Rollup merge of #158044 - petrochenkov:partest, r=lqd

Add more tests for parallel frontend issues

Issues:
- https://github.com/rust-lang/rust/issues/153366
- https://github.com/rust-lang/rust/issues/154056
- https://github.com/rust-lang/rust/issues/154560

2 issues still reproduce (and therefore marked with `//@ ignore-parallel-frontend query`), 1 issue doesn't reproduce.

Closes https://github.com/rust-lang/rust/issues/153366.

tests/ui/parallel-rustc/dyn-trait-ice-153366.rs

@@ -0,0 +1,25 @@
+// Regression test for ICE from issue #153366.
+
+#![feature(unboxed_closures)]
+
+fn iso<A>(a: Fn) -> Option<_>
+//~^ ERROR missing generics for trait `Fn`
+//~| ERROR the placeholder `_` is not allowed within types on item signatures for return types
+//~| WARN trait objects without an explicit `dyn` are deprecated
+//~| WARN this is accepted in the current edition
+where
+    dyn Fn(A) -> (): Sized,
+{
+    Box::new(iso_un_option)
+    //~^ ERROR mismatched types
+}
+fn iso_un_option<B>() -> Box<_> {
+//~^ ERROR the placeholder `_` is not allowed within types on item signatures for return types
+    iso(())
+    //~^ ERROR the size for values of type `(dyn Fn(_) + 'static)` cannot be known at compilation
+}
+
+fn main() {
+    iso(())
+    //~^ ERROR the size for values of type `(dyn Fn(_) + 'static)` cannot be known at compilation
+}

tests/ui/parallel-rustc/dyn-trait-ice-153366.stderr

@@ -0,0 +1,93 @@
+warning: trait objects without an explicit `dyn` are deprecated
+  --> $DIR/dyn-trait-ice-153366.rs:5:14
+   |
+LL | fn iso<A>(a: Fn) -> Option<_>
+   |              ^^
+   |
+   = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
+   = note: for more information, see <https://doc.rust-lang.org/edition-guide/rust-2021/warnings-promoted-to-error.html>
+   = note: `#[warn(bare_trait_objects)]` (part of `#[warn(rust_2021_compatibility)]`) on by default
+help: if this is a dyn-compatible trait, use `dyn`
+   |
+LL | fn iso<A>(a: dyn Fn) -> Option<_>
+   |              +++
+
+error[E0107]: missing generics for trait `Fn`
+  --> $DIR/dyn-trait-ice-153366.rs:5:14
+   |
+LL | fn iso<A>(a: Fn) -> Option<_>
+   |              ^^ expected 1 generic argument
+   |
+help: add missing generic argument
+   |
+LL | fn iso<A>(a: Fn<Args>) -> Option<_>
+   |                ++++++
+
+error[E0277]: the size for values of type `(dyn Fn(_) + 'static)` cannot be known at compilation time
+  --> $DIR/dyn-trait-ice-153366.rs:18:5
+   |
+LL |     iso(())
+   |     ^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `(dyn Fn(_) + 'static)`
+note: required by a bound in `iso`
+  --> $DIR/dyn-trait-ice-153366.rs:11:22
+   |
+LL | fn iso<A>(a: Fn) -> Option<_>
+   |    --- required by a bound in this function
+...
+LL |     dyn Fn(A) -> (): Sized,
+   |                      ^^^^^ required by this bound in `iso`
+
+error[E0121]: the placeholder `_` is not allowed within types on item signatures for return types
+  --> $DIR/dyn-trait-ice-153366.rs:16:30
+   |
+LL | fn iso_un_option<B>() -> Box<_> {
+   |                              ^ not allowed in type signatures
+
+error[E0308]: mismatched types
+  --> $DIR/dyn-trait-ice-153366.rs:13:5
+   |
+LL | fn iso<A>(a: Fn) -> Option<_>
+   |                     --------- expected `Option<_>` because of return type
+...
+LL |     Box::new(iso_un_option)
+   |     ^^^^^^^^^^^^^^^^^^^^^^^ expected `Option<_>`, found `Box<fn() -> ... {iso_un_option::<_>}>`
+   |
+   = note: expected enum `Option<_>`
+            found struct `Box<fn() -> {type error} {iso_un_option::<_>}>`
+help: use parentheses to call this function
+   |
+LL |     Box::new(iso_un_option)()
+   |                            ++
+help: try wrapping the expression in `Some`
+   |
+LL |     Some(Box::new(iso_un_option))
+   |     +++++                       +
+
+error[E0121]: the placeholder `_` is not allowed within types on item signatures for return types
+  --> $DIR/dyn-trait-ice-153366.rs:5:28
+   |
+LL | fn iso<A>(a: Fn) -> Option<_>
+   |                            ^ not allowed in type signatures
+
+error[E0277]: the size for values of type `(dyn Fn(_) + 'static)` cannot be known at compilation time
+  --> $DIR/dyn-trait-ice-153366.rs:23:5
+   |
+LL |     iso(())
+   |     ^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `(dyn Fn(_) + 'static)`
+note: required by a bound in `iso`
+  --> $DIR/dyn-trait-ice-153366.rs:11:22
+   |
+LL | fn iso<A>(a: Fn) -> Option<_>
+   |    --- required by a bound in this function
+...
+LL |     dyn Fn(A) -> (): Sized,
+   |                      ^^^^^ required by this bound in `iso`
+
+error: aborting due to 6 previous errors; 1 warning emitted
+
+Some errors have detailed explanations: E0107, E0121, E0277, E0308.
+For more information about an error, try `rustc --explain E0107`.

