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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;
}
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