first_in_statement.js

import {
    AST_Binary,
    AST_Conditional,
    AST_Chain,
    AST_Dot,
    AST_Object,
    AST_Sequence,
    AST_Statement,
    AST_Sub,
    AST_UnaryPostfix,
    AST_PrefixedTemplateString
} from "../ast.js";

// return true if the node at the top of the stack (that means the
// innermost node in the current output) is lexically the first in
// a statement.
function first_in_statement(stack) {
    let node = stack.parent(-1);
    for (let i = 0, p; p = stack.parent(i); i++) {
        if (p instanceof AST_Statement && p.body === node)
            return true;
        if ((p instanceof AST_Sequence && p.expressions[0] === node) ||
            (p.TYPE === "Call" && p.expression === node) ||
            (p instanceof AST_PrefixedTemplateString && p.prefix === node) ||
            (p instanceof AST_Dot && p.expression === node) ||
            (p instanceof AST_Sub && p.expression === node) ||
            (p instanceof AST_Chain && p.expression === node) ||
            (p instanceof AST_Conditional && p.condition === node) ||
            (p instanceof AST_Binary && p.left === node) ||
            (p instanceof AST_UnaryPostfix && p.expression === node)
        ) {
            node = p;
        } else {
            return false;
        }
    }
}

// Returns whether the leftmost item in the expression is an object
function left_is_object(node) {
    if (node instanceof AST_Object) return true;
    if (node instanceof AST_Sequence) return left_is_object(node.expressions[0]);
    if (node.TYPE === "Call") return left_is_object(node.expression);
    if (node instanceof AST_PrefixedTemplateString) return left_is_object(node.prefix);
    if (node instanceof AST_Dot || node instanceof AST_Sub) return left_is_object(node.expression);
    if (node instanceof AST_Chain) return left_is_object(node.expression);
    if (node instanceof AST_Conditional) return left_is_object(node.condition);
    if (node instanceof AST_Binary) return left_is_object(node.left);
    if (node instanceof AST_UnaryPostfix) return left_is_object(node.expression);
    return false;
}

export { first_in_statement, left_is_object };