text/template: add back pointer to Nodes for better error generation

ErrorContext now has all the information it needs from the Node,
rather than depending on the template that contains it. This makes
it easier for html/template to generate correct locations in its
error messages.

Updated html/template to use this ability where it is easy, which is
not everywhere, but more work can probably push it through.

Fixes #8577.

LGTM=adg
R=golang-codereviews, adg
CC=golang-codereviews
https://golang.org/cl/130620043

src/pkg/html/template/error.go

@@ -6,12 +6,16 @@ package template
 
 import (
 	"fmt"
+	"text/template/parse"
 )
 
 // Error describes a problem encountered during template Escaping.
 type Error struct {
 	// ErrorCode describes the kind of error.
 	ErrorCode ErrorCode
+	// Node is the node that caused the problem, if known.
+	// If not nil, it overrides Name and Line.
+	Node parse.Node
 	// Name is the name of the template in which the error was encountered.
 	Name string
 	// Line is the line number of the error in the template source or 0.
@@ -182,9 +186,13 @@ const (
 )
 
 func (e *Error) Error() string {
-	if e.Line != 0 {
+	switch {
+	case e.Node != nil:
+		loc, _ := (*parse.Tree)(nil).ErrorContext(e.Node)
+		return fmt.Sprintf("html/template:%s: %s", loc, e.Description)
+	case e.Line != 0:
 		return fmt.Sprintf("html/template:%s:%d: %s", e.Name, e.Line, e.Description)
-	} else if e.Name != "" {
+	case e.Name != "":
 		return fmt.Sprintf("html/template:%s: %s", e.Name, e.Description)
 	}
 	return "html/template: " + e.Description
@@ -192,6 +200,6 @@ func (e *Error) Error() string {
 
 // errorf creates an error given a format string f and args.
 // The template Name still needs to be supplied.
-func errorf(k ErrorCode, line int, f string, args ...interface{}) *Error {
-	return &Error{k, "", line, fmt.Sprintf(f, args...)}
+func errorf(k ErrorCode, node parse.Node, line int, f string, args ...interface{}) *Error {
+	return &Error{k, node, "", line, fmt.Sprintf(f, args...)}
 }

src/pkg/html/template/escape.go

@@ -13,41 +13,33 @@ import (
 	"text/template/parse"
 )
 
-// escapeTemplates rewrites the named templates, which must be
+// escapeTemplate rewrites the named template, which must be
 // associated with t, to guarantee that the output of any of the named
-// templates is properly escaped.  Names should include the names of
-// all templates that might be Executed but need not include helper
-// templates.  If no error is returned, then the named templates have
+// templates is properly escaped.  If no error is returned, then the named templates have
 // been modified.  Otherwise the named templates have been rendered
 // unusable.
-func escapeTemplates(tmpl *Template, names ...string) error {
+func escapeTemplate(tmpl *Template, node parse.Node, name string) error {
 	e := newEscaper(tmpl)
-	for _, name := range names {
-		c, _ := e.escapeTree(context{}, name, 0)
-		var err error
-		if c.err != nil {
-			err, c.err.Name = c.err, name
-		} else if c.state != stateText {
-			err = &Error{ErrEndContext, name, 0, fmt.Sprintf("ends in a non-text context: %v", c)}
-		}
-		if err != nil {
-			// Prevent execution of unsafe templates.
-			for _, name := range names {
-				if t := tmpl.set[name]; t != nil {
-					t.escapeErr = err
-					t.text.Tree = nil
-					t.Tree = nil
-				}
-			}
-			return err
+	c, _ := e.escapeTree(context{}, node, name, 0)
+	var err error
+	if c.err != nil {
+		err, c.err.Name = c.err, name
+	} else if c.state != stateText {
+		err = &Error{ErrEndContext, nil, name, 0, fmt.Sprintf("ends in a non-text context: %v", c)}
+	}
+	if err != nil {
+		// Prevent execution of unsafe templates.
+		if t := tmpl.set[name]; t != nil {
+			t.escapeErr = err
+			t.text.Tree = nil
+			t.Tree = nil
 		}
+		return err
 	}
 	e.commit()
-	for _, name := range names {
-		if t := tmpl.set[name]; t != nil {
-			t.escapeErr = escapeOK
-			t.Tree = t.text.Tree
-		}
+	if t := tmpl.set[name]; t != nil {
+		t.escapeErr = escapeOK
+		t.Tree = t.text.Tree
 	}
 	return nil
 }
@@ -169,7 +161,7 @@ func (e *escaper) escapeAction(c context, n *parse.ActionNode) context {
 		case urlPartUnknown:
 			return context{
 				state: stateError,
-				err:   errorf(ErrAmbigContext, n.Line, "%s appears in an ambiguous URL context", n),
+				err:   errorf(ErrAmbigContext, n, n.Line, "%s appears in an ambiguous URL context", n),
 			}
 		default:
 			panic(c.urlPart.String())
@@ -339,7 +331,7 @@ func escFnsEq(a, b string) bool {
 func newIdentCmd(identifier string, pos parse.Pos) *parse.CommandNode {
 	return &parse.CommandNode{
 		NodeType: parse.NodeCommand,
-		Args:     []parse.Node{parse.NewIdentifier(identifier).SetPos(pos)},
+		Args:     []parse.Node{parse.NewIdentifier(identifier).SetTree(nil).SetPos(pos)}, // TODO: SetTree.
 	}
 }
 
