cmd/compile/internal/gc: add some Node methods

Focus on "isfoo" funcs that take a *Node, and conver them to isFoo
methods instead. This makes for more idiomatic Go code, and also more
readable func names.

Found candidates with grep, and applied most changes with sed. The funcs
chosen were isgoconst, isnil, and isblank. All had the same signature,
func(*Node) bool.

While at it, camelCase the isliteral and iszero function names. Don't
move these to methods, as they are only used in the backend part of gc,
which might one day be split into a separate package.

Passes toolstash -cmp on std cmd.

Change-Id: I4df081b12d36c46c253167c8841c5a841f1c5a16
Reviewed-on: https://go-review.googlesource.com/105555
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

src/cmd/compile/internal/gc/closure.go

@@ -136,7 +136,7 @@ func closurename(outerfunc *Node) *types.Sym {
 		// There may be multiple functions named "_". In those
 		// cases, we can't use their individual Closgens as it
 		// would lead to name clashes.
-		if !isblank(outerfunc.Func.Nname) {
+		if !outerfunc.Func.Nname.isBlank() {
 			gen = &outerfunc.Func.Closgen
 		}
 	}

src/cmd/compile/internal/gc/const.go

@@ -1506,12 +1506,14 @@ func nonnegintconst(n *Node) int64 {
 	return vi.Int64()
 }
 
-// Is n a Go language constant (as opposed to a compile-time constant)?
+// isGoConst reports whether n is a Go language constant (as opposed to a
+// compile-time constant).
+//
 // Expressions derived from nil, like string([]byte(nil)), while they
 // may be known at compile time, are not Go language constants.
 // Only called for expressions known to evaluated to compile-time
 // constants.
-func isgoconst(n *Node) bool {
+func (n *Node) isGoConst() bool {
 	if n.Orig != nil {
 		n = n.Orig
 	}
@@ -1545,18 +1547,18 @@ func isgoconst(n *Node) bool {
 		OCOMPLEX,
 		OREAL,
 		OIMAG:
-		if isgoconst(n.Left) && (n.Right == nil || isgoconst(n.Right)) {
+		if n.Left.isGoConst() && (n.Right == nil || n.Right.isGoConst()) {
 			return true
 		}
 
 	case OCONV:
-		if okforconst[n.Type.Etype] && isgoconst(n.Left) {
+		if okforconst[n.Type.Etype] && n.Left.isGoConst() {
 			return true
 		}
 
 	case OLEN, OCAP:
 		l := n.Left
-		if isgoconst(l) {
+		if l.isGoConst() {
 			return true
 		}
 

src/cmd/compile/internal/gc/dcl.go

@@ -64,7 +64,7 @@ func declare(n *Node, ctxt Class) {
 		return
 	}
 
-	if isblank(n) {
+	if n.isBlank() {
 		return
 	}
 
@@ -178,7 +178,7 @@ func variter(vl []*Node, t *Node, el []*Node) []*Node {
 		declare(v, dclcontext)
 		v.Name.Param.Ntype = t
 
-		if e != nil || Curfn != nil || isblank(v) {
+		if e != nil || Curfn != nil || v.isBlank() {
 			if Curfn != nil {
 				init = append(init, nod(ODCL, v, nil))
 			}
@@ -326,7 +326,7 @@ func colasdefn(left []*Node, defn *Node) {
 
 	var nnew, nerr int
 	for i, n := range left {
-		if isblank(n) {
+		if n.isBlank() {
 			continue
 		}
 		if !colasname(n) {
@@ -367,7 +367,7 @@ func ifacedcl(n *Node) {
 		Fatalf("ifacedcl")
 	}
 
-	if isblank(n.Left) {
+	if n.Left.isBlank() {
 		yyerror("methods must have a unique non-blank name")
 	}
 }
@@ -457,7 +457,7 @@ func funcargs(nt *Node) {
 		// TODO: n->left->missing = 1;
 		n.Left.Op = ONAME
 
