error[E0277]: the size for values of type `U` cannot be known at compilation time
  --> $DIR/suggest-where-clause.rs:7:20
   |
LL | fn check<T: Iterator, U: ?Sized>() {
   |                       - this type parameter needs to be `Sized`
LL |     // suggest a where-clause, if needed
LL |     mem::size_of::<U>();
   |                    ^ doesn't have a size known at compile-time
   |
note: required by an implicit `Sized` bound in `std::mem::size_of`
  --> $SRC_DIR/core/src/mem/mod.rs:LL:COL
help: consider removing the `?Sized` bound to make the type parameter `Sized`
   |
LL - fn check<T: Iterator, U: ?Sized>() {
LL + fn check<T: Iterator, U>() {
   |

error[E0277]: the size for values of type `U` cannot be known at compilation time
  --> $DIR/suggest-where-clause.rs:10:20
   |
LL | fn check<T: Iterator, U: ?Sized>() {
   |                       - this type parameter needs to be `Sized`
...
LL |     mem::size_of::<Misc<U>>();
   |                    ^^^^^^^ doesn't have a size known at compile-time
   |
note: required because it appears within the type `Misc<U>`
  --> $DIR/suggest-where-clause.rs:3:8
   |
LL | struct Misc<T:?Sized>(T);
   |        ^^^^
note: required by an implicit `Sized` bound in `std::mem::size_of`
  --> $SRC_DIR/core/src/mem/mod.rs:LL:COL
help: consider removing the `?Sized` bound to make the type parameter `Sized`
   |
LL - fn check<T: Iterator, U: ?Sized>() {
LL + fn check<T: Iterator, U>() {
   |

error[E0277]: the trait bound `u64: From<T>` is not satisfied
  --> $DIR/suggest-where-clause.rs:15:6
   |
LL |     <u64 as From<T>>::from;
   |      ^^^ the trait `From<T>` is not implemented for `u64`
   |
help: consider introducing a `where` clause, but there might be an alternative better way to express this requirement
   |
LL | fn check<T: Iterator, U: ?Sized>() where u64: From<T> {
   |                                    ++++++++++++++++++

error[E0277]: the trait bound `u64: From<<T as Iterator>::Item>` is not satisfied
  --> $DIR/suggest-where-clause.rs:18:6
   |
LL |     <u64 as From<<T as Iterator>::Item>>::from;
   |      ^^^ the trait `From<<T as Iterator>::Item>` is not implemented for `u64`
   |
help: consider introducing a `where` clause, but there might be an alternative better way to express this requirement
   |
LL | fn check<T: Iterator, U: ?Sized>() where u64: From<<T as Iterator>::Item> {
   |                                    ++++++++++++++++++++++++++++++++++++++

error[E0277]: the trait bound `Misc<_>: From<T>` is not satisfied
  --> $DIR/suggest-where-clause.rs:23:6
   |
LL |     <Misc<_> as From<T>>::from;
   |      ^^^^^^^ the trait `From<T>` is not implemented for `Misc<_>`

error[E0277]: the size for values of type `[T]` cannot be known at compilation time
  --> $DIR/suggest-where-clause.rs:28:20
   |
LL |     mem::size_of::<[T]>();
   |                    ^^^ doesn't have a size known at compile-time
   |
   = help: the trait `Sized` is not implemented for `[T]`
note: required by an implicit `Sized` bound in `std::mem::size_of`
  --> $SRC_DIR/core/src/mem/mod.rs:LL:COL

error[E0277]: the size for values of type `[&U]` cannot be known at compilation time
  --> $DIR/suggest-where-clause.rs:31:20
   |
LL |     mem::size_of::<[&U]>();
   |                    ^^^^ doesn't have a size known at compile-time
   |
   = help: the trait `Sized` is not implemented for `[&U]`
note: required by an implicit `Sized` bound in `std::mem::size_of`
  --> $SRC_DIR/core/src/mem/mod.rs:LL:COL

error: aborting due to 7 previous errors

For more information about this error, try `rustc --explain E0277`.