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// Copyright 2020 CUE Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// walk provides functions for visiting the nodes of an ADT tree.
package walk
import (
"fmt"
"cuelang.org/go/internal/core/adt"
)
// Features calls f for all features used in x and indicates whether the
// feature is used as a reference or not.
func Features(x adt.Expr, f func(label adt.Feature, src adt.Node)) {
w := Visitor{
Feature: f,
}
w.Elem(x)
}
// A Visitor walks over all elements in an ADT, recursively.
type Visitor struct {
// Feature is invoked for all field names.
Feature func(f adt.Feature, src adt.Node)
// Before is invoked for all nodes in pre-order traversal.
// Returning false prevents the visitor from visiting the node's
// children.
Before func(adt.Node) bool
}
func (w *Visitor) Elem(x adt.Elem) {
w.node(x)
}
func (w *Visitor) feature(x adt.Feature, src adt.Node) {
if w.Feature != nil {
w.Feature(x, src)
}
}
func (w *Visitor) node(n adt.Node) {
if w.Before != nil && !w.Before(n) {
return
}
switch x := n.(type) {
case nil:
// TODO: special-case Vertex?
case adt.Value:
case *adt.ConjunctGroup:
for _, x := range *x {
w.Elem(x.Elem())
}
case *adt.ListLit:
for _, x := range x.Elems {
w.node(x)
}
case *adt.StructLit:
for _, x := range x.Decls {
w.node(x)
}
case *adt.FieldReference:
w.feature(x.Label, x)
case *adt.ValueReference:
w.feature(x.Label, x)
case *adt.LabelReference:
case *adt.DynamicReference:
case *adt.ImportReference:
w.feature(x.ImportPath, x)
w.feature(x.Label, x)
case *adt.LetReference:
w.feature(x.Label, x)
case *adt.SelectorExpr:
w.node(x.X)
w.feature(x.Sel, x)
case *adt.IndexExpr:
w.node(x.X)
w.node(x.Index)
case *adt.SliceExpr:
w.node(x.X)
w.node(x.Lo)
w.node(x.Hi)
w.node(x.Stride)
case *adt.Interpolation:
for _, x := range x.Parts {
w.node(x)
}
case *adt.BoundExpr:
w.node(x.Expr)
case *adt.UnaryExpr:
w.node(x.X)
case *adt.BinaryExpr:
w.node(x.X)
w.node(x.Y)
case *adt.CallExpr:
w.node(x.Fun)
for _, arg := range x.Args {
w.node(arg)
}
case *adt.DisjunctionExpr:
for _, d := range x.Values {
w.node(d.Val)
}
// Fields
case *adt.Ellipsis:
if x.Value != nil {
w.node(x.Value)
}
case *adt.Field:
w.feature(x.Label, x)
w.node(x.Value)
case *adt.LetField:
w.feature(x.Label, x)
w.node(x.Value)
case *adt.BulkOptionalField:
w.node(x.Filter)
w.node(x.Value)
case *adt.DynamicField:
w.node(x.Key)
w.node(x.Value)
// Yielders
case *adt.Comprehension:
for _, c := range x.Clauses {
w.node(c)
}
w.node(adt.ToExpr(x.Value))
case *adt.ForClause:
w.feature(x.Key, x)
w.feature(x.Value, x)
case *adt.IfClause:
w.node(x.Condition)
case *adt.LetClause:
w.feature(x.Label, x)
w.node(x.Expr)
case *adt.ValueClause:
default:
panic(fmt.Sprintf("unknown field %T", x))
}
}
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