I think the problem lies in SB-C:SOURCE-TRANSFORM-ARRAY-TYPEP in src/compiler/typetran.lisp.
The predicate ARRAY-TYPE-COMPLEXP returns :MAYBE when applied to both STYPE and TYPE for the test case. I'm not sure whether the /then/ clause of the IF expression should be changed to handle this case or the condition should be altered.
I think the problem lies in SB-C:SOURCE- TRANSFORM- ARRAY-TYPEP in src/compiler/ typetran. lisp.
The predicate ARRAY-TYPE-COMPLEXP returns :MAYBE when applied to both STYPE and TYPE for the test case. I'm not sure whether the /then/ clause of the IF expression should be changed to handle this case or the condition should be altered.