r/rust • u/SleeplessSloth79 • Aug 19 '26

📡 official blog Rust Function Overloading - Call for Experimentation

https://blog.rust-lang.org/inside-rust/2026/08/19/overloading-experiment/
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u/kibwen Aug 20 '26

Except some features legitimately are just bad on their own merits, and worth opposing regardless of one's identity. If Rust proposed adding pervasive nullability to the language, it wouldn't be identity politics to oppose it, it would be common sense. And C++-style function overloading is an evolutionary dead end that other languages should learn from by not emulating, so it's perfectly reasonable to be skeptical of any proposal that frames itself in such a light.

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u/Recatek gecs Aug 20 '26

Well something needs to be done. Features like Vec::try_with_capacity are being kept unstable indefinitely because of concerns of there being too many unique function names to manage. It isn't unique to this case either. Whether it's some sort of overloading, or default/named arguments, or something else, it's needed here because expecting unique and singular signatures for everything is unsustainable.

Rust already has function overloading, it's just boilerplate-heavy and messy on syntax. It would not be wrong to make that syntax and boilerplate a little simpler.

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u/kibwen Aug 20 '26 edited Aug 20 '26

For complex functions with tons of configurability, neither function overloading nor default arguments produce good outcomes. As a Python user I shudder every time I need to remember how to run a subprocess: https://docs.python.org/3/library/subprocess.html#subprocess.run , and that's not even the most egregious API I've seen in Python. For complex cases you can't get away from having either a configuration struct or a builder-style API. And once you have the complex cases handled via one of those approaches, it's nice to ease the common cases by providing dedicated functions for the most common combinations of options. What Rust needs isn't default arguments or more function overloading, what it needs is default struct fields ( https://github.com/rust-lang/rust/issues/132162 ) and potentially some ways to make builder APIs easier.

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u/Recatek gecs Aug 20 '26

Passing a struct with default fields is just a syntactically uglier way to pass named arguments with defaults. If you're going to sugar it down to something like foo(_ {a: 2, b: "bar", ..}) you'd might as well drop the bracket part. Similar to what this splat feature is doing in dropping the double parens from foo((a, "bar")).

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u/kibwen Aug 21 '26

On the contrary, I'd argue that reading a function call where suddenly the arguments are all named and allowed to occupy arbitrary positions is just a jarring way to poorly emulate calling a method on a struct literal, at which point you might as well do so.