-		if isblank(n.Left) {
+		if n.Left.isBlank() {
 			// Give it a name so we can assign to it during return. ~b stands for 'blank'.
 			// The name must be different from ~r above because if you have
 			//	func f() (_ int)

src/cmd/compile/internal/gc/esc.go

@@ -1066,7 +1066,7 @@ func (e *EscState) escassignSinkWhyWhere(dst, src *Node, reason string, call *No
 // evaluated in curfn.	For expr==nil, dst must still be examined for
 // evaluations inside it (e.g *f(x) = y)
 func (e *EscState) escassign(dst, src *Node, step *EscStep) {
-	if isblank(dst) || dst == nil || src == nil || src.Op == ONONAME || src.Op == OXXX {
+	if dst.isBlank() || dst == nil || src == nil || src.Op == ONONAME || src.Op == OXXX {
 		return
 	}
 

src/cmd/compile/internal/gc/gsubr.go

@@ -174,7 +174,7 @@ func (f *Func) initLSym() {
 		Fatalf("Func.initLSym called twice")
 	}
 
-	if nam := f.Nname; !isblank(nam) {
+	if nam := f.Nname; !nam.isBlank() {
 		f.lsym = nam.Sym.Linksym()
 		if f.Pragma&Systemstack != 0 {
 			f.lsym.Set(obj.AttrCFunc, true)

src/cmd/compile/internal/gc/init.go

@@ -26,7 +26,7 @@ func anyinit(n []*Node) bool {
 		switch ln.Op {
 		case ODCLFUNC, ODCLCONST, ODCLTYPE, OEMPTY:
 		case OAS:
-			if !isblank(ln.Left) || !candiscard(ln.Right) {
+			if !ln.Left.isBlank() || !candiscard(ln.Right) {
 				return true
 			}
 		default:

src/cmd/compile/internal/gc/inl.go

@@ -753,7 +753,7 @@ func mkinlcall(n *Node, fn *Node) *Node {
 }
 
 func tinlvar(t *types.Field, inlvars map[*Node]*Node) *Node {
-	if asNode(t.Nname) != nil && !isblank(asNode(t.Nname)) {
+	if asNode(t.Nname) != nil && !asNode(t.Nname).isBlank() {
 		inlvar := inlvars[asNode(t.Nname)]
 		if inlvar == nil {
 			Fatalf("missing inlvar for %v\n", asNode(t.Nname))
@@ -885,7 +885,7 @@ func mkinlcall1(n, fn *Node) *Node {
 	for i, t := range fn.Type.Results().Fields().Slice() {
 		var m *Node
 		var mpos src.XPos
-		if t != nil && asNode(t.Nname) != nil && !isblank(asNode(t.Nname)) {
+		if t != nil && asNode(t.Nname) != nil && !asNode(t.Nname).isBlank() {
 			mpos = asNode(t.Nname).Pos
 			m = inlvar(asNode(t.Nname))
 			m = typecheck(m, Erv)

src/cmd/compile/internal/gc/noder.go

@@ -654,7 +654,7 @@ func (p *noder) expr(expr syntax.Expr) *Node {
 		n := p.nod(expr, OTYPESW, nil, p.expr(expr.X))
 		if expr.Lhs != nil {
 			n.Left = p.declName(expr.Lhs)
-			if isblank(n.Left) {
+			if n.Left.isBlank() {
 				yyerror("invalid variable name %v in type switch", n.Left)
 			}
 		}

src/cmd/compile/internal/gc/order.go

@@ -461,7 +461,7 @@ func (o *Order) mapAssign(n *Node) {
 					m.Right = o.copyExpr(m.Right, m.Right.Type, false)
 				}
 				fallthrough
-			case instrumenting && n.Op == OAS2FUNC && !isblank(m):
+			case instrumenting && n.Op == OAS2FUNC && !m.isBlank():
 				t := o.newTemp(m.Type, false)
 				n.List.SetIndex(i, t)
 				a := nod(OAS, m, t)
@@ -700,7 +700,7 @@ func (o *Order) stmt(n *Node) {
 			Fatalf("orderstmt range %v", n.Type)
 
 		case TARRAY, TSLICE:
-			if n.List.Len() < 2 || isblank(n.List.Second()) {
+			if n.List.Len() < 2 || n.List.Second().isBlank() {
 				// for i := range x will only use x once, to compute len(x).
 				// No need to copy it.
 				break
@@ -812,7 +812,7 @@ func (o *Order) stmt(n *Node) {
 				// temporary per distinct type, sharing the temp among all receives
 				// with that temp. Similarly one ok bool could be shared among all
 				// the x,ok receives. Not worth doing until there's a clear need.
-				if r.Left != nil && isblank(r.Left) {
+				if r.Left != nil && r.Left.isBlank() {
 					r.Left = nil
 				}
 				if r.Left != nil {
@@ -833,7 +833,7 @@ func (o *Order) stmt(n *Node) {
 					n2.Ninit.Append(tmp2)
 				}
 
