Rollup merge of rust-lang#86011 - tlyu:correct-sized-bound-spans, r=e…

…stebank

move implicit `Sized` predicate to end of list

In `Bounds::predicates()`, move the implicit `Sized` predicate to the
end of the generated list. This means that if there is an explicit
`Sized` bound, it will be checked first, and any resulting
diagnostics will have a more useful span.

Fixes rust-lang#85998, at least partially. ~~Based on rust-lang#85979, but only the last 2 commits are new for this pull request.~~ (edit: rebased) A full fix would need to deal with where-clauses, and that seems difficult. Basically, predicates are being collected in multiple stages, and there are two places where implicit `Sized` predicates can be inserted: once for generic parameters, and once for where-clauses. I think this insertion is happening too early, and we should actually do it only at points where we collect all of the relevant trait bounds for a type parameter.

I could use some help interpreting the changes to the stderr output. It looks like reordering the predicates changed some diagnostics that don't obviously have anything to do with `Sized` bounds. Possibly some error reporting code is making assumptions about ordering of predicates? The diagnostics for src/test/ui/derives/derives-span-Hash-*.rs seem to have improved, no longer pointing at the type parameter identifier, but src/test/ui/type-alias-impl-trait/generic_duplicate_param_use9.rs became less verbose for some reason.

I also ran into an instance of rust-lang#84970 while working on this, but I kind of expected that could happen, because I'm reordering predicates. I can open a separate issue on that if it would be helpful.

`@estebank` this seems likely to conflict (slightly?) with your work on rust-lang#85947; how would you like to resolve that?

compiler/rustc_typeck/src/bounds.rs

@@ -64,16 +64,16 @@ impl<'tcx> Bounds<'tcx> {
             })
         });
 
-        sized_predicate
-            .into_iter()
-            .chain(self.region_bounds.iter().map(|&(region_bound, span)| {
+        self.region_bounds
+            .iter()
+            .map(|&(region_bound, span)| {
                 (
                     region_bound
                         .map_bound(|region_bound| ty::OutlivesPredicate(param_ty, region_bound))
                         .to_predicate(tcx),
                     span,
                 )
-            }))
+            })
             .chain(self.trait_bounds.iter().map(|&(bound_trait_ref, span, constness)| {
                 let predicate = bound_trait_ref.with_constness(constness).to_predicate(tcx);
                 (predicate, span)
@@ -83,6 +83,7 @@ impl<'tcx> Bounds<'tcx> {
                     .iter()
                     .map(|&(projection, span)| (projection.to_predicate(tcx), span)),
             )
+            .chain(sized_predicate.into_iter())
             .collect()
     }
 }

src/test/ui/derives/derives-span-Hash-enum-struct-variant.stderr

@@ -11,7 +11,7 @@ note: required by a bound in `std::hash::Hash::hash`
   --> $SRC_DIR/core/src/hash/mod.rs:LL:COL
    |
 LL |     fn hash<H: Hasher>(&self, state: &mut H);
-   |             ^ required by this bound in `std::hash::Hash::hash`
+   |                ^^^^^^ required by this bound in `std::hash::Hash::hash`
    = note: this error originates in the derive macro `Hash` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to previous error

src/test/ui/derives/derives-span-Hash-enum.stderr

@@ -11,7 +11,7 @@ note: required by a bound in `std::hash::Hash::hash`
   --> $SRC_DIR/core/src/hash/mod.rs:LL:COL
    |
 LL |     fn hash<H: Hasher>(&self, state: &mut H);
-   |             ^ required by this bound in `std::hash::Hash::hash`
+   |                ^^^^^^ required by this bound in `std::hash::Hash::hash`
    = note: this error originates in the derive macro `Hash` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to previous error

src/test/ui/derives/derives-span-Hash-struct.stderr

@@ -11,7 +11,7 @@ note: required by a bound in `std::hash::Hash::hash`
   --> $SRC_DIR/core/src/hash/mod.rs:LL:COL
    |
 LL |     fn hash<H: Hasher>(&self, state: &mut H);
-   |             ^ required by this bound in `std::hash::Hash::hash`
+   |                ^^^^^^ required by this bound in `std::hash::Hash::hash`
    = note: this error originates in the derive macro `Hash` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to previous error

src/test/ui/derives/derives-span-Hash-tuple-struct.stderr

@@ -11,7 +11,7 @@ note: required by a bound in `std::hash::Hash::hash`
   --> $SRC_DIR/core/src/hash/mod.rs:LL:COL
    |
 LL |     fn hash<H: Hasher>(&self, state: &mut H);
-   |             ^ required by this bound in `std::hash::Hash::hash`
+   |                ^^^^^^ required by this bound in `std::hash::Hash::hash`
    = note: this error originates in the derive macro `Hash` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to previous error

