Auto merge of #87434 - Manishearth:rollup-b09njin, r=Manishearth

Rollup of 9 pull requests

Successful merges:

 - #87348 (Fix span when suggesting to add an associated type bound)
 - #87359 (Remove detection of rustup and cargo in 'missing extern crate' diagnostics)
 - #87370 (Add support for powerpc-unknown-freebsd)
 - #87389 (Rename `known_attrs` to `expanded_inert_attrs` and move to rustc_expand)
 - #87395 (Clear up std::env::set_var panic section.)
 - #87403 (Implement `AssignToDroppingUnionField` in THIR unsafeck)
 - #87410 (Mark `format_args_nl` as `#[doc(hidden)]`)
 - #87419 (IEEE 754 is not an RFC)
 - #87422 (DOC: remove unnecessary feature crate attribute from example code)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

8 files changed, 361 insertions, 5 deletions

diff --git a/src/test/ui/associated-types/issue-87261.rs b/src/test/ui/associated-types/issue-87261.rs
new file mode 100644
index 00000000000..a70f771e482
--- /dev/null
+++ b/src/test/ui/associated-types/issue-87261.rs
@@ -0,0 +1,99 @@
+trait Foo {}
+
+trait Trait {
+    type Associated;
+}
+trait DerivedTrait: Trait {}
+trait GenericTrait<A> {
+    type Associated;
+}
+
+struct Impl;
+impl Foo for Impl {}
+impl Trait for Impl {
+    type Associated = ();
+}
+impl DerivedTrait for Impl {}
+impl<A> GenericTrait<A> for Impl {
+    type Associated = ();
+}
+
+fn returns_opaque() -> impl Trait + 'static {
+    Impl
+}
+fn returns_opaque_derived() -> impl DerivedTrait + 'static {
+    Impl
+}
+fn returns_opaque_foo() -> impl Trait + Foo {
+    Impl
+}
+fn returns_opaque_derived_foo() -> impl DerivedTrait + Foo {
+    Impl
+}
+fn returns_opaque_generic() -> impl GenericTrait<()> + 'static {
+    Impl
+}
+fn returns_opaque_generic_foo() -> impl GenericTrait<()> + Foo {
+    Impl
+}
+fn returns_opaque_generic_duplicate() -> impl GenericTrait<()> + GenericTrait<u8> {
+    Impl
+}
+
+fn accepts_trait<T: Trait<Associated = ()>>(_: T) {}
+fn accepts_generic_trait<T: GenericTrait<(), Associated = ()>>(_: T) {}
+
+fn check_generics<A, B, C, D, E, F, G>(a: A, b: B, c: C, d: D, e: E, f: F, g: G)
+where
+    A: Trait + 'static,
+    B: DerivedTrait + 'static,
+    C: Trait + Foo,
+    D: DerivedTrait + Foo,
+    E: GenericTrait<()> + 'static,
+    F: GenericTrait<()> + Foo,
+    G: GenericTrait<()> + GenericTrait<u8>,
+{
+    accepts_trait(a);
+    //~^ ERROR type mismatch resolving `<A as Trait>::Associated == ()`
+
+    accepts_trait(b);
+    //~^ ERROR type mismatch resolving `<B as Trait>::Associated == ()`
+
+    accepts_trait(c);
+    //~^ ERROR type mismatch resolving `<C as Trait>::Associated == ()`
+
+    accepts_trait(d);
+    //~^ ERROR type mismatch resolving `<D as Trait>::Associated == ()`
+
+    accepts_generic_trait(e);
+    //~^ ERROR type mismatch resolving `<E as GenericTrait<()>>::Associated == ()`
+
+    accepts_generic_trait(f);
+    //~^ ERROR type mismatch resolving `<F as GenericTrait<()>>::Associated == ()`
+
+    accepts_generic_trait(g);
+    //~^ ERROR type mismatch resolving `<G as GenericTrait<()>>::Associated == ()`
+}
+
+fn main() {
+    accepts_trait(returns_opaque());
+    //~^ ERROR type mismatch resolving `<impl Trait as Trait>::Associated == ()`
+
+    accepts_trait(returns_opaque_derived());
