error[E0015]: cannot call non-const fn `<() as Foo>::foo` in constant functions --> $DIR/non-const-op-const-closure-non-const-outer.rs:13:22 | LL | (const || { (()).foo() })(); | ^^^^^ | = note: calls in constant functions are limited to constant functions, tuple structs and tuple variants = help: add `#![feature(effects)]` to the crate attributes to enable error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0015`.