+++ /dev/null
-// 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 assign defines an Analyzer that detects useless assignments.
-package assign
-
-// TODO(adonovan): check also for assignments to struct fields inside
-// methods that are on T instead of *T.
-
-import (
- "fmt"
- "go/ast"
- "go/token"
- "reflect"
-
- "golang.org/x/tools/go/analysis"
- "golang.org/x/tools/go/analysis/passes/inspect"
- "golang.org/x/tools/go/analysis/passes/internal/analysisutil"
- "golang.org/x/tools/go/ast/inspector"
-)
-
-const Doc = `check for useless assignments
-
-This checker reports assignments of the form x = x or a[i] = a[i].
-These are almost always useless, and even when they aren't they are
-usually a mistake.`
-
-var Analyzer = &analysis.Analyzer{
- Name: "assign",
- Doc: Doc,
- Requires: []*analysis.Analyzer{inspect.Analyzer},
- Run: run,
-}
-
-func run(pass *analysis.Pass) (interface{}, error) {
- inspect := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector)
-
- nodeFilter := []ast.Node{
- (*ast.AssignStmt)(nil),
- }
- inspect.Preorder(nodeFilter, func(n ast.Node) {
- stmt := n.(*ast.AssignStmt)
- if stmt.Tok != token.ASSIGN {
- return // ignore :=
- }
- if len(stmt.Lhs) != len(stmt.Rhs) {
- // If LHS and RHS have different cardinality, they can't be the same.
- return
- }
- for i, lhs := range stmt.Lhs {
- rhs := stmt.Rhs[i]
- if analysisutil.HasSideEffects(pass.TypesInfo, lhs) ||
- analysisutil.HasSideEffects(pass.TypesInfo, rhs) {
- continue // expressions may not be equal
- }
- if reflect.TypeOf(lhs) != reflect.TypeOf(rhs) {
- continue // short-circuit the heavy-weight gofmt check
- }
- le := analysisutil.Format(pass.Fset, lhs)
- re := analysisutil.Format(pass.Fset, rhs)
- if le == re {
- pass.Report(analysis.Diagnostic{
- Pos: stmt.Pos(), Message: fmt.Sprintf("self-assignment of %s to %s", re, le),
- SuggestedFixes: []analysis.SuggestedFix{
- {Message: "Remove", TextEdits: []analysis.TextEdit{
- {Pos: stmt.Pos(), End: stmt.End(), NewText: []byte{}},
- }},
- },
- })
- }
- }
- })
-
- return nil, nil
-}