Constexpr is a feature found in statically compiled programming languages that allows evaluation of expressions in a program at compile time. Different languages have different terminology for it. For example, in zig lang, it's called comptime. Common lisp macros, in lisps that compile to native code, might also be grouped in this category.
This feature allows automatic generation of complex static data at compile time, and the runtime code can just use the result of compile time evaluated data. Variable inlining is a simple form of compile time evaluation. Ideally, the language/compiler should allow the users to turn any eligible piece of code "constexpr" with some annotations. The eligibility criteria being that the code must not depend on any runtime data.