@@ -373,7 +365,7 @@ func nudge(c context) context {
 // join joins the two contexts of a branch template node. The result is an
 // error context if either of the input contexts are error contexts, or if the
 // the input contexts differ.
-func join(a, b context, line int, nodeName string) context {
+func join(a, b context, node parse.Node, nodeName string) context {
 	if a.state == stateError {
 		return a
 	}
@@ -406,14 +398,14 @@ func join(a, b context, line int, nodeName string) context {
 	// ends in an unquoted value state even though the else branch
 	// ends in stateBeforeValue.
 	if c, d := nudge(a), nudge(b); !(c.eq(a) && d.eq(b)) {
-		if e := join(c, d, line, nodeName); e.state != stateError {
+		if e := join(c, d, node, nodeName); e.state != stateError {
 			return e
 		}
 	}
 
 	return context{
 		state: stateError,
-		err:   errorf(ErrBranchEnd, line, "{{%s}} branches end in different contexts: %v, %v", nodeName, a, b),
+		err:   errorf(ErrBranchEnd, node, 0, "{{%s}} branches end in different contexts: %v, %v", nodeName, a, b),
 	}
 }
 
@@ -425,7 +417,7 @@ func (e *escaper) escapeBranch(c context, n *parse.BranchNode, nodeName string)
 		// We check that executing n.List once results in the same context
 		// as executing n.List twice.
 		c1, _ := e.escapeListConditionally(c0, n.List, nil)
-		c0 = join(c0, c1, n.Line, nodeName)
+		c0 = join(c0, c1, n, nodeName)
 		if c0.state == stateError {
 			// Make clear that this is a problem on loop re-entry
 			// since developers tend to overlook that branch when
@@ -436,7 +428,7 @@ func (e *escaper) escapeBranch(c context, n *parse.BranchNode, nodeName string)
 		}
 	}
 	c1 := e.escapeList(c, n.ElseList)
-	return join(c0, c1, n.Line, nodeName)
+	return join(c0, c1, n, nodeName)
 }
 
 // escapeList escapes a list template node.
@@ -488,7 +480,7 @@ func (e *escaper) escapeListConditionally(c context, n *parse.ListNode, filter f
 
 // escapeTemplate escapes a {{template}} call node.
 func (e *escaper) escapeTemplate(c context, n *parse.TemplateNode) context {
-	c, name := e.escapeTree(c, n.Name, n.Line)
+	c, name := e.escapeTree(c, n, n.Name, n.Line)
 	if name != n.Name {
 		e.editTemplateNode(n, name)
 	}
@@ -497,7 +489,7 @@ func (e *escaper) escapeTemplate(c context, n *parse.TemplateNode) context {
 
