go/ast: provide complete node text range info

- add End() method to all nodes; the text range of a node n is [n.Pos(), n.End())
- various small bug fixes in the process
- fixed several comments

R=r, rsc
CC=golang-dev
https://golang.org/cl/3769042

src/cmd/cgo/ast.go

@@ -241,9 +241,11 @@ func (f *File) walk(x interface{}, context string, visit func(*File, interface{}
 		f.walk(&n.Index, "expr", visit)
 	case *ast.SliceExpr:
 		f.walk(&n.X, "expr", visit)
-		f.walk(&n.Index, "expr", visit)
+		if n.Low != nil {
-		if n.End != nil {
+			f.walk(&n.Low, "expr", visit)
-			f.walk(&n.End, "expr", visit)
+		}
+		if n.High != nil {
+			f.walk(&n.High, "expr", visit)
 		}
 	case *ast.TypeAssertExpr:
 		f.walk(&n.X, "expr", visit)

src/pkg/exp/eval/expr.go

@@ -597,19 +597,19 @@ func (a *exprCompiler) compile(x ast.Expr, callCtx bool) *expr {
 	case *ast.SliceExpr:
 		var lo, hi *expr
 		arr := a.compile(x.X, false)
-		if x.Index == nil {
+		if x.Low == nil {
 			// beginning was omitted, so we need to provide it
 			ei := &exprInfo{a.compiler, x.Pos()}
 			lo = ei.compileIntLit("0")
 		} else {
-			lo = a.compile(x.Index, false)
+			lo = a.compile(x.Low, false)
 		}
-		if x.End == nil {
+		if x.High == nil {
 			// End was omitted, so we need to compute len(x.X)
 			ei := &exprInfo{a.compiler, x.Pos()}
 			hi = ei.compileBuiltinCallExpr(a.block, lenType, []*expr{arr})
 		} else {
-			hi = a.compile(x.End, false)
+			hi = a.compile(x.High, false)
 		}
 		if arr == nil || lo == nil || hi == nil {
 			return nil

src/pkg/go/ast/ast.go

@@ -34,8 +34,8 @@ import (
 
 // All node types implement the Node interface.
 type Node interface {
-	// Pos returns the (beginning) position of the node.
+	Pos() token.Pos // position of first character belonging to the node
-	Pos() token.Pos
+	End() token.Pos // position of first character immediately after the node
 }
 
 
@@ -71,6 +71,7 @@ type Comment struct {
 
 
 func (c *Comment) Pos() token.Pos { return c.Slash }
+func (c *Comment) End() token.Pos { return token.Pos(int(c.Slash) + len(c.Text)) }
 
 
 // A CommentGroup represents a sequence of comments
@@ -82,6 +83,7 @@ type CommentGroup struct {
 
 
 func (g *CommentGroup) Pos() token.Pos { return g.List[0].Pos() }
+func (g *CommentGroup) End() token.Pos { return g.List[len(g.List)-1].End() }
 
 
 // ----------------------------------------------------------------------------
@@ -108,6 +110,14 @@ func (f *Field) Pos() token.Pos {
 }
 
 
+func (f *Field) End() token.Pos {
+	if f.Tag != nil {
+		return f.Tag.End()
+	}
+	return f.Type.End()
+}
+
+
 // A FieldList represents a list of Fields, enclosed by parentheses or braces.
 type FieldList struct {
 	Opening token.Pos // position of opening parenthesis/brace
@@ -117,6 +127,7 @@ type FieldList struct {
 
 
 func (list *FieldList) Pos() token.Pos { return list.Opening }
+func (list *FieldList) End() token.Pos { return list.Closing + 1 }
 
 
 // NumFields returns the number of (named and anonymous fields) in a FieldList.
@@ -144,7 +155,7 @@ type (
 	// created.
 	//
 	BadExpr struct {
-		Begin token.Pos // beginning position of bad expression
+		From, To token.Pos // position range of bad expression
 	}
 
 	// An Ident node represents an identifier.
@@ -159,7 +170,7 @@ type (
 	//
 	Ellipsis struct {
 		Ellipsis token.Pos // position of "..."
-		Elt      Expr      // ellipsis element type (parameter lists only)
+		Elt      Expr      // ellipsis element type (parameter lists only); or nil
 	}
 
