woodpecker/vendor/github.com/kyoh86/exportloopref/exportloopref.go

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package exportloopref
import (
"fmt"
"go/ast"
"go/token"
"go/types"
"golang.org/x/tools/go/analysis"
"golang.org/x/tools/go/analysis/passes/inspect"
"golang.org/x/tools/go/ast/inspector"
)
var Analyzer = &analysis.Analyzer{
Name: "exportloopref",
Doc: "checks for pointers to enclosing loop variables",
Run: run,
RunDespiteErrors: true,
Requires: []*analysis.Analyzer{inspect.Analyzer},
// ResultType reflect.Type
// FactTypes []Fact
}
func init() {
// Analyzer.Flags.StringVar(&v, "name", "default", "description")
}
func run(pass *analysis.Pass) (interface{}, error) {
inspect := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector)
search := &Searcher{
Stats: map[token.Pos]struct{}{},
Vars: map[token.Pos]map[token.Pos]struct{}{},
Types: pass.TypesInfo.Types,
}
nodeFilter := []ast.Node{
(*ast.RangeStmt)(nil),
(*ast.ForStmt)(nil),
(*ast.DeclStmt)(nil),
(*ast.AssignStmt)(nil),
(*ast.UnaryExpr)(nil),
}
inspect.WithStack(nodeFilter, func(n ast.Node, push bool, stack []ast.Node) bool {
id, insert, digg := search.Check(n, stack)
if id != nil {
dMsg := fmt.Sprintf("exporting a pointer for the loop variable %s", id.Name)
fMsg := fmt.Sprintf("loop variable %s should be pinned", id.Name)
var suggest []analysis.SuggestedFix
if insert != token.NoPos {
suggest = []analysis.SuggestedFix{{
Message: fMsg,
TextEdits: []analysis.TextEdit{{
Pos: insert,
End: insert,
NewText: []byte(fmt.Sprintf("%[1]s := %[1]s\n", id.Name)),
}},
}}
}
d := analysis.Diagnostic{Pos: id.Pos(),
End: id.End(),
Message: dMsg,
Category: "exportloopref",
SuggestedFixes: suggest,
}
pass.Report(d)
}
return digg
})
return nil, nil
}
type Searcher struct {
// Statement variables : map to collect positions that
// variables are declared like below.
// - for <KEY>, <VALUE> := range ...
// - var <X> int
// - D := ...
Stats map[token.Pos]struct{}
// Local variables maps loop-position, decl-location to ignore
// safe pointers for variable which declared in the loop.
Vars map[token.Pos]map[token.Pos]struct{}
Types map[ast.Expr]types.TypeAndValue
}
func (s *Searcher) Check(n ast.Node, stack []ast.Node) (*ast.Ident, token.Pos, bool) {
switch typed := n.(type) {
case *ast.RangeStmt:
s.parseRangeStmt(typed)
case *ast.ForStmt:
s.parseForStmt(typed)
case *ast.DeclStmt:
s.parseDeclStmt(typed, stack)
case *ast.AssignStmt:
s.parseAssignStmt(typed, stack)
case *ast.UnaryExpr:
return s.checkUnaryExpr(typed, stack)
}
return nil, token.NoPos, true
}
func (s *Searcher) parseRangeStmt(n *ast.RangeStmt) {
s.addStat(n.Key)
s.addStat(n.Value)
}
func (s *Searcher) parseForStmt(n *ast.ForStmt) {
switch post := n.Post.(type) {
case *ast.AssignStmt:
// e.g. for p = head; p != nil; p = p.next
for _, lhs := range post.Lhs {
s.addStat(lhs)
}
case *ast.IncDecStmt:
// e.g. for i := 0; i < n; i++
s.addStat(post.X)
}
}
func (s *Searcher) addStat(expr ast.Expr) {
if id, ok := expr.(*ast.Ident); ok {
s.Stats[id.Pos()] = struct{}{}
}
}
func (s *Searcher) parseDeclStmt(n *ast.DeclStmt, stack []ast.Node) {
loop, _ := s.innermostLoop(stack)
if loop == nil {
return
}
// Register declaring variables
if genDecl, ok := n.Decl.(*ast.GenDecl); ok && genDecl.Tok == token.VAR {
for _, spec := range genDecl.Specs {
for _, name := range spec.(*ast.ValueSpec).Names {
s.addVar(loop, name)
}
}
}
}
func (s *Searcher) parseAssignStmt(n *ast.AssignStmt, stack []ast.Node) {
