C++ only supports capturing a variable with a lifetime at least as long as the closure. In other words, you can't _return_ a closure from a function that captures an automatic variable (i.e. "stack-allocated" variable), or pass the closure to another thread of control that such that it outlives the original function invocation. AFAIK Go will automatically heap allocate any variable that is captured. (Theoretically, it could attempt to prove it won't out-live the enclosing function(s).) Automatic heap allocation requires automated GC.

C++ has lots of syntactic sugar, but at the end of the day, like C and Rust it's a fundamentally pass-by-value language.

Here's a good paper which describes some of the complexities and design decisions for a full and complete closure implementation that doesn't require decoration and compiler hinting:

  http://www.cs.tufts.edu/~nr/cs257/archive/roberto-ierusalimschy/closures-draft.pdf

More general issue: https://en.wikipedia.org/wiki/Funarg_problem

This is important nuance that makes complete sense but that I didn't actually appreciate. Thank you.

That was kind of my understanding of closure in Go:

https://gobyexample.com/closures