Rework ptr-to-ref conversion suggestion for method calls
If we have a value `z` of type `*const u8` and try to call `z.to_string()`, the upstream compiler will show you a note suggesting to call `<*const u8>::as_ref` first.
This PR extends that:
- The note will only be shown when the method would exist on the corresponding reference type
- It can now suggest any of `<*const u8>::as_ref`, `<*mut u8>::as_ref` and `<*mut u8>::as_mut`, depending on what the method needs.
I didn't introduce a `help` message because that's not a good idea with `unsafe` functions (and you'd also need to unwrap the `Option<&_>` somehow).
People should check the safety requirements.
For the simplest case
```rust
fn main() {
let x = 8u8;
let z: *const u8 = &x;
// issue #21596
println!("{}", z.to_string()); //~ ERROR E0599
}
```
the output changes like this:
```diff
error[E0599]: `*const u8` doesn't implement `std::fmt::Display`
--> $DIR/suggest-convert-ptr-to-ref.rs:5:22
|
LL | println!("{}", z.to_string());
| ^^^^^^^^^ `*const u8` cannot be formatted with the default formatter
|
- = note: try using `<*const T>::as_ref()` to get a reference to the type behind the pointer: https://doc.rust-lang.org/std/primitive.pointer.html#method.as_ref
- = note: using `<*const T>::as_ref()` on a pointer which is unaligned or points to invalid or uninitialized memory is undefined behavior
+note: the method `to_string` exists on the type `&u8`
+ --> $SRC_DIR/alloc/src/string.rs:LL:COL
+ = note: try using the unsafe method `<*const T>::as_ref` to get an optional reference to the value behind the pointer: https://doc.rust-lang.org/std/primitive.pointer.html#method.as_ref
= note: the following trait bounds were not satisfied:
`*const u8: std::fmt::Display`
which is required by `*const u8: ToString`
```
I removed the separate note about the safety requirements because it was incomplete and the linked doc page already has the information you need.
Fixes#83695, but that's more of a side effect. The upstream compiler already suggests the right method name here.
Use `fn` ptr signature instead of `{closure@..}` in infer error
When suggesting a type on inference error, do not use `{closure@..}`. Instead, replace with an appropriate `fn` ptr.
On the error message, use `short_ty_string` and write long types to disk.
```
error[E0284]: type annotations needed for `Select<{closure@lib.rs:2782:13}, _, Expression<'_>, _>`
--> crates/lang/src/parser.rs:41:13
|
41 | let lit = select! {
| ^^^
42 | Token::Int(i) = e => Expression::new(Expr::Lit(ast::Lit::Int(i.parse().unwrap())), e.span()),
| ---- type must be known at this point
|
= note: the full type name has been written to '/home/gh-estebank/iowo/target/debug/deps/lang-e2d6e25819442273.long-type-4587393693885174369.txt'
= note: cannot satisfy `<_ as chumsky::input::Input<'_>>::Span == SimpleSpan`
help: consider giving `lit` an explicit type, where the type for type parameter `I` is specified
|
41 | let lit: Select<for<'a, 'b> fn(tokens::Token<'_>, &'a mut MapExtra<'_, 'b, _, _>) -> Option<Expression<'_>>, _, Expression<'_>, _> = select! {
| +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
```
instead of
```
error[E0284]: type annotations needed for `Select<{closure@/home/gh-estebank/.cargo/registry/src/index.crates.io-6f17d22bba15001f/chumsky-1.0.0-alpha.6/src/lib.rs:2782:13: 2782:28}, _, Expression<'_>, _>`
--> crates/lang/src/parser.rs:41:13
|
41 | let lit = select! {
| ^^^
42 | Token::Int(i) = e => Expression::new(Expr::Lit(ast::Lit::Int(i.parse().unwrap())), e.span()),
| ---- type must be known at this point
|
= note: cannot satisfy `<_ as chumsky::input::Input<'_>>::Span == SimpleSpan`
help: consider giving `lit` an explicit type, where the type for type parameter `I` is specified
|
41 | let lit: Select<{closure@/home/gh-estebank/.cargo/registry/src/index.crates.io-6f17d22bba15001f/chumsky-1.0.0-alpha.6/src/lib.rs:2782:13: 2782:28}, _, Expression<'_>, _> = select! {
| ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
```
Address #123630 (test missing).
When suggesting a type on inference error, do not use `{closure@..}`.
Instead, replace with an appropriate `fn` ptr.
On the error message, use `short_ty_string` and write long types to
disk.
