error[E0015]: cannot call non-const closure in constants --> $DIR/issue-68542-closure-in-array-len.rs:6:13 | LL | a: [(); (|| { 0 })()] | ^^^^^^^^^^^^ | = note: closures need an RFC before allowed to be called in constants = note: calls in constants are limited to constant functions, tuple structs and tuple variants error: aborting due to previous error For more information about this error, try `rustc --explain E0015`.