 // escapeTree escapes the named template starting in the given context as
 // necessary and returns its output context.
-func (e *escaper) escapeTree(c context, name string, line int) (context, string) {
+func (e *escaper) escapeTree(c context, node parse.Node, name string, line int) (context, string) {
 	// Mangle the template name with the input context to produce a reliable
 	// identifier.
 	dname := c.mangle(name)
@@ -513,12 +505,12 @@ func (e *escaper) escapeTree(c context, name string, line int) (context, string)
 		if e.tmpl.set[name] != nil {
 			return context{
 				state: stateError,
-				err:   errorf(ErrNoSuchTemplate, line, "%q is an incomplete or empty template", name),
+				err:   errorf(ErrNoSuchTemplate, node, line, "%q is an incomplete or empty template", name),
 			}, dname
 		}
 		return context{
 			state: stateError,
-			err:   errorf(ErrNoSuchTemplate, line, "no such template %q", name),
+			err:   errorf(ErrNoSuchTemplate, node, line, "no such template %q", name),
 		}, dname
 	}
 	if dname != name {
@@ -550,8 +542,7 @@ func (e *escaper) computeOutCtx(c context, t *template.Template) context {
 	if !ok && c1.state != stateError {
 		return context{
 			state: stateError,
-			// TODO: Find the first node with a line in t.text.Tree.Root
-			err: errorf(ErrOutputContext, 0, "cannot compute output context for template %s", t.Name()),
+			err:   errorf(ErrOutputContext, t.Tree.Root, 0, "cannot compute output context for template %s", t.Name()),
 		}
 	}
 	return c1
@@ -695,7 +686,7 @@ func contextAfterText(c context, s []byte) (context, int) {
 		if j := bytes.IndexAny(s[:i], "\"'<=`"); j >= 0 {
 			return context{
 				state: stateError,
-				err:   errorf(ErrBadHTML, 0, "%q in unquoted attr: %q", s[j:j+1], s[:i]),
+				err:   errorf(ErrBadHTML, nil, 0, "%q in unquoted attr: %q", s[j:j+1], s[:i]),
 			}, len(s)
 		}
 	}

src/pkg/html/template/escape_test.go

@@ -861,29 +861,29 @@ func TestErrors(t *testing.T) {
 		// Error cases.
 		{
 			"{{if .Cond}}<a{{end}}",
-			"z:1: {{if}} branches",
+			"z:1:5: {{if}} branches",
 		},
 		{
 			"{{if .Cond}}\n{{else}}\n<a{{end}}",
-			"z:1: {{if}} branches",
+			"z:1:5: {{if}} branches",
 		},
 		{
 			// Missing quote in the else branch.
 			`{{if .Cond}}<a href="foo">{{else}}<a href="bar>{{end}}`,
-			"z:1: {{if}} branches",
+			"z:1:5: {{if}} branches",
 		},
 		{
 			// Different kind of attribute: href implies a URL.
 			"<a {{if .Cond}}href='{{else}}title='{{end}}{{.X}}'>",
-			"z:1: {{if}} branches",
+			"z:1:8: {{if}} branches",
 		},
 		{
 			"\n{{with .X}}<a{{end}}",
-			"z:2: {{with}} branches",
+			"z:2:7: {{with}} branches",
 		},
 		{
 			"\n{{with .X}}<a>{{else}}<a{{end}}",
-			"z:2: {{with}} branches",
+			"z:2:7: {{with}} branches",
 		},
 		{
 			"{{range .Items}}<a{{end}}",
@@ -891,7 +891,7 @@ func TestErrors(t *testing.T) {
 		},
 		{
 			"\n{{range .Items}} x='<a{{end}}",
-			"z:2: on range loop re-entry: {{range}} branches",
+			"z:2:8: on range loop re-entry: {{range}} branches",
 		},
 		{
 			"<a b=1 c={{.H}}",
@@ -903,7 +903,7 @@ func TestErrors(t *testing.T) {
 		},
 		{
 			`<a href="{{if .F}}/foo?a={{else}}/bar/{{end}}{{.H}}">`,
-			"z:1: {{.H}} appears in an ambiguous URL context",
+			"z:1:47: {{.H}} appears in an ambiguous URL context",
 		},
 		{
 			`<a onclick="alert('Hello \`,
@@ -932,7 +932,7 @@ func TestErrors(t *testing.T) {
 		},
 		{
 			`{{template "foo"}}`,
-			"z:1: no such template \"foo\"",
+			"z:1:11: no such template \"foo\"",
 		},
 		{
 			`<div{{template "y"}}>` +

src/pkg/html/template/template.go

@@ -56,7 +56,7 @@ func (t *Template) escape() error {
 	t.nameSpace.mu.Lock()
 	defer t.nameSpace.mu.Unlock()
 	if t.escapeErr == nil {
-		if err := escapeTemplates(t, t.Name()); err != nil {
+		if err := escapeTemplate(t, t.text.Root, t.Name()); err != nil {
 			return err
 		}
 	} else if t.escapeErr != escapeOK {
@@ -112,7 +112,7 @@ func (t *Template) lookupAndEscapeTemplate(name string) (tmpl *Template, err err
 		panic("html/template internal error: template escaping out of sync")
 	}
 	if tmpl.escapeErr == nil {
-		err = escapeTemplates(tmpl, name)
+		err = escapeTemplate(tmpl, tmpl.text.Root, name)
 	}
 	return tmpl, err
 }

