cmd/compile: add setNodeSeq, and use it in bimport.go

Also rewrite bexport.go to use nodeSeqIterate.

The new setNodeSeq is a transitional generic function to set either a
NodeList or a slice to either a NodeList or a slice.  This should permit
us to flip fields from *NodeList to []*Node, or Nodes, without changing
other code.

Passes toolstash -cmp.

Change-Id: I872cbfe45bc5f432595737c1f6da641c502b1ab6
Reviewed-on: https://go-review.googlesource.com/20194Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

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

@@ -335,7 +335,7 @@ func Export(out *obj.Biobuf, trace bool) int {
 		if p.trace {
 			p.tracef("{ %s }\n", Hconvslice(f.Inl.Slice(), obj.FmtSharp))
 		}
-		p.nodeSlice(f.Inl.Slice())
+		p.nodeList(f.Inl)
 		if p.trace {
 			p.tracef("\n")
 		}
@@ -806,45 +806,25 @@ func (p *exporter) inlinedBody(n *Node) {
 	p.int(index)
 }
 
-func (p *exporter) nodeSlice(list []*Node) {
+func (p *exporter) nodeList(list nodesOrNodeList) {
+	it := nodeSeqIterate(list)
 	if p.trace {
 		p.tracef("[ ")
 	}
-	p.int(len(list))
+	p.int(it.Len())
 	if p.trace {
-		if len(list) == 0 {
+		if it.Len() == 0 {
 			p.tracef("] {}")
 		} else {
 			p.tracef("] {>")
 			defer p.tracef("<\n}")
 		}
 	}
-	for _, n := range list {
+	for ; !it.Done(); it.Next() {
 		if p.trace {
 			p.tracef("\n")
 		}
-		p.node(n)
-	}
-}
-
-func (p *exporter) nodeList(list *NodeList) {
-	if p.trace {
-		p.tracef("[ ")
-	}
-	p.int(count(list))
-	if p.trace {
-		if list == nil {
-			p.tracef("] {}")
-		} else {
-			p.tracef("] {>")
-			defer p.tracef("<\n}")
-		}
-	}
-	for q := list; q != nil; q = q.Next {
-		if p.trace {
-			p.tracef("\n")
-		}
-		p.node(q.N)
+		p.node(it.N())
 	}
 }
 
@@ -982,20 +962,20 @@ func (p *exporter) node(n *Node) {
 	case OIF:
 		p.nodeList(n.Ninit)
 		p.node(n.Left)
-		p.nodeSlice(n.Nbody.Slice())
+		p.nodeList(n.Nbody)
 		p.nodeList(n.Rlist)
 
 	case OFOR:
 		p.nodeList(n.Ninit)
 		p.nodesOrNil(n.Left, n.Right)
-		p.nodeSlice(n.Nbody.Slice())
+		p.nodeList(n.Nbody)
 
 	case ORANGE:
 		if p.bool(n.List != nil) {
 			p.nodeList(n.List)
 		}
 		p.node(n.Right)
-		p.nodeSlice(n.Nbody.Slice())
+		p.nodeList(n.Nbody)
 
 	case OSELECT, OSWITCH:
 		p.nodeList(n.Ninit)
@@ -1006,7 +986,7 @@ func (p *exporter) node(n *Node) {
 		if p.bool(n.List != nil) {
 			p.nodeList(n.List)
 		}
-		p.nodeSlice(n.Nbody.Slice())
+		p.nodeList(n.Nbody)
 
 	case OBREAK, OCONTINUE, OGOTO, OFALL, OXFALL:
 		p.nodesOrNil(n.Left, nil)

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

@@ -113,7 +113,7 @@ func Import(in *obj.Biobuf) {
 	// read inlined functions bodies
 	n := p.int()
 	for i := 0; i < n; i++ {
-		body := p.nodeSlice()
+		body := p.nodeList()
 		const hookup = false // TODO(gri) enable and remove this condition
 		if hookup {
 			p.inlined[i].Inl.Set(body)
@@ -550,20 +550,13 @@ func (p *importer) float(x *Mpflt) {
 // Inlined function bodies
 
