Earlier quoted context omitted.
The Rust language knows nothing about the heap. The standard library does assume this, but it's not an inherent language issue. Most people who are in resource constrained environments won't be using the standard library anyway.
Rust also made the same mistake that Go did: it tried to appease the "exceptions are bad" crowd and ended up adding exceptions as an afterthought. I'm angry: Rust is merely good, but with a few early tweaks, it could have been great .
Rust does not have exceptions, not even in the limited capacity that Go sort-of has. It's legal for a Rust implementation to translate panics into aborts, which means that they cannot be relied upon as an error-handling mechanism. Furthermore, the means to halt unwinding in Rust exists only to prevent memory unsafety from occurring when Rust is embedded in another language via the C interface, because unwinding across an FFI boundary is undefined behavior. In fact the exact mechanism used in the aforementioned role has deliberately arbitrary restrictions placed upon it in order to prevent anyone from using it as a general-purpose error-handling mechanism. Finally, the prevailing Rust culture overwhelmingly discourages using anything other than Result for error handling, to such an extreme that I've never in all my days even seen anyone attempt to "catch" a panic as an error-recovery mechanism.