src/test/ui/generic-associated-types/issue-74816.stderr

@@ -1,34 +1,34 @@
-error[E0277]: the trait bound `Self: Trait1` is not satisfied
+error[E0277]: the size for values of type `Self` cannot be known at compilation time
   --> $DIR/issue-74816.rs:9:5
    |
 LL |     type Associated: Trait1 = Self;
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Trait1` is not implemented for `Self`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
    |
 note: required by a bound in `Trait2::Associated`
-  --> $DIR/issue-74816.rs:9:22
+  --> $DIR/issue-74816.rs:9:5
    |
 LL |     type Associated: Trait1 = Self;
-   |                      ^^^^^^ required by this bound in `Trait2::Associated`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `Trait2::Associated`
 help: consider further restricting `Self`
    |
-LL | trait Trait2: Trait1 {
-   |             ++++++++
+LL | trait Trait2: Sized {
+   |             +++++++
 
-error[E0277]: the size for values of type `Self` cannot be known at compilation time
+error[E0277]: the trait bound `Self: Trait1` is not satisfied
   --> $DIR/issue-74816.rs:9:5
    |
 LL |     type Associated: Trait1 = Self;
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Trait1` is not implemented for `Self`
    |
 note: required by a bound in `Trait2::Associated`
-  --> $DIR/issue-74816.rs:9:5
+  --> $DIR/issue-74816.rs:9:22
    |
 LL |     type Associated: Trait1 = Self;
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `Trait2::Associated`
+   |                      ^^^^^^ required by this bound in `Trait2::Associated`
 help: consider further restricting `Self`
    |
-LL | trait Trait2: Sized {
-   |             +++++++
+LL | trait Trait2: Trait1 {
+   |             ++++++++
 
 error: aborting due to 2 previous errors
 

src/test/ui/generic-associated-types/issue-86483.stderr

@@ -20,13 +20,13 @@ LL |     for<'a> T: 'a,
    |                ^^
 
 error[E0311]: the parameter type `T` may not live long enough
-  --> $DIR/issue-86483.rs:9:5
+  --> $DIR/issue-86483.rs:9:19
    |
 LL | pub trait IceIce<T>
    |                  - help: consider adding an explicit lifetime bound...: `T: 'a`
 ...
 LL |     type Ice<'v>: IntoIterator<Item = &'v T>;
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ...so that the type `T` will meet its required lifetime bounds...
+   |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^ ...so that the type `T` will meet its required lifetime bounds...
    |
 note: ...that is required by this bound
   --> $DIR/issue-86483.rs:7:16

src/test/ui/generics/issue-61631-default-type-param-can-reference-self-in-trait.stderr

@@ -6,10 +6,10 @@ LL | impl Tsized for () {}
    |
    = help: the trait `Sized` is not implemented for `[()]`
 note: required by a bound in `Tsized`
-  --> $DIR/issue-61631-default-type-param-can-reference-self-in-trait.rs:17:14
+  --> $DIR/issue-61631-default-type-param-can-reference-self-in-trait.rs:17:17
    |
 LL | trait Tsized<P: Sized = [Self]> {}
-   |              ^ required by this bound in `Tsized`
+   |                 ^^^^^ required by this bound in `Tsized`
 
 error: aborting due to previous error
 

src/test/ui/issues/issue-16966.stderr

@@ -1,11 +1,21 @@
-error[E0282]: type annotations needed
+error[E0283]: type annotations needed
   --> $DIR/issue-16966.rs:2:5
    |
 LL |     panic!(std::default::Default::default());
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot infer type for type parameter `M` declared on the function `begin_panic`
    |
+   = note: cannot satisfy `_: Any`
+note: required by a bound in `begin_panic`
+  --> $SRC_DIR/std/src/panicking.rs:LL:COL
+   |
+LL | pub fn begin_panic<M: Any + Send>(msg: M) -> ! {
+   |                       ^^^ required by this bound in `begin_panic`
    = note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
+help: consider specifying the type argument in the function call
+   |
+LL |         $crate::rt::begin_panic::<M>($msg)
+   |                                +++++
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0282`.
+For more information about this error, try `rustc --explain E0283`.