-				if r.List.Len() != 0 && isblank(r.List.First()) {
+				if r.List.Len() != 0 && r.List.First().isBlank() {
 					r.List.Set(nil)
 				}
 				if r.List.Len() != 0 {
@@ -1178,7 +1178,7 @@ func (o *Order) expr(n, lhs *Node) *Node {
 // okas creates and returns an assignment of val to ok,
 // including an explicit conversion if necessary.
 func okas(ok, val *Node) *Node {
-	if !isblank(ok) {
+	if !ok.isBlank() {
 		val = conv(val, ok.Type)
 	}
 	return nod(OAS, ok, val)
@@ -1196,7 +1196,7 @@ func (o *Order) as2(n *Node) {
 	tmplist := []*Node{}
 	left := []*Node{}
 	for _, l := range n.List.Slice() {
-		if !isblank(l) {
+		if !l.isBlank() {
 			tmp := o.newTemp(l.Type, types.Haspointers(l.Type))
 			tmplist = append(tmplist, tmp)
 			left = append(left, l)
@@ -1213,7 +1213,7 @@ func (o *Order) as2(n *Node) {
 
 	ti := 0
 	for ni, l := range n.List.Slice() {
-		if !isblank(l) {
+		if !l.isBlank() {
 			n.List.SetIndex(ni, tmplist[ti])
 			ti++
 		}
@@ -1224,12 +1224,12 @@ func (o *Order) as2(n *Node) {
 // Just like as2, this also adds temporaries to ensure left-to-right assignment.
 func (o *Order) okAs2(n *Node) {
 	var tmp1, tmp2 *Node
-	if !isblank(n.List.First()) {
+	if !n.List.First().isBlank() {
 		typ := n.Rlist.First().Type
 		tmp1 = o.newTemp(typ, types.Haspointers(typ))
 	}
 
-	if !isblank(n.List.Second()) {
+	if !n.List.Second().isBlank() {
 		tmp2 = o.newTemp(types.Types[TBOOL], false)
 	}
 

src/cmd/compile/internal/gc/range.go

@@ -106,7 +106,7 @@ func typecheckrangeExpr(n *Node) {
 	// "if the second iteration variable is the blank identifier, the range
 	// clause is equivalent to the same clause with only the first variable
 	// present."
-	if isblank(v2) {
+	if v2.isBlank() {
 		if v1 != nil {
 			n.List.Set1(v1)
 		}
@@ -177,11 +177,11 @@ func walkrange(n *Node) *Node {
 		v2 = n.List.Second()
 	}
 
-	if isblank(v2) {
+	if v2.isBlank() {
 		v2 = nil
 	}
 
-	if isblank(v1) && v2 == nil {
+	if v1.isBlank() && v2 == nil {
 		v1 = nil
 	}
 
@@ -478,7 +478,7 @@ func memclrrange(n, v1, v2, a *Node) bool {
 		return false
 	}
 	elemsize := n.Type.Elem().Width
-	if elemsize <= 0 || !iszero(stmt.Right) {
+	if elemsize <= 0 || !isZero(stmt.Right) {
 		return false
 	}
 

