//! `#![feature(unsized_fn_params)]` lets you use unsized function parameters. In particular this //! is load bearing for `Box: FnOnce()`. To do that, borrowck relaxes the requirement //! that certain places must be `Sized`. But in #142911 we removed alloca support, so these //! arguments cannot be put in temporaries (or ICE at codegen) That means when `unsized_fn_params` //! is enabled, we must explicitly check that unsized function arguments are place expressions. //! //! Also see tests/ui/unsized_locals/unsized-exprs-rpass.rs #![feature(unsized_fn_params)] fn foo() -> Box<[u8]> { Box::new(*b"foo") } fn udrop(_x: T) {} fn main(){ // NB The ordering of the following operations matters, otherwise errors get swallowed somehow. udrop::<[u8]>(if true { *foo() } else { *foo() }); //~ERROR the size for values of type `[u8]` cannot be known at compilation time udrop::<[u8]>({ *foo() }); //~ERROR the size for values of type `[u8]` cannot be known at compilation time udrop(match foo() { x => *x }); //~ERROR the size for values of type `[u8]` cannot be known at compilation time udrop::<[u8]>({ loop { break *foo(); } }); //~ERROR the size for values of type `[u8]` cannot be known at compilation time { *foo() }; //~ERROR the size for values of type `[u8]` cannot be known at compilation time { loop { break *foo(); } }; //~ERROR the size for values of type `[u8]` cannot be known at compilation time }