 	// A BasicLit node represents a literal of basic type.
@@ -179,7 +190,7 @@ type (
 	CompositeLit struct {
 		Type   Expr      // literal type; or nil
 		Lbrace token.Pos // position of "{"
-		Elts   []Expr    // list of composite elements
+		Elts   []Expr    // list of composite elements; or nil
 		Rbrace token.Pos // position of "}"
 	}
 
@@ -204,9 +215,9 @@ type (
 
 	// An SliceExpr node represents an expression followed by slice indices.
 	SliceExpr struct {
-		X     Expr // expression
+		X    Expr // expression
-		Index Expr // beginning of slice range; or nil
+		Low  Expr // begin of slice range; or nil
-		End   Expr // end of slice range; or nil
+		High Expr // end of slice range; or nil
 	}
 
 	// A TypeAssertExpr node represents an expression followed by a
@@ -221,7 +232,7 @@ type (
 	CallExpr struct {
 		Fun      Expr      // function expression
 		Lparen   token.Pos // position of "("
-		Args     []Expr    // function arguments
+		Args     []Expr    // function arguments; or nil
 		Ellipsis token.Pos // position of "...", if any
 		Rparen   token.Pos // position of ")"
 	}
@@ -324,9 +335,9 @@ type (
 )
 
 
-// Pos() implementations for expression/type nodes.
+// Pos and End implementations for expression/type nodes.
 //
-func (x *BadExpr) Pos() token.Pos  { return x.Begin }
+func (x *BadExpr) Pos() token.Pos  { return x.From }
 func (x *Ident) Pos() token.Pos    { return x.NamePos }
 func (x *Ellipsis) Pos() token.Pos { return x.Ellipsis }
 func (x *BasicLit) Pos() token.Pos { return x.ValuePos }
@@ -355,6 +366,40 @@ func (x *MapType) Pos() token.Pos        { return x.Map }
 func (x *ChanType) Pos() token.Pos       { return x.Begin }
 
 
+func (x *BadExpr) End() token.Pos { return x.To }
+func (x *Ident) End() token.Pos   { return token.Pos(int(x.NamePos) + len(x.Name)) }
+func (x *Ellipsis) End() token.Pos {
+	if x.Elt != nil {
+		return x.Elt.End()
+	}
+	return x.Ellipsis + 3 // len("...")
+}
+func (x *BasicLit) End() token.Pos       { return token.Pos(int(x.ValuePos) + len(x.Value)) }
+func (x *FuncLit) End() token.Pos        { return x.Body.End() }
+func (x *CompositeLit) End() token.Pos   { return x.Rbrace + 1 }
+func (x *ParenExpr) End() token.Pos      { return x.Rparen + 1 }
+func (x *SelectorExpr) End() token.Pos   { return x.Sel.End() }
+func (x *IndexExpr) End() token.Pos      { return x.Index.End() }
+func (x *SliceExpr) End() token.Pos      { return x.High.End() }
+func (x *TypeAssertExpr) End() token.Pos { return x.Type.End() }
+func (x *CallExpr) End() token.Pos       { return x.Rparen + 1 }
+func (x *StarExpr) End() token.Pos       { return x.X.End() }
+func (x *UnaryExpr) End() token.Pos      { return x.X.End() }
+func (x *BinaryExpr) End() token.Pos     { return x.Y.End() }
+func (x *KeyValueExpr) End() token.Pos   { return x.Value.End() }
+func (x *ArrayType) End() token.Pos      { return x.Elt.End() }
+func (x *StructType) End() token.Pos     { return x.Fields.End() }
+func (x *FuncType) End() token.Pos {
+	if x.Results != nil {
+		return x.Results.End()
+	}
+	return x.Params.End()
+}
+func (x *InterfaceType) End() token.Pos { return x.Methods.End() }
+func (x *MapType) End() token.Pos       { return x.Value.End() }
+func (x *ChanType) End() token.Pos      { return x.Value.End() }
+
+
 // exprNode() ensures that only expression/type nodes can be
 // assigned to an ExprNode.
 //
@@ -429,7 +474,7 @@ type (
 	// created.
 	//
 	BadStmt struct {
-		Begin token.Pos // beginning position of bad statement
+		From, To token.Pos // position range of bad statement
 	}
 
 	// A DeclStmt node represents a declaration in a statement list.
@@ -448,6 +493,7 @@ type (
 	// A LabeledStmt node represents a labeled statement.
 	LabeledStmt struct {
 		Label *Ident
+		Colon token.Pos // position of ":"
 		Stmt  Stmt
 	}
 