src/pkg/html/template/transition.go

@@ -102,7 +102,7 @@ func tTag(c context, s []byte) (context, int) {
 	if i == j {
 		return context{
 			state: stateError,
-			err:   errorf(ErrBadHTML, 0, "expected space, attr name, or end of tag, but got %q", s[i:]),
+			err:   errorf(ErrBadHTML, nil, 0, "expected space, attr name, or end of tag, but got %q", s[i:]),
 		}, len(s)
 	}
 	switch attrType(string(s[i:j])) {
@@ -245,7 +245,7 @@ func tJS(c context, s []byte) (context, int) {
 		default:
 			return context{
 				state: stateError,
-				err:   errorf(ErrSlashAmbig, 0, "'/' could start a division or regexp: %.32q", s[i:]),
+				err:   errorf(ErrSlashAmbig, nil, 0, "'/' could start a division or regexp: %.32q", s[i:]),
 			}, len(s)
 		}
 	default:
@@ -277,7 +277,7 @@ func tJSDelimited(c context, s []byte) (context, int) {
 			if i == len(s) {
 				return context{
 					state: stateError,
-					err:   errorf(ErrPartialEscape, 0, "unfinished escape sequence in JS string: %q", s),
+					err:   errorf(ErrPartialEscape, nil, 0, "unfinished escape sequence in JS string: %q", s),
 				}, len(s)
 			}
 		case '[':
@@ -299,7 +299,7 @@ func tJSDelimited(c context, s []byte) (context, int) {
 		// into charsets is desired.
 		return context{
 			state: stateError,
-			err:   errorf(ErrPartialCharset, 0, "unfinished JS regexp charset: %q", s),
+			err:   errorf(ErrPartialCharset, nil, 0, "unfinished JS regexp charset: %q", s),
 		}, len(s)
 	}
 
@@ -459,7 +459,7 @@ func tCSSStr(c context, s []byte) (context, int) {
 			if i == len(s) {
 				return context{
 					state: stateError,
-					err:   errorf(ErrPartialEscape, 0, "unfinished escape sequence in CSS string: %q", s),
+					err:   errorf(ErrPartialEscape, nil, 0, "unfinished escape sequence in CSS string: %q", s),
 				}, len(s)
 			}
 		} else {
@@ -489,7 +489,7 @@ func eatAttrName(s []byte, i int) (int, *Error) {
 			// These result in a parse warning in HTML5 and are
 			// indicative of serious problems if seen in an attr
 			// name in a template.
-			return -1, errorf(ErrBadHTML, 0, "%q in attribute name: %.32q", s[j:j+1], s)
+			return -1, errorf(ErrBadHTML, nil, 0, "%q in attribute name: %.32q", s[j:j+1], s)
 		default:
 			// No-op.
 		}

src/pkg/text/template/parse/parse.go

@@ -129,9 +129,15 @@ func New(name string, funcs ...map[string]interface{}) *Tree {
 }
 
 // ErrorContext returns a textual representation of the location of the node in the input text.
+// The receiver is only used when the node does not have a pointer to the tree inside,
+// which can occur in old code.
 func (t *Tree) ErrorContext(n Node) (location, context string) {
 	pos := int(n.Position())
-	text := t.text[:pos]
+	tree := n.tree()
+	if tree == nil {
+		tree = t
+	}
+	text := tree.text[:pos]
 	byteNum := strings.LastIndex(text, "\n")
 	if byteNum == -1 {
 		byteNum = pos // On first line.
@@ -144,7 +150,7 @@ func (t *Tree) ErrorContext(n Node) (location, context string) {
 	if len(context) > 20 {
 		context = fmt.Sprintf("%.20s...", context)
 	}
-	return fmt.Sprintf("%s:%d:%d", t.ParseName, lineNum, byteNum), context
+	return fmt.Sprintf("%s:%d:%d", tree.ParseName, lineNum, byteNum), context
 }
 
