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// Copyright 2025 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package edge defines identifiers for each field of an ast.Node
// struct type that refers to another Node.
package edge
import (
"fmt"
"go/ast"
"reflect"
)
// A Kind describes a field of an ast.Node struct.
type Kind uint8
// String returns a description of the edge kind.
func (k Kind) String() string {
if k == Invalid {
return "<invalid>"
}
info := fieldInfos[k]
return fmt.Sprintf("%v.%s", info.nodeType.Elem().Name(), info.name)
}
// NodeType returns the pointer-to-struct type of the ast.Node implementation.
func (k Kind) NodeType() reflect.Type { return fieldInfos[k].nodeType }
// FieldName returns the name of the field.
func (k Kind) FieldName() string { return fieldInfos[k].name }
// FieldType returns the declared type of the field.
func (k Kind) FieldType() reflect.Type { return fieldInfos[k].fieldType }
// Get returns the direct child of n identified by (k, idx).
// n's type must match k.NodeType().
// idx must be a valid slice index, or -1 for a non-slice.
func (k Kind) Get(n ast.Node, idx int) ast.Node {
if k.NodeType() != reflect.TypeOf(n) {
panic(fmt.Sprintf("%v.Get(%T): invalid node type", k, n))
}
v := reflect.ValueOf(n).Elem().Field(fieldInfos[k].index)
if idx != -1 {
v = v.Index(idx) // asserts valid index
} else {
// (The type assertion below asserts that v is not a slice.)
}
return v.Interface().(ast.Node) // may be nil
}
const (
Invalid Kind = iota // for nodes at the root of the traversal
// Kinds are sorted alphabetically.
// Numbering is not stable.
// Each is named Type_Field, where Type is the
// ast.Node struct type and Field is the name of the field
ArrayType_Elt
ArrayType_Len
AssignStmt_Lhs
AssignStmt_Rhs
BinaryExpr_X
BinaryExpr_Y
BlockStmt_List
BranchStmt_Label
CallExpr_Args
CallExpr_Fun
CaseClause_Body
CaseClause_List
ChanType_Value
CommClause_Body
CommClause_Comm
CommentGroup_List
CompositeLit_Elts
CompositeLit_Type
DeclStmt_Decl
DeferStmt_Call
Ellipsis_Elt
ExprStmt_X
FieldList_List
Field_Comment
Field_Doc
Field_Names
Field_Tag
Field_Type
File_Decls
File_Doc
File_Name
ForStmt_Body
ForStmt_Cond
ForStmt_Init
ForStmt_Post
FuncDecl_Body
FuncDecl_Doc
FuncDecl_Name
FuncDecl_Recv
FuncDecl_Type
FuncLit_Body
FuncLit_Type
FuncType_Params
FuncType_Results
FuncType_TypeParams
GenDecl_Doc
GenDecl_Specs
GoStmt_Call
IfStmt_Body
IfStmt_Cond
IfStmt_Else
IfStmt_Init
ImportSpec_Comment
ImportSpec_Doc
ImportSpec_Name
ImportSpec_Path
IncDecStmt_X
IndexExpr_Index
IndexExpr_X
IndexListExpr_Indices
IndexListExpr_X
InterfaceType_Methods
KeyValueExpr_Key
KeyValueExpr_Value
LabeledStmt_Label
LabeledStmt_Stmt
MapType_Key
MapType_Value
ParenExpr_X
RangeStmt_Body
RangeStmt_Key
RangeStmt_Value
RangeStmt_X
ReturnStmt_Results
SelectStmt_Body
SelectorExpr_Sel
SelectorExpr_X
SendStmt_Chan
SendStmt_Value
SliceExpr_High
SliceExpr_Low
SliceExpr_Max
SliceExpr_X
StarExpr_X
StructType_Fields
SwitchStmt_Body
SwitchStmt_Init
SwitchStmt_Tag
TypeAssertExpr_Type
TypeAssertExpr_X
TypeSpec_Comment
TypeSpec_Doc
TypeSpec_Name
TypeSpec_Type
TypeSpec_TypeParams
TypeSwitchStmt_Assign
TypeSwitchStmt_Body
TypeSwitchStmt_Init
UnaryExpr_X
ValueSpec_Comment
ValueSpec_Doc
ValueSpec_Names
ValueSpec_Type
ValueSpec_Values
maxKind
)
// Assert that the encoding fits in 7 bits,
// as the inspector relies on this.
