error[E0391]: cycle detected when computing type of `foo::{opaque#0}`
  --> $DIR/in-defining-scope.rs:6:13
   |
LL | fn foo() -> impl Sized {
   |             ^^^^^^^^^^
   |
note: ...which requires computing type of opaque `foo::{opaque#0}`...
  --> $DIR/in-defining-scope.rs:6:13
   |
LL | fn foo() -> impl Sized {
   |             ^^^^^^^^^^
note: ...which requires type-checking `foo`...
  --> $DIR/in-defining-scope.rs:6:1
   |
LL | fn foo() -> impl Sized {
   | ^^^^^^^^^^^^^^^^^^^^^^
   = note: ...which requires computing layout of `foo::{opaque#0}`...
   = note: ...which requires normalizing `foo::{opaque#0}`...
   = note: ...which again requires computing type of `foo::{opaque#0}`, completing the cycle
note: cycle used when checking that `foo::{opaque#0}` is well-formed
  --> $DIR/in-defining-scope.rs:6:13
   |
LL | fn foo() -> impl Sized {
   |             ^^^^^^^^^^
   = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information

warning: function cannot return without recursing
  --> $DIR/in-defining-scope.rs:6:1
   |
LL | fn foo() -> impl Sized {
   | ^^^^^^^^^^^^^^^^^^^^^^ cannot return without recursing
...
LL |         transmute::<_, u8>(foo());
   |                            ----- recursive call site
   |
   = help: a `loop` may express intention better if this is on purpose
   = note: `#[warn(unconditional_recursion)]` on by default

error: aborting due to 1 previous error; 1 warning emitted

For more information about this error, try `rustc --explain E0391`.