[dev.regabi] cmd/compile: add NewNamed

The start of abstracting away Type fields. This adds a new constructor
for named types, styled after go/types.NewNamed. Along with helper
methods for SetNod and Pos, this allows hiding Nod.

Change-Id: Ica107034b6346c7b523bf6ae2a34009e350a9aa8
Reviewed-on: https://go-review.googlesource.com/c/go/+/274434
Trust: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Russ Cox <rsc@golang.org>

src/cmd/compile/fmtmap_test.go

@@ -130,6 +130,7 @@ var knownFormats = map[string]string{
 	"cmd/compile/internal/types.EType %d":             "",
 	"cmd/compile/internal/types.EType %s":             "",
 	"cmd/compile/internal/types.EType %v":             "",
+	"cmd/compile/internal/types.IRNode %v":            "",
 	"cmd/internal/obj.ABI %v":                         "",
 	"error %v":                                        "",
 	"float64 %.2f":                                    "",

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

@@ -205,7 +205,7 @@ func findTypeLoop(t *types.Type, path *[]*types.Type) bool {
 		}
 
 		*path = append(*path, t)
-		if findTypeLoop(ir.AsNode(t.Nod).Name().Ntype.Type(), path) {
+		if findTypeLoop(t.Obj().(*ir.Name).Ntype.Type(), path) {
 			return true
 		}
 		*path = (*path)[:len(*path)-1]
@@ -314,8 +314,8 @@ func dowidth(t *types.Type) {
 	defercheckwidth()
 
 	lno := base.Pos
-	if ir.AsNode(t.Nod) != nil {
-		base.Pos = ir.AsNode(t.Nod).Pos()
+	if pos := t.Pos(); pos.IsKnown() {
+		base.Pos = pos
 	}
 
 	t.Width = -2

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

@@ -101,9 +101,7 @@ func importsym(ipkg *types.Pkg, s *types.Sym, op ir.Op) ir.Node {
 func importtype(ipkg *types.Pkg, pos src.XPos, s *types.Sym) *types.Type {
 	n := importsym(ipkg, s, ir.OTYPE)
 	if n.Op() != ir.OTYPE {
-		t := types.New(types.TFORW)
-		t.Sym = s
-		t.Nod = n
+		t := types.NewNamed(n)
 
 		n.SetOp(ir.OTYPE)
 		n.SetPos(pos)

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

@@ -640,7 +640,7 @@ func (w *exportWriter) doTyp(t *types.Type) {
 		}
 
 		w.startType(definedType)
-		w.qualifiedIdent(ir.TypeNode(t))
+		w.qualifiedIdent(t.Obj().(*ir.Name))
 		return
 	}
 

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

@@ -316,7 +316,7 @@ func (r *importReader) doDecl(n ir.Node) {
 		// after the underlying type has been assigned.
 		defercheckwidth()
 		underlying := r.typ()
-		types.SetUnderlying(t, underlying)
+		t.SetUnderlying(underlying)
 		resumecheckwidth()
 
 		if underlying.IsInterface() {

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

@@ -1490,9 +1490,9 @@ func ifaceData(pos src.XPos, n ir.Node, t *types.Type) ir.Node {
 // typePos returns the position associated with t.
 // This is where t was declared or where it appeared as a type expression.
 func typePos(t *types.Type) src.XPos {
-	n := ir.AsNode(t.Nod)
-	if n == nil || !n.Pos().IsKnown() {
-		base.Fatalf("bad type: %v", t)
+	if pos := t.Pos(); pos.IsKnown() {
+		return pos
 	}
-	return n.Pos()
+	base.Fatalf("bad type: %v", t)
+	panic("unreachable")
 }

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

@@ -3432,10 +3432,8 @@ func typecheckdeftype(n *ir.Name) {
 		defer tracePrint("typecheckdeftype", n)(nil)
 	}
 
