I had the same problem as him and in my case was the tsconfig.json.
There is a parameter called files like so:
.....,
"files": [
"app/app.ts"]
.....
or something like that. Well it was showing the whole file with green squiggly lines (VS Code) and after deleting that parameter everything worked perfectly after I restarted VS Code.
current tsconfig file:
{
"compilerOptions": {
"target": "es5",
"module": "commonjs",
"noEmitOnError": false,
"rootDir": ".",
"emitDecoratorMetadata": true,
"experimentalDecorators": true,
"sourceMap": false,
"sourceRoot": "",
"inlineSourceMap": false,
"inlineSources": false
},
"exclude": [
"node_modules"
],
"compileOnSave": false
}