[dev.typeparams] cmd/compile/internal/syntax: export NewName and use it

Most syntax.Nodes are allocated in one place and there didn't
seem a need to provide factory methods - so as a matter of
API design, all nodes are "naked", without any constructors.

However, Name nodes are frequently used/replaced and also
are created as helper nodes in clients (types2). Make an
exception and export NewName.

Change-Id: I4b5c499d65bba74592dea68b0936c118b3edaca7
Reviewed-on: https://go-review.googlesource.com/c/go/+/277572
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

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

@@ -122,6 +122,13 @@ type Group struct {
 // ----------------------------------------------------------------------------
 // Expressions
 
+func NewName(pos Pos, value string) *Name {
+	n := new(Name)
+	n.pos = pos
+	n.Value = value
+	return n
+}
+
 type (
 	Expr interface {
 		Node

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

@@ -533,7 +533,7 @@ func (p *parser) importDecl(group *Group) Decl {
 	case _Name:
 		d.LocalPkgName = p.name()
 	case _Dot:
-		d.LocalPkgName = p.newName(".")
+		d.LocalPkgName = NewName(p.pos(), ".")
 		p.next()
 	}
 	d.Path = p.oliteral()
@@ -1409,9 +1409,7 @@ func (p *parser) interfaceType() *InterfaceType {
 		case _Type:
 			if p.mode&AllowGenerics != 0 {
 				// TODO(gri) factor this better
-				type_ := new(Name)
+				type_ := NewName(p.pos(), "type") // cannot have a method named "type"
-				type_.pos = p.pos()
-				type_.Value = "type" // cannot have a method named "type"
 				p.next()
 				if p.tok != _Semi && p.tok != _Rbrace {
 					f := new(Field)
@@ -1833,9 +1831,7 @@ func (p *parser) paramList(name *Name, close token) (list []*Field) {
 				typ = par.Type
 				if par.Name == nil {
 					pos = typ.Pos()
-					n := p.newName("_")
+					par.Name = NewName(pos, "_")
-					n.pos = pos // correct position
-					par.Name = n
 				}
 			} else if typ != nil {
 				par.Type = typ
@@ -2468,23 +2464,16 @@ func (p *parser) argList() (list []Expr, hasDots bool) {
 // ----------------------------------------------------------------------------
 // Common productions
 
-func (p *parser) newName(value string) *Name {
-	n := new(Name)
-	n.pos = p.pos()
-	n.Value = value
-	return n
-}
-
 func (p *parser) name() *Name {
 	// no tracing to avoid overly verbose output
 
 	if p.tok == _Name {
-		n := p.newName(p.lit)
+		n := NewName(p.pos(), p.lit)
 		p.next()
 		return n
 	}
 
-	n := p.newName("_")
+	n := NewName(p.pos(), "_")
 	p.syntaxError("expecting name")
 	p.advance()
 	return n
@@ -2522,7 +2511,7 @@ func (p *parser) qualifiedName(name *Name) Expr {
 	case p.tok == _Name:
 		x = p.name()
 	default:
-		x = p.newName("_")
+		x = NewName(p.pos(), "_")
 		p.syntaxError("expecting name")
 		p.advance(_Dot, _Semi, _Rbrace)
 	}

src/cmd/compile/internal/types2/resolver.go

@@ -523,7 +523,7 @@ L: // unpack receiver type
 					check.errorf(arg, "receiver type parameter %s must be an identifier", arg)
 				}
 				if par == nil {
-					par = newName(arg.Pos(), "_")
+					par = syntax.NewName(arg.Pos(), "_")
 				}
 				tparams = append(tparams, par)
 			}

src/cmd/compile/internal/types2/stmt.go

@@ -596,14 +596,6 @@ func (check *Checker) stmt(ctxt stmtContext, s syntax.Stmt) {
 	}
 }
 
-func newName(pos syntax.Pos, value string) *syntax.Name {
-	n := new(syntax.Name)
-	// TODO(gri) why does this not work?
-	//n.pos = pos
-	n.Value = value
-	return n
-}
-
 func (check *Checker) switchStmt(inner stmtContext, s *syntax.SwitchStmt) {
 	// init statement already handled
 
@@ -624,7 +616,7 @@ func (check *Checker) switchStmt(inner stmtContext, s *syntax.SwitchStmt) {
 		if len(s.Body) > 0 {
 			pos = s.Body[0].Pos()
 		}
-		x.expr = newName(pos, "true")
+		x.expr = syntax.NewName(pos, "true")
 	}
 
 	check.multipleSwitchDefaults(s.Body)