// (We are currently at 104.)
var _ = [1 << 7]struct{}{}[maxKind]
type fieldInfo struct {
nodeType reflect.Type // pointer-to-struct type of ast.Node implementation
name string
index int
fieldType reflect.Type
}
func info[N ast.Node](fieldName string) fieldInfo {
nodePtrType := reflect.TypeFor[N]()
f, ok := nodePtrType.Elem().FieldByName(fieldName)
if !ok {
panic(fieldName)
}
return fieldInfo{nodePtrType, fieldName, f.Index[0], f.Type}
}
var fieldInfos = [...]fieldInfo{
Invalid: {},
ArrayType_Elt: info[*ast.ArrayType]("Elt"),
ArrayType_Len: info[*ast.ArrayType]("Len"),
AssignStmt_Lhs: info[*ast.AssignStmt]("Lhs"),
AssignStmt_Rhs: info[*ast.AssignStmt]("Rhs"),
BinaryExpr_X: info[*ast.BinaryExpr]("X"),
BinaryExpr_Y: info[*ast.BinaryExpr]("Y"),
BlockStmt_List: info[*ast.BlockStmt]("List"),
BranchStmt_Label: info[*ast.BranchStmt]("Label"),
CallExpr_Args: info[*ast.CallExpr]("Args"),
CallExpr_Fun: info[*ast.CallExpr]("Fun"),
CaseClause_Body: info[*ast.CaseClause]("Body"),
CaseClause_List: info[*ast.CaseClause]("List"),
ChanType_Value: info[*ast.ChanType]("Value"),
CommClause_Body: info[*ast.CommClause]("Body"),
CommClause_Comm: info[*ast.CommClause]("Comm"),
CommentGroup_List: info[*ast.CommentGroup]("List"),
CompositeLit_Elts: info[*ast.CompositeLit]("Elts"),
CompositeLit_Type: info[*ast.CompositeLit]("Type"),
DeclStmt_Decl: info[*ast.DeclStmt]("Decl"),
DeferStmt_Call: info[*ast.DeferStmt]("Call"),
Ellipsis_Elt: info[*ast.Ellipsis]("Elt"),
ExprStmt_X: info[*ast.ExprStmt]("X"),
FieldList_List: info[*ast.FieldList]("List"),
Field_Comment: info[*ast.Field]("Comment"),
Field_Doc: info[*ast.Field]("Doc"),
Field_Names: info[*ast.Field]("Names"),
Field_Tag: info[*ast.Field]("Tag"),
Field_Type: info[*ast.Field]("Type"),
File_Decls: info[*ast.File]("Decls"),
File_Doc: info[*ast.File]("Doc"),
File_Name: info[*ast.File]("Name"),
ForStmt_Body: info[*ast.ForStmt]("Body"),
ForStmt_Cond: info[*ast.ForStmt]("Cond"),
ForStmt_Init: info[*ast.ForStmt]("Init"),
ForStmt_Post: info[*ast.ForStmt]("Post"),
FuncDecl_Body: info[*ast.FuncDecl]("Body"),
FuncDecl_Doc: info[*ast.FuncDecl]("Doc"),
FuncDecl_Name: info[*ast.FuncDecl]("Name"),
FuncDecl_Recv: info[*ast.FuncDecl]("Recv"),
FuncDecl_Type: info[*ast.FuncDecl]("Type"),
FuncLit_Body: info[*ast.FuncLit]("Body"),
FuncLit_Type: info[*ast.FuncLit]("Type"),
FuncType_Params: info[*ast.FuncType]("Params"),
FuncType_Results: info[*ast.FuncType]("Results"),
FuncType_TypeParams: info[*ast.FuncType]("TypeParams"),
GenDecl_Doc: info[*ast.GenDecl]("Doc"),
GenDecl_Specs: info[*ast.GenDecl]("Specs"),
GoStmt_Call: info[*ast.GoStmt]("Call"),
IfStmt_Body: info[*ast.IfStmt]("Body"),
