> I think this overstates the difficulty. This of course depends a lot on the language, but for a reasonable one (not C++) you can just go and write the parser by hand. I’d ballpark this as three weeks, if you know how the thing is supposed to work.
Having a parser which generates an AST is just the first step. Then, you actually need to implement all the rules of the language, so for instance the scoping rules, how the object system works, any other built-in compound/aggregate types, other constructs like decorators, generics, namespaces or module systems, and on and on and on. Depending on the language, this will usually be the main work.
And then of course there's dynamic typing - if you want to enable smart completions for a dynamically typed language, you need to implement some kind of type deduction. This alone can take a lot of time to implement.
If you want syntax highlighting, the AST is enough to generate pretty colours for the source code. If you want semantic highlighting… sure, that's another story entirely. And even then you don't necessarily have to do as much work as the compiler itself.
And don't even try to be smart with dynamically typed languages, it cannot possibly be reliable, short of actually executing the program. If your program are short enough you won't need it, and if you do need such static analysis… consider switching to a statically typed language instead.
Having a parser which generates an AST is just the first step. Then, you actually need to implement all the rules of the language, so for instance the scoping rules, how the object system works, any other built-in compound/aggregate types, other constructs like decorators, generics, namespaces or module systems, and on and on and on. Depending on the language, this will usually be the main work.
And then of course there's dynamic typing - if you want to enable smart completions for a dynamically typed language, you need to implement some kind of type deduction. This alone can take a lot of time to implement.