+    //~^ ERROR type mismatch resolving `<impl DerivedTrait as Trait>::Associated == ()`
+
+    accepts_trait(returns_opaque_foo());
+    //~^ ERROR type mismatch resolving `<impl Trait+Foo as Trait>::Associated == ()`
+
+    accepts_trait(returns_opaque_derived_foo());
+    //~^ ERROR type mismatch resolving `<impl DerivedTrait+Foo as Trait>::Associated == ()`
+
+    accepts_generic_trait(returns_opaque_generic());
+    //~^ ERROR type mismatch resolving `<impl GenericTrait<()> as GenericTrait<()>>::Associated == ()`
+
+    accepts_generic_trait(returns_opaque_generic_foo());
+    //~^ ERROR type mismatch resolving `<impl GenericTrait<()>+Foo as GenericTrait<()>>::Associated == ()`
+
+    accepts_generic_trait(returns_opaque_generic_duplicate());
+    //~^ ERROR type mismatch resolving `<impl GenericTrait<()>+GenericTrait<u8> as GenericTrait<()>>::Associated == ()`
+}
diff --git a/src/test/ui/associated-types/issue-87261.stderr b/src/test/ui/associated-types/issue-87261.stderr
new file mode 100644
index 00000000000..0725acfe537
--- /dev/null
+++ b/src/test/ui/associated-types/issue-87261.stderr
@@ -0,0 +1,238 @@
+error[E0271]: type mismatch resolving `<A as Trait>::Associated == ()`
+  --> $DIR/issue-87261.rs:56:5
+   |
+LL | fn accepts_trait<T: Trait<Associated = ()>>(_: T) {}
+   |                           --------------- required by this bound in `accepts_trait`
+...
+LL |     accepts_trait(a);
+   |     ^^^^^^^^^^^^^ expected `()`, found associated type
+   |
+   = note:    expected unit type `()`
+           found associated type `<A as Trait>::Associated`
+help: consider constraining the associated type `<A as Trait>::Associated` to `()`
+   |
+LL |     A: Trait<Associated = ()> + 'static,
+   |             ^^^^^^^^^^^^^^^^^
+
+error[E0271]: type mismatch resolving `<B as Trait>::Associated == ()`
+  --> $DIR/issue-87261.rs:59:5
+   |
+LL | fn accepts_trait<T: Trait<Associated = ()>>(_: T) {}
+   |                           --------------- required by this bound in `accepts_trait`
+...
+LL |     accepts_trait(b);
+   |     ^^^^^^^^^^^^^ expected `()`, found associated type
+   |
+   = note:    expected unit type `()`
+           found associated type `<B as Trait>::Associated`
+   = help: consider constraining the associated type `<B as Trait>::Associated` to `()`
+   = note: for more information, visit https://doc.rust-lang.org/book/ch19-03-advanced-traits.html
+
+error[E0271]: type mismatch resolving `<C as Trait>::Associated == ()`
+  --> $DIR/issue-87261.rs:62:5
+   |
+LL | fn accepts_trait<T: Trait<Associated = ()>>(_: T) {}
+   |                           --------------- required by this bound in `accepts_trait`
+...
+LL |     accepts_trait(c);
+   |     ^^^^^^^^^^^^^ expected `()`, found associated type
+   |
+   = note:    expected unit type `()`
+           found associated type `<C as Trait>::Associated`
+help: consider constraining the associated type `<C as Trait>::Associated` to `()`
+   |
+LL |     C: Trait<Associated = ()> + Foo,
+   |             ^^^^^^^^^^^^^^^^^
+
+error[E0271]: type mismatch resolving `<D as Trait>::Associated == ()`
+  --> $DIR/issue-87261.rs:65:5
+   |
+LL | fn accepts_trait<T: Trait<Associated = ()>>(_: T) {}
+   |                           --------------- required by this bound in `accepts_trait`
+...
