rejects valid shift expressions with different types

[robpike]

The following program sample.go triggers a compile-time error:

package main

func main() {
	var u uint64
	var v uint32
	println(u << v)
}

Expected result:

$ go run ./sample.go
0

Got:

$ yaegi ./sample.go
x.go:6:10: mismatched types .uint64 and .uint32

In a way I find this amusing, as shifts are a bitch to get right in Go. Took us ages even to figure out the spec.