gccgo successfully compiles the following program: ``` go package a var a = 0 << complex64(1) ``` go/types say: ``` go.go:2: invalid operation: 0 << complex64(1) (shift count type complex64, must be unsigned integer) ``` gccgo must unlearn how to shift by complex numbers. https://github.com/golang/go/issues/11567