+LL |     accepts_trait(d);
+   |     ^^^^^^^^^^^^^ expected `()`, found associated type
+   |
+   = note:    expected unit type `()`
+           found associated type `<D as Trait>::Associated`
+   = help: consider constraining the associated type `<D as Trait>::Associated` to `()`
+   = note: for more information, visit https://doc.rust-lang.org/book/ch19-03-advanced-traits.html
+
+error[E0271]: type mismatch resolving `<E as GenericTrait<()>>::Associated == ()`
+  --> $DIR/issue-87261.rs:68:5
+   |
+LL | fn accepts_generic_trait<T: GenericTrait<(), Associated = ()>>(_: T) {}
+   |                                              --------------- required by this bound in `accepts_generic_trait`
+...
+LL |     accepts_generic_trait(e);
+   |     ^^^^^^^^^^^^^^^^^^^^^ expected `()`, found associated type
+   |
+   = note:    expected unit type `()`
+           found associated type `<E as GenericTrait<()>>::Associated`
+help: consider constraining the associated type `<E as GenericTrait<()>>::Associated` to `()`
+   |
+LL |     E: GenericTrait<(), Associated = ()> + 'static,
+   |                       ^^^^^^^^^^^^^^^^^
+
+error[E0271]: type mismatch resolving `<F as GenericTrait<()>>::Associated == ()`
+  --> $DIR/issue-87261.rs:71:5
+   |
+LL | fn accepts_generic_trait<T: GenericTrait<(), Associated = ()>>(_: T) {}
+   |                                              --------------- required by this bound in `accepts_generic_trait`
+...
+LL |     accepts_generic_trait(f);
+   |     ^^^^^^^^^^^^^^^^^^^^^ expected `()`, found associated type
+   |
+   = note:    expected unit type `()`
+           found associated type `<F as GenericTrait<()>>::Associated`
+help: consider constraining the associated type `<F as GenericTrait<()>>::Associated` to `()`
+   |
+LL |     F: GenericTrait<(), Associated = ()> + Foo,
+   |                       ^^^^^^^^^^^^^^^^^
+
+error[E0271]: type mismatch resolving `<G as GenericTrait<()>>::Associated == ()`
+  --> $DIR/issue-87261.rs:74:5
+   |
+LL | fn accepts_generic_trait<T: GenericTrait<(), Associated = ()>>(_: T) {}
+   |                                              --------------- required by this bound in `accepts_generic_trait`
+...
+LL |     accepts_generic_trait(g);
+   |     ^^^^^^^^^^^^^^^^^^^^^ expected `()`, found associated type
+   |
+   = note:    expected unit type `()`
+           found associated type `<G as GenericTrait<()>>::Associated`
+   = help: consider constraining the associated type `<G as GenericTrait<()>>::Associated` to `()`
+   = note: for more information, visit https://doc.rust-lang.org/book/ch19-03-advanced-traits.html
+
+error[E0271]: type mismatch resolving `<impl Trait as Trait>::Associated == ()`
+  --> $DIR/issue-87261.rs:79:5
+   |
+LL | fn returns_opaque() -> impl Trait + 'static {
+   |                        -------------------- the found opaque type
+...
+LL | fn accepts_trait<T: Trait<Associated = ()>>(_: T) {}
+   |                           --------------- required by this bound in `accepts_trait`
+...
