github.com/amarpal/go-tools@v0.0.0-20240422043104-40142f59f616/staticcheck/sa4024/sa4024.go (about)

     1  package sa4024
     2  
     3  import (
     4  	"fmt"
     5  	"go/ast"
     6  
     7  	"github.com/amarpal/go-tools/analysis/code"
     8  	"github.com/amarpal/go-tools/analysis/lint"
     9  	"github.com/amarpal/go-tools/analysis/report"
    10  	"github.com/amarpal/go-tools/pattern"
    11  
    12  	"golang.org/x/tools/go/analysis"
    13  	"golang.org/x/tools/go/analysis/passes/inspect"
    14  )
    15  
    16  var SCAnalyzer = lint.InitializeAnalyzer(&lint.Analyzer{
    17  	Analyzer: &analysis.Analyzer{
    18  		Name:     "SA4024",
    19  		Run:      run,
    20  		Requires: []*analysis.Analyzer{inspect.Analyzer},
    21  	},
    22  	Doc: &lint.Documentation{
    23  		Title: `Checking for impossible return value from a builtin function`,
    24  		Text: `Return values of the \'len\' and \'cap\' builtins cannot be negative.
    25  
    26  See https://golang.org/pkg/builtin/#len and https://golang.org/pkg/builtin/#cap.
    27  
    28  Example:
    29  
    30      if len(slice) < 0 {
    31          fmt.Println("unreachable code")
    32      }`,
    33  		Since:    "2021.1",
    34  		Severity: lint.SeverityWarning,
    35  		MergeIf:  lint.MergeIfAny,
    36  	},
    37  })
    38  
    39  var Analyzer = SCAnalyzer.Analyzer
    40  
    41  var builtinLessThanZeroQ = pattern.MustParse(`
    42  	(Or
    43  		(BinaryExpr
    44  			(IntegerLiteral "0")
    45  			">"
    46  			(CallExpr builtin@(Builtin (Or "len" "cap")) _))
    47  		(BinaryExpr
    48  			(CallExpr builtin@(Builtin (Or "len" "cap")) _)
    49  			"<"
    50  			(IntegerLiteral "0")))
    51  `)
    52  
    53  func run(pass *analysis.Pass) (interface{}, error) {
    54  	fn := func(node ast.Node) {
    55  		matcher, ok := code.Match(pass, builtinLessThanZeroQ, node)
    56  		if !ok {
    57  			return
    58  		}
    59  
    60  		builtin := matcher.State["builtin"].(*ast.Ident)
    61  		report.Report(pass, node, fmt.Sprintf("builtin function %s does not return negative values", builtin.Name))
    62  	}
    63  	code.Preorder(pass, fn, (*ast.BinaryExpr)(nil))
    64  
    65  	return nil, nil
    66  }