Rust function requires return keyword. Why?

Question

I've been playing with Rust a bit, and I'm experimenting with eliminating return statements that aren't necessary. In one case, I feel as though a return statement shouldn't be required here, but I'm getting complaints that "the body has no tail". It seems like it should with the following code:

use sqlite; use sqlite::Connection fn main() { let connection = connect(); query(connection); } // The offending function fn connect() -> Connection { // Simple example, shouldn't use unwrap sqlite::open(":memory:").unwrap(); }

I can add a return statement to the offending function like the following:

fn connect() -> Connection { return sqlite::open(":memory:").unwrap(); }

But I'm curious why this doesn't work.

Sébastien Renauld · Accepted Answer · 2019-10-11 17:34:36Z

fn connect() -> Connection { sqlite::open(":memory:").unwrap() }

Removing the semi-colon, changes the line from a statement to an expression, which has a return value, which Rust can then infer as a return value for the function.

This is covered at the very end Chapter 3 of the Rust language book as a specific example.

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