79 lines
2.3 KiB
Go
79 lines
2.3 KiB
Go
package s1018
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import (
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"go/ast"
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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/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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"honnef.co/go/tools/go/types/typeutil"
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"honnef.co/go/tools/pattern"
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"golang.org/x/tools/go/analysis"
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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: "S1018",
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Run: run,
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Requires: append([]*analysis.Analyzer{generated.Analyzer}, code.RequiredAnalyzers...),
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},
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Doc: &lint.RawDocumentation{
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Title: `Use \"copy\" for sliding elements`,
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Text: `\'copy()\' permits using the same source and destination slice, even with
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overlapping ranges. This makes it ideal for sliding elements in a
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slice.`,
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Before: `
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for i := 0; i < n; i++ {
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bs[i] = bs[offset+i]
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}`,
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After: `copy(bs[:n], bs[offset:])`,
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Since: "2017.1",
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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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var (
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checkLoopSlideQ = pattern.MustParse(`
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(ForStmt
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(AssignStmt initvar@(Ident _) _ (IntegerLiteral "0"))
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(BinaryExpr initvar "<" limit@(Ident _))
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(IncDecStmt initvar "++")
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[(AssignStmt
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(IndexExpr slice@(Ident _) initvar)
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"="
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(IndexExpr slice (BinaryExpr offset@(Ident _) "+" initvar)))])`)
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checkLoopSlideR = pattern.MustParse(`
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(CallExpr
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(Ident "copy")
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[(SliceExpr slice nil limit nil)
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(SliceExpr slice offset nil nil)])`)
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)
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func run(pass *analysis.Pass) (any, error) {
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// TODO(dh): detect bs[i+offset] in addition to bs[offset+i]
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// TODO(dh): consider merging this function with LintLoopCopy
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// TODO(dh): detect length that is an expression, not a variable name
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// TODO(dh): support sliding to a different offset than the beginning of the slice
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for node, m := range code.Matches(pass, checkLoopSlideQ) {
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typ := pass.TypesInfo.TypeOf(m.State["slice"].(*ast.Ident))
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// The pattern probably needs a core type, but All is fine, too. Either way we only accept slices.
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if !typeutil.All(typ, typeutil.IsSlice) {
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continue
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}
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edits := code.EditMatch(pass, node, m, checkLoopSlideR)
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report.Report(pass, node, "should use copy() instead of loop for sliding slice elements",
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report.ShortRange(),
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report.FilterGenerated(),
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report.Fixes(edit.Fix("Use copy() instead of loop", edits...)))
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}
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return nil, nil
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}
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