@@ -460,8 +506,9 @@ type (
 
 	// An IncDecStmt node represents an increment or decrement statement.
 	IncDecStmt struct {
-		X   Expr
+		X      Expr
-		Tok token.Token // INC or DEC
+		TokPos token.Pos   // position of Tok
+		Tok    token.Token // INC or DEC
 	}
 
 	// An AssignStmt node represents an assignment or
@@ -489,7 +536,7 @@ type (
 	// A ReturnStmt node represents a return statement.
 	ReturnStmt struct {
 		Return  token.Pos // position of "return" keyword
-		Results []Expr
+		Results []Expr    // result expressions; or nil
 	}
 
 	// A BranchStmt node represents a break, continue, goto,
@@ -585,9 +632,9 @@ type (
 )
 
 
-// Pos() implementations for statement nodes.
+// Pos and End implementations for statement nodes.
 //
-func (s *BadStmt) Pos() token.Pos        { return s.Begin }
+func (s *BadStmt) Pos() token.Pos        { return s.From }
 func (s *DeclStmt) Pos() token.Pos       { return s.Decl.Pos() }
 func (s *EmptyStmt) Pos() token.Pos      { return s.Semicolon }
 func (s *LabeledStmt) Pos() token.Pos    { return s.Label.Pos() }
@@ -610,6 +657,63 @@ func (s *ForStmt) Pos() token.Pos        { return s.For }
 func (s *RangeStmt) Pos() token.Pos      { return s.For }
 
 
+func (s *BadStmt) End() token.Pos  { return s.To }
+func (s *DeclStmt) End() token.Pos { return s.Decl.End() }
+func (s *EmptyStmt) End() token.Pos {
+	return s.Semicolon + 1 /* len(";") */
+}
+func (s *LabeledStmt) End() token.Pos { return s.Stmt.End() }
+func (s *ExprStmt) End() token.Pos    { return s.X.End() }
+func (s *IncDecStmt) End() token.Pos {
+	return s.TokPos + 2 /* len("++") */
+}
+func (s *AssignStmt) End() token.Pos { return s.Rhs[len(s.Rhs)-1].End() }
+func (s *GoStmt) End() token.Pos     { return s.Call.End() }
+func (s *DeferStmt) End() token.Pos  { return s.Call.End() }
+func (s *ReturnStmt) End() token.Pos {
+	if n := len(s.Results); n > 0 {
+		return s.Results[n-1].End()
+	}
+	return s.Return + 6 // len("return")
+}
+func (s *BranchStmt) End() token.Pos {
+	if s.Label != nil {
+		return s.Label.End()
+	}
+	return token.Pos(int(s.TokPos) + len(s.Tok.String()))
+}
+func (s *BlockStmt) End() token.Pos { return s.Rbrace + 1 }
+func (s *IfStmt) End() token.Pos {
+	if s.Else != nil {
+		return s.Else.End()
+	}
+	return s.Body.End()
+}
+func (s *CaseClause) End() token.Pos {
+	if n := len(s.Body); n > 0 {
+		return s.Body[n-1].End()
+	}
+	return s.Colon + 1
+}
+func (s *SwitchStmt) End() token.Pos { return s.Body.End() }
+func (s *TypeCaseClause) End() token.Pos {
+	if n := len(s.Body); n > 0 {
+		return s.Body[n-1].End()
+	}
+	return s.Colon + 1
+}
+func (s *TypeSwitchStmt) End() token.Pos { return s.Body.End() }
+func (s *CommClause) End() token.Pos {
+	if n := len(s.Body); n > 0 {
+		return s.Body[n-1].End()
+	}
+	return s.Colon + 1
+}
+func (s *SelectStmt) End() token.Pos { return s.Body.End() }
+func (s *ForStmt) End() token.Pos    { return s.Body.End() }
+func (s *RangeStmt) End() token.Pos  { return s.Body.End() }
+
+
 // stmtNode() ensures that only statement nodes can be
 // assigned to a StmtNode.
 //
@@ -662,7 +766,7 @@ type (
 	//
 	ValueSpec struct {
 		Doc     *CommentGroup // associated documentation; or nil
-		Names   []*Ident      // value names
+		Names   []*Ident      // value names (len(Names) > 0)
 		Type    Expr          // value type; or nil
 		Values  []Expr        // initial values; or nil
 		Comment *CommentGroup // line comments; or nil
@@ -678,7 +782,7 @@ type (
 )
 
