Fix span of redundant generic arguments
Fixes#71563
Above issue is about lifetime arguments, but generic arguments also have same problem.
This PR fixes both help messages.
Fix incorrect suggestions for E0605
Fixes#84598. Here is a simplified version of the problem presented in issue #84598:
```Rust
#![allow(unused_variables)]
#![allow(dead_code)]
trait T { fn t(&self) -> i32; }
unsafe fn foo(t: *mut dyn T) {
(t as &dyn T).t();
}
fn main() {}
```
The current output is:
```
error[E0605]: non-primitive cast: `*mut (dyn T + 'static)` as `&dyn T`
--> src/main.rs:7:5
|
7 | (t as &dyn T).t();
| ^^^^^^^^^^^^^ invalid cast
|
help: borrow the value for the cast to be valid
|
7 | (&t as &dyn T).t();
| ^
```
This is incorrect, though: The cast will _not_ be valid when writing `&t` instead of `t`:
```
error[E0277]: the trait bound `*mut (dyn T + 'static): T` is not satisfied
--> t4.rs:7:6
|
7 | (&t as &dyn T).t();
| ^^ the trait `T` is not implemented for `*mut (dyn T + 'static)`
|
= note: required for the cast to the object type `dyn T`
```
The correct suggestion is `&*t`, which I have implemented in this pull request. Of course, this suggestion will always require an unsafe block, but arguably, that's what the user really wants if they're trying to cast a pointer to a reference.
In any case, claiming that the cast will be valid after implementing the suggestion is overly optimistic, as the coercion logic doesn't seem to resolve all nested obligations, i.e. the cast may still be invalid after implementing the suggestion. I have therefore rephrased the suggestion slightly ("consider borrowing the value" instead of "borrow the value for the cast to be valid").
Additionally, I have fixed another incorrect suggestion not mentioned in #84598, which relates to casting immutable references to mutable ones:
```rust
fn main() {
let mut x = 0;
let m = &x as &mut i32;
}
```
currently leads to
```
error[E0605]: non-primitive cast: `&i32` as `&mut i32`
--> t5.rs:3:13
|
3 | let m = &x as &mut i32;
| ^^^^^^^^^^^^^^ invalid cast
|
help: borrow the value for the cast to be valid
|
3 | let m = &mut &x as &mut i32;
| ^^^^
```
which is obviously incorrect:
```
error[E0596]: cannot borrow data in a `&` reference as mutable
--> t5.rs:3:13
|
3 | let m = &mut &x as &mut i32;
| ^^^^^^^ cannot borrow as mutable
```
I've changed the suggestion to a note explaining the problem:
```
error[E0605]: non-primitive cast: `&i32` as `&mut i32`
--> t5.rs:3:13
|
3 | let m = &x as &mut i32;
| ^^^^^^^^^^^^^^ invalid cast
|
note: this reference is immutable
--> t5.rs:3:13
|
3 | let m = &x as &mut i32;
| ^^
note: trying to cast to a mutable reference type
--> t5.rs:3:19
|
3 | let m = &x as &mut i32;
| ^^^^^^^^
```
In this example, it would have been even nicer to suggest replacing `&x` with `&mut x`, but this would be much more complex because we would have to take apart the expression to be cast (currently, we only look at its type), and `&x` could be stored in a variable, where such a suggestion would not even be directly applicable:
```rust
fn main() {
let mut x = 0;
let r = &x;
let m = r as &mut i32;
}
```
My solution covers this case, too.
Introduce the beginning of a THIR unsafety checker
This poses the foundations for the THIR unsafety checker, so that it can be implemented incrementally:
- implements a rudimentary `Visitor` for the THIR (which will definitely need some tweaking in the future)
- introduces a new `-Zthir-unsafeck` flag which tells the compiler to use THIR unsafeck instead of MIR unsafeck
- implements detection of unsafe functions
- adds revisions to the UI tests to test THIR unsafeck alongside MIR unsafeck
This uses a very simple query design, where bodies are unsafety-checked on a body per body basis. This however has some big flaws:
- the unsafety-checker builds the THIR itself, which means a lot of work is duplicated with MIR building constructing its own copy of the THIR
- unsafety-checking closures is currently completely wrong: closures should take into account the "safety context" in which they are created, here we are considering that closures are always a safe context
I had intended to fix these problems in follow-up PRs since they are always gated under the `-Zthir-unsafeck` flag (which is explicitely noted to be unsound).
r? `@nikomatsakis`
cc https://github.com/rust-lang/project-thir-unsafeck/issues/3https://github.com/rust-lang/project-thir-unsafeck/issues/7
Add more info for common trait resolution and async/await errors
* Suggest `Pin::new`/`Box::new`/`Arc::new`/`Box::pin` in more cases
* Point at `impl` and type defs introducing requirements on E0277
Allow specifying alignment for functions
Fixes#75072
This allows the user to specify alignment for functions, which can be useful for low level work where functions need to necessarily be aligned to a specific value.
