'a'

mh-two-thousand-and-two

2024-04-12 44d2c92345cd156a59fc327b3060292a282d2893

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#!/usr/bin/env node
 
// This script converts for and do-while loops into equivalent while loops.
// Note that for-in statements are left unmodified, as they do not have a
// simple analogy to while loops. Also note that labeled continue statements
// are not correctly handled at this point, and will trigger an assertion
// failure if encountered.
 
var assert = require("assert");
var recast = require("recast");
var types = recast.types;
var n = types.namedTypes;
var b = types.builders;
 
recast.run(function(ast, callback) {
    recast.visit(ast, {
        visitForStatement: function(path) {
            var fst = path.node;
 
            path.replace(
                fst.init,
                b.whileStatement(
                    fst.test,
                    insertBeforeLoopback(fst, fst.update)
                )
            );
 
            this.traverse(path);
        },
 
        visitDoWhileStatement: function(path) {
            var dwst = path.node;
            return b.whileStatement(
                b.literal(true),
                insertBeforeLoopback(
                    dwst,
                    b.ifStatement(
                        dwst.test,
                        b.breakStatement()
                    )
                )
            );
        }
    });
 
    callback(ast);
});
 
function insertBeforeLoopback(loop, toInsert) {
    var body = loop.body;
 
    if (!n.Statement.check(toInsert)) {
        toInsert = b.expressionStatement(toInsert);
    }
 
    if (n.BlockStatement.check(body)) {
        body.body.push(toInsert);
    } else {
        body = b.blockStatement([body, toInsert]);
        loop.body = body;
    }
 
    recast.visit(body, {
        visitContinueStatement: function(path) {
            var cst = path.node;
 
            assert.equal(
                cst.label, null,
                "Labeled continue statements are not yet supported."
            );
 
            path.replace(toInsert, path.node);
            return false;
        },
 
        // Do not descend into nested loops.
        visitWhileStatement: function() {},
        visitForStatement: function() {},
        visitForInStatement: function() {},
        visitDoWhileStatement: function() {}
    });
 
    return body;
}