 // go.y:stmt_list
-func (p *importer) nodeSlice() []*Node {
-	var l []*Node
-	for i := p.int(); i > 0; i-- {
-		l = append(l, p.node())
-	}
-	return l
-}
-
-func (p *importer) nodeList() *NodeList {
-	var l *NodeList
-	for i := p.int(); i > 0; i-- {
-		l = list(l, p.node())
+func (p *importer) nodeList() []*Node {
+	c := p.int()
+	s := make([]*Node, 0, c)
+	for i := 0; i < c; i++ {
+		s = append(s, p.node())
 	}
-	return l
+	return s
 }
 
 func (p *importer) node() *Node {
@@ -597,7 +590,7 @@ func (p *importer) node() *Node {
 	// expressions
 	case OMAKEMAP, OMAKECHAN, OMAKESLICE:
 		if p.bool() {
-			n.List = p.nodeList()
+			setNodeSeq(&n.List, p.nodeList())
 		}
 		n.Left, n.Right = p.nodesOrNil()
 		n.Type = p.typ()
@@ -612,19 +605,19 @@ func (p *importer) node() *Node {
 		n.Right = p.node()
 
 	case OADDSTR:
-		n.List = p.nodeList()
+		setNodeSeq(&n.List, p.nodeList())
 
 	case OPTRLIT:
 		n.Left = p.node()
 
 	case OSTRUCTLIT:
 		n.Type = p.typ()
-		n.List = p.nodeList()
+		setNodeSeq(&n.List, p.nodeList())
 		n.Implicit = p.bool()
 
 	case OARRAYLIT, OMAPLIT:
 		n.Type = p.typ()
-		n.List = p.nodeList()
+		setNodeSeq(&n.List, p.nodeList())
 		n.Implicit = p.bool()
 
 	case OKEY:
@@ -639,13 +632,13 @@ func (p *importer) node() *Node {
 		// if p.bool() {
 		// 	n.Left = p.node()
 		// } else {
-		// 	n.List = p.nodeList()
+		// 	setNodeSeq(&n.List, p.nodeList())
 		// }
 		x := Nod(OCALL, p.typ().Nod, nil)
 		if p.bool() {
 			x.List = list1(p.node())
 		} else {
-			x.List = p.nodeList()
+			setNodeSeq(&x.List, p.nodeList())
 		}
 		return x
 
@@ -675,12 +668,12 @@ func (p *importer) node() *Node {
 	case OREAL, OIMAG, OAPPEND, OCAP, OCLOSE, ODELETE, OLEN, OMAKE, ONEW, OPANIC,
 		ORECOVER, OPRINT, OPRINTN:
 		n.Left, _ = p.nodesOrNil()
-		n.List = p.nodeList()
+		setNodeSeq(&n.List, p.nodeList())
 		n.Isddd = p.bool()
 
 	case OCALL, OCALLFUNC, OCALLMETH, OCALLINTER, OGETG:
 		n.Left = p.node()
-		n.List = p.nodeList()
+		setNodeSeq(&n.List, p.nodeList())
 		n.Isddd = p.bool()
 
 	case OCMPSTR, OCMPIFACE:
@@ -706,47 +699,47 @@ func (p *importer) node() *Node {
 		n.Etype = EType(p.int())
 
 	case OAS2, OASWB:
-		n.List = p.nodeList()
-		n.Rlist = p.nodeList()
+		setNodeSeq(&n.List, p.nodeList())
+		setNodeSeq(&n.Rlist, p.nodeList())
 
 	case OAS2DOTTYPE, OAS2FUNC, OAS2MAPR, OAS2RECV:
-		n.List = p.nodeList()
-		n.Rlist = p.nodeList()
+		setNodeSeq(&n.List, p.nodeList())
+		setNodeSeq(&n.Rlist, p.nodeList())
 
 	case ORETURN:
-		n.List = p.nodeList()
+		setNodeSeq(&n.List, p.nodeList())
 
 	case OPROC, ODEFER:
 		n.Left = p.node()
 
 	case OIF:
-		n.Ninit = p.nodeList()
+		setNodeSeq(&n.Ninit, p.nodeList())
 		n.Left = p.node()
-		n.Nbody.Set(p.nodeSlice())
-		n.Rlist = p.nodeList()
+		n.Nbody.Set(p.nodeList())
+		setNodeSeq(&n.Rlist, p.nodeList())
 
 	case OFOR:
-		n.Ninit = p.nodeList()
+		setNodeSeq(&n.Ninit, p.nodeList())
 		n.Left, n.Right = p.nodesOrNil()
-		n.Nbody.Set(p.nodeSlice())
+		n.Nbody.Set(p.nodeList())
 
 	case ORANGE:
 		if p.bool() {
-			n.List = p.nodeList()
+			setNodeSeq(&n.List, p.nodeList())
 		}
 		n.Right = p.node()
-		n.Nbody.Set(p.nodeSlice())
+		n.Nbody.Set(p.nodeList())
 
 	case OSELECT, OSWITCH:
-		n.Ninit = p.nodeList()
+		setNodeSeq(&n.Ninit, p.nodeList())
 		n.Left, _ = p.nodesOrNil()
-		n.List = p.nodeList()
+		setNodeSeq(&n.List, p.nodeList())
 
 	case OCASE, OXCASE:
 		if p.bool() {
-			n.List = p.nodeList()
+			setNodeSeq(&n.List, p.nodeList())
 		}
-		n.Nbody.Set(p.nodeSlice())
+		n.Nbody.Set(p.nodeList())
 
 	case OBREAK, OCONTINUE, OGOTO, OFALL, OXFALL:
 		n.Left, _ = p.nodesOrNil()