src/cmd/compile/internal/gc/sinit.go

@@ -56,7 +56,7 @@ func init1(n *Node, out *[]*Node) {
 	switch n.Class() {
 	case PEXTERN, PFUNC:
 	default:
-		if isblank(n) && n.Name.Curfn == nil && n.Name.Defn != nil && n.Name.Defn.Initorder() == InitNotStarted {
+		if n.isBlank() && n.Name.Curfn == nil && n.Name.Defn != nil && n.Name.Defn.Initorder() == InitNotStarted {
 			// blank names initialization is part of init() but not
 			// when they are inside a function.
 			break
@@ -115,7 +115,7 @@ func init1(n *Node, out *[]*Node) {
 				Dump("defn", defn)
 				Fatalf("init1: bad defn")
 			}
-			if isblank(defn.Left) && candiscard(defn.Right) {
+			if defn.Left.isBlank() && candiscard(defn.Right) {
 				defn.Op = OEMPTY
 				defn.Left = nil
 				defn.Right = nil
@@ -126,7 +126,7 @@ func init1(n *Node, out *[]*Node) {
 			if Debug['j'] != 0 {
 				fmt.Printf("%v\n", n.Sym)
 			}
-			if isblank(n) || !staticinit(n, out) {
+			if n.isBlank() || !staticinit(n, out) {
 				if Debug['%'] != 0 {
 					Dump("nonstatic", defn)
 				}
@@ -303,7 +303,7 @@ func staticcopy(l *Node, r *Node, out *[]*Node) bool {
 		return true
 
 	case OLITERAL:
-		if iszero(r) {
+		if isZero(r) {
 			return true
 		}
 		gdata(l, r, int(l.Type.Width))
@@ -380,7 +380,7 @@ func staticassign(l *Node, r *Node, out *[]*Node) bool {
 		return staticcopy(l, r, out)
 
 	case OLITERAL:
-		if iszero(r) {
+		if isZero(r) {
 			return true
 		}
 		gdata(l, r, int(l.Type.Width))
@@ -578,7 +578,7 @@ func staticname(t *types.Type) *Node {
 	return n
 }
 
-func isliteral(n *Node) bool {
+func isLiteral(n *Node) bool {
 	// Treat nils as zeros rather than literals.
 	return n.Op == OLITERAL && n.Val().Ctype() != CTNIL
 }
@@ -607,7 +607,7 @@ const (
 func getdyn(n *Node, top bool) initGenType {
 	switch n.Op {
 	default:
-		if isliteral(n) {
+		if isLiteral(n) {
 			return initConst
 		}
 		return initDynamic
@@ -742,7 +742,7 @@ func fixedlit(ctxt initContext, kind initKind, n *Node, var_ *Node, init *Nodes)
 			continue
 		}
 
-		islit := isliteral(value)
+		islit := isLiteral(value)
 		if (kind == initKindStatic && !islit) || (kind == initKindDynamic && islit) {
 			continue
 		}
@@ -898,7 +898,7 @@ func slicelit(ctxt initContext, n *Node, var_ *Node, init *Nodes) {
 			continue
 		}
 
-		if isliteral(value) {
+		if isLiteral(value) {
 			continue
 		}
 
@@ -1264,7 +1264,7 @@ func initplan(n *Node) {
 
 func addvalue(p *InitPlan, xoffset int64, n *Node) {
 	// special case: zero can be dropped entirely
-	if iszero(n) {
+	if isZero(n) {
 		return
 	}
 
@@ -1284,13 +1284,13 @@ func addvalue(p *InitPlan, xoffset int64, n *Node) {
 	p.E = append(p.E, InitEntry{Xoffset: xoffset, Expr: n})
 }
 
-func iszero(n *Node) bool {
+func isZero(n *Node) bool {
 	switch n.Op {
 	case OLITERAL:
 		switch u := n.Val().U.(type) {
 		default:
 			Dump("unexpected literal", n)
-			Fatalf("iszero")
+			Fatalf("isZero")
 		case *NilVal:
 			return true
 		case string:
@@ -1310,7 +1310,7 @@ func iszero(n *Node) bool {
 			if n1.Op == OKEY {
 				n1 = n1.Right
 			}
-			if !iszero(n1) {
+			if !isZero(n1) {
 				return false
 			}
 		}
@@ -1318,7 +1318,7 @@ func iszero(n *Node) bool {
 
 	case OSTRUCTLIT:
 		for _, n1 := range n.List.Slice() {
-			if !iszero(n1.Left) {
+			if !isZero(n1.Left) {
 				return false
 			}
 		}

src/cmd/compile/internal/gc/ssa.go

@@ -800,7 +800,7 @@ func (s *state) stmt(n *Node) {
 				// All literals with nonzero fields have already been
 				// rewritten during walk. Any that remain are just T{}
 				// or equivalents. Use the zero value.
-				if !iszero(rhs) {
+				if !isZero(rhs) {
 					Fatalf("literal with nonzero value in SSA: %v", rhs)
 				}
 				rhs = nil
@@ -828,7 +828,7 @@ func (s *state) stmt(n *Node) {
 			}
 		}
 
