_linters/src/honnef.co/go/tools/ssa/builder.go
func (b *builder) assignOp(fn *Function, loc lvalue, incr Value, op token.Token, pos token.Pos) {
	oldv := loc.load(fn)
	loc.store(fn, emitArith(fn, op, oldv, emitConv(fn, incr, oldv.Type()), loc.typ(), pos))
}
func (b *builder) assignOp(fn *Function, loc lvalue, incr Value, op token.Token, pos token.Pos) {
	oldv := loc.load(fn)
	loc.store(fn, emitArith(fn, op, oldv, emitConv(fn, incr, oldv.Type()), loc.typ(), pos))
}
// assignOp emits to fn code to perform loc += incr or loc -= incr.