-	t := types.New(types.TFORW)
-	t.Sym = n.Sym()
+	t := types.NewNamed(n)
 	t.Vargen = n.Vargen
-	t.Nod = n
 	if n.Pragma()&ir.NotInHeap != 0 {
 		t.SetNotInHeap(true)
 	}
@@ -3448,7 +3446,7 @@ func typecheckdeftype(n *ir.Name) {
 	errorsBefore := base.Errors()
 	n.Ntype = typecheckNtype(n.Ntype)
 	if underlying := n.Ntype.Type(); underlying != nil {
-		types.SetUnderlying(t, underlying)
+		t.SetUnderlying(underlying)
 	} else {
 		n.SetDiag(true)
 		n.SetType(nil)
@@ -3895,14 +3893,6 @@ func deadcodeexpr(n ir.Node) ir.Node {
 	return n
 }
 
-func toTypeNode(orig ir.Node, t *types.Type) ir.Node {
-	n := ir.Nod(ir.OTYPE, nil, nil)
-	n.SetPos(orig.Pos())
-	n.SetType(t)
-	t.Nod = n
-	return n
-}
-
 // getIotaValue returns the current value for "iota",
 // or -1 if not within a ConstSpec.
 func getIotaValue() int64 {

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

@@ -337,11 +337,12 @@ func makeErrorInterface() *types.Type {
 
 func lexinit1() {
 	// error type
-	s := ir.BuiltinPkg.Lookup("error")
-	types.Errortype = makeErrorInterface()
-	types.Errortype.Sym = s
-	types.Errortype.Orig = makeErrorInterface()
-	s.Def = ir.TypeNode(types.Errortype)
+	n := ir.NewNameAt(src.NoXPos, ir.BuiltinPkg.Lookup("error"))
+	types.Errortype = types.NewNamed(n)
+	types.Errortype.SetUnderlying(makeErrorInterface())
+	n.SetOp(ir.OTYPE)
+	n.SetType(types.Errortype)
+	n.Sym().Def = n
 	dowidth(types.Errortype)
 
 	// We create separate byte and rune types for better error messages
@@ -353,7 +354,7 @@ func lexinit1() {
 	// type aliases, albeit at the cost of having to deal with it everywhere).
 
 	// byte alias
-	s = ir.BuiltinPkg.Lookup("byte")
+	s := ir.BuiltinPkg.Lookup("byte")
 	types.Bytetype = types.New(types.TUINT8)
 	types.Bytetype.Sym = s
 	s.Def = ir.TypeNode(types.Bytetype)

src/cmd/compile/internal/ir/expr.go

@@ -545,9 +545,7 @@ func (*ParenExpr) CanBeNtype() {}
 func (n *ParenExpr) SetOTYPE(t *types.Type) {
 	n.op = OTYPE
 	n.typ = t
-	if t.Nod == nil {
-		t.Nod = n
-	}
+	t.SetNod(n)
 }
 
 // A ResultExpr represents a direct access to a result slot on the stack frame.
@@ -762,9 +760,7 @@ func (n *StarExpr) SetOTYPE(t *types.Type) {
 	n.op = OTYPE
 	n.X = nil
 	n.typ = t
-	if t.Nod == nil {
-		t.Nod = n
-	}
+	t.SetNod(n)
 }
 
 func (n *StarExpr) DeepCopy(pos src.XPos) Node {

src/cmd/compile/internal/ir/type.go

@@ -5,6 +5,7 @@
 package ir
 
 import (
+	"cmd/compile/internal/base"
 	"cmd/compile/internal/types"
 	"cmd/internal/src"
 	"fmt"
@@ -51,12 +52,7 @@ func (n *miniType) setOTYPE(t *types.Type, self Node) {
 	}
 	n.op = OTYPE
 	n.typ = t
-
-	// t.Nod can be non-nil already
-	// in the case of shared *type.Types, like []byte or interface{}.
-	if t.Nod == nil {
-		t.Nod = self
-	}
+	t.SetNod(self)
 }
 
 func (n *miniType) Sym() *types.Sym { return nil }   // for Format OTYPE
@@ -362,20 +358,11 @@ func (n *typeNode) CanBeNtype()                   {}
 