-		if isblank(n.Left) {
+		if n.Left.isBlank() {
 			// _ = rhs
 			// Just evaluate rhs for side-effects.
 			if rhs != nil {
@@ -2115,7 +2115,7 @@ func (s *state) expr(n *Node) *ssa.Value {
 			// All literals with nonzero fields have already been
 			// rewritten during walk. Any that remain are just T{}
 			// or equivalents. Use the zero value.
-			if !iszero(n.Left) {
+			if !isZero(n.Left) {
 				Fatalf("literal with nonzero value in SSA: %v", n.Left)
 			}
 			return s.zeroVal(n.Type)
@@ -2267,7 +2267,7 @@ func (s *state) expr(n *Node) *ssa.Value {
 		// All literals with nonzero fields have already been
 		// rewritten during walk. Any that remain are just T{}
 		// or equivalents. Use the zero value.
-		if !iszero(n) {
+		if !isZero(n) {
 			Fatalf("literal with nonzero value in SSA: %v", n)
 		}
 		return s.zeroVal(n.Type)
@@ -2495,7 +2495,7 @@ const (
 // If deref is true and right == nil, just do left = 0.
 // skip indicates assignments (at the top level) that can be avoided.
 func (s *state) assign(left *Node, right *ssa.Value, deref bool, skip skipMask) {
-	if left.Op == ONAME && isblank(left) {
+	if left.Op == ONAME && left.isBlank() {
 		return
 	}
 	t := left.Type

src/cmd/compile/internal/gc/subr.go

@@ -438,8 +438,8 @@ func treecopy(n *Node, pos src.XPos) *Node {
 	}
 }
 
-// isnil reports whether n represents the universal untyped zero value "nil".
-func isnil(n *Node) bool {
+// isNil reports whether n represents the universal untyped zero value "nil".
+func (n *Node) isNil() bool {
 	// Check n.Orig because constant propagation may produce typed nil constants,
 	// which don't exist in the Go spec.
 	return Isconst(n.Orig, CTNIL)
@@ -462,7 +462,7 @@ func isptrto(t *types.Type, et types.EType) bool {
 	return true
 }
 
-func isblank(n *Node) bool {
+func (n *Node) isBlank() bool {
 	if n == nil {
 		return false
 	}

src/cmd/compile/internal/gc/swt.go

@@ -70,7 +70,7 @@ func typecheckswitch(n *Node) {
 		if t != nil && !t.IsInterface() {
 			yyerrorl(n.Pos, "cannot type switch on non-interface value %L", n.Left.Right)
 		}
-		if v := n.Left.Left; v != nil && !isblank(v) && n.List.Len() == 0 {
+		if v := n.Left.Left; v != nil && !v.isBlank() && n.List.Len() == 0 {
 			// We don't actually declare the type switch's guarded
 			// declaration itself. So if there are no cases, we
 			// won't notice that it went unused.
@@ -143,7 +143,7 @@ func typecheckswitch(n *Node) {
 						} else {
 							yyerrorl(ncase.Pos, "invalid case %v in switch (mismatched types %v and bool)", n1, n1.Type)
 						}
-					case nilonly != "" && !isnil(n1):
+					case nilonly != "" && !n1.isNil():
 						yyerrorl(ncase.Pos, "invalid case %v in switch (can only compare %s %v to nil)", n1, nilonly, n.Left)
 					case t.IsInterface() && !n1.Type.IsInterface() && !IsComparable(n1.Type):
 						yyerrorl(ncase.Pos, "invalid case %L in switch (incomparable type)", n1)

src/cmd/compile/internal/gc/typecheck.go

@@ -307,7 +307,7 @@ func typecheck1(n *Node, top int) *Node {
 
 		if top&Easgn == 0 {
 			// not a write to the variable
-			if isblank(n) {
+			if n.isBlank() {
 				yyerror("cannot use _ as value")
 				n.Type = nil
 				return n
@@ -673,19 +673,19 @@ func typecheck1(n *Node, top int) *Node {
 			return n
 		}
 
-		if l.Type.IsSlice() && !isnil(l) && !isnil(r) {
+		if l.Type.IsSlice() && !l.isNil() && !r.isNil() {
 			yyerror("invalid operation: %v (slice can only be compared to nil)", n)
 			n.Type = nil
 			return n
 		}
 
