Hi everyone,
I hit the same issue described in the first post of this topic, then proceeded to update typescript to 2.7.2 and still got other issues of similar style.
So, I rolled back my typescript update to the original version in the project:
"typescript": "2.3.4"
Then I added "types": [] to the "compilerOptions" parameter of tsconfig.json as suggested here and here.
Problem fixed!
How did I get the issue?
I started to work again on an Ionic 3 project that I did not modify for a year or so. What I did modify surely was the nodejs version installed on my laptop. I did not change anything inside the project itself.
Thank you!
Gustavo.