```
error[E0284]: type annotations needed for `Select<{closure@lib.rs:2782:13}, _, Expression<'_>, _>`
--> crates/lang/src/parser.rs:41:13
|
41 | let lit = select! {
| ^^^
42 | Token::Int(i) = e => Expression::new(Expr::Lit(ast::Lit::Int(i.parse().unwrap())), e.span()),
| ---- type must be known at this point
|
= note: the full type name has been written to '/home/gh-estebank/iowo/target/debug/deps/lang-e2d6e25819442273.long-type-4587393693885174369.txt'
= note: cannot satisfy `<_ as chumsky::input::Input<'_>>::Span == SimpleSpan`
help: consider giving `lit` an explicit type, where the type for type parameter `I` is specified
|
41 | let lit: Select<for<'a, 'b> fn(tokens::Token<'_>, &'a mut MapExtra<'_, 'b, _, _>) -> Option<Expression<'_>>, _, Expression<'_>, _> = select! {
| +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
```
instead of
```
error[E0284]: type annotations needed for `Select<{closure@/home/gh-estebank/.cargo/registry/src/index.crates.io-6f17d22bba15001f/chumsky-1.0.0-alpha.6/src/lib.rs:2782:13: 2782:28}, _, Expression<'_>, _>`
--> crates/lang/src/parser.rs:41:13
|
41 | let lit = select! {
| ^^^
42 | Token::Int(i) = e => Expression::new(Expr::Lit(ast::Lit::Int(i.parse().unwrap())), e.span()),
| ---- type must be known at this point
|
= note: cannot satisfy `<_ as chumsky::input::Input<'_>>::Span == SimpleSpan`
help: consider giving `lit` an explicit type, where the type for type parameter `I` is specified
|
41 | let lit: Select<{closure@/home/gh-estebank/.cargo/registry/src/index.crates.io-6f17d22bba15001f/chumsky-1.0.0-alpha.6/src/lib.rs:2782:13: 2782:28}, _, Expression<'_>, _> = select! {
| ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
```
Fix#123630.
Use root obligation on E0277 for some cases
When encountering trait bound errors that satisfy some heuristics that tell us that the relevant trait for the user comes from the root obligation and not the current obligation, we use the root predicate for the main message.
This allows to talk about "X doesn't implement Pattern<'_>" over the most specific case that just happened to fail, like "char doesn't implement Fn(&mut char)" in
`tests/ui/traits/suggest-dereferences/root-obligation.rs`
The heuristics are:
- the type of the leaf predicate is (roughly) the same as the type from the root predicate, as a proxy for "we care about the root"
- the leaf trait and the root trait are different, so as to avoid talking about `&mut T: Trait` and instead remain talking about `T: Trait` instead
- the root trait is not `Unsize`, as to avoid talking about it in `tests/ui/coercion/coerce-issue-49593-box-never.rs`.
```
error[E0277]: the trait bound `&char: Pattern<'_>` is not satisfied
--> $DIR/root-obligation.rs:6:38
|
LL | .filter(|c| "aeiou".contains(c))
| -------- ^ the trait `Fn<(char,)>` is not implemented for `&char`, which is required by `&char: Pattern<'_>`
| |
| required by a bound introduced by this call
|
= note: required for `&char` to implement `FnOnce<(char,)>`
= note: required for `&char` to implement `Pattern<'_>`
note: required by a bound in `core::str::<impl str>::contains`
--> $SRC_DIR/core/src/str/mod.rs:LL:COL
help: consider dereferencing here
|
LL | .filter(|c| "aeiou".contains(*c))
| +
```
Fix#79359, fix#119983, fix#118779, cc #118415 (the suggestion needs to change), cc #121398 (doesn't fix the underlying issue).
```
error[E0599]: no method named `map` found for struct `Vec<bool>` in the current scope
--> $DIR/vec-on-unimplemented.rs:3:23
|
LL | vec![true, false].map(|v| !v).collect::<Vec<_>>();
| ^^^ `Vec<bool>` is not an iterator
|
help: call `.into_iter()` first
|
LL | vec![true, false].into_iter().map(|v| !v).collect::<Vec<_>>();
| ++++++++++++
```
We used to provide some help through `rustc_on_unimplemented` on non-`impl Trait` and non-type-params, but this lets us get rid of some otherwise unnecessary conditions in the annotation on `Iterator`.
Account for non-overlapping unmet trait bounds in suggestion
When a method not found on a type parameter could have been provided by any
of multiple traits, suggest each trait individually, instead of a single
suggestion to restrict the type parameter with *all* of them.