-		if l.Type.IsMap() && !isnil(l) && !isnil(r) {
+		if l.Type.IsMap() && !l.isNil() && !r.isNil() {
 			yyerror("invalid operation: %v (map can only be compared to nil)", n)
 			n.Type = nil
 			return n
 		}
 
-		if l.Type.Etype == TFUNC && !isnil(l) && !isnil(r) {
+		if l.Type.Etype == TFUNC && !l.isNil() && !r.isNil() {
 			yyerror("invalid operation: %v (func can only be compared to nil)", n)
 			n.Type = nil
 			return n
@@ -3304,7 +3304,7 @@ func typecheckas(n *Node) {
 	if n.Left.Typecheck() == 0 {
 		n.Left = typecheck(n.Left, Erv|Easgn)
 	}
-	if !isblank(n.Left) {
+	if !n.Left.isBlank() {
 		checkwidth(n.Left.Type) // ensure width is calculated for backend
 	}
 }
@@ -3664,7 +3664,7 @@ func typecheckdef(n *Node) {
 			goto ret
 		}
 
-		if e.Type != nil && e.Op != OLITERAL || !isgoconst(e) {
+		if e.Type != nil && e.Op != OLITERAL || !e.isGoConst() {
 			if !e.Diag() {
 				yyerror("const initializer %v is not a constant", e)
 				e.SetDiag(true)

src/cmd/compile/internal/gc/walk.go

@@ -703,7 +703,7 @@ opswitch:
 			break
 		}
 
-		if !instrumenting && iszero(n.Right) {
+		if !instrumenting && isZero(n.Right) {
 			break
 		}
 
@@ -783,7 +783,7 @@ opswitch:
 		walkexprlistsafe(n.List.Slice(), init)
 		r.Left = walkexpr(r.Left, init)
 		var n1 *Node
-		if isblank(n.List.First()) {
+		if n.List.First().isBlank() {
 			n1 = nodnil()
 		} else {
 			n1 = nod(OADDR, n.List.First(), nil)
@@ -834,14 +834,14 @@ opswitch:
 		// mapaccess2* returns a typed bool, but due to spec changes,
 		// the boolean result of i.(T) is now untyped so we make it the
 		// same type as the variable on the lhs.
-		if ok := n.List.Second(); !isblank(ok) && ok.Type.IsBoolean() {
+		if ok := n.List.Second(); !ok.isBlank() && ok.Type.IsBoolean() {
 			r.Type.Field(1).Type = ok.Type
 		}
 		n.Rlist.Set1(r)
 		n.Op = OAS2FUNC
 
 		// don't generate a = *var if a is _
-		if !isblank(a) {
+		if !a.isBlank() {
 			var_ := temp(types.NewPtr(t.Val()))
 			var_.SetTypecheck(1)
 			var_.SetNonNil(true) // mapaccess always returns a non-nil pointer
@@ -1216,7 +1216,7 @@ opswitch:
 		n.Left = walkexpr(n.Left, init)
 		low, high, max := n.SliceBounds()
 		low = walkexpr(low, init)
-		if low != nil && iszero(low) {
+		if low != nil && isZero(low) {
 			// Reduce x[0:j] to x[:j] and x[0:j:k] to x[:j:k].
 			low = nil
 		}
@@ -1848,7 +1848,7 @@ func ascompatet(nl Nodes, nr *types.Type) []*Node {
 
 	var nn, mm Nodes
 	for i, l := range nl.Slice() {
-		if isblank(l) {
+		if l.isBlank() {
 			continue
 		}
 		r := nr.Field(i)
@@ -1967,7 +1967,7 @@ func nodarg(t interface{}, fp int) *Node {
 	// Rewrite argument named _ to __,
 	// or else the assignment to _ will be
 	// discarded during code generation.
-	if isblank(n) {
+	if n.isBlank() {
 		n.Sym = lookup("__")
 	}
 
@@ -2268,7 +2268,7 @@ func convas(n *Node, init *Nodes) *Node {
 		return n
 	}
 
-	if isblank(n.Left) {
+	if n.Left.isBlank() {
 		n.Right = defaultlit(n.Right, nil)
 		return n
 	}