 
-// Pos() implementations for spec nodes.
+// Pos and End implementations for spec nodes.
 //
 func (s *ImportSpec) Pos() token.Pos {
 	if s.Name != nil {
@@ -690,6 +794,19 @@ func (s *ValueSpec) Pos() token.Pos { return s.Names[0].Pos() }
 func (s *TypeSpec) Pos() token.Pos  { return s.Name.Pos() }
 
 
+func (s *ImportSpec) End() token.Pos { return s.Path.End() }
+func (s *ValueSpec) End() token.Pos {
+	if n := len(s.Values); n > 0 {
+		return s.Values[n-1].End()
+	}
+	if s.Type != nil {
+		return s.Type.End()
+	}
+	return s.Names[len(s.Names)-1].End()
+}
+func (s *TypeSpec) End() token.Pos { return s.Type.End() }
+
+
 // specNode() ensures that only spec nodes can be
 // assigned to a Spec.
 //
@@ -706,7 +823,7 @@ type (
 	// created.
 	//
 	BadDecl struct {
-		Begin token.Pos // beginning position of bad declaration
+		From, To token.Pos // position range of bad declaration
 	}
 
 	// A GenDecl node (generic declaration node) represents an import,
@@ -740,13 +857,28 @@ type (
 )
 
 
-// Pos implementations for declaration nodes.
+// Pos and End implementations for declaration nodes.
 //
-func (d *BadDecl) Pos() token.Pos  { return d.Begin }
+func (d *BadDecl) Pos() token.Pos  { return d.From }
 func (d *GenDecl) Pos() token.Pos  { return d.TokPos }
 func (d *FuncDecl) Pos() token.Pos { return d.Type.Pos() }
 
 
+func (d *BadDecl) End() token.Pos { return d.To }
+func (d *GenDecl) End() token.Pos {
+	if d.Rparen.IsValid() {
+		return d.Rparen + 1
+	}
+	return d.Specs[0].End()
+}
+func (d *FuncDecl) End() token.Pos {
+	if d.Body != nil {
+		return d.Body.End()
+	}
+	return d.Type.End()
+}
+
+
 // declNode() ensures that only declaration nodes can be
 // assigned to a DeclNode.
 //
@@ -768,12 +900,18 @@ type File struct {
 	Doc      *CommentGroup   // associated documentation; or nil
 	Package  token.Pos       // position of "package" keyword
 	Name     *Ident          // package name
-	Decls    []Decl          // top-level declarations
+	Decls    []Decl          // top-level declarations; or nil
 	Comments []*CommentGroup // list of all comments in the source file
 }
 
 
 func (f *File) Pos() token.Pos { return f.Package }
+func (f *File) End() token.Pos {
+	if n := len(f.Decls); n > 0 {
+		return f.Decls[n-1].End()
+	}
+	return f.Name.End()
+}
 
 
 // A Package node represents a set of source files
@@ -786,11 +924,5 @@ type Package struct {
 }
 
 
-func (p *Package) Pos() (pos token.Pos) {
+func (p *Package) Pos() token.Pos { return token.NoPos }
-	// get the position of the package clause of the first file, if any
+func (p *Package) End() token.Pos { return token.NoPos }
-	for _, f := range p.Files {
-		pos = f.Pos()
-		break
-	}
-	return
-}

src/pkg/go/ast/walk.go

@@ -90,9 +90,14 @@ func Walk(v Visitor, node Node) {
 		}
 
 	// Expressions
-	case *BadExpr, *Ident, *Ellipsis, *BasicLit:
+	case *BadExpr, *Ident, *BasicLit:
 		// nothing to do
 
+	case *Ellipsis:
+		if n.Elt != nil {
+			Walk(v, n.Elt)
+		}
+
 	case *FuncLit:
 		Walk(v, n.Type)
 		Walk(v, n.Body)
@@ -116,11 +121,11 @@ func Walk(v Visitor, node Node) {
 
 	case *SliceExpr:
 		Walk(v, n.X)
-		if n.Index != nil {
+		if n.Low != nil {
-			Walk(v, n.Index)
+			Walk(v, n.Low)
 		}
-		if n.End != nil {
+		if n.High != nil {
-			Walk(v, n.End)
+			Walk(v, n.High)
 		}
 
 	case *TypeAssertExpr:

src/pkg/go/parser/parser.go

@@ -251,7 +251,7 @@ func (p *parser) expect(tok token.Token) token.Pos {
 	if p.tok != tok {
 		p.errorExpected(pos, "'"+tok.String()+"'")
 	}
-	p.next() // make progress in any case
+	p.next() // make progress
 	return pos
 }
 