Before:
```
error[E0599]: the method `cmp` exists for reference `&T`, but its trait bounds were not satisfied
--> $DIR/method-on-unbounded-type-param.rs:5:10
|
LL | (&a).cmp(&b)
| ^^^ method cannot be called on `&T` due to unsatisfied trait bounds
|
= note: the following trait bounds were not satisfied:
`T: Ord`
which is required by `&T: Ord`
`&T: Iterator`
which is required by `&mut &T: Iterator`
`T: Iterator`
which is required by `&mut T: Iterator`
help: consider restricting the type parameters to satisfy the trait bounds
|
LL | fn g<T>(a: T, b: T) -> std::cmp::Ordering where T: Iterator, T: Ord {
| +++++++++++++++++++++++++
```
After:
```
error[E0599]: the method `cmp` exists for reference `&T`, but its trait bounds were not satisfied
--> $DIR/method-on-unbounded-type-param.rs:5:10
|
LL | (&a).cmp(&b)
| ^^^ method cannot be called on `&T` due to unsatisfied trait bounds
|
= note: the following trait bounds were not satisfied:
`T: Ord`
which is required by `&T: Ord`
`&T: Iterator`
which is required by `&mut &T: Iterator`
`T: Iterator`
which is required by `&mut T: Iterator`
= help: items from traits can only be used if the type parameter is bounded by the trait
help: the following traits define an item `cmp`, perhaps you need to restrict type parameter `T` with one of them:
|
LL | fn g<T: Ord>(a: T, b: T) -> std::cmp::Ordering {
| +++++
LL | fn g<T: Iterator>(a: T, b: T) -> std::cmp::Ordering {
| ++++++++++
```
Fix#108428.
Follow up to #120396, only last commit is relevant.
```
error[E0277]: the size for values of type `[i32]` cannot be known at compilation time
--> f100.rs:2:33
|
2 | let _ = std::mem::size_of::<[i32]>();
| ^^^^^ doesn't have a size known at compile-time
|
= help: the trait `Sized` is not implemented for `[i32]`
note: required by an implicit `Sized` bound in `std::mem::size_of`
--> /home/gh-estebank/rust/library/core/src/mem/mod.rs:312:22
|
312 | pub const fn size_of<T>() -> usize {
| ^ required by the implicit `Sized` requirement on this bound in `size_of`
```
Fix#120178.
When a method not found on a type parameter could have been provided by any
of multiple traits, suggest each trait individually, instead of a single
suggestion to restrict the type parameter with *all* of them.
Before:
```
error[E0599]: the method `cmp` exists for reference `&T`, but its trait bounds were not satisfied
--> $DIR/method-on-unbounded-type-param.rs:5:10
|
LL | (&a).cmp(&b)
| ^^^ method cannot be called on `&T` due to unsatisfied trait bounds
|
= note: the following trait bounds were not satisfied:
`T: Ord`
which is required by `&T: Ord`
`&T: Iterator`
which is required by `&mut &T: Iterator`
`T: Iterator`
which is required by `&mut T: Iterator`
help: consider restricting the type parameters to satisfy the trait bounds
|
LL | fn g<T>(a: T, b: T) -> std::cmp::Ordering where T: Iterator, T: Ord {
| +++++++++++++++++++++++++
```
After:
```
error[E0599]: the method `cmp` exists for reference `&T`, but its trait bounds were not satisfied
--> $DIR/method-on-unbounded-type-param.rs:5:10
|
LL | (&a).cmp(&b)
| ^^^ method cannot be called on `&T` due to unsatisfied trait bounds
|
= note: the following trait bounds were not satisfied:
`T: Ord`
which is required by `&T: Ord`
`&T: Iterator`
which is required by `&mut &T: Iterator`
`T: Iterator`
which is required by `&mut T: Iterator`
= help: items from traits can only be used if the type parameter is bounded by the trait
help: the following traits define an item `cmp`, perhaps you need to restrict type parameter `T` with one of them:
|
LL | fn g<T: Ord>(a: T, b: T) -> std::cmp::Ordering {
| +++++
LL | fn g<T: Iterator>(a: T, b: T) -> std::cmp::Ordering {
| ++++++++++
```
Fix#108428.
When encountering a type mismatch error involving `dyn Trait`, mention
the existence of boxed trait objects if the other type involved
implements `Trait`.
Partially addresses #102629.
In `report_fullfillment_errors` push back `T: Sized`, `T: WellFormed`
and coercion errors to the end of the list. The pre-existing
deduplication logic eliminates redundant errors better that way, keeping
the resulting output with fewer errors than before, while also having
more detail.
This option guards the logic of writing long type names in files and
instead using short forms in error messages in rustc_middle/ty/error
behind a flag. The main motivation for this change is to disable this
behaviour when running ui tests.
This logic can be triggered by running tests in a directory that has a
long enough path, e.g. /my/very-long-path/where/rust-codebase/exists/
This means ui tests can fail depending on how long the path to their
file is.
Some ui tests actually rely on this behaviour for their assertions,
so for those we enable the flag manually.