+LL |     accepts_trait(returns_opaque());
+   |     ^^^^^^^^^^^^^ expected `()`, found associated type
+   |
+   = note:    expected unit type `()`
+           found associated type `<impl Trait as Trait>::Associated`
+help: consider constraining the associated type `<impl Trait as Trait>::Associated` to `()`
+   |
+LL | fn returns_opaque() -> impl Trait<Associated = ()> + 'static {
+   |                                  ^^^^^^^^^^^^^^^^^
+
+error[E0271]: type mismatch resolving `<impl DerivedTrait as Trait>::Associated == ()`
+  --> $DIR/issue-87261.rs:82:5
+   |
+LL | fn returns_opaque_derived() -> impl DerivedTrait + 'static {
+   |                                --------------------------- the found opaque type
+...
+LL | fn accepts_trait<T: Trait<Associated = ()>>(_: T) {}
+   |                           --------------- required by this bound in `accepts_trait`
+...
+LL |     accepts_trait(returns_opaque_derived());
+   |     ^^^^^^^^^^^^^ expected `()`, found associated type
+   |
+   = note:    expected unit type `()`
+           found associated type `<impl DerivedTrait as Trait>::Associated`
+help: consider constraining the associated type `<impl DerivedTrait as Trait>::Associated` to `()`
+   |
+LL | fn returns_opaque_derived() -> impl DerivedTrait<Associated = ()> + 'static {
+   |                                                 ^^^^^^^^^^^^^^^^^
+
+error[E0271]: type mismatch resolving `<impl Trait+Foo as Trait>::Associated == ()`
+  --> $DIR/issue-87261.rs:85:5
+   |
+LL | fn returns_opaque_foo() -> impl Trait + Foo {
+   |                            ---------------- the found opaque type
+...
+LL | fn accepts_trait<T: Trait<Associated = ()>>(_: T) {}
+   |                           --------------- required by this bound in `accepts_trait`
+...
+LL |     accepts_trait(returns_opaque_foo());
+   |     ^^^^^^^^^^^^^ expected `()`, found associated type
+   |
+   = note:    expected unit type `()`
+           found associated type `<impl Trait+Foo as Trait>::Associated`
+help: consider constraining the associated type `<impl Trait+Foo as Trait>::Associated` to `()`
+   |
+LL | fn returns_opaque_foo() -> impl Trait<Associated = ()> + Foo {
+   |                                      ^^^^^^^^^^^^^^^^^
+
+error[E0271]: type mismatch resolving `<impl DerivedTrait+Foo as Trait>::Associated == ()`
+  --> $DIR/issue-87261.rs:88:5
+   |
+LL | fn returns_opaque_derived_foo() -> impl DerivedTrait + Foo {
+   |                                    ----------------------- the found opaque type
+...
+LL | fn accepts_trait<T: Trait<Associated = ()>>(_: T) {}
+   |                           --------------- required by this bound in `accepts_trait`
+...
+LL |     accepts_trait(returns_opaque_derived_foo());
+   |     ^^^^^^^^^^^^^ expected `()`, found associated type
+   |
+   = note:    expected unit type `()`
+           found associated type `<impl DerivedTrait+Foo as Trait>::Associated`
+   = help: consider constraining the associated type `<impl DerivedTrait+Foo as Trait>::Associated` to `()`
+   = note: for more information, visit https://doc.rust-lang.org/book/ch19-03-advanced-traits.html
+
+error[E0271]: type mismatch resolving `<impl GenericTrait<()> as GenericTrait<()>>::Associated == ()`
+  --> $DIR/issue-87261.rs:91:5
+   |
+LL | fn returns_opaque_generic() -> impl GenericTrait<()> + 'static {
+   |                                ------------------------------- the found opaque type
+...
+LL | fn accepts_generic_trait<T: GenericTrait<(), Associated = ()>>(_: T) {}
+   |                                              --------------- required by this bound in `accepts_generic_trait`
+...
