alt Hacker NewsGenuine question, does Rust know if `expensive_to_compute()` has side effects? There are no params, so could it be compiled out if the return value is ignored? Ex: `expensive_to_compute()` What about: `(void) expensive_to_compute()`?
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IshKebab • today at 8:16 AM
No, Rust is the same as C++ in terms of tracking side effects. It doesn't matter that there are no parameters. It could manipulate globals or call other functions that have side effects (e.g. printing).
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No, in general Rust doesn't (and can't) know whether an arbitrary function has side effects. The compiler does arguably have a leg up since Rust code is typically all built from source, but there's still things like FFI that act as visibility barriers for the compiler.