intellisense become invalidated

[chenqiangkobe]

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { FormsModule } from '@angular/forms';
import { AppComponent } from './app.component';
import { MonacoEditorModule, NgxMonacoEditorConfig } from 'ngx-monaco-editor';

export function onMonacoLoad() {
const monaco = (window as any).monaco;

monaco.languages.typescript.javascriptDefaults.setDiagnosticsOptions({
noSemanticValidation: true,
noSyntaxValidation: false
});
// compiler options
monaco.languages.typescript.javascriptDefaults.setCompilerOptions({
target: monaco.languages.typescript.ScriptTarget.ES2015,
allowNonTsExtensions: true,
allowJS: true,
});
// extra libraries
const libSource = [
'declare class Facts {',
' /**',
' * Returns the next fact',
' */',
' static next():string',
' middle():string',
' static prev():string',
'}',
].join('\n');
monaco.languages.typescript.javascriptDefaults.addExtraLib(libSource);
// When resolving definitions and references, the editor will try to use created models.
// Creating a model for the library allows "peek definition/references" commands to work with the library.
monaco.editor.createModel(libSource, 'typescript');

}
const monacoConfig: NgxMonacoEditorConfig = {
baseUrl: 'assets',
defaultOptions: { scrollBeyondLastLine: false },
onMonacoLoad
};
@NgModule({
declarations: [
AppComponent
],
imports: [
BrowserModule,
FormsModule,
MonacoEditorModule.forRoot(monacoConfig) // use forRoot() in main app module only.
],
providers: [],
bootstrap: [AppComponent]
})

in editor, intellisense will work(Facts.next()) but soon be invalidated
why?