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Rollup merge of #132933 - compiler-errors:never-lint-arg-bug, r=WaffleLapkin

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Make sure that we suggest turbofishing the right type arg for never suggestion

I had a bug where rust would suggest the wrong arg to turbofish `()` if there were any early-bound lifetimes...

r? WaffleLapkin
This commit is contained in:
Matthias Krüger 2024-11-12 06:27:20 +01:00 • committed by GitHub
commit 506f52c7f3
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GPG key ID: B5690EEEBB952194
5 changed files with 122 additions and 10 deletions
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6
compiler/rustc_hir_typeck/src/fallback.rs
View file

@ -621,7 +621,11 @@ impl<'tcx> AnnotateUnitFallbackVisitor<'_, 'tcx> {
.iter()
.filter(|arg| matches!(arg.unpack(), ty::GenericArgKind::Type(_)))
.count();
for (idx, arg) in args.iter().enumerate() {
for (idx, arg) in args
.iter()
.filter(|arg| matches!(arg.unpack(), ty::GenericArgKind::Type(_)))
.enumerate()
{
if let Some(ty) = arg.as_type()
&& let Some(vid) = self.fcx.root_vid(ty)
&& self.reachable_vids.contains(&vid)

52
tests/ui/editions/never-type-fallback-breaking.e2021.fixed Normal file
View file

@ -0,0 +1,52 @@
//@ revisions: e2021 e2024
//
//@[e2021] edition: 2021
//@[e2024] edition: 2024
//@[e2024] compile-flags: -Zunstable-options
//
//@[e2021] run-pass
//@[e2021] run-rustfix
//@[e2024] check-fail
fn main() {
m();
q();
let _ = meow();
}
fn m() {
//[e2021]~^ this function depends on never type fallback being `()`
//[e2021]~| this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
let x: () = match true {
true => Default::default(),
//[e2024]~^ error: the trait bound `!: Default` is not satisfied
false => panic!("..."),
};
dbg!(x);
}
fn q() -> Option<()> {
//[e2021]~^ this function depends on never type fallback being `()`
//[e2021]~| this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
fn deserialize<T: Default>() -> Option<T> {
Some(T::default())
}
deserialize::<()>()?;
//[e2024]~^ error: the trait bound `!: Default` is not satisfied
None
}
// Make sure we turbofish the right argument
fn help<'a: 'a, T: Into<()>, U>(_: U) -> Result<T, ()> {
Err(())
}
fn meow() -> Result<(), ()> {
//[e2021]~^ this function depends on never type fallback being `()`
//[e2021]~| this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
help::<(), _>(1)?;
//[e2024]~^ error: the trait bound `(): From<!>` is not satisfied
Ok(())
}

29
tests/ui/editions/never-type-fallback-breaking.e2021.stderr
View file

@ -1,5 +1,5 @@
warning: this function depends on never type fallback being `()`
--> $DIR/never-type-fallback-breaking.rs:15:1
--> $DIR/never-type-fallback-breaking.rs:17:1
|
LL | fn m() {
| ^^^^^^
@ -8,7 +8,7 @@ LL | fn m() {
= note: for more information, see issue #123748 <https://github.com/rust-lang/rust/issues/123748>
= help: specify the types explicitly
note: in edition 2024, the requirement `!: Default` will fail
--> $DIR/never-type-fallback-breaking.rs:19:17
--> $DIR/never-type-fallback-breaking.rs:21:17
|
LL | true => Default::default(),
| ^^^^^^^^^^^^^^^^^^
@ -19,7 +19,7 @@ LL | let x: () = match true {
| ++++
warning: this function depends on never type fallback being `()`
--> $DIR/never-type-fallback-breaking.rs:27:1
--> $DIR/never-type-fallback-breaking.rs:29:1
|
LL | fn q() -> Option<()> {
| ^^^^^^^^^^^^^^^^^^^^
@ -28,7 +28,7 @@ LL | fn q() -> Option<()> {
= note: for more information, see issue #123748 <https://github.com/rust-lang/rust/issues/123748>
= help: specify the types explicitly
note: in edition 2024, the requirement `!: Default` will fail
--> $DIR/never-type-fallback-breaking.rs:34:5
--> $DIR/never-type-fallback-breaking.rs:36:5
|
LL | deserialize()?;
| ^^^^^^^^^^^^^
@ -37,5 +37,24 @@ help: use `()` annotations to avoid fallback changes
LL | deserialize::<()>()?;
| ++++++
warning: 2 warnings emitted
warning: this function depends on never type fallback being `()`
--> $DIR/never-type-fallback-breaking.rs:46:1
|
LL | fn meow() -> Result<(), ()> {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
= note: for more information, see issue #123748 <https://github.com/rust-lang/rust/issues/123748>
= help: specify the types explicitly
note: in edition 2024, the requirement `(): From<!>` will fail
--> $DIR/never-type-fallback-breaking.rs:49:5
|
LL | help(1)?;
| ^^^^^^^
help: use `()` annotations to avoid fallback changes
|
LL | help::<(), _>(1)?;
| +++++++++
warning: 3 warnings emitted

