I am on the OSx platform, and I had the same error after updating only the SDK folder, without updating any other tools, the ect editor ...
I decided temporarily with running pub serv manually using terminal
pub serve --port 1234
But to solve the problem in the Eclipse editor, I have to clear all the Dart installation files using "AppCleaner" and reinstall everything with a new installation. With this solution, I solved the problem.
source share