使用 submodel 的时候，报 the submodel ComplexRequest.instance is inexist 错误

[wenzuochao]

// source 代码
init();

model Request = {
  accesskey?: string(name='accesskey', description='accesskey'),
  region?: string(name='region', description='region'),
  instance: {
    instanceId: string(name='instanceId', description='instanceId'),
  }(name='instance', description='instance'),
}

// 错误代码
import Source;

model ComplexRequest = {
  instance: Source.Request.instance,
}

model Response {
  instance: ComplexRequest.instance,
}

SyntaxError: the submodel ComplexRequest.instance is inexist
at TypeChecker.error (node_modules/@[email protected]@@darabonba/parser/lib/semantic.js:338:11)
at TypeChecker.checkType (node_modules/@[email protected]@@darabonba/parser/lib/semantic.js:743:16)
at TypeChecker.flatModel (node_modules/@[email protected]@@darabonba/parser/lib/semantic.js:2107:16)
at TypeChecker.visitModel (node_modules/@[email protected]@@darabonba/parser/lib/semantic.js:2132:10)
at models.forEach (node_modules/@[email protected]@@darabonba/parser/lib/semantic.js:356:12)
at Array.forEach ()
at TypeChecker.checkModels (node_modules/@[email protected]@@darabonba/parser/lib/semantic.js:355:12)
at TypeChecker.check (node_modules/@[email protected]@@darabonba/parser/lib/semantic.js:524:10)
at getChecker (node_modules/@[email protected]@@darabonba/parser/lib/semantic.js:2140:44)
at analyze (node_modules/@[email protected]@@darabonba/parser/lib/semantic.js:2144:19)
at Object.parse (node_modules/@[email protected]@@darabonba/parser/index.js:13:15)
at check (test/main.test.js:19:19)