31
tests/ui/editions/never-type-fallback-breaking.e2024.stderr
View file

@ -1,5 +1,5 @@
error[E0277]: the trait bound `!: Default` is not satisfied
--> $DIR/never-type-fallback-breaking.rs:19:17
--> $DIR/never-type-fallback-breaking.rs:21:17
|
LL | true => Default::default(),
| ^^^^^^^^^^^^^^^^^^ the trait `Default` is not implemented for `!`
@ -8,7 +8,7 @@ LL | true => Default::default(),
= help: did you intend to use the type `()` here instead?
error[E0277]: the trait bound `!: Default` is not satisfied
--> $DIR/never-type-fallback-breaking.rs:34:5
--> $DIR/never-type-fallback-breaking.rs:36:5
|
LL | deserialize()?;
| ^^^^^^^^^^^^^ the trait `Default` is not implemented for `!`
@ -16,11 +16,34 @@ LL | deserialize()?;
= note: this error might have been caused by changes to Rust's type-inference algorithm (see issue #48950 <https://github.com/rust-lang/rust/issues/48950> for more information)
= help: did you intend to use the type `()` here instead?
note: required by a bound in `deserialize`
--> $DIR/never-type-fallback-breaking.rs:30:23
--> $DIR/never-type-fallback-breaking.rs:32:23
|
LL | fn deserialize<T: Default>() -> Option<T> {
| ^^^^^^^ required by this bound in `deserialize`
error: aborting due to 2 previous errors
error[E0277]: the trait bound `(): From<!>` is not satisfied
--> $DIR/never-type-fallback-breaking.rs:49:5
|
LL | help(1)?;
| ^^^^^^^ the trait `From<!>` is not implemented for `()`
|
= help: the following other types implement trait `From<T>`:
`(T, T)` implements `From<[T; 2]>`
`(T, T, T)` implements `From<[T; 3]>`
`(T, T, T, T)` implements `From<[T; 4]>`
`(T, T, T, T, T)` implements `From<[T; 5]>`
`(T, T, T, T, T, T)` implements `From<[T; 6]>`
`(T, T, T, T, T, T, T)` implements `From<[T; 7]>`
`(T, T, T, T, T, T, T, T)` implements `From<[T; 8]>`
`(T, T, T, T, T, T, T, T, T)` implements `From<[T; 9]>`
and 4 others
= note: required for `!` to implement `Into<()>`
note: required by a bound in `help`
--> $DIR/never-type-fallback-breaking.rs:43:20
|
LL | fn help<'a: 'a, T: Into<()>, U>(_: U) -> Result<T, ()> {
| ^^^^^^^^ required by this bound in `help`
error: aborting due to 3 previous errors
For more information about this error, try `rustc --explain E0277`.

14
tests/ui/editions/never-type-fallback-breaking.rs
View file

@ -5,11 +5,13 @@
//@[e2024] compile-flags: -Zunstable-options
//
//@[e2021] run-pass
//@[e2021] run-rustfix
//@[e2024] check-fail
fn main() {
m();
q();
let _ = meow();
}
fn m() {
@ -36,3 +38,15 @@ fn q() -> Option<()> {
None
}
// Make sure we turbofish the right argument
fn help<'a: 'a, T: Into<()>, U>(_: U) -> Result<T, ()> {
Err(())
}
fn meow() -> Result<(), ()> {
//[e2021]~^ this function depends on never type fallback being `()`
//[e2021]~| this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
help(1)?;
//[e2024]~^ error: the trait bound `(): From<!>` is not satisfied
Ok(())
}