 // errorf formats the error and terminates processing.
@@ -268,7 +274,7 @@ func IsEmptyTree(n Node) bool {
 // as itemList except it also parses {{define}} actions.
 // It runs to EOF.
 func (t *Tree) parse(treeSet map[string]*Tree) (next Node) {
-	t.Root = newList(t.peek().pos)
+	t.Root = t.newList(t.peek().pos)
 	for t.peek().typ != itemEOF {
 		if t.peek().typ == itemLeftDelim {
 			delim := t.next()
@@ -316,7 +322,7 @@ func (t *Tree) parseDefinition(treeSet map[string]*Tree) {
 //	textOrAction*
 // Terminates at {{end}} or {{else}}, returned separately.
 func (t *Tree) itemList() (list *ListNode, next Node) {
-	list = newList(t.peekNonSpace().pos)
+	list = t.newList(t.peekNonSpace().pos)
 	for t.peekNonSpace().typ != itemEOF {
 		n := t.textOrAction()
 		switch n.Type() {
@@ -334,7 +340,7 @@ func (t *Tree) itemList() (list *ListNode, next Node) {
 func (t *Tree) textOrAction() Node {
 	switch token := t.nextNonSpace(); token.typ {
 	case itemText:
-		return newText(token.pos, token.val)
+		return t.newText(token.pos, token.val)
 	case itemLeftDelim:
 		return t.action()
 	default:
@@ -365,7 +371,7 @@ func (t *Tree) action() (n Node) {
 	}
 	t.backup()
 	// Do not pop variables; they persist until "end".
-	return newAction(t.peek().pos, t.lex.lineNumber(), t.pipeline("command"))
+	return t.newAction(t.peek().pos, t.lex.lineNumber(), t.pipeline("command"))
 }
 
 // Pipeline:
@@ -384,7 +390,7 @@ func (t *Tree) pipeline(context string) (pipe *PipeNode) {
 			tokenAfterVariable := t.peek()
 			if next := t.peekNonSpace(); next.typ == itemColonEquals || (next.typ == itemChar && next.val == ",") {
 				t.nextNonSpace()
-				variable := newVariable(v.pos, v.val)
+				variable := t.newVariable(v.pos, v.val)
 				decl = append(decl, variable)
 				t.vars = append(t.vars, v.val)
 				if next.typ == itemChar && next.val == "," {
@@ -401,7 +407,7 @@ func (t *Tree) pipeline(context string) (pipe *PipeNode) {
 		}
 		break
 	}
-	pipe = newPipeline(pos, t.lex.lineNumber(), decl)
+	pipe = t.newPipeline(pos, t.lex.lineNumber(), decl)
 	for {
 		switch token := t.nextNonSpace(); token.typ {
 		case itemRightDelim, itemRightParen:
@@ -442,7 +448,7 @@ func (t *Tree) parseControl(allowElseIf bool, context string) (pos Pos, line int
 			// TODO: Should we allow else-if in with and range?
 			if t.peek().typ == itemIf {
 				t.next() // Consume the "if" token.
-				elseList = newList(next.Position())
+				elseList = t.newList(next.Position())
 				elseList.append(t.ifControl())
 				// Do not consume the next item - only one {{end}} required.
 				break
@@ -461,7 +467,7 @@ func (t *Tree) parseControl(allowElseIf bool, context string) (pos Pos, line int
 //	{{if pipeline}} itemList {{else}} itemList {{end}}
 // If keyword is past.
 func (t *Tree) ifControl() Node {
-	return newIf(t.parseControl(true, "if"))
+	return t.newIf(t.parseControl(true, "if"))
 }
 
 // Range:
@@ -469,7 +475,7 @@ func (t *Tree) ifControl() Node {
 //	{{range pipeline}} itemList {{else}} itemList {{end}}
 // Range keyword is past.
 func (t *Tree) rangeControl() Node {
-	return newRange(t.parseControl(false, "range"))
+	return t.newRange(t.parseControl(false, "range"))
 }
 
 // With:
@@ -477,14 +483,14 @@ func (t *Tree) rangeControl() Node {
 //	{{with pipeline}} itemList {{else}} itemList {{end}}
 // If keyword is past.
 func (t *Tree) withControl() Node {
-	return newWith(t.parseControl(false, "with"))
+	return t.newWith(t.parseControl(false, "with"))
 }
 
 // End:
 //	{{end}}
 // End keyword is past.
 func (t *Tree) endControl() Node {
-	return newEnd(t.expect(itemRightDelim, "end").pos)
+	return t.newEnd(t.expect(itemRightDelim, "end").pos)
 }
 
 // Else:
@@ -495,9 +501,9 @@ func (t *Tree) elseControl() Node {
 	peek := t.peekNonSpace()
 	if peek.typ == itemIf {
 		// We see "{{else if ... " but in effect rewrite it to {{else}}{{if ... ".
-		return newElse(peek.pos, t.lex.lineNumber())
+		return t.newElse(peek.pos, t.lex.lineNumber())
 	}
-	return newElse(t.expect(itemRightDelim, "else").pos, t.lex.lineNumber())
+	return t.newElse(t.expect(itemRightDelim, "else").pos, t.lex.lineNumber())
 }
 
