78 lines
2.0 KiB
Go
78 lines
2.0 KiB
Go
package st1015
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import (
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"go/ast"
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"go/token"
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"honnef.co/go/tools/analysis/code"
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"honnef.co/go/tools/analysis/facts/generated"
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"honnef.co/go/tools/analysis/lint"
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"honnef.co/go/tools/analysis/report"
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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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)
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var SCAnalyzer = lint.InitializeAnalyzer(&lint.Analyzer{
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Analyzer: &analysis.Analyzer{
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Name: "ST1015",
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Run: run,
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Requires: []*analysis.Analyzer{inspect.Analyzer, generated.Analyzer},
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},
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Doc: &lint.RawDocumentation{
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Title: `A switch's default case should be the first or last case`,
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Since: "2019.1",
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MergeIf: lint.MergeIfAny,
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},
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})
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var Analyzer = SCAnalyzer.Analyzer
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func run(pass *analysis.Pass) (any, error) {
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hasFallthrough := func(clause ast.Stmt) bool {
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// A valid fallthrough statement may be used only as the final non-empty statement in a case clause. Thus we can
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// easily avoid falsely matching fallthroughs in nested switches by not descending into blocks.
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body := clause.(*ast.CaseClause).Body
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for i := len(body) - 1; i >= 0; i-- {
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last := body[i]
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switch stmt := last.(type) {
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case *ast.EmptyStmt:
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// Fallthrough may be followed by empty statements
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case *ast.BranchStmt:
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return stmt.Tok == token.FALLTHROUGH
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default:
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return false
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}
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}
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return false
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}
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fn := func(node ast.Node) {
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stmt := node.(*ast.SwitchStmt)
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list := stmt.Body.List
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defaultIdx := -1
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for i, c := range list {
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if c.(*ast.CaseClause).List == nil {
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defaultIdx = i
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break
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}
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}
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if defaultIdx == -1 || defaultIdx == 0 || defaultIdx == len(list)-1 {
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// No default case, or it's the first or last case
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return
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}
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if hasFallthrough(list[defaultIdx-1]) || hasFallthrough(list[defaultIdx]) {
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// We either fall into or out of this case; don't mess with the order
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return
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}
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report.Report(pass, list[defaultIdx], "default case should be first or last in switch statement", report.FilterGenerated())
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}
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code.Preorder(pass, fn, (*ast.SwitchStmt)(nil))
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return nil, nil
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}
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