error[E0015]: cannot convert `std::ops::Range` into an iterator in constants --> $DIR/const-for.rs:5:14 | LL | for _ in 0..5 {} | ^^^^ | note: impl defined here, but it is not `const` --> $SRC_DIR/core/src/iter/traits/collect.rs:LL:COL = note: calls in constants are limited to constant functions, tuple structs and tuple variants help: add `#![feature(const_trait_impl)]` to the crate attributes to enable | LL + #![feature(const_trait_impl)] | error[E0015]: cannot call non-const fn ` as Iterator>::next` in constants --> $DIR/const-for.rs:5:14 | LL | for _ in 0..5 {} | ^^^^ | = note: calls in constants are limited to constant functions, tuple structs and tuple variants help: add `#![feature(const_trait_impl)]` to the crate attributes to enable | LL + #![feature(const_trait_impl)] | error: aborting due to 2 previous errors For more information about this error, try `rustc --explain E0015`.