 // TypeNode returns the Node representing the type t.
 func TypeNode(t *types.Type) Ntype {
-	return TypeNodeAt(src.NoXPos, t)
-}
-
-// TypeNodeAt returns the Node representing the type t.
-// If the node must be created, TypeNodeAt uses the position pos.
-// TODO(rsc): Does anyone actually use position on these type nodes?
-func TypeNodeAt(pos src.XPos, t *types.Type) Ntype {
-	// If we copied another type with *t = *u,
-	// then t.Nod might be out of date, so check t.Nod.Type() too.
-	n := AsNode(t.Nod)
-	if n == nil || n.Type() != t {
-		n := newTypeNode(pos, t) // t.Sym may be nil
-		t.Nod = n
-		return n
+	if n := t.Obj(); n != nil {
+		if n.Type() != t {
+			base.Fatalf("type skew: %v has type %v, but expected %v", n, n.Type(), t)
+		}
+		return n.(Ntype)
 	}
-	return n.(Ntype)
+	return newTypeNode(src.NoXPos, t)
 }

src/cmd/compile/internal/types/type.go

@@ -14,7 +14,11 @@ import (
 // IRNode represents an ir.Node, but without needing to import cmd/compile/internal/ir,
 // which would cause an import cycle. The uses in other packages must type assert
 // values of type IRNode to ir.Node or a more specific type.
-type IRNode interface{ Type() *Type }
+type IRNode interface {
+	Pos() src.XPos
+	Sym() *Sym
+	Type() *Type
+}
 
 //go:generate stringer -type EType -trimprefix T
 
@@ -142,7 +146,7 @@ type Type struct {
 	methods    Fields
 	allMethods Fields
 
-	Nod  IRNode // canonical OTYPE node
+	nod  IRNode // canonical OTYPE node
 	Orig *Type  // original type (type literal or predefined type)
 
 	// Cache of composite types, with this type being the element type.
@@ -180,6 +184,24 @@ func (t *Type) SetNoalg(b bool)      { t.flags.set(typeNoalg, b) }
 func (t *Type) SetDeferwidth(b bool) { t.flags.set(typeDeferwidth, b) }
 func (t *Type) SetRecur(b bool)      { t.flags.set(typeRecur, b) }
 
+// SetNod associates t with syntax node n.
+func (t *Type) SetNod(n IRNode) {
+	// t.nod can be non-nil already
+	// in the case of shared *Types, like []byte or interface{}.
+	if t.nod == nil {
+		t.nod = n
+	}
+}
+
+// Pos returns a position associated with t, if any.
+// This should only be used for diagnostics.
+func (t *Type) Pos() src.XPos {
+	if t.nod != nil {
+		return t.nod.Pos()
+	}
+	return src.NoXPos
+}
+
 // Pkg returns the package that t appeared in.
 //
 // Pkg is only defined for function, struct, and interface types
@@ -1519,7 +1541,24 @@ var (
 	TypeInt128  = newSSA("int128")
 )
 
-func SetUnderlying(t, underlying *Type) {
+// NewNamed returns a new named type for the given type name.
+func NewNamed(obj IRNode) *Type {
+	t := New(TFORW)
+	t.Sym = obj.Sym()
+	t.nod = obj
+	return t
+}
+
+// Obj returns the type name for the named type t.
+func (t *Type) Obj() IRNode {
+	if t.Sym != nil {
+		return t.nod
+	}
+	return nil
+}
+
+// SetUnderlying sets the underlying type.
+func (t *Type) SetUnderlying(underlying *Type) {
 	if underlying.Etype == TFORW {
 		// This type isn't computed yet; when it is, update n.
 		underlying.ForwardType().Copyto = append(underlying.ForwardType().Copyto, t)
@@ -1546,13 +1585,13 @@ func SetUnderlying(t, underlying *Type) {
 	// to the existing type, but the method set of an interface
 	// type [...] remains unchanged."
 	if t.IsInterface() {
-		*t.Methods() = *underlying.Methods()
-		*t.AllMethods() = *underlying.AllMethods()
+		t.methods = underlying.methods
+		t.allMethods = underlying.allMethods
 	}
 
 	// Update types waiting on this type.
 	for _, w := range ft.Copyto {
-		SetUnderlying(w, t)
+		w.SetUnderlying(t)
 	}
 
 	// Double-check use of type as embedded type.