Lift some Sized checks.

src/test/ui/associated-types/associated-types-unsized.stderr

@@ -8,6 +8,7 @@ LL |     let x = t.get(); //~ ERROR the size for values of type
    = note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
    = help: consider adding a `where <T as Get>::Value: std::marker::Sized` bound
    = note: all local variables must have a statically known size
+   = help: unsized locals are gated as an unstable feature
 
 error: aborting due to previous error
 

src/test/ui/error-codes/E0277.stderr

@@ -8,6 +8,7 @@ LL | fn f(p: Path) { }
    = note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
    = note: required because it appears within the type `std::path::Path`
    = note: all local variables must have a statically known size
+   = help: unsized locals are gated as an unstable feature
 
 error[E0277]: the trait bound `i32: Foo` is not satisfied
   --> $DIR/E0277.rs:27:5

src/test/ui/feature-gate-unsized_locals.stderr

@@ -7,6 +7,7 @@ LL | fn f(f: FnOnce()) {}
    = help: the trait `std::marker::Sized` is not implemented for `(dyn std::ops::FnOnce() + 'static)`
    = note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
    = note: all local variables must have a statically known size
+   = help: unsized locals are gated as an unstable feature
 
 error: aborting due to previous error
 

src/test/ui/issues/issue-15756.stderr

@@ -7,6 +7,7 @@ LL |     &mut something
    = help: the trait `std::marker::Sized` is not implemented for `[T]`
    = note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
    = note: all local variables must have a statically known size
+   = help: unsized locals are gated as an unstable feature
 
 error: aborting due to previous error
 

src/test/ui/issues/issue-27078.stderr

@@ -8,6 +8,7 @@ LL |     fn foo(self) -> &'static i32 {
    = note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
    = help: consider adding a `where Self: std::marker::Sized` bound
    = note: all local variables must have a statically known size
+   = help: unsized locals are gated as an unstable feature
 
 error: aborting due to previous error
 

src/test/ui/issues/issue-38954.stderr

@@ -7,6 +7,7 @@ LL | fn _test(ref _p: str) {}
    = help: the trait `std::marker::Sized` is not implemented for `str`
    = note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
    = note: all function arguments must have a statically known size
+   = help: unsized locals are gated as an unstable feature
 
 error: aborting due to previous error
 

src/test/ui/issues/issue-41229-ref-str.stderr

@@ -7,6 +7,7 @@ LL | pub fn example(ref s: str) {}
    = help: the trait `std::marker::Sized` is not implemented for `str`
    = note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
    = note: all function arguments must have a statically known size
+   = help: unsized locals are gated as an unstable feature
 
 error: aborting due to previous error
 

src/test/ui/issues/issue-42312.stderr

@@ -8,6 +8,7 @@ LL |     fn baz(_: Self::Target) where Self: Deref {}
    = note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
    = help: consider adding a `where <Self as std::ops::Deref>::Target: std::marker::Sized` bound
    = note: all function arguments must have a statically known size
+   = help: unsized locals are gated as an unstable feature
 
 error[E0277]: the size for values of type `(dyn std::string::ToString + 'static)` cannot be known at compilation time
   --> $DIR/issue-42312.rs:18:23
@@ -18,6 +19,7 @@ LL | pub fn f(_: ToString) {}
    = help: the trait `std::marker::Sized` is not implemented for `(dyn std::string::ToString + 'static)`
    = note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
    = note: all function arguments must have a statically known size
+   = help: unsized locals are gated as an unstable feature
 
 error: aborting due to 2 previous errors
 

src/test/ui/issues/issue-5883.stderr

@@ -7,6 +7,7 @@ LL | fn new_struct(r: A+'static)
    = help: the trait `std::marker::Sized` is not implemented for `(dyn A + 'static)`
    = note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
    = note: all local variables must have a statically known size
+   = help: unsized locals are gated as an unstable feature
 
 error[E0277]: the size for values of type `(dyn A + 'static)` cannot be known at compilation time
   --> $DIR/issue-5883.rs:18:8

src/test/ui/resolve/issue-5035-2.stderr

@@ -7,6 +7,7 @@ LL | fn foo(_x: K) {}
    = help: the trait `std::marker::Sized` is not implemented for `(dyn I + 'static)`
    = note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
    = note: all local variables must have a statically known size
+   = help: unsized locals are gated as an unstable feature
 
