cmd/compile: factor out Pkg, Sym, and Type into package types

- created new package cmd/compile/internal/types
- moved Pkg, Sym, Type to new package
- to break cycles, for now we need the (ugly) types/utils.go
  file which contains a handful of functions that must be installed
  early by the gc frontend
- to break cycles, for now we need two functions to convert between
  *gc.Node and *types.Node (the latter is a dummy type)
- adjusted the gc's code to use the new package and the conversion
  functions as needed
- made several Pkg, Sym, and Type methods functions as needed
- renamed constructors typ, typPtr, typArray, etc. to types.New,
  types.NewPtr, types.NewArray, etc.

Passes toolstash-check -all.

Change-Id: I8adfa5e85c731645d0a7fd2030375ed6ebf54b72
Reviewed-on: https://go-review.googlesource.com/39855
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

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

@@ -4,14 +4,17 @@
 
 package gc
 
-import "unicode/utf8"
+import (
+	"cmd/compile/internal/types"
+	"unicode/utf8"
+)
 
 // range
 func typecheckrange(n *Node) {
 	var toomany int
 	var why string
-	var t1 *Type
-	var t2 *Type
+	var t1 *types.Type
+	var t2 *types.Type
 	var v1 *Node
 	var v2 *Node
 	var ls []*Node
@@ -52,7 +55,7 @@ func typecheckrange(n *Node) {
 		goto out
 
 	case TARRAY, TSLICE:
-		t1 = Types[TINT]
+		t1 = types.Types[TINT]
 		t2 = t.Elem()
 
 	case TMAP:
@@ -72,8 +75,8 @@ func typecheckrange(n *Node) {
 		}
 
 	case TSTRING:
-		t1 = Types[TINT]
-		t2 = runetype
+		t1 = types.Types[TINT]
+		t2 = types.Runetype
 	}
 
 	if n.List.Len() > 2 || toomany != 0 {
@@ -187,15 +190,15 @@ func walkrange(n *Node) *Node {
 		// orderstmt arranged for a copy of the array/slice variable if needed.
 		ha := a
 
-		hv1 := temp(Types[TINT])
-		hn := temp(Types[TINT])
+		hv1 := temp(types.Types[TINT])
+		hn := temp(types.Types[TINT])
 		var hp *Node
 
 		init = append(init, nod(OAS, hv1, nil))
 		init = append(init, nod(OAS, hn, nod(OLEN, ha, nil)))
 
 		if v2 != nil {
-			hp = temp(typPtr(n.Type.Elem()))
+			hp = temp(types.NewPtr(n.Type.Elem()))
 			tmp := nod(OINDEX, ha, nodintconst(0))
 			tmp.SetBounded(true)
 			init = append(init, nod(OAS, hp, nod(OADDR, tmp, nil)))
@@ -229,7 +232,7 @@ func walkrange(n *Node) *Node {
 
 			tmp.Type = hp.Type
 			tmp.Typecheck = 1
-			tmp.Right.Type = Types[Tptr]
+			tmp.Right.Type = types.Types[types.Tptr]
 			tmp.Right.Typecheck = 1
 			a = nod(OAS, hp, tmp)
 			a = typecheck(a, Etop)
@@ -281,10 +284,10 @@ func walkrange(n *Node) *Node {
 
 		hv1 := temp(t.Elem())
 		hv1.Typecheck = 1
-		if haspointers(t.Elem()) {
+		if types.Haspointers(t.Elem()) {
 			init = append(init, nod(OAS, hv1, nil))
 		}
-		hb := temp(Types[TBOOL])
+		hb := temp(types.Types[TBOOL])
 
 		n.Left = nod(ONE, hb, nodbool(false))
 		a := nod(OAS2RECV, nil, nil)
@@ -321,9 +324,9 @@ func walkrange(n *Node) *Node {
 		// orderstmt arranged for a copy of the string variable.
 		ha := a
 
-		hv1 := temp(Types[TINT])
-		hv1t := temp(Types[TINT])
-		hv2 := temp(runetype)
+		hv1 := temp(types.Types[TINT])
+		hv1t := temp(types.Types[TINT])
+		hv2 := temp(types.Runetype)
 
 		// hv1 := 0
 		init = append(init, nod(OAS, hv1, nil))
@@ -339,7 +342,7 @@ func walkrange(n *Node) *Node {
 		// hv2 := rune(ha[hv1])
 		nind := nod(OINDEX, ha, hv1)
 		nind.SetBounded(true)
-		body = append(body, nod(OAS, hv2, conv(nind, runetype)))
+		body = append(body, nod(OAS, hv2, conv(nind, types.Runetype)))
 
 		// if hv2 < utf8.RuneSelf
 		nif := nod(OIF, nil, nil)
@@ -448,25 +451,25 @@ func memclrrange(n, v1, v2, a *Node) bool {
 	n.Left = nod(ONE, nod(OLEN, a, nil), nodintconst(0))
 
 	// hp = &a[0]
-	hp := temp(Types[TUNSAFEPTR])
+	hp := temp(types.Types[TUNSAFEPTR])
 
 	tmp := nod(OINDEX, a, nodintconst(0))
 	tmp.SetBounded(true)
 	tmp = nod(OADDR, tmp, nil)
 	tmp = nod(OCONVNOP, tmp, nil)
-	tmp.Type = Types[TUNSAFEPTR]
+	tmp.Type = types.Types[TUNSAFEPTR]
 	n.Nbody.Append(nod(OAS, hp, tmp))
 
 	// hn = len(a) * sizeof(elem(a))
-	hn := temp(Types[TUINTPTR])
+	hn := temp(types.Types[TUINTPTR])
 
 	tmp = nod(OLEN, a, nil)
 	tmp = nod(OMUL, tmp, nodintconst(elemsize))
-	tmp = conv(tmp, Types[TUINTPTR])
+	tmp = conv(tmp, types.Types[TUINTPTR])
 	n.Nbody.Append(nod(OAS, hn, tmp))
 
 	var fn *Node
-	if haspointers(a.Type.Elem()) {
+	if types.Haspointers(a.Type.Elem()) {
 		// memclrHasPointers(hp, hn)
 		fn = mkcall("memclrHasPointers", nil, nil, hp, hn)
 	} else {