 // Template:
@@ -523,7 +529,7 @@ func (t *Tree) templateControl() Node {
 		// Do not pop variables; they persist until "end".
 		pipe = t.pipeline("template")
 	}
-	return newTemplate(token.pos, t.lex.lineNumber(), name, pipe)
+	return t.newTemplate(token.pos, t.lex.lineNumber(), name, pipe)
 }
 
 // command:
@@ -531,7 +537,7 @@ func (t *Tree) templateControl() Node {
 // space-separated arguments up to a pipeline character or right delimiter.
 // we consume the pipe character but leave the right delim to terminate the action.
 func (t *Tree) command() *CommandNode {
-	cmd := newCommand(t.peekNonSpace().pos)
+	cmd := t.newCommand(t.peekNonSpace().pos)
 	for {
 		t.peekNonSpace() // skip leading spaces.
 		operand := t.operand()
@@ -568,7 +574,7 @@ func (t *Tree) operand() Node {
 		return nil
 	}
 	if t.peek().typ == itemField {
-		chain := newChain(t.peek().pos, node)
+		chain := t.newChain(t.peek().pos, node)
 		for t.peek().typ == itemField {
 			chain.Add(t.next().val)
 		}
@@ -578,9 +584,9 @@ func (t *Tree) operand() Node {
 		// TODO: Switch to Chains always when we can.
 		switch node.Type() {
 		case NodeField:
-			node = newField(chain.Position(), chain.String())
+			node = t.newField(chain.Position(), chain.String())
 		case NodeVariable:
-			node = newVariable(chain.Position(), chain.String())
+			node = t.newVariable(chain.Position(), chain.String())
 		default:
 			node = chain
 		}
@@ -605,19 +611,19 @@ func (t *Tree) term() Node {
 		if !t.hasFunction(token.val) {
 			t.errorf("function %q not defined", token.val)
 		}
-		return NewIdentifier(token.val).SetPos(token.pos)
+		return NewIdentifier(token.val).SetTree(t).SetPos(token.pos)
 	case itemDot:
-		return newDot(token.pos)
+		return t.newDot(token.pos)
 	case itemNil:
-		return newNil(token.pos)
+		return t.newNil(token.pos)
 	case itemVariable:
 		return t.useVar(token.pos, token.val)
 	case itemField:
-		return newField(token.pos, token.val)
+		return t.newField(token.pos, token.val)
 	case itemBool:
-		return newBool(token.pos, token.val == "true")
+		return t.newBool(token.pos, token.val == "true")
 	case itemCharConstant, itemComplex, itemNumber:
-		number, err := newNumber(token.pos, token.val, token.typ)
+		number, err := t.newNumber(token.pos, token.val, token.typ)
 		if err != nil {
 			t.error(err)
 		}
@@ -633,7 +639,7 @@ func (t *Tree) term() Node {
 		if err != nil {
 			t.error(err)
 		}
-		return newString(token.pos, token.val, s)
+		return t.newString(token.pos, token.val, s)
 	}
 	t.backup()
 	return nil
@@ -660,7 +666,7 @@ func (t *Tree) popVars(n int) {
 // useVar returns a node for a variable reference. It errors if the
 // variable is not defined.
 func (t *Tree) useVar(pos Pos, name string) Node {
-	v := newVariable(pos, name)
+	v := t.newVariable(pos, name)
 	for _, varName := range t.vars {
 		if varName == v.Ident[0] {
 			return v

src/pkg/text/template/parse/parse_test.go

@@ -77,6 +77,7 @@ func TestNumberParse(t *testing.T) {
 		// because imaginary comes out as a number.
 		var c complex128
 		typ := itemNumber
+		var tree *Tree
 		if test.text[0] == '\'' {
 			typ = itemCharConstant
 		} else {
@@ -85,7 +86,7 @@ func TestNumberParse(t *testing.T) {
 				typ = itemComplex
 			}
 		}
-		n, err := newNumber(0, test.text, typ)
+		n, err := tree.newNumber(0, test.text, typ)
 		ok := test.isInt || test.isUint || test.isFloat || test.isComplex
 		if ok && err != nil {
 			t.Errorf("unexpected error for %q: %s", test.text, err)