loop, _ := s.innermostLoop(stack)
if loop == nil {
return
}
// Find statements declaring local variable
if n.Tok == token.DEFINE {
for _, h := range n.Lhs {
s.addVar(loop, h)
}
}
}
func (s *Searcher) addVar(loop ast.Node, expr ast.Expr) {
loopPos := loop.Pos()
id, ok := expr.(*ast.Ident)
if !ok {
return
}
vars, ok := s.Vars[loopPos]
if !ok {
vars = map[token.Pos]struct{}{}
}
vars[id.Obj.Pos()] = struct{}{}
s.Vars[loopPos] = vars
}
func insertionPosition(block *ast.BlockStmt) token.Pos {
if len(block.List) > 0 {
return block.List[0].Pos()
}
return token.NoPos
}
func (s *Searcher) innermostLoop(stack []ast.Node) (ast.Node, token.Pos) {
for i := len(stack) - 1; i >= 0; i-- {
switch typed := stack[i].(type) {
case *ast.RangeStmt:
return typed, insertionPosition(typed.Body)
case *ast.ForStmt:
return typed, insertionPosition(typed.Body)
}
}
return nil, token.NoPos
}
func (s *Searcher) checkUnaryExpr(n *ast.UnaryExpr, stack []ast.Node) (*ast.Ident, token.Pos, bool) {
loop, insert := s.innermostLoop(stack)
if loop == nil {
return nil, token.NoPos, true
}
if n.Op != token.AND {
return nil, token.NoPos, true
}
// Get identity of the referred item
id := s.getIdentity(n.X)
if id == nil {
return nil, token.NoPos, true
}
// If the identity is not the loop statement variable,
// it will not be reported.
if _, isStat := s.Stats[id.Obj.Pos()]; !isStat {
return nil, token.NoPos, true
}
// check stack append(), []X{}, map[Type]X{}, Struct{}, &Struct{}, X.(Type), (X)
// in the <outer> =
var mayRHPos token.Pos
for i := len(stack) - 2; i >= 0; i-- {
switch typed := stack[i].(type) {
case (*ast.UnaryExpr):
// noop
case (*ast.CompositeLit):
// noop
case (*ast.KeyValueExpr):
// noop
case (*ast.CallExpr):
fun, ok := typed.Fun.(*ast.Ident)
if !ok {
return nil, token.NoPos, false // it's calling a function other of `append`. It cannot be checked
}
if fun.Name != "append" {
return nil, token.NoPos, false // it's calling a function other of `append`. It cannot be checked
}
case (*ast.AssignStmt):
if len(typed.Rhs) != len(typed.Lhs) {
return nil, token.NoPos, false // dead logic
}
// search x where Rhs[x].Pos() == mayRHPos
var index int
for ri, rh := range typed.Rhs {
if rh.Pos() == mayRHPos {
index = ri
break
}
}
// check Lhs[x] is not local variable
lh := typed.Lhs[index]
isVar := s.isVar(loop, lh)
if !isVar {
return id, insert, false
}
return nil, token.NoPos, true
default:
// Other statement is not able to be checked.
return nil, token.NoPos, false
}
// memory an expr that may be right-hand in the AssignStmt
mayRHPos = stack[i].Pos()
}
return nil, token.NoPos, true
}
func (s *Searcher) isVar(loop ast.Node, expr ast.Expr) bool {
vars := s.Vars[loop.Pos()] // map[token.Pos]struct{}
if vars == nil {
return false
}
switch typed := expr.(type) {
case (*ast.Ident):
_, isVar := vars[typed.Obj.Pos()]
return isVar
case (*ast.IndexExpr): // like X[Y], check X
return s.isVar(loop, typed.X)
case (*ast.SelectorExpr): // like X.Y, check X
return s.isVar(loop, typed.X)
}
return false
}
// Get variable identity
func (s *Searcher) getIdentity(expr ast.Expr) *ast.Ident {
switch typed := expr.(type) {
case *ast.SelectorExpr:
// Ignore if the parent is pointer ref (fix for #2)
if _, ok := s.Types[typed.X].Type.(*types.Pointer); ok {
return nil
}
// Get parent identity; i.e. `a.b` of the `a.b.c`.
return s.getIdentity(typed.X)
case *ast.Ident:
// Get simple identity; i.e. `a` of the `a`.
if typed.Obj == nil {
return nil
}
return typed
}
return nil
}