support for ...T parameters (go/* packages)

R=rsc
CC=golang-dev
https://golang.org/cl/194126

src/pkg/exp/parser/parser.go

@@ -379,7 +379,7 @@ func (p *parser) parseArrayType(ellipsisOk bool) ast.Expr {
 	lbrack := p.expect(token.LBRACK)
 	var len ast.Expr
 	if ellipsisOk && p.tok == token.ELLIPSIS {
-		len = &ast.Ellipsis{p.pos}
+		len = &ast.Ellipsis{p.pos, nil}
 		p.next()
 	} else if p.tok != token.RBRACK {
 		len = p.parseExpr()
@@ -499,11 +499,11 @@ func (p *parser) tryParameterType(ellipsisOk bool) ast.Expr {
 	if ellipsisOk && p.tok == token.ELLIPSIS {
 		pos := p.pos
 		p.next()
+		typ := p.tryType()
 		if p.tok != token.RPAREN {
-			// "..." always must be at the very end of a parameter list
-			p.Error(pos, "expected type, found '...'")
+			p.Error(pos, "can use '...' for last parameter only")
 		}
-		return &ast.Ellipsis{pos}
+		return &ast.Ellipsis{pos, typ}
 	}
 	return p.tryType()
 }

src/pkg/go/ast/ast.go

@@ -125,7 +125,8 @@ type (
 	// parameter list or the "..." length in an array type.
 	//
 	Ellipsis struct {
-		token.Position // position of "..."
+		token.Position      // position of "..."
+		Elt            Expr // ellipsis element type (parameter lists only)
 	}
 
 	// A BasicLit node represents a literal of basic type.

src/pkg/go/parser/interface.go

@@ -164,7 +164,7 @@ func ParseDir(path string, filter func(*os.Dir) bool, mode uint) (map[string]*as
 		return nil, err
 	}
 
-	scope := ast.NewScope(nil)
+	var scope *ast.Scope = nil // for now tracking of declarations is disabled
 	pkgs := make(map[string]*ast.Package)
 	for i := 0; i < len(list); i++ {
 		entry := &list[i]

src/pkg/go/parser/parser.go

@@ -81,10 +81,7 @@ func (p *parser) init(filename string, src []byte, scope *ast.Scope, mode uint)
 	p.mode = mode
 	p.trace = mode&Trace != 0 // for convenience (p.trace is used frequently)
 	if scope != nil {
-		// Disabled for now.  Causes error with "godoc http":
-		//    parser.parseDir: src/pkg/http/server.go:159:16: 'Write' declared already at src/pkg/http/request.go:140:21 (and 4 more errors)
-
-		// p.checkDecl = true
+		p.checkDecl = true
 	} else {
 		scope = ast.NewScope(nil) // provide a dummy scope
 	}
@@ -480,7 +477,7 @@ func (p *parser) parseArrayType(ellipsisOk bool) ast.Expr {
 	lbrack := p.expect(token.LBRACK)
 	var len ast.Expr
 	if ellipsisOk && p.tok == token.ELLIPSIS {
-		len = &ast.Ellipsis{p.pos}
+		len = &ast.Ellipsis{p.pos, nil}
 		p.next()
 	} else if p.tok != token.RBRACK {
 		len = p.parseExpr()
@@ -600,11 +597,11 @@ func (p *parser) tryParameterType(ellipsisOk bool) ast.Expr {
 	if ellipsisOk && p.tok == token.ELLIPSIS {
 		pos := p.pos
 		p.next()
+		typ := p.tryType()
 		if p.tok != token.RPAREN {
-			// "..." always must be at the very end of a parameter list
-			p.Error(pos, "expected type, found '...'")
+			p.Error(pos, "can use '...' for last parameter only")
 		}
-		return &ast.Ellipsis{pos}
+		return &ast.Ellipsis{pos, typ}
 	}
 	return p.tryType()
 }
@@ -1824,6 +1821,9 @@ func parseImportSpec(p *parser, doc *ast.CommentGroup) ast.Spec {
 		p.next()
 	} else if p.tok == token.IDENT {
 		ident = p.parseIdent(ast.Pkg)
+		// TODO(gri) Make sure the ident is not already declared in the
+		//           package scope. Also, cannot add the same name to
+		//           the package scope later.
 		p.declIdent(p.fileScope, ident)
 	}
 

src/pkg/go/parser/parser_test.go

@@ -36,6 +36,8 @@ var validPrograms = []interface{}{
 	`package main; func main() { _ = (<-chan int)(x) }` + "\n",
 	`package main; func main() { _ = (<-chan <-chan int)(x) }` + "\n",
 	`package main; func f(func() func() func())` + "\n",
+	`package main; func f(...)` + "\n",
+	`package main; func f(float, ...int)` + "\n",
 }
 
 

src/pkg/go/printer/nodes.go

@@ -759,6 +759,9 @@ func (p *printer) expr1(expr ast.Expr, prec1, depth int, ctxt exprContext, multi
 
 	case *ast.Ellipsis:
 		p.print(token.ELLIPSIS)
+		if x.Elt != nil {
+			p.expr(x.Elt, multiLine)
+		}
 
 	case *ast.ArrayType:
 		p.print(token.LBRACK)

src/pkg/go/printer/testdata/declarations.golden

@@ -547,3 +547,27 @@ func _() {	// opening "{" must move up
 
 	var _ = x	// comment
 }
+
+
+// ellipsis parameters
+func _(...)
+func _(...int)
+func _(...*int)
+func _(...[]int)
+func _(...struct{})
+func _(bool, ...interface{})
+func _(bool, ...func())
+func _(bool, ...func(...))
+func _(bool, ...map[string]int)
+func _(bool, ...chan int)
+
+func _(b bool, x ...)
+func _(b bool, x ...int)
+func _(b bool, x ...*int)
+func _(b bool, x ...[]int)
+func _(b bool, x ...struct{})
+func _(x ...interface{})
+func _(x ...func())
+func _(x ...func(...))
+func _(x ...map[string]int)
+func _(x ...chan int)

src/pkg/go/printer/testdata/declarations.input

@@ -551,3 +551,27 @@ func _()  // opening "{" must move up
 	var _  // comment
 	= x;
 }
+
+
+// ellipsis parameters
+func _(...)
+func _(...int)
+func _(...*int)
+func _(...[]int)
+func _(...struct{})
+func _(bool, ...interface{})
+func _(bool, ...func())
+func _(bool, ...func(...))
+func _(bool, ...map[string]int)
+func _(bool, ...chan int)
+
+func _(b bool, x ...)
+func _(b bool, x ...int)
+func _(b bool, x ...*int)
+func _(b bool, x ...[]int)
+func _(b bool, x ...struct{})
+func _(x ...interface{})
+func _(x ...func())
+func _(x ...func(...))
+func _(x ...map[string]int)
+func _(x ...chan int)