+LL |     accepts_generic_trait(returns_opaque_generic());
+   |     ^^^^^^^^^^^^^^^^^^^^^ expected `()`, found associated type
+   |
+   = note:    expected unit type `()`
+           found associated type `<impl GenericTrait<()> as GenericTrait<()>>::Associated`
+help: consider constraining the associated type `<impl GenericTrait<()> as GenericTrait<()>>::Associated` to `()`
+   |
+LL | fn returns_opaque_generic() -> impl GenericTrait<(), Associated = ()> + 'static {
+   |                                                    ^^^^^^^^^^^^^^^^^
+
+error[E0271]: type mismatch resolving `<impl GenericTrait<()>+Foo as GenericTrait<()>>::Associated == ()`
+  --> $DIR/issue-87261.rs:94:5
+   |
+LL | fn returns_opaque_generic_foo() -> impl GenericTrait<()> + Foo {
+   |                                    --------------------------- the found opaque type
+...
+LL | fn accepts_generic_trait<T: GenericTrait<(), Associated = ()>>(_: T) {}
+   |                                              --------------- required by this bound in `accepts_generic_trait`
+...
+LL |     accepts_generic_trait(returns_opaque_generic_foo());
+   |     ^^^^^^^^^^^^^^^^^^^^^ expected `()`, found associated type
+   |
+   = note:    expected unit type `()`
+           found associated type `<impl GenericTrait<()>+Foo as GenericTrait<()>>::Associated`
+help: consider constraining the associated type `<impl GenericTrait<()>+Foo as GenericTrait<()>>::Associated` to `()`
+   |
+LL | fn returns_opaque_generic_foo() -> impl GenericTrait<(), Associated = ()> + Foo {
+   |                                                        ^^^^^^^^^^^^^^^^^
+
+error[E0271]: type mismatch resolving `<impl GenericTrait<()>+GenericTrait<u8> as GenericTrait<()>>::Associated == ()`
+  --> $DIR/issue-87261.rs:97:5
+   |
+LL | fn returns_opaque_generic_duplicate() -> impl GenericTrait<()> + GenericTrait<u8> {
+   |                                          ---------------------------------------- the found opaque type
+...
+LL | fn accepts_generic_trait<T: GenericTrait<(), Associated = ()>>(_: T) {}
+   |                                              --------------- required by this bound in `accepts_generic_trait`
+...
+LL |     accepts_generic_trait(returns_opaque_generic_duplicate());
+   |     ^^^^^^^^^^^^^^^^^^^^^ expected `()`, found associated type
+   |
+   = note:    expected unit type `()`
+           found associated type `<impl GenericTrait<()>+GenericTrait<u8> as GenericTrait<()>>::Associated`
+   = help: consider constraining the associated type `<impl GenericTrait<()>+GenericTrait<u8> as GenericTrait<()>>::Associated` to `()`
+   = note: for more information, visit https://doc.rust-lang.org/book/ch19-03-advanced-traits.html
+
+error: aborting due to 14 previous errors
+
+For more information about this error, try `rustc --explain E0271`.