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

@@ -495,6 +495,18 @@ func (n *Nodes) AppendNodeList(l *NodeList) {
 	}
 }
 
+// nodesOrNodeList must be either type Nodes or type *NodeList, or, in
+// some cases, []*Node. It exists during the transition from NodeList
+// to Nodes only and then should be deleted. See nodeSeqIterate to
+// return an iterator from a nodesOrNodeList.
+type nodesOrNodeList interface{}
+
+// nodesOrNodeListPtr must be type *Nodes or type **NodeList, or, in
+// some cases, *[]*Node. It exists during the transition from NodeList
+// to Nodes only, and then should be deleted. See setNodeSeq to assign
+// to a generic value.
+type nodesOrNodeListPtr interface{}
+
 // nodeSeqIterator is an interface used to iterate over a sequence of nodes.
 // TODO(iant): Remove after conversion from NodeList to Nodes is complete.
 type nodeSeqIterator interface {
@@ -506,6 +518,8 @@ type nodeSeqIterator interface {
 	N() *Node
 	// Return the address of the current node.
 	P() **Node
+	// Return the number of items remaining in the iteration.
+	Len() int
 }
 
 // nodeListIterator is a type that implements nodeSeqIterator using a
@@ -530,6 +544,10 @@ func (nli *nodeListIterator) P() **Node {
 	return &nli.l.N
 }
 
+func (nli *nodeListIterator) Len() int {
+	return count(nli.l)
+}
+
 // nodesIterator implements nodeSeqIterator using a Nodes.
 type nodesIterator struct {
 	n Nodes
@@ -552,8 +570,12 @@ func (ni *nodesIterator) P() **Node {
 	return &ni.n.Slice()[ni.i]
 }
 
+func (ni *nodesIterator) Len() int {
+	return len(ni.n.Slice())
+}
+
 // nodeSeqIterate returns an iterator over either a *Nodelist or a *Nodes.
-func nodeSeqIterate(ns interface{}) nodeSeqIterator {
+func nodeSeqIterate(ns nodesOrNodeList) nodeSeqIterator {
 	switch ns := ns.(type) {
 	case *NodeList:
 		return &nodeListIterator{ns}
@@ -563,3 +585,51 @@ func nodeSeqIterate(ns interface{}) nodeSeqIterator {
 		panic("can't happen")
 	}
 }
+
+// setNodeSeq implements *a = b.
+// a must have type **NodeList, *Nodes, or *[]*Node.
+// b must have type *NodeList, Nodes, or []*Node.
+// This is an interim function during the transition from NodeList to Nodes.
+// TODO(iant): Remove when transition is complete.
+func setNodeSeq(a nodesOrNodeListPtr, b nodesOrNodeList) {
+	// Simplify b to either *Nodelist or []*Node.
+	if n, ok := b.(Nodes); ok {
+		b = n.Slice()
+	}
+
+	if l, ok := a.(**NodeList); ok {
+		switch b := b.(type) {
+		case *NodeList:
+			*l = b
+		case []*Node:
+			var ll *NodeList
+			for _, n := range b {
+				ll = list(ll, n)
+			}
+			*l = ll
+		default:
+			panic("can't happen")
+		}
+	} else {
+		var s []*Node
+		switch b := b.(type) {
+		case *NodeList:
+			for l := b; l != nil; l = l.Next {
+				s = append(s, l.N)
+			}
+		case []*Node:
+			s = b
+		default:
+			panic("can't happen")
+		}
+
+		switch a := a.(type) {
+		case *Nodes:
+			a.Set(s)
+		case *[]*Node:
+			*a = s
+		default:
+			panic("can't happen")
+		}
+	}
+}

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

@@ -34,7 +34,7 @@ func resolve(n *Node) *Node {
 	return n
 }
 
-func typechecklist(l interface{}, top int) {
+func typechecklist(l nodesOrNodeList, top int) {
 	for it := nodeSeqIterate(l); !it.Done(); it.Next() {
 		typecheck(it.P(), top)
 	}