I believe the error cases not covered in the match are caught earlier based on my testing so I had them just return `None`.
This is step 2 towards fixing #77548.
In the codegen and codegen-units test suites, the `//` comment markers
were kept in order not to affect any source locations. This is because
these tests cannot be automatically `--bless`ed.
fix the false 'defined here' messages
Closes#80853.
Take this code:
```rust
struct S;
fn repro_ref(thing: S) {
thing();
}
```
Previously, the error message would be this:
```
error[E0618]: expected function, found `S`
--> src/lib.rs:4:5
|
3 | fn repro_ref(thing: S) {
| ----- `S` defined here
4 | thing();
| ^^^^^--
| |
| call expression requires function
error: aborting due to previous error
```
This is incorrect as `S` is not defined in the function arguments, `thing` is defined there. With this change, the following is emitted:
```
error[E0618]: expected function, found `S`
--> $DIR/80853.rs:4:5
|
LL | fn repro_ref(thing: S) {
| ----- is of type `S`
LL | thing();
| ^^^^^--
| |
| call expression requires function
|
= note: local variable `S` is not a function
error: aborting due to previous error
```
As you can see, this error message points out that `thing` is of type `S` and later in a note, that `S` is not a function. This change does seem like a downside for some error messages. Take this example:
```
LL | struct Empty2;
| -------------- is of type `Empty2`
```
As you can see, the error message shows that the definition of `Empty2` is of type `Empty2`. Although this isn't wrong, it would be more helpful if it would say something like this (which was there previously):
```
LL | struct Empty2;
| -------------- `Empty2` defined here
```
If there is a better way of doing this, where the `Empty2` example would stay the same as without this change, please inform me.
**Update: This is now fixed**
CC `@camelid`
don't suggest erroneous trailing comma after `..`
In #76612, suggestions were added for missing fields in patterns. However, the suggestions are being inserted just at the end
of the last field in the pattern—before any trailing comma after the last field. This resulted in the "if you don't care about missing fields" suggestion to recommend code with a trailing comma after the field ellipsis (`..,`), which is actually not legal ("`..` must be at the end and cannot have a trailing comma")!
Incidentally, the doc-comment on `error_unmentioned_fields` was using `you_cant_use_this_field` as an example field name (presumably copy-paste inherited from the description of Issue #76077), but the present author found this confusing, because unmentioned fields aren't necessarily unusable.
The suggested code in the diff this commit introduces to `destructuring-assignment/struct_destructure_fail.stderr` doesn't work, but it didn't work beforehand, either (because of the "found reserved identifier `_`" thing), so you can't really call it a regression; it could be fixed in a separate PR.
Resolves#78511.
r? `@davidtwco` or `@estebank`
In #76612, suggestions were added for missing fields in
patterns. However, the suggestions are being inserted just at the end
of the last field in the pattern—before any trailing comma after the
last field. This resulted in the "if you don't care about missing
fields" suggestion to recommend code with a trailing comma after the
field ellipsis (`..,`), which is actually not legal ("`..` must be at
the end and cannot have a trailing comma")!
Incidentally, the doc-comment on `error_unmentioned_fields` was using
`you_cant_use_this_field` as an example field name (presumably
copy-paste inherited from the description of Issue #76077), but
the present author found this confusing, because unmentioned fields
aren't necessarily unusable.
The suggested code in the diff this commit introduces to
`destructuring-assignment/struct_destructure_fail.stderr` doesn't
work, but it didn't work beforehand, either (because of the "found
reserved identifier `_`" thing), so you can't really call it a
regression; it could be fixed in a separate PR.
Resolves#78511.
Rework diagnostics for wrong number of generic args (fixes#66228 and #71924)
This PR reworks the `wrong number of {} arguments` message, so that it provides more details and contextual hints.
For example, this code:
struct S(i32, f32);
let S(x) = S(0, 1.0);
will make the compiler suggest either:
let S(x, _) = S(0, 1.0);
or:
let S(x, ..) = S(0, 1.0);
On structured suggestion for `let` -> `const` and `const` -> `let`, use
a proper `Span` and update tests to check the correct application.
Follow up to #80012.