@@ -323,9 +323,10 @@ func (p *parser) parseType() ast.Expr {
 	typ := p.tryType()
 
 	if typ == nil {
-		p.errorExpected(p.pos, "type")
+		pos := p.pos
+		p.errorExpected(pos, "type")
 		p.next() // make progress
-		return &ast.BadExpr{p.pos}
+		return &ast.BadExpr{pos, p.pos}
 	}
 
 	return typ
@@ -417,10 +418,10 @@ func (p *parser) parseFieldDecl() *ast.Field {
 	} else {
 		// ["*"] TypeName (AnonymousField)
 		typ = list[0] // we always have at least one element
-		if len(list) > 1 || !isTypeName(deref(typ)) {
+		if n := len(list); n > 1 || !isTypeName(deref(typ)) {
 			pos := typ.Pos()
 			p.errorExpected(pos, "anonymous field")
-			typ = &ast.BadExpr{pos}
+			typ = &ast.BadExpr{pos, list[n-1].End()}
 		}
 	}
 
@@ -469,7 +470,7 @@ func (p *parser) tryVarType(isParam bool) ast.Expr {
 		typ := p.tryType() // don't use parseType so we can provide better error message
 		if typ == nil {
 			p.error(pos, "'...' parameter is missing type")
-			typ = &ast.BadExpr{pos}
+			typ = &ast.BadExpr{pos, p.pos}
 		}
 		if p.tok != token.RPAREN {
 			p.error(pos, "can use '...' with last parameter type only")
@@ -483,9 +484,10 @@ func (p *parser) tryVarType(isParam bool) ast.Expr {
 func (p *parser) parseVarType(isParam bool) ast.Expr {
 	typ := p.tryVarType(isParam)
 	if typ == nil {
-		p.errorExpected(p.pos, "type")
+		pos := p.pos
+		p.errorExpected(pos, "type")
 		p.next() // make progress
-		typ = &ast.BadExpr{p.pos}
+		typ = &ast.BadExpr{pos, p.pos}
 	}
 	return typ
 }
@@ -826,9 +828,10 @@ func (p *parser) parseOperand() ast.Expr {
 		}
 	}
 
-	p.errorExpected(p.pos, "operand")
+	pos := p.pos
+	p.errorExpected(pos, "operand")
 	p.next() // make progress
-	return &ast.BadExpr{p.pos}
+	return &ast.BadExpr{pos, p.pos}
 }
 
 
@@ -984,7 +987,7 @@ func (p *parser) checkExpr(x ast.Expr) ast.Expr {
 		if t.Type == nil {
 			// the form X.(type) is only allowed in type switch expressions
 			p.errorExpected(x.Pos(), "expression")
-			x = &ast.BadExpr{x.Pos()}
+			x = &ast.BadExpr{x.Pos(), x.End()}
 		}
 	case *ast.CallExpr:
 	case *ast.StarExpr:
@@ -992,13 +995,13 @@ func (p *parser) checkExpr(x ast.Expr) ast.Expr {
 		if t.Op == token.RANGE {
 			// the range operator is only allowed at the top of a for statement
 			p.errorExpected(x.Pos(), "expression")
-			x = &ast.BadExpr{x.Pos()}
+			x = &ast.BadExpr{x.Pos(), x.End()}
 		}
 	case *ast.BinaryExpr:
 	default:
 		// all other nodes are not proper expressions
 		p.errorExpected(x.Pos(), "expression")
-		x = &ast.BadExpr{x.Pos()}
+		x = &ast.BadExpr{x.Pos(), x.End()}
 	}
 	return x
 }
@@ -1066,12 +1069,12 @@ func (p *parser) checkExprOrType(x ast.Expr) ast.Expr {
 		if t.Op == token.RANGE {
 			// the range operator is only allowed at the top of a for statement
 			p.errorExpected(x.Pos(), "expression")
-			x = &ast.BadExpr{x.Pos()}
+			x = &ast.BadExpr{x.Pos(), x.End()}
 		}
 	case *ast.ArrayType:
 		if len, isEllipsis := t.Len.(*ast.Ellipsis); isEllipsis {
 			p.error(len.Pos(), "expected array length, found '...'")
-			x = &ast.BadExpr{x.Pos()}
+			x = &ast.BadExpr{x.Pos(), x.End()}
 		}
 	}
 
