait {
| ---------- the expected opaque type
...
LL | let _ = if true {
| _____________-
LL | | bar()
| | ----- expected because of this
LL | | } else {
LL | | Struct
| | ^^^^^^ expected opaque type, found `Struct`
LL | | };
| |_____- `if` and `else` have incompatible types
|
= note: expected opaque type `impl Trait`
found struct `Struct`
help: `Struct` implements `Trait` so you can box both arms and coerce to the trait object `Box<dyn Trait>`
|
LL ~ Box::new(bar()) as Box<dyn Trait>
LL | } else {
LL ~ Box::new(Struct)
|
error: aborting due to 4 previous errors
For more information about this error, try `rustc --explain E0308`.