Re: Parsing user-defined types

I've just found the problem described on Wikipedia 
(https://en.wikipedia.org/wiki/The_lexer_hack), but not much practical 
information on actually handling it.

On 08/05/2019 18:48, EML wrote:
> I'm having trouble seeing how to handle user-defined types without lots 
> of feedback from the parser to the lexer. For example, consider a C-like 
> language with a struct declaration:
> 
> foo() {
>    struct a {...};  // type defn
>    struct a b;      // declare object 'b' of user-defined type 'a'
> }
> 
> this is easy to parse, but if you add a typedef, or go to C++, you can 
> have code that looks like this:
> 
> foo() {
>    struct a {...};
>    a b;
> }
> 
> With a simple flex/bison setup this is likely to lead to a lot of 
> conflicts. So how do you handle this? Do you just work through the 
> conflicts, if possible, or is this a job for a hand-coded lexer, which 
> can be told about new types at runtime?
> 
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