gccgo: bad "incompatible types" error when comparing untyped expressions

[mdempsky]

gccgo incorrectly reports error: incompatible types in binary expression for this test program:

package main

func main() {
        var v uint = 32
        println(1 << v == '\002' << v)
}

The Go spec says:

If the left operand of a non-constant shift expression is an untyped constant, it is first implicitly converted to the type it would assume if the shift expression were replaced by its left operand alone.

So 1 and '\002' should take on the types that they would in the comparison 1 == '\002', which is rune/int32.

For comparison, the program prints true when compiled with cmd/compile, and it type checks with go/types.

/cc @ianlancetaylor