 error: aborting due to previous error
 

src/test/ui/str/str-array-assignment.stderr

@@ -30,6 +30,7 @@ LL |   let v = s[..2];
    = help: the trait `std::marker::Sized` is not implemented for `str`
    = note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
    = note: all local variables must have a statically known size
+   = help: unsized locals are gated as an unstable feature
 
 error[E0308]: mismatched types
   --> $DIR/str-array-assignment.rs:19:17

src/test/ui/traits/trait-bounds-not-on-bare-trait.stderr

@@ -7,6 +7,7 @@ LL | fn foo(_x: Foo + Send) {
    = help: the trait `std::marker::Sized` is not implemented for `(dyn Foo + std::marker::Send + 'static)`
    = note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
    = note: all local variables must have a statically known size
+   = help: unsized locals are gated as an unstable feature
 
 error: aborting due to previous error
 

src/test/ui/unsized6.stderr

@@ -8,6 +8,7 @@ LL |     let y: Y;
    = note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
    = help: consider adding a `where Y: std::marker::Sized` bound
    = note: all local variables must have a statically known size
+   = help: unsized locals are gated as an unstable feature
 
 error[E0277]: the size for values of type `X` cannot be known at compilation time
   --> $DIR/unsized6.rs:17:12
@@ -41,6 +42,7 @@ LL |     let y: X;
    = note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
    = help: consider adding a `where X: std::marker::Sized` bound
    = note: all local variables must have a statically known size
+   = help: unsized locals are gated as an unstable feature
 
 error[E0277]: the size for values of type `Y` cannot be known at compilation time
   --> $DIR/unsized6.rs:27:12
@@ -63,6 +65,7 @@ LL |     let y: X = *x1;
    = note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
    = help: consider adding a `where X: std::marker::Sized` bound
    = note: all local variables must have a statically known size
+   = help: unsized locals are gated as an unstable feature
 
 error[E0277]: the size for values of type `X` cannot be known at compilation time
   --> $DIR/unsized6.rs:34:9
@@ -74,6 +77,7 @@ LL |     let y = *x2;
    = note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
    = help: consider adding a `where X: std::marker::Sized` bound
    = note: all local variables must have a statically known size
+   = help: unsized locals are gated as an unstable feature
 
 error[E0277]: the size for values of type `X` cannot be known at compilation time
   --> $DIR/unsized6.rs:36:10
@@ -85,6 +89,7 @@ LL |     let (y, z) = (*x3, 4);
    = note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
    = help: consider adding a `where X: std::marker::Sized` bound
    = note: all local variables must have a statically known size
+   = help: unsized locals are gated as an unstable feature
 
 error[E0277]: the size for values of type `X` cannot be known at compilation time
   --> $DIR/unsized6.rs:40:9
@@ -96,6 +101,7 @@ LL |     let y: X = *x1;
    = note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
    = help: consider adding a `where X: std::marker::Sized` bound
    = note: all local variables must have a statically known size
+   = help: unsized locals are gated as an unstable feature
 
 error[E0277]: the size for values of type `X` cannot be known at compilation time
   --> $DIR/unsized6.rs:42:9
@@ -107,6 +113,7 @@ LL |     let y = *x2;
    = note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
    = help: consider adding a `where X: std::marker::Sized` bound
    = note: all local variables must have a statically known size
+   = help: unsized locals are gated as an unstable feature
 
 error[E0277]: the size for values of type `X` cannot be known at compilation time
   --> $DIR/unsized6.rs:44:10
@@ -118,6 +125,7 @@ LL |     let (y, z) = (*x3, 4);
    = note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
    = help: consider adding a `where X: std::marker::Sized` bound
    = note: all local variables must have a statically known size
+   = help: unsized locals are gated as an unstable feature
 
 error[E0277]: the size for values of type `X` cannot be known at compilation time
   --> $DIR/unsized6.rs:48:18
@@ -129,6 +137,7 @@ LL | fn g1<X: ?Sized>(x: X) {}
    = note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
    = help: consider adding a `where X: std::marker::Sized` bound
    = note: all local variables must have a statically known size
+   = help: unsized locals are gated as an unstable feature
 
 error[E0277]: the size for values of type `X` cannot be known at compilation time
   --> $DIR/unsized6.rs:50:22
@@ -140,6 +149,7 @@ LL | fn g2<X: ?Sized + T>(x: X) {}
    = note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
    = help: consider adding a `where X: std::marker::Sized` bound
    = note: all local variables must have a statically known size
+   = help: unsized locals are gated as an unstable feature
 
 error: aborting due to 13 previous errors