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sa4024.go (1414B)

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