The compiler is smart enough to deduce lifetimes — that’s why it can throw a compile error — but fixing them (auto-keeping temporaries) might introduce extra memory consumption/leaks that the programmer did not intend. Requiring the programmer to explicitly assign a temporary to a variable makes the programmer’s intent more clear.

A comparison: in C++, the behavior of auto-extending the lifetime of const references to temporaries (but not non-const references) is considered a wart in the language design. (Really, you should just assign a temporary to a value because the compiler can elide the copy. : https://abseil.io/tips/101 .)