src/test/ui/issues/issue-21160.stderr

@@ -10,7 +10,7 @@ note: required by a bound in `std::hash::Hash::hash`
   --> $SRC_DIR/core/src/hash/mod.rs:LL:COL
    |
 LL |     fn hash<H: Hasher>(&self, state: &mut H);
-   |             ^ required by this bound in `std::hash::Hash::hash`
+   |                ^^^^^^ required by this bound in `std::hash::Hash::hash`
    = note: this error originates in the derive macro `Hash` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to previous error

src/test/ui/issues/issue-23122-2.stderr

@@ -1,4 +1,4 @@
-error[E0275]: overflow evaluating the requirement `<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<T as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next: Sized`
+error[E0275]: overflow evaluating the requirement `<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<T as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next: Next`
   --> $DIR/issue-23122-2.rs:9:17
    |
 LL |     type Next = <GetNext<T::Next> as Next>::Next;

src/test/ui/issues/issue-54954.stderr

@@ -12,10 +12,10 @@ LL | const ARR_LEN: usize = Tt::const_val::<[i8; 123]>();
    |
    = note: cannot satisfy `_: Tt`
 note: required by a bound in `Tt::const_val`
-  --> $DIR/issue-54954.rs:5:24
+  --> $DIR/issue-54954.rs:5:27
    |
 LL |     const fn const_val<T: Sized>() -> usize {
-   |                        ^ required by this bound in `Tt::const_val`
+   |                           ^^^^^ required by this bound in `Tt::const_val`
 
 error: aborting due to 2 previous errors
 

src/test/ui/rfc-2632-const-trait-impl/trait-where-clause.stderr

@@ -20,11 +20,11 @@ error[E0277]: the trait bound `T: Bar` is not satisfied
 LL |     T::c::<T>();
    |     ^^^^^^^^^ the trait `Bar` is not implemented for `T`
    |
-note: required by `Foo::c`
-  --> $DIR/trait-where-clause.rs:9:5
+note: required by a bound in `Foo::c`
+  --> $DIR/trait-where-clause.rs:9:10
    |
 LL |     fn c<T: ~const Bar>();
-   |     ^^^^^^^^^^^^^^^^^^^^^^
+   |          ^ required by this bound in `Foo::c`
 help: consider further restricting this bound
    |
 LL | const fn test1<T: ~const Foo + Bar + Bar>() {
@@ -52,11 +52,11 @@ error[E0277]: the trait bound `T: Bar` is not satisfied
 LL |     T::c::<T>();
    |     ^^^^^^^^^ the trait `Bar` is not implemented for `T`
    |
-note: required by `Foo::c`
-  --> $DIR/trait-where-clause.rs:9:5
+note: required by a bound in `Foo::c`
+  --> $DIR/trait-where-clause.rs:9:10
    |
 LL |     fn c<T: ~const Bar>();
-   |     ^^^^^^^^^^^^^^^^^^^^^^
+   |          ^ required by this bound in `Foo::c`
 help: consider further restricting this bound
    |
 LL | fn test3<T: Foo + Bar>() {

src/test/ui/suggestions/issue-84973-blacklist.stderr

@@ -49,10 +49,10 @@ LL |     f_sized(*ref_cl);
    |
    = help: the trait `Sized` is not implemented for `dyn Fn()`
 note: required by a bound in `f_sized`
-  --> $DIR/issue-84973-blacklist.rs:9:12
+  --> $DIR/issue-84973-blacklist.rs:9:15
    |
 LL | fn f_sized<T: Sized>(t: T) {}
-   |            ^ required by this bound in `f_sized`
+   |               ^^^^^ required by this bound in `f_sized`
 
 error[E0277]: `Rc<{integer}>` cannot be sent between threads safely
   --> $DIR/issue-84973-blacklist.rs:27:12

src/test/ui/suggestions/slice-issue-87994.stderr

@@ -1,4 +1,4 @@
-error[E0277]: the size for values of type `[i32]` cannot be known at compilation time
+error[E0277]: `[i32]` is not an iterator
   --> $DIR/slice-issue-87994.rs:3:12
    |
 LL |   for _ in v[1..] {
@@ -18,7 +18,7 @@ LL |   for _ in &v[1..] {
 LL |   for _ in &mut v[1..] {
    |            ++++
 
-error[E0277]: `[i32]` is not an iterator
+error[E0277]: the size for values of type `[i32]` cannot be known at compilation time
   --> $DIR/slice-issue-87994.rs:3:12
    |
 LL |   for _ in v[1..] {
@@ -38,7 +38,7 @@ LL |   for _ in &v[1..] {
 LL |   for _ in &mut v[1..] {
    |            ++++
 
-error[E0277]: the size for values of type `[K]` cannot be known at compilation time
+error[E0277]: `[K]` is not an iterator
   --> $DIR/slice-issue-87994.rs:11:13
    |
 LL |   for i2 in v2[1..] {
@@ -58,7 +58,7 @@ LL |   for i2 in &v2[1..] {
 LL |   for i2 in &mut v2[1..] {
    |             ++++
 
