s1020.go raw

   1  package s1020
   2  
   3  import (
   4  	"fmt"
   5  	"go/ast"
   6  	"go/types"
   7  
   8  	"honnef.co/go/tools/analysis/code"
   9  	"honnef.co/go/tools/analysis/facts/generated"
  10  	"honnef.co/go/tools/analysis/lint"
  11  	"honnef.co/go/tools/analysis/report"
  12  	"honnef.co/go/tools/pattern"
  13  
  14  	"golang.org/x/tools/go/analysis"
  15  	"golang.org/x/tools/go/analysis/passes/inspect"
  16  )
  17  
  18  var SCAnalyzer = lint.InitializeAnalyzer(&lint.Analyzer{
  19  	Analyzer: &analysis.Analyzer{
  20  		Name:     "S1020",
  21  		Run:      run,
  22  		Requires: []*analysis.Analyzer{inspect.Analyzer, generated.Analyzer},
  23  	},
  24  	Doc: &lint.RawDocumentation{
  25  		Title:   `Omit redundant nil check in type assertion`,
  26  		Before:  `if _, ok := i.(T); ok && i != nil {}`,
  27  		After:   `if _, ok := i.(T); ok {}`,
  28  		Since:   "2017.1",
  29  		MergeIf: lint.MergeIfAny,
  30  	},
  31  })
  32  
  33  var Analyzer = SCAnalyzer.Analyzer
  34  
  35  var (
  36  	checkAssertNotNilFn1Q = pattern.MustParse(`
  37  		(IfStmt
  38  			(AssignStmt [(Ident "_") ok@(Object _)] _ [(TypeAssertExpr assert@(Object _) _)])
  39  			(Or
  40  				(BinaryExpr ok "&&" (BinaryExpr assert "!=" (Builtin "nil")))
  41  				(BinaryExpr (BinaryExpr assert "!=" (Builtin "nil")) "&&" ok))
  42  			_
  43  			_)`)
  44  	checkAssertNotNilFn2Q = pattern.MustParse(`
  45  		(IfStmt
  46  			nil
  47  			(BinaryExpr lhs@(Object _) "!=" (Builtin "nil"))
  48  			[
  49  				ifstmt@(IfStmt
  50  					(AssignStmt [(Ident "_") ok@(Object _)] _ [(TypeAssertExpr lhs _)])
  51  					ok
  52  					_
  53  					nil)
  54  			]
  55  			nil)`)
  56  )
  57  
  58  func run(pass *analysis.Pass) (interface{}, error) {
  59  	fn1 := func(node ast.Node) {
  60  		m, ok := code.Match(pass, checkAssertNotNilFn1Q, node)
  61  		if !ok {
  62  			return
  63  		}
  64  		assert := m.State["assert"].(types.Object)
  65  		assign := m.State["ok"].(types.Object)
  66  		report.Report(pass, node, fmt.Sprintf("when %s is true, %s can't be nil", assign.Name(), assert.Name()),
  67  			report.ShortRange(),
  68  			report.FilterGenerated())
  69  	}
  70  	fn2 := func(node ast.Node) {
  71  		m, ok := code.Match(pass, checkAssertNotNilFn2Q, node)
  72  		if !ok {
  73  			return
  74  		}
  75  		ifstmt := m.State["ifstmt"].(*ast.IfStmt)
  76  		lhs := m.State["lhs"].(types.Object)
  77  		assignIdent := m.State["ok"].(types.Object)
  78  		report.Report(pass, ifstmt, fmt.Sprintf("when %s is true, %s can't be nil", assignIdent.Name(), lhs.Name()),
  79  			report.ShortRange(),
  80  			report.FilterGenerated())
  81  	}
  82  	// OPT(dh): merge fn1 and fn2
  83  	code.Preorder(pass, fn1, (*ast.IfStmt)(nil))
  84  	code.Preorder(pass, fn2, (*ast.IfStmt)(nil))
  85  	return nil, nil
  86  }
  87