error: invalid `?` in type
  --> $DIR/issue-103748-ICE-wrong-braces.rs:3:36
   |
LL | struct Apple((Apple, Option(Banana ? Citron)));
   |                                    ^ `?` is only allowed on expressions, not types
   |
help: if you meant to express that the type might not contain a value, use the `Option` wrapper type
   |
LL | struct Apple((Apple, Option(Option<Banana > Citron)));
   |                             +++++++       ~

error: expected one of `)` or `,`, found `Citron`
  --> $DIR/issue-103748-ICE-wrong-braces.rs:3:38
   |
LL | struct Apple((Apple, Option(Banana ? Citron)));
   |                                     -^^^^^^ expected one of `)` or `,`
   |                                     |
   |                                     help: missing `,`

error[E0412]: cannot find type `Citron` in this scope
  --> $DIR/issue-103748-ICE-wrong-braces.rs:3:38
   |
LL | struct Apple((Apple, Option(Banana ? Citron)));
   |                                      ^^^^^^ not found in this scope

error[E0214]: parenthesized type parameters may only be used with a `Fn` trait
  --> $DIR/issue-103748-ICE-wrong-braces.rs:3:22
   |
LL | struct Apple((Apple, Option(Banana ? Citron)));
   |                      ^^^^^^^^^^^^^^^^^^^^^^^ only `Fn` traits may use parentheses
   |
help: use angle brackets instead
   |
LL | struct Apple((Apple, Option<Banana ? Citron>));
   |                            ~               ~

error: aborting due to 4 previous errors

Some errors have detailed explanations: E0214, E0412.
For more information about an error, try `rustc --explain E0214`.