in src/type-generator.ts [273:286]
public emitCustomType(typeName: string, emitter: TypeEmitter | CodeEmitter) {
if (typeName in this.emittedTypes) {
return;
}
this.typesToEmit[typeName] = code => {
const result = emitter(code);
if (typeof(result) === 'object') {
return result;
} else {
return { type: typeName, toJson: x => x };
}
};
}