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package rule
import (
"fmt"
"go/ast"
"github.com/mgechev/revive/lint"
)
// RangeValInClosureRule lints given else constructs.
type RangeValInClosureRule struct{}
// Apply applies the rule to given file.
func (r *RangeValInClosureRule) Apply(file *lint.File, _ lint.Arguments) []lint.Failure {
var failures []lint.Failure
walker := rangeValInClosure{
onFailure: func(failure lint.Failure) {
failures = append(failures, failure)
},
}
ast.Walk(walker, file.AST)
return failures
}
// Name returns the rule name.
func (r *RangeValInClosureRule) Name() string {
return "range-val-in-closure"
}
type rangeValInClosure struct {
onFailure func(lint.Failure)
}
func (w rangeValInClosure) Visit(node ast.Node) ast.Visitor {
// Find the variables updated by the loop statement.
var vars []*ast.Ident
addVar := func(expr ast.Expr) {
if id, ok := expr.(*ast.Ident); ok {
vars = append(vars, id)
}
}
var body *ast.BlockStmt
switch n := node.(type) {
case *ast.RangeStmt:
body = n.Body
addVar(n.Key)
addVar(n.Value)
case *ast.ForStmt:
body = n.Body
switch post := n.Post.(type) {
case *ast.AssignStmt:
// e.g. for p = head; p != nil; p = p.next
for _, lhs := range post.Lhs {
addVar(lhs)
}
case *ast.IncDecStmt:
// e.g. for i := 0; i < n; i++
addVar(post.X)
}
}
if vars == nil {
return w
}
// Inspect a go or defer statement
// if it's the last one in the loop body.
// (We give up if there are following statements,
// because it's hard to prove go isn't followed by wait,
// or defer by return.)
if len(body.List) == 0 {
return w
}
var last *ast.CallExpr
switch s := body.List[len(body.List)-1].(type) {
case *ast.GoStmt:
last = s.Call
case *ast.DeferStmt:
last = s.Call
default:
return w
}
lit, ok := last.Fun.(*ast.FuncLit)
if !ok {
return w
}
if lit.Type == nil {
// Not referring to a variable (e.g. struct field name)
return w
}
ast.Inspect(lit.Body, func(n ast.Node) bool {
id, ok := n.(*ast.Ident)
if !ok || id.Obj == nil {
return true
}
for _, v := range vars {
if v.Obj == id.Obj {
w.onFailure(lint.Failure{
Confidence: 1,
Failure: fmt.Sprintf("loop variable %v captured by func literal", id.Name),
Node: n,
})
}
}
return true
})
return w
}
|
