in packages/transform/src/emit.js [169:182]
Ep.jumpIf = function(test, toLoc) {
const t = util.getTypes();
t.assertExpression(test);
t.assertLiteral(toLoc);
this.emit(t.ifStatement(
test,
t.blockStatement([
this.assign(this.contextProperty("next"), toLoc),
t.breakStatement()
])
));
};