exp/template: delete upward evaluation.

It was an ill-advised carryover from the previous template package.
Also clean up function evaluation.
Also add a Name method to Template.

R=golang-dev, gri
CC=golang-dev
https://golang.org/cl/4657088

src/pkg/exp/template/exec.go

@@ -22,21 +22,6 @@ type state struct {
 	wr   io.Writer
 	set  *Set
 	line int // line number for errors
-	// parent holds the state for the surrounding data object,
-	// typically the structure containing the field we are evaluating.
-	parent struct {
-		state *state
-		data  reflect.Value
-	}
-}
-
-// down returns a new state representing a child of the current state.
-// data represents the parent of the child.
-func (s *state) down(data reflect.Value) *state {
-	var child = *s
-	child.parent.state = s
-	child.parent.data = data
-	return &child
 }
 
 var zero reflect.Value
@@ -118,7 +103,7 @@ func (s *state) walkIfOrWith(typ nodeType, data reflect.Value, pipe *pipeNode, l
 	}
 	if truth {
 		if typ == nodeWith {
-			s.down(data).walk(val, list)
+			s.walk(val, list)
 		} else {
 			s.walk(data, list)
 		}
@@ -153,14 +138,13 @@ func isTrue(val reflect.Value) (truth, ok bool) {
 
 func (s *state) walkRange(data reflect.Value, r *rangeNode) {
 	val := s.evalPipeline(data, r.pipe)
-	down := s.down(data)
 	switch val.Kind() {
 	case reflect.Array, reflect.Slice:
 		if val.Len() == 0 {
 			break
 		}
 		for i := 0; i < val.Len(); i++ {
-			down.walk(val.Index(i), r.list)
+			s.walk(val.Index(i), r.list)
 		}
 		return
 	case reflect.Map:
@@ -168,7 +152,7 @@ func (s *state) walkRange(data reflect.Value, r *rangeNode) {
 			break
 		}
 		for _, key := range val.MapKeys() {
-			down.walk(val.MapIndex(key), r.list)
+			s.walk(val.MapIndex(key), r.list)
 		}
 		return
 	default:
@@ -216,7 +200,8 @@ func (s *state) evalCommand(data reflect.Value, cmd *commandNode, final reflect.
 	case *fieldNode:
 		return s.evalFieldNode(data, n, cmd.args, final)
 	case *identifierNode:
-		return s.evalField(data, n.ident, cmd.args, final, true, true)
+		// Must be a function.
+		return s.evalFunction(data, n.ident, cmd.args, final)
 	}
 	if len(cmd.args) > 1 || final.IsValid() {
 		s.errorf("can't give argument to non-function %s", cmd.args[0])
@@ -251,10 +236,18 @@ func (s *state) evalFieldNode(data reflect.Value, field *fieldNode, args []node,
 	// Up to the last entry, it must be a field.
 	n := len(field.ident)
 	for i := 0; i < n-1; i++ {
-		data = s.evalField(data, field.ident[i], nil, zero, i == 0, false)
+		data = s.evalField(data, field.ident[i], nil, zero, false)
 	}
 	// Now it can be a field or method and if a method, gets arguments.
-	return s.evalField(data, field.ident[n-1], args, final, len(field.ident) == 1, true)
+	return s.evalField(data, field.ident[n-1], args, final, true)
+}
+
+func (s *state) evalFunction(data reflect.Value, name string, args []node, final reflect.Value) reflect.Value {
+	function, ok := findFunction(name, s.tmpl, s.set)
+	if !ok {
+		s.errorf("%q is not a defined function", name)
+	}
+	return s.evalCall(data, function, name, false, args, final)
 }
 
 // Is this an exported - upper case - name?
@@ -268,17 +261,9 @@ func isExported(name string) bool {
 // value of the pipeline, if any.
 // If we're in a chain, such as (.X.Y.Z), .X and .Y cannot be methods;
 // canBeMethod will be true only for the last element of such chains (here .Z).
-// The isFirst argument tells whether this is the first element of a chain (here .X).
-// If true, evaluation is allowed to examine the parent to resolve the reference.
 func (s *state) evalField(data reflect.Value, fieldName string, args []node, final reflect.Value,
-isFirst, canBeMethod bool) reflect.Value {
-	topState, topData := s, data // Remember initial state for diagnostics.
-	// Is it a function?
-	if function, ok := findFunction(fieldName, s.tmpl, s.set); ok {
-		return s.evalCall(data, function, fieldName, false, args, final)
-	}
-	// Look for methods and fields at this level, and then in the parent.
-	for s != nil {
+canBeMethod bool) reflect.Value {
+	typ := data.Type()
 	var isNil bool
 	data, isNil = indirect(data)
 	if canBeMethod {
@@ -304,17 +289,10 @@ isFirst, canBeMethod bool) reflect.Value {
 			}
 		}
 	}
-		if !isFirst {
-			// We check for nil pointers only if there's no possibility of resolution
-			// in the parent.
 	if isNil {
-				s.errorf("nil pointer evaluating %s.%s", topData.Type(), fieldName)
-			}
-			break
-		}
-		s, data = s.parent.state, s.parent.data
+		s.errorf("nil pointer evaluating %s.%s", typ, fieldName)
 	}
-	topState.errorf("can't handle evaluation of field %s in type %s", fieldName, topData.Type())
+	s.errorf("can't handle evaluation of field %s in type %s", fieldName, typ)
 	panic("not reached")
 }
 
@@ -489,7 +467,7 @@ func (s *state) evalEmptyInterface(data reflect.Value, typ reflect.Type, n node)
 	case *fieldNode:
 		return s.evalFieldNode(data, n, nil, zero)
 	case *identifierNode:
-		return s.evalField(data, n.ident, nil, zero, false, true)
+		return s.evalFunction(data, n.ident, nil, zero)
 	case *numberNode:
 		if n.isComplex {
 			return reflect.ValueOf(n.complex128)

src/pkg/exp/template/exec_test.go

@@ -249,12 +249,6 @@ var execTests = []execTest{
 	{"with map", "{{with .MSIone}}{{.}}{{else}}EMPTY{{end}}", "map[one:1]", tVal, true},
 	{"with empty interface, struct field", "{{with .Empty4}}{{.V}}{{end}}", "v", tVal, true},
 
-	// Fields and methods in parent struct.
-	{"with .U, get .I", "{{with .U}}{{.I}}{{end}}", "17", tVal, true},
-	{"with .U, do .Method0", "{{with .U}}{{.Method0}}{{end}}", "M0", tVal, true},
-	{"range .SI .I", "{{range .SI}}<{{.I}}>{{end}}", "<17><17><17>", tVal, true},
-	{"range .SI .Method0", "{{range .SI}}{{.Method0}}{{end}}", "M0M0M0", tVal, true},
-
 	// Range.
 	{"range []int", "{{range .SI}}-{{.}}-{{end}}", "-3--4--5-", tVal, true},
 	{"range empty no else", "{{range .SIEmpty}}-{{.}}-{{end}}", "", tVal, true},

src/pkg/exp/template/parse.go

@@ -27,6 +27,11 @@ type Template struct {
 	peekCount int
 }
 
+// Name returns the name of the template.
+func (t *Template) Name() string {
+	return t.name
+}
+
 // next returns the next token.
 func (t *Template) next() item {
 	if t.peekCount > 0 {