Add += operator to pest grammar

[mxmsll]

I am implementing a series of parsers that are based on some common syntax, but all have different extensions. I hope to extend a defined rule by introducing the '+=' operator.

Example

base.pest

base_type_spec = { integer_type }

string,pest

base_type_spec += { string_type }

any.pest

base_type_spec += { any_type }

parser.rs

pub mod parser_with_string {
#[derive(Parser)]
#[grammar = "base.pest"]
#[grammar = "string.pest"]
pub struct MyParser;
}

pub mod parser_with_any {
#[derive(Parser)]
#[grammar = "base.pest"]
#[grammar = "any.pest"]
pub struct MyParser;
}

[tomtau]

what should that operator do? override base_type_spec rule or do { integer_type ~ string_type } ...?

[mxmsll]

override base_type_spec rule as: { integer_type | string_type }

[NoahTheDuke]

I feel this is best handled by being explicit. Inheritance gets complicated quickly. Better to write both versions than try to parse/remember where exactly a given rule is defined.