Go code that requires language (or stdlib) features first present in Go v1.n will not compile with any version of Go 1.m, m <= n. There have been a few of these

Go code that requires language (or stdlib) features first present in Go v1.n will not compile with any version of Go 1.m, m <= n. There have been a few of these (modules, soft-launched in (IIRC) 1.11, there were one or a few in 1.15, now generics in 1.18). But, the backwards compatibility guarantee is that code that worked with Go v 1.n will work with Go v 1.j, for j >= n. Next para is based on my recollection of the discussion around generics. Specifically for generics, any code that doesn't use generics is untouched by the presence of generics elsewhere. Code that is, in and of itself, not generic will, in most cases, being able to call functions that are declared generic without extra hassle (there are most probably a few cases where a type annotation on the function using generics would be required). Code using generic data types probably needs to type-annotate, but there may be cases where it's not necessary.