What language is used to describe an Abstract Syntax Tree in ESTree?

问题

I am referring the ESTree documentation for ECMAScript 2015 here.

For instance, it uses the following syntax:

extend interface Program {
    sourceType: "script" | "module";
    body: [ Statement | ModuleDeclaration ];
}

interface ForOfStatement <: ForInStatement {
    type: "ForOfStatement";
}

What language is this representation of the AST? Where can we read about the specification used to describe an AST or explanation of the custom format used?

回答1:

As also pointed out by Bergi, the README states

The spec uses a custom syntax to describe its structures.

The core model is described in es5.md and contains most of the basics required to understand the extensions described in higher specifications (ES2015+).

来源：https://stackoverflow.com/questions/55060072/what-language-is-used-to-describe-an-abstract-syntax-tree-in-estree