IfStmt_Cond: info[*ast.IfStmt]("Cond"),
IfStmt_Else: info[*ast.IfStmt]("Else"),
IfStmt_Init: info[*ast.IfStmt]("Init"),
ImportSpec_Comment: info[*ast.ImportSpec]("Comment"),
ImportSpec_Doc: info[*ast.ImportSpec]("Doc"),
ImportSpec_Name: info[*ast.ImportSpec]("Name"),
ImportSpec_Path: info[*ast.ImportSpec]("Path"),
IncDecStmt_X: info[*ast.IncDecStmt]("X"),
IndexExpr_Index: info[*ast.IndexExpr]("Index"),
IndexExpr_X: info[*ast.IndexExpr]("X"),
IndexListExpr_Indices: info[*ast.IndexListExpr]("Indices"),
IndexListExpr_X: info[*ast.IndexListExpr]("X"),
InterfaceType_Methods: info[*ast.InterfaceType]("Methods"),
KeyValueExpr_Key: info[*ast.KeyValueExpr]("Key"),
KeyValueExpr_Value: info[*ast.KeyValueExpr]("Value"),
LabeledStmt_Label: info[*ast.LabeledStmt]("Label"),
LabeledStmt_Stmt: info[*ast.LabeledStmt]("Stmt"),
MapType_Key: info[*ast.MapType]("Key"),
MapType_Value: info[*ast.MapType]("Value"),
ParenExpr_X: info[*ast.ParenExpr]("X"),
RangeStmt_Body: info[*ast.RangeStmt]("Body"),
RangeStmt_Key: info[*ast.RangeStmt]("Key"),
RangeStmt_Value: info[*ast.RangeStmt]("Value"),
RangeStmt_X: info[*ast.RangeStmt]("X"),
ReturnStmt_Results: info[*ast.ReturnStmt]("Results"),
SelectStmt_Body: info[*ast.SelectStmt]("Body"),
SelectorExpr_Sel: info[*ast.SelectorExpr]("Sel"),
SelectorExpr_X: info[*ast.SelectorExpr]("X"),
SendStmt_Chan: info[*ast.SendStmt]("Chan"),
SendStmt_Value: info[*ast.SendStmt]("Value"),
SliceExpr_High: info[*ast.SliceExpr]("High"),
SliceExpr_Low: info[*ast.SliceExpr]("Low"),
SliceExpr_Max: info[*ast.SliceExpr]("Max"),
SliceExpr_X: info[*ast.SliceExpr]("X"),
StarExpr_X: info[*ast.StarExpr]("X"),
StructType_Fields: info[*ast.StructType]("Fields"),
SwitchStmt_Body: info[*ast.SwitchStmt]("Body"),
SwitchStmt_Init: info[*ast.SwitchStmt]("Init"),
SwitchStmt_Tag: info[*ast.SwitchStmt]("Tag"),
TypeAssertExpr_Type: info[*ast.TypeAssertExpr]("Type"),
TypeAssertExpr_X: info[*ast.TypeAssertExpr]("X"),
TypeSpec_Comment: info[*ast.TypeSpec]("Comment"),
TypeSpec_Doc: info[*ast.TypeSpec]("Doc"),
TypeSpec_Name: info[*ast.TypeSpec]("Name"),
TypeSpec_Type: info[*ast.TypeSpec]("Type"),
TypeSpec_TypeParams: info[*ast.TypeSpec]("TypeParams"),
TypeSwitchStmt_Assign: info[*ast.TypeSwitchStmt]("Assign"),
TypeSwitchStmt_Body: info[*ast.TypeSwitchStmt]("Body"),
TypeSwitchStmt_Init: info[*ast.TypeSwitchStmt]("Init"),
UnaryExpr_X: info[*ast.UnaryExpr]("X"),
ValueSpec_Comment: info[*ast.ValueSpec]("Comment"),
ValueSpec_Doc: info[*ast.ValueSpec]("Doc"),
ValueSpec_Names: info[*ast.ValueSpec]("Names"),
ValueSpec_Type: info[*ast.ValueSpec]("Type"),
ValueSpec_Values: info[*ast.ValueSpec]("Values"),
}
|
