75 lines
1.7 KiB
Go
75 lines
1.7 KiB
Go
// Copyright 2013 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package nilfunc defines an Analyzer that checks for useless
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// comparisons against nil.
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package nilfunc
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import (
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"go/ast"
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"go/token"
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"go/types"
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"golang.org/x/tools/go/analysis"
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"golang.org/x/tools/go/analysis/passes/inspect"
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"golang.org/x/tools/go/ast/inspector"
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)
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const Doc = `check for useless comparisons between functions and nil
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A useless comparison is one like f == nil as opposed to f() == nil.`
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var Analyzer = &analysis.Analyzer{
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Name: "nilfunc",
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Doc: Doc,
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Requires: []*analysis.Analyzer{inspect.Analyzer},
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Run: run,
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}
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func run(pass *analysis.Pass) (interface{}, error) {
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inspect := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector)
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nodeFilter := []ast.Node{
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(*ast.BinaryExpr)(nil),
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}
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inspect.Preorder(nodeFilter, func(n ast.Node) {
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e := n.(*ast.BinaryExpr)
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// Only want == or != comparisons.
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if e.Op != token.EQL && e.Op != token.NEQ {
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return
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}
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// Only want comparisons with a nil identifier on one side.
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var e2 ast.Expr
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switch {
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case pass.TypesInfo.Types[e.X].IsNil():
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e2 = e.Y
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case pass.TypesInfo.Types[e.Y].IsNil():
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e2 = e.X
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default:
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return
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}
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// Only want identifiers or selector expressions.
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var obj types.Object
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switch v := e2.(type) {
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case *ast.Ident:
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obj = pass.TypesInfo.Uses[v]
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case *ast.SelectorExpr:
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obj = pass.TypesInfo.Uses[v.Sel]
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default:
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return
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}
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// Only want functions.
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if _, ok := obj.(*types.Func); !ok {
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return
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}
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pass.Reportf(e.Pos(), "comparison of function %v %v nil is always %v", obj.Name(), e.Op, e.Op == token.NEQ)
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})
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return nil, nil
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}
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