@@ -1190,14 +1193,15 @@ func (p *parser) parseSimpleStmt(labelOk bool) ast.Stmt {
 	switch p.tok {
 	case token.COLON:
 		// labeled statement
+		colon := p.pos
 		p.next()
 		if labelOk && len(x) == 1 {
 			if label, isIdent := x[0].(*ast.Ident); isIdent {
-				return &ast.LabeledStmt{label, p.parseStmt()}
+				return &ast.LabeledStmt{label, colon, p.parseStmt()}
 			}
 		}
 		p.error(x[0].Pos(), "illegal label declaration")
-		return &ast.BadStmt{x[0].Pos()}
+		return &ast.BadStmt{x[0].Pos(), colon + 1}
 
 	case
 		token.DEFINE, token.ASSIGN, token.ADD_ASSIGN,
@@ -1218,7 +1222,7 @@ func (p *parser) parseSimpleStmt(labelOk bool) ast.Stmt {
 
 	if p.tok == token.INC || p.tok == token.DEC {
 		// increment or decrement
-		s := &ast.IncDecStmt{x[0], p.tok}
+		s := &ast.IncDecStmt{x[0], p.pos, p.tok}
 		p.next() // consume "++" or "--"
 		return s
 	}
@@ -1247,7 +1251,7 @@ func (p *parser) parseGoStmt() ast.Stmt {
 	call := p.parseCallExpr()
 	p.expectSemi()
 	if call == nil {
-		return &ast.BadStmt{pos}
+		return &ast.BadStmt{pos, pos + 2} // len("go")
 	}
 
 	return &ast.GoStmt{pos, call}
@@ -1263,7 +1267,7 @@ func (p *parser) parseDeferStmt() ast.Stmt {
 	call := p.parseCallExpr()
 	p.expectSemi()
 	if call == nil {
-		return &ast.BadStmt{pos}
+		return &ast.BadStmt{pos, pos + 5} // len("defer")
 	}
 
 	return &ast.DeferStmt{pos, call}
@@ -1311,7 +1315,7 @@ func (p *parser) makeExpr(s ast.Stmt) ast.Expr {
 		return p.checkExpr(es.X)
 	}
 	p.error(s.Pos(), "expected condition, found simple statement")
-	return &ast.BadExpr{s.Pos()}
+	return &ast.BadExpr{s.Pos(), s.End()}
 }
 
 
@@ -1547,7 +1551,7 @@ func (p *parser) parseForStmt() ast.Stmt {
 		// possibly a for statement with a range clause; check assignment operator
 		if as.Tok != token.ASSIGN && as.Tok != token.DEFINE {
 			p.errorExpected(as.TokPos, "'=' or ':='")
-			return &ast.BadStmt{pos}
+			return &ast.BadStmt{pos, body.End()}
 		}
 		// check lhs
 		var key, value ast.Expr
@@ -1558,19 +1562,19 @@ func (p *parser) parseForStmt() ast.Stmt {
 			key = as.Lhs[0]
 		default:
 			p.errorExpected(as.Lhs[0].Pos(), "1 or 2 expressions")
-			return &ast.BadStmt{pos}
+			return &ast.BadStmt{pos, body.End()}
 		}
 		// check rhs
 		if len(as.Rhs) != 1 {
 			p.errorExpected(as.Rhs[0].Pos(), "1 expressions")
-			return &ast.BadStmt{pos}
+			return &ast.BadStmt{pos, body.End()}
 		}
 		if rhs, isUnary := as.Rhs[0].(*ast.UnaryExpr); isUnary && rhs.Op == token.RANGE {
 			// rhs is range expression; check lhs
 			return &ast.RangeStmt{pos, key, value, as.TokPos, as.Tok, rhs.X, body}
 		} else {
 			p.errorExpected(s2.Pos(), "range clause")
-			return &ast.BadStmt{pos}
+			return &ast.BadStmt{pos, body.End()}
 		}
 	} else {
 		// regular for statement
@@ -1628,9 +1632,10 @@ func (p *parser) parseStmt() (s ast.Stmt) {
 		s = &ast.EmptyStmt{p.pos}
 	default:
 		// no statement found
-		p.errorExpected(p.pos, "statement")
+		pos := p.pos
+		p.errorExpected(pos, "statement")
 		p.next() // make progress
-		s = &ast.BadStmt{p.pos}
+		s = &ast.BadStmt{pos, p.pos}
 	}
 
