Compiler crash when using simple return expression

[bungcip]

This simple code

foo = return 4

causing compiler to panic

thread 'main' panicked at 'you cannot add an instruction to a block already filled', /home/bungcip/.cargo/registry/src/github.com-1ecc6299db9ec823/cranelift-frontend-0.86.1/src/frontend.rs:417:13
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

[jfecher]

Apologies for the very delayed response!

This is a known error, although it is one that is somewhat cumbersome to solve well as it requires a more thorough checking of where return is in code. A proper fix is two-fold:

1. Creating a new warning for when there is code sequenced after a return
2. Fixing the backend to stop code generation in a block after a return, or remove all offending Ast nodes in advance beforehand.