alt Hacker News> Bidirectional type inference is a type inference style where you traverse the syntax tree once.
Yes, in my language I just build code directly from syntax tree in single pass (with a couple of minor exceptions). No complex machinery for type deduction is involved. So, now I assume it's called bidirectional type inference.
Personally I find what Rust does with possibility to avoid specifying types for variables isn't that great. It allows writing code which is hard to read, since no type information is present in source code. Also I suppose that it makes compilation slower, since solving all these equations isn't so easy and computationally-cheap.
It's unclear from your comment whether you inadvertently have bidirectional type inference or if you just...don't have type inference.
So, just to be clear, bidirectional type inference is a particular kind of machinery for type deduction (complexity is in the eye of the beholder). The defining characteristic of bidirectional type inference is that type information flows in both directions, not that it takes a single pass for type checking over the tree.
And that's, again, a single pass for type checking - the compiler as a whole can and usually does still take many passes to go from syntax tree to code. Pascal was famously designed to be compiled in a single pass, but it doesn't have any type inference to speak of.