t := types.Types[types.TBOOL]
	if n.Tag != nil {
		n.Tag = Expr(n.Tag)
		n.Tag = DefaultLit(n.Tag, nil)
		t = n.Tag.Type()
	}

	var nilonly string
	if t != nil {
		switch {
		case t.IsMap():
			nilonly = "map"
		case t.Kind() == types.TFUNC:
			nilonly = "func"
		case t.IsSlice():
			nilonly = "slice"

		case !types.IsComparable(t):
			if t.IsStruct() {

		return l, r, nil
	}

	if l.Type().IsSlice() && !ir.IsNil(l) && !ir.IsNil(r) {
		base.Errorf("invalid operation: %v (slice can only be compared to nil)", n)
		return l, r, nil
	}

	if l.Type().IsMap() && !ir.IsNil(l) && !ir.IsNil(r) {
		base.Errorf("invalid operation: %v (map can only be compared to nil)", n)
		return l, r, nil
	}

	if l.Type().Kind() == types.TFUNC && !ir.IsNil(l) && !ir.IsNil(r) {

	if n.Op() != ir.OAS {
		return nil
	}
	as := n.(*ir.AssignStmt)
	if ir.IsBlank(as.X) || as.X.Op() != ir.ONAME {
		return nil
	}
	nm := as.X.(*ir.Name)
	if !nm.Type().IsMap() {
		return nil
	}

	// Determine size of RHS.
	rsiz := 0
	ir.Any(as.Y, func(n ir.Node) bool {
		rsiz++
		return false
	})
	if base.Debug.WrapGlobalMapDbg > 0 {

		if n := arrayClear(n.X.Pos(), n.X, nil); n != nil {
			return n
		}
		// If n == nil, we are clearing an array which takes zero memory, do nothing.
		return ir.NewBlockStmt(n.Pos(), nil)
	case typ.IsMap():
		return mapClear(n.X, reflectdata.TypePtrAt(n.X.Pos(), n.X.Type()))
	}
	panic("unreachable")
}

// walkClose walks an OCLOSE node.
func walkClose(n *ir.UnaryExpr, init *ir.Nodes) ir.Node {