tests/ui/parallel-rustc/fn-sig-cycle-ice-154560.rs

@@ -0,0 +1,14 @@
+// Regression test for ICE from issue #154056.
+
+//@ ignore-parallel-frontend query cycle + ICE
+
+#![feature(min_generic_const_args)]
+#![feature(return_type_notation)]
+
+trait IntFactory {
+    fn stream(&self) -> impl IntFactory<stream(..): Send>;
+    //~^ ERROR cycle detected when resolving lifetimes for `IntFactory::stream`
+}
+trait SendIntFactory: IntFactory<stream(..): Send> + Send {}
+
+fn main() {}

tests/ui/parallel-rustc/fn-sig-cycle-ice-154560.stderr

@@ -0,0 +1,19 @@
+error[E0391]: cycle detected when resolving lifetimes for `IntFactory::stream`
+  --> $DIR/fn-sig-cycle-ice-154560.rs:9:5
+   |
+LL |     fn stream(&self) -> impl IntFactory<stream(..): Send>;
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: ...which requires computing function signature of `IntFactory::stream`...
+   = note: ...which requires looking up late bound vars inside `IntFactory::stream`...
+   = note: ...which again requires resolving lifetimes for `IntFactory::stream`, completing the cycle
+note: cycle used when listing captured lifetimes for opaque `IntFactory::stream::{opaque#0}`
+  --> $DIR/fn-sig-cycle-ice-154560.rs:9:25
+   |
+LL |     fn stream(&self) -> impl IntFactory<stream(..): Send>;
+   |                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: for more information, see <https://rustc-dev-guide.rust-lang.org/overview.html#queries> and <https://rustc-dev-guide.rust-lang.org/query.html>
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0391`.

tests/ui/parallel-rustc/variances-cycle-ice-154560.rs

@@ -0,0 +1,16 @@
+// Regression test for ICE from issue #154560.
+//~^ ERROR cycle detected when computing the variances for items in this crate
+
+//@ ignore-parallel-frontend query cycle + ICE
+
+pub struct T<'a>(&'a str);
+
+pub fn f<T>() -> _ {
+    T
+}
+
+pub fn g<'a>(val: T<'a>) -> _ {
+    T
+}
+
+fn main() {}

tests/ui/parallel-rustc/variances-cycle-ice-154560.stderr

@@ -0,0 +1,24 @@
+error[E0391]: cycle detected when computing the variances for items in this crate
+   |
+note: ...which requires computing function signature of `f`...
+  --> $DIR/variances-cycle-ice-154560.rs:8:1
+   |
+LL | pub fn f<T>() -> _ {
+   | ^^^^^^^^^^^^^^^^^^
+   = note: ...which requires type-checking `f`...
+note: ...which requires computing the variances of `T`...
+  --> $DIR/variances-cycle-ice-154560.rs:6:1
+   |
+LL | pub struct T<'a>(&'a str);
+   | ^^^^^^^^^^^^^^^^
+   = note: ...which again requires computing the variances for items in this crate, completing the cycle
+note: cycle used when computing the variances of `T`
+  --> $DIR/variances-cycle-ice-154560.rs:6:1
+   |
+LL | pub struct T<'a>(&'a str);
+   | ^^^^^^^^^^^^^^^^
+   = note: for more information, see <https://rustc-dev-guide.rust-lang.org/overview.html#queries> and <https://rustc-dev-guide.rust-lang.org/query.html>
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0391`.