diff --git a/src/test/ui/crate-loading/missing-std.rs b/src/test/ui/crate-loading/missing-std.rs
index de4ccc18560..1a34c21ba54 100644
--- a/src/test/ui/crate-loading/missing-std.rs
+++ b/src/test/ui/crate-loading/missing-std.rs
@@ -1,7 +1,6 @@
 // compile-flags: --target x86_64-unknown-uefi
 // needs-llvm-components: x86
 // rustc-env:CARGO=/usr/bin/cargo
-// rustc-env:RUSTUP_HOME=/home/bors/.rustup
 #![no_core]
 extern crate core;
 //~^ ERROR can't find crate for `core`
diff --git a/src/test/ui/crate-loading/missing-std.stderr b/src/test/ui/crate-loading/missing-std.stderr
index e61486fdc6f..25808efdfa6 100644
--- a/src/test/ui/crate-loading/missing-std.stderr
+++ b/src/test/ui/crate-loading/missing-std.stderr
@@ -1,5 +1,5 @@
 error[E0463]: can't find crate for `core`
-  --> $DIR/missing-std.rs:6:1
+  --> $DIR/missing-std.rs:5:1
    |
 LL | extern crate core;
    | ^^^^^^^^^^^^^^^^^^ can't find crate
diff --git a/src/test/ui/issues/issue-37131.stderr b/src/test/ui/issues/issue-37131.stderr
index 660a6935f36..b45574f0c49 100644
--- a/src/test/ui/issues/issue-37131.stderr
+++ b/src/test/ui/issues/issue-37131.stderr
@@ -1,6 +1,8 @@
 error[E0463]: can't find crate for `std`
    |
    = note: the `thumbv6m-none-eabi` target may not be installed
+   = help: consider downloading the target with `rustup target add thumbv6m-none-eabi`
+   = help: consider building the standard library from source with `cargo build -Zbuild-std`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/issues/issue-49851/compiler-builtins-error.stderr b/src/test/ui/issues/issue-49851/compiler-builtins-error.stderr
index 7e23e0fd747..d963c07ea91 100644
--- a/src/test/ui/issues/issue-49851/compiler-builtins-error.stderr
+++ b/src/test/ui/issues/issue-49851/compiler-builtins-error.stderr
@@ -1,6 +1,8 @@
 error[E0463]: can't find crate for `core`
    |
    = note: the `thumbv7em-none-eabihf` target may not be installed
+   = help: consider downloading the target with `rustup target add thumbv7em-none-eabihf`
+   = help: consider building the standard library from source with `cargo build -Zbuild-std`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/union/union-unsafe.rs b/src/test/ui/union/union-unsafe.rs
index e8414903d54..3cb3a18cb75 100644
--- a/src/test/ui/union/union-unsafe.rs
+++ b/src/test/ui/union/union-unsafe.rs
@@ -36,8 +36,8 @@ fn deref_union_field(mut u: URef) {
 
 fn assign_noncopy_union_field(mut u: URefCell) {
     // FIXME(thir-unsafeck)
-    u.a = (RefCell::new(0), 1); //[mir]~ ERROR assignment to union field that might need dropping
-    u.a.0 = RefCell::new(0); //[mir]~ ERROR assignment to union field that might need dropping
+    u.a = (RefCell::new(0), 1); //~ ERROR assignment to union field that might need dropping
+    u.a.0 = RefCell::new(0); //~ ERROR assignment to union field that might need dropping
     u.a.1 = 1; // OK
 }
 
diff --git a/src/test/ui/union/union-unsafe.thir.stderr b/src/test/ui/union/union-unsafe.thir.stderr
index 51f19879c81..e88642b0ff7 100644
--- a/src/test/ui/union/union-unsafe.thir.stderr
+++ b/src/test/ui/union/union-unsafe.thir.stderr
@@ -6,6 +6,22 @@ LL |     *(u.p) = 13;
    |
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
+error[E0133]: assignment to union field that might need dropping is unsafe and requires unsafe function or block
+  --> $DIR/union-unsafe.rs:39:5
+   |
+LL |     u.a = (RefCell::new(0), 1);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^ assignment to union field that might need dropping
+   |
+   = note: the previous content of the field will be dropped, which causes undefined behavior if the field was not properly initialized
+
+error[E0133]: assignment to union field that might need dropping is unsafe and requires unsafe function or block
+  --> $DIR/union-unsafe.rs:40:5
+   |
+LL |     u.a.0 = RefCell::new(0);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^ assignment to union field that might need dropping
+   |
+   = note: the previous content of the field will be dropped, which causes undefined behavior if the field was not properly initialized
+
 error[E0133]: access to union field is unsafe and requires unsafe function or block
   --> $DIR/union-unsafe.rs:47:6
    |
@@ -70,6 +86,6 @@ LL |     *u3.a = String::from("new");
    |
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
-error: aborting due to 9 previous errors
+error: aborting due to 11 previous errors
 
 For more information about this error, try `rustc --explain E0133`.