src

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git clone git://code.dwrz.net/src
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st1015.go (2046B)

      1 package st1015
      2 
      3 import (
      4 	"go/ast"
      5 	"go/token"
      6 
      7 	"honnef.co/go/tools/analysis/code"
      8 	"honnef.co/go/tools/analysis/facts/generated"
      9 	"honnef.co/go/tools/analysis/lint"
     10 	"honnef.co/go/tools/analysis/report"
     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:     "ST1015",
     19 		Run:      run,
     20 		Requires: []*analysis.Analyzer{inspect.Analyzer, generated.Analyzer},
     21 	},
     22 	Doc: &lint.RawDocumentation{
     23 		Title:   `A switch's default case should be the first or last case`,
     24 		Since:   "2019.1",
     25 		MergeIf: lint.MergeIfAny,
     26 	},
     27 })
     28 
     29 var Analyzer = SCAnalyzer.Analyzer
     30 
     31 func run(pass *analysis.Pass) (any, error) {
     32 	hasFallthrough := func(clause ast.Stmt) bool {
     33 		// A valid fallthrough statement may be used only as the final non-empty statement in a case clause. Thus we can
     34 		// easily avoid falsely matching fallthroughs in nested switches by not descending into blocks.
     35 
     36 		body := clause.(*ast.CaseClause).Body
     37 		for i := len(body) - 1; i >= 0; i-- {
     38 			last := body[i]
     39 			switch stmt := last.(type) {
     40 			case *ast.EmptyStmt:
     41 				// Fallthrough may be followed by empty statements
     42 			case *ast.BranchStmt:
     43 				return stmt.Tok == token.FALLTHROUGH
     44 			default:
     45 				return false
     46 			}
     47 		}
     48 
     49 		return false
     50 	}
     51 
     52 	fn := func(node ast.Node) {
     53 		stmt := node.(*ast.SwitchStmt)
     54 		list := stmt.Body.List
     55 		defaultIdx := -1
     56 		for i, c := range list {
     57 			if c.(*ast.CaseClause).List == nil {
     58 				defaultIdx = i
     59 				break
     60 			}
     61 		}
     62 
     63 		if defaultIdx == -1 || defaultIdx == 0 || defaultIdx == len(list)-1 {
     64 			// No default case, or it's the first or last case
     65 			return
     66 		}
     67 
     68 		if hasFallthrough(list[defaultIdx-1]) || hasFallthrough(list[defaultIdx]) {
     69 			// We either fall into or out of this case; don't mess with the order
     70 			return
     71 		}
     72 
     73 		report.Report(pass, list[defaultIdx], "default case should be first or last in switch statement", report.FilterGenerated())
     74 	}
     75 	code.Preorder(pass, fn, (*ast.SwitchStmt)(nil))
     76 	return nil, nil
     77 }