147 lines
3.4 KiB
Go
147 lines
3.4 KiB
Go
package qf1002
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import (
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"fmt"
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"go/ast"
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"go/token"
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"strings"
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"honnef.co/go/tools/analysis/code"
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"honnef.co/go/tools/analysis/edit"
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"honnef.co/go/tools/analysis/lint"
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"honnef.co/go/tools/analysis/report"
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"honnef.co/go/tools/go/ast/astutil"
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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: "QF1002",
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Run: run,
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Requires: []*analysis.Analyzer{inspect.Analyzer},
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},
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Doc: &lint.RawDocumentation{
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Title: "Convert untagged switch to tagged switch",
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Text: `
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An untagged switch that compares a single variable against a series of
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values can be replaced with a tagged switch.`,
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Before: `
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switch {
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case x == 1 || x == 2, x == 3:
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...
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case x == 4:
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...
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default:
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...
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}`,
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After: `
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switch x {
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case 1, 2, 3:
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...
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case 4:
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...
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default:
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...
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}`,
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Since: "2021.1",
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Severity: lint.SeverityHint,
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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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fn := func(node ast.Node) {
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swtch := node.(*ast.SwitchStmt)
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if swtch.Tag != nil || len(swtch.Body.List) == 0 {
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return
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}
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pairs := make([][]*ast.BinaryExpr, len(swtch.Body.List))
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for i, stmt := range swtch.Body.List {
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stmt := stmt.(*ast.CaseClause)
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for _, cond := range stmt.List {
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if !findSwitchPairs(pass, cond, &pairs[i]) {
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return
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}
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}
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}
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var x ast.Expr
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for _, pair := range pairs {
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if len(pair) == 0 {
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continue
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}
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if x == nil {
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x = pair[0].X
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} else {
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if !astutil.Equal(x, pair[0].X) {
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return
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}
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}
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}
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if x == nil {
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// the switch only has a default case
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if len(pairs) > 1 {
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panic("found more than one case clause with no pairs")
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}
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return
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}
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edits := make([]analysis.TextEdit, 0, len(swtch.Body.List)+1)
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for i, stmt := range swtch.Body.List {
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stmt := stmt.(*ast.CaseClause)
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if stmt.List == nil {
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continue
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}
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var values []string
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for _, binexpr := range pairs[i] {
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y := binexpr.Y
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if p, ok := y.(*ast.ParenExpr); ok {
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y = p.X
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}
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values = append(values, report.Render(pass, y))
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}
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edits = append(edits, edit.ReplaceWithString(edit.Range{stmt.List[0].Pos(), stmt.Colon}, strings.Join(values, ", ")))
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}
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pos := swtch.Body.Lbrace
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edits = append(edits, edit.ReplaceWithString(edit.Range{pos, pos}, " "+report.Render(pass, x)))
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report.Report(pass, swtch, fmt.Sprintf("could use tagged switch on %s", report.Render(pass, x)),
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report.Fixes(edit.Fix("Replace with tagged switch", edits...)),
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report.ShortRange())
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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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func findSwitchPairs(pass *analysis.Pass, expr ast.Expr, pairs *[]*ast.BinaryExpr) bool {
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binexpr, ok := astutil.Unparen(expr).(*ast.BinaryExpr)
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if !ok {
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return false
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}
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switch binexpr.Op {
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case token.EQL:
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if code.MayHaveSideEffects(pass, binexpr.X, nil) || code.MayHaveSideEffects(pass, binexpr.Y, nil) {
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return false
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}
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// syntactic identity should suffice. we do not allow side
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// effects in the case clauses, so there should be no way for
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// values to change.
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if len(*pairs) > 0 && !astutil.Equal(binexpr.X, (*pairs)[0].X) {
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return false
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}
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*pairs = append(*pairs, binexpr)
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return true
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case token.LOR:
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return findSwitchPairs(pass, binexpr.X, pairs) && findSwitchPairs(pass, binexpr.Y, pairs)
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default:
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return false
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}
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}
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