float vec!

What this Rust language fundamentals question tests

This is an easy Rust question that probes your understanding of how the language's macro system and type inference work together. It's the kind of foundational knowledge that underpins writing correct, idiomatic Rust code — especially in performance-critical domains like quantitative finance where systems code reliability matters.

To answer questions like this, you need to trace through macro expansion and understand how Rust's type system infers types in collection literals. The question rewards careful reading of what the code actually says rather than what you might assume it does at a glance.

• Macro expansion and syntax rules
• Type inference in generic contexts
• Vector initialization patterns