Kill the syntax `alias this = sym;`
Fixes Issue 9479 - Suppress mismatch of return type when return expression is an error.
Merge pull request #1648 from AndrejMitrovic/Fix9479

Issue 9479 - Suppress mismatch of return type diagnostic when return expression is an error
Merge pull request #1413 from 9rnsr/x3011

Kill the syntax `alias this = sym`;