bjoernager/rust
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Auto merge of #124157 - wutchzone:partial_eq, r=estebank

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Do not add leading asterisk in the `PartialEq`

I think we should address this issue, however I am not exactly sure, if this is the right way to do it. It is related to the #123056.

Imagine the simplified code:

```rust
trait MyTrait {}

impl PartialEq for dyn MyTrait {
    fn eq(&self, _other: &Self) -> bool {
        true
    }
}

#[derive(PartialEq)]
enum Bar {
    Foo(Box<dyn MyTrait>),
}
```

On the nightly compiler, the `derive` produces invalid code with the weird error message:
```
error[E0507]: cannot move out of `*__arg1_0` which is behind a shared reference
  --> src/main.rs:11:9
   |
9  | #[derive(PartialEq)]
   |          --------- in this derive macro expansion
10 | enum Things {
11 |     Foo(Box<dyn MyTrait>),
   |         ^^^^^^^^^^^^^^^^ move occurs because `*__arg1_0` has type `Box<dyn MyTrait>`, which does not implement the `Copy` trait
   |
   = note: this error originates in the derive macro `PartialEq` (in Nightly builds, run with -Z macro-backtrace for more info)
```

It may be related to the perfect derive problem, although requiring the _type_ to be `Copy` seems unfortunate because it is not necessary. Besides, we are adding the extra dereference only for the diagnostics?
This commit is contained in:
bors 2024-05-09 08:34:14 +00:00
commit cb93c24bf3
7 changed files with 54 additions and 17 deletions
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6
compiler/rustc_builtin_macros/src/format.rs
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@ -315,7 +315,7 @@ fn make_format_args(
let mut used = vec![false; args.explicit_args().len()];
let mut invalid_refs = Vec::new();
let mut numeric_refences_to_named_arg = Vec::new();
let mut numeric_references_to_named_arg = Vec::new();
enum ArgRef<'a> {
Index(usize),
@ -336,7 +336,7 @@ fn make_format_args(
used[index] = true;
if arg.kind.ident().is_some() {
// This was a named argument, but it was used as a positional argument.
numeric_refences_to_named_arg.push((index, span, used_as));
numeric_references_to_named_arg.push((index, span, used_as));
}
Ok(index)
} else {
@ -544,7 +544,7 @@ fn make_format_args(
// Only check for unused named argument names if there are no other errors to avoid causing
// too much noise in output errors, such as when a named argument is entirely unused.
if invalid_refs.is_empty() && !has_unused && !unnamed_arg_after_named_arg {
for &(index, span, used_as) in &numeric_refences_to_named_arg {
for &(index, span, used_as) in &numeric_references_to_named_arg {
let (position_sp_to_replace, position_sp_for_msg) = match used_as {
Placeholder(pspan) => (span, pspan),
Precision => {