[Bug]: Using a type function in an implements statement segfaults

[jabraham17]

The following code results in a segfault

interface foo { }
proc get type do return foo;

record R { }
R implements get;

This is because the compiler is expecting that in R implements get, get is a plain interface symbol.

If get is a type alias, the compiler gives an error that get is not an interface. If the record is written as record R: get { }, then the compiler gives an error about an illegal super class.

Whether or not TYPE implements function_returning_interface should be valid Chapel is an interesting design question (I think it should be), but at the very least it should not be an internal error.