 	return
@@ -1754,7 +1759,8 @@ func (p *parser) parseReceiver() *ast.FieldList {
 	// must have exactly one receiver
 	if par.NumFields() != 1 {
 		p.errorExpected(pos, "exactly one receiver")
-		par.List = []*ast.Field{&ast.Field{Type: &ast.BadExpr{token.NoPos}}}
+		// TODO determine a better range for BadExpr below
+		par.List = []*ast.Field{&ast.Field{Type: &ast.BadExpr{pos, pos}}}
 		return par
 	}
 
@@ -1763,7 +1769,7 @@ func (p *parser) parseReceiver() *ast.FieldList {
 	base := deref(recv.Type)
 	if _, isIdent := base.(*ast.Ident); !isIdent {
 		p.errorExpected(base.Pos(), "(unqualified) identifier")
-		par.List = []*ast.Field{&ast.Field{Type: &ast.BadExpr{recv.Pos()}}}
+		par.List = []*ast.Field{&ast.Field{Type: &ast.BadExpr{recv.Pos(), recv.End()}}}
 	}
 
 	return par
@@ -1818,8 +1824,8 @@ func (p *parser) parseDecl() ast.Decl {
 	default:
 		pos := p.pos
 		p.errorExpected(pos, "declaration")
-		decl := &ast.BadDecl{pos}
+		p.next() // make progress
-		p.next() // make progress in any case
+		decl := &ast.BadDecl{pos, p.pos}
 		return decl
 	}
 

src/pkg/go/printer/nodes.go

@@ -714,7 +714,7 @@ func splitSelector(expr ast.Expr) (body, suffix ast.Expr) {
 	case *ast.SliceExpr:
 		body, suffix = splitSelector(x.X)
 		if body != nil {
-			suffix = &ast.SliceExpr{suffix, x.Index, x.End}
+			suffix = &ast.SliceExpr{suffix, x.Low, x.High}
 			return
 		}
 	case *ast.TypeAssertExpr:
@@ -845,17 +845,17 @@ func (p *printer) expr1(expr ast.Expr, prec1, depth int, ctxt exprContext, multi
 		// TODO(gri): should treat[] like parentheses and undo one level of depth
 		p.expr1(x.X, token.HighestPrec, 1, 0, multiLine)
 		p.print(token.LBRACK)
-		if x.Index != nil {
+		if x.Low != nil {
-			p.expr0(x.Index, depth+1, multiLine)
+			p.expr0(x.Low, depth+1, multiLine)
 		}
 		// blanks around ":" if both sides exist and either side is a binary expression
-		if depth <= 1 && x.Index != nil && x.End != nil && (isBinary(x.Index) || isBinary(x.End)) {
+		if depth <= 1 && x.Low != nil && x.High != nil && (isBinary(x.Low) || isBinary(x.High)) {
 			p.print(blank, token.COLON, blank)
 		} else {
 			p.print(token.COLON)
 		}
-		if x.End != nil {
+		if x.High != nil {
-			p.expr0(x.End, depth+1, multiLine)
+			p.expr0(x.High, depth+1, multiLine)
 		}
 		p.print(token.RBRACK)
 
@@ -1071,7 +1071,7 @@ func (p *printer) stmt(stmt ast.Stmt, nextIsRBrace bool, multiLine *bool) {
 		// between (see writeWhitespace)
 		p.print(unindent)
 		p.expr(s.Label, multiLine)
-		p.print(token.COLON, indent)
+		p.print(s.Colon, token.COLON, indent)
 		if e, isEmpty := s.Stmt.(*ast.EmptyStmt); isEmpty {
 			if !nextIsRBrace {
 				p.print(newline, e.Pos(), token.SEMICOLON)
@@ -1089,7 +1089,7 @@ func (p *printer) stmt(stmt ast.Stmt, nextIsRBrace bool, multiLine *bool) {
 	case *ast.IncDecStmt:
 		const depth = 1
 		p.expr0(s.X, depth+1, multiLine)
-		p.print(s.Tok)
+		p.print(s.TokPos, s.Tok)
 
 	case *ast.AssignStmt:
 		var depth = 1