-error[E0277]: `[K]` is not an iterator
+error[E0277]: the size for values of type `[K]` cannot be known at compilation time
   --> $DIR/slice-issue-87994.rs:11:13
    |
 LL |   for i2 in v2[1..] {

src/test/ui/type-alias-impl-trait/generic_duplicate_param_use9.rs

@@ -5,7 +5,7 @@ use std::fmt::Debug;
 fn main() {}
 
 type Two<A, B> = impl Debug;
-//~^ ERROR the trait bound `A: Foo` is not satisfied in `(A, B, <A as Foo>::Bar)`
+//~^ ERROR the trait bound `A: Foo` is not satisfied
 //~| ERROR `A` doesn't implement `Debug`
 //~| ERROR `B` doesn't implement `Debug`
 

src/test/ui/type-alias-impl-trait/generic_duplicate_param_use9.stderr

@@ -10,18 +10,6 @@ note: previous use here
 LL | fn two<T: Debug + Foo, U: Debug>(t: T, u: U) -> Two<T, U> {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error[E0277]: the trait bound `A: Foo` is not satisfied in `(A, B, <A as Foo>::Bar)`
-  --> $DIR/generic_duplicate_param_use9.rs:7:18
-   |
-LL | type Two<A, B> = impl Debug;
-   |                  ^^^^^^^^^^ within `(A, B, <A as Foo>::Bar)`, the trait `Foo` is not implemented for `A`
-   |
-   = note: required because it appears within the type `(A, B, <A as Foo>::Bar)`
-help: consider restricting type parameter `A`
-   |
-LL | type Two<A: Foo, B> = impl Debug;
-   |           +++++
-
 error[E0277]: `A` doesn't implement `Debug`
   --> $DIR/generic_duplicate_param_use9.rs:7:18
    |
@@ -46,6 +34,18 @@ help: consider restricting type parameter `B`
 LL | type Two<A, B: std::fmt::Debug> = impl Debug;
    |              +++++++++++++++++
 
+error[E0277]: the trait bound `A: Foo` is not satisfied
+  --> $DIR/generic_duplicate_param_use9.rs:7:18
+   |
+LL | type Two<A, B> = impl Debug;
+   |                  ^^^^^^^^^^ the trait `Foo` is not implemented for `A`
+   |
+   = note: required because of the requirements on the impl of `Debug` for `(A, B, <A as Foo>::Bar)`
+help: consider restricting type parameter `A`
+   |
+LL | type Two<A: Foo, B> = impl Debug;
+   |           +++++
+
 error: aborting due to 4 previous errors
 
 For more information about this error, try `rustc --explain E0277`.

src/test/ui/unique-object-noncopyable.stderr

@@ -19,10 +19,10 @@ LL | | >(Unique<T>, A);
    | |________________- doesn't satisfy `Box<dyn Foo>: Clone`
    |
    = note: the following trait bounds were not satisfied:
-           `dyn Foo: Sized`
-           which is required by `Box<dyn Foo>: Clone`
            `dyn Foo: Clone`
            which is required by `Box<dyn Foo>: Clone`
+           `dyn Foo: Sized`
+           which is required by `Box<dyn Foo>: Clone`
 
 error: aborting due to previous error
 

src/test/ui/unsized/unsized-bare-typaram.stderr

@@ -7,10 +7,10 @@ LL | fn foo<T: ?Sized>() { bar::<T>() }
    |        this type parameter needs to be `std::marker::Sized`
    |
 note: required by a bound in `bar`
-  --> $DIR/unsized-bare-typaram.rs:1:8
+  --> $DIR/unsized-bare-typaram.rs:1:11
    |
 LL | fn bar<T: Sized>() { }
-   |        ^ required by this bound in `bar`
+   |           ^^^^^ required by this bound in `bar`
 help: consider removing the `?Sized` bound to make the type parameter `Sized`
    |
 LL - fn foo<T: ?Sized>() { bar::<T>() }

src/test/ui/unsized/unsized-struct.stderr

@@ -38,10 +38,10 @@ note: required because it appears within the type `Bar<T>`
 LL | struct Bar<T: ?Sized> { data: T }
    |        ^^^
 note: required by a bound in `is_sized`
-  --> $DIR/unsized-struct.rs:1:13
+  --> $DIR/unsized-struct.rs:1:15
    |
 LL | fn is_sized<T:Sized>() { }
-   |             ^ required by this bound in `is_sized`
+   |               ^^^^^ required by this bound in `is_sized`
 help: consider removing the `?Sized` bound to make the type parameter `Sized`
    |
 LL - fn bar2<T: ?Sized>() { is_sized::<Bar<T>>() }