| // 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 nilfunc |
| |
| import ( |
| "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: "nilfunc", |
| Doc: `check for useless comparisons between functions and nil |
| |
| A useless comparison is one like f == nil as opposed to f() == nil.`, |
| 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.BinaryExpr)(nil), |
| } |
| inspect.Preorder(nodeFilter, func(n ast.Node) { |
| e := n.(*ast.BinaryExpr) |
| |
| // Only want == or != comparisons. |
| if e.Op != token.EQL && e.Op != token.NEQ { |
| return |
| } |
| |
| // Only want comparisons with a nil identifier on one side. |
| var e2 ast.Expr |
| switch { |
| case pass.TypesInfo.Types[e.X].IsNil(): |
| e2 = e.Y |
| case pass.TypesInfo.Types[e.Y].IsNil(): |
| e2 = e.X |
| default: |
| return |
| } |
| |
| // Only want identifiers or selector expressions. |
| var obj types.Object |
| switch v := e2.(type) { |
| case *ast.Ident: |
| obj = pass.TypesInfo.Uses[v] |
| case *ast.SelectorExpr: |
| obj = pass.TypesInfo.Uses[v.Sel] |
| default: |
| return |
| } |
| |
| // Only want functions. |
| if _, ok := obj.(*types.Func); !ok { |
| return |
| } |
| |
| pass.Reportf(e.Pos(), "comparison of function %v %v nil is always %v", obj.Name(), e.Op, e.Op == token.NEQ) |
| }) |
| return nil, nil |
| } |