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// Copyright 2013 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 main
import (
"bytes"
"go/ast"
"go/printer"
"go/token"
"go/types"
"sort"
"golang.org/x/tools/cmd/guru/serial"
"golang.org/x/tools/go/loader"
)
// freevars displays the lexical (not package-level) free variables of
// the selection.
//
// It treats A.B.C as a separate variable from A to reveal the parts
// of an aggregate type that are actually needed.
// This aids refactoring.
//
// TODO(adonovan): optionally display the free references to
// file/package scope objects, and to objects from other packages.
// Depending on where the resulting function abstraction will go,
// these might be interesting. Perhaps group the results into three
// bands.
func freevars(q *Query) error {
lconf := loader.Config{Build: q.Build}
allowErrors(&lconf)
if _, err := importQueryPackage(q.Pos, &lconf); err != nil {
return err
}
// Load/parse/type-check the program.
lprog, err := lconf.Load()
if err != nil {
return err
}
qpos, err := parseQueryPos(lprog, q.Pos, false)
if err != nil {
return err
}
file := qpos.path[len(qpos.path)-1] // the enclosing file
fileScope := qpos.info.Scopes[file]
pkgScope := fileScope.Parent()
// The id and sel functions return non-nil if they denote an
// object o or selection o.x.y that is referenced by the
// selection but defined neither within the selection nor at
// file scope, i.e. it is in the lexical environment.
var id func(n *ast.Ident) types.Object
var sel func(n *ast.SelectorExpr) types.Object
sel = func(n *ast.SelectorExpr) types.Object {
switch x := unparen(n.X).(type) {
case *ast.SelectorExpr:
return sel(x)
case *ast.Ident:
return id(x)
}
return nil
}
id = func(n *ast.Ident) types.Object {
obj := qpos.info.Uses[n]
if obj == nil {
return nil // not a reference
}
if _, ok := obj.(*types.PkgName); ok {
return nil // imported package
}
if !(file.Pos() <= obj.Pos() && obj.Pos() <= file.End()) {
return nil // not defined in this file
}
scope := obj.Parent()
if scope == nil {
return nil // e.g. interface method, struct field
}
if scope == fileScope || scope == pkgScope {
return nil // defined at file or package scope
}
if qpos.start <= obj.Pos() && obj.Pos() <= qpos.end {
return nil // defined within selection => not free
}
return obj
}
// Maps each reference that is free in the selection
// to the object it refers to.
// The map de-duplicates repeated references.
refsMap := make(map[string]freevarsRef)
// Visit all the identifiers in the selected ASTs.
ast.Inspect(qpos.path[0], func(n ast.Node) bool {
if n == nil {
return true // popping DFS stack
}
// Is this node contained within the selection?
// (freevars permits inexact selections,
// like two stmts in a block.)
if qpos.start <= n.Pos() && n.End() <= qpos.end {
var obj types.Object
var prune bool
switch n := n.(type) {
case *ast.Ident:
obj = id(n)
case *ast.SelectorExpr:
obj = sel(n)
prune = true
}
if obj != nil {
var kind string
switch obj.(type) {
case *types.Var:
kind = "var"
case *types.Func:
kind = "func"
case *types.TypeName:
kind = "type"
case *types.Const:
kind = "const"
case *types.Label:
kind = "label"
default:
panic(obj)
}
typ := qpos.info.TypeOf(n.(ast.Expr))
ref := freevarsRef{kind, printNode(lprog.Fset, n), typ, obj}
refsMap[ref.ref] = ref
if prune {
return false // don't descend
}
}
}
return true // descend
})
refs := make([]freevarsRef, 0, len(refsMap))
for _, ref := range refsMap {
refs = append(refs, ref)
}
sort.Sort(byRef(refs))
q.Output(lprog.Fset, &freevarsResult{
qpos: qpos,
refs: refs,
})
return nil
}
type freevarsResult struct {
qpos *queryPos
refs []freevarsRef
}
type freevarsRef struct {
kind string
ref string
typ types.Type
obj types.Object
}
func (r *freevarsResult) PrintPlain(printf printfFunc) {
if len(r.refs) == 0 {
printf(r.qpos, "No free identifiers.")
} else {
printf(r.qpos, "Free identifiers:")
qualifier := types.RelativeTo(r.qpos.info.Pkg)
for _, ref := range r.refs {
// Avoid printing "type T T".
var typstr string
if ref.kind != "type" && ref.kind != "label" {
typstr = " " + types.TypeString(ref.typ, qualifier)
}
printf(ref.obj, "%s %s%s", ref.kind, ref.ref, typstr)
}
}
}
func (r *freevarsResult) JSON(fset *token.FileSet) []byte {
var buf bytes.Buffer
for i, ref := range r.refs {
if i > 0 {
buf.WriteByte('\n')
}
buf.Write(toJSON(serial.FreeVar{
Pos: fset.Position(ref.obj.Pos()).String(),
Kind: ref.kind,
Ref: ref.ref,
Type: ref.typ.String(),
}))
}
return buf.Bytes()
}
// -------- utils --------
type byRef []freevarsRef
func (p byRef) Len() int { return len(p) }
func (p byRef) Less(i, j int) bool { return p[i].ref < p[j].ref }
func (p byRef) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
// printNode returns the pretty-printed syntax of n.
func printNode(fset *token.FileSet, n ast.Node) string {
var buf bytes.Buffer
printer.Fprint(&buf, fset, n)
return buf.String()
}
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