sa6001

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• Variables

Variables

var Analyzer = SCAnalyzer.Analyzer

var SCAnalyzer = lint.InitializeAnalyzer(&lint.Analyzer{
	Analyzer: &analysis.Analyzer{
		Name:     "SA6001",
		Run:      run,
		Requires: []*analysis.Analyzer{buildir.Analyzer},
	},
	Doc: &lint.RawDocumentation{
		Title: `Missing an optimization opportunity when indexing maps by byte slices`,

		Text: `Map keys must be comparable, which precludes the use of byte slices.
This usually leads to using string keys and converting byte slices to
strings.

Normally, a conversion of a byte slice to a string needs to copy the data and
causes allocations. The compiler, however, recognizes \'m[string(b)]\' and
uses the data of \'b\' directly, without copying it, because it knows that
the data can't change during the map lookup. This leads to the
counter-intuitive situation that

    k := string(b)
    println(m[k])
    println(m[k])

will be less efficient than

    println(m[string(b)])
    println(m[string(b)])

because the first version needs to copy and allocate, while the second
one does not.

For some history on this optimization, check out commit
f5f5a8b6209f84961687d993b93ea0d397f5d5bf in the Go repository.`,
		Since:    "2017.1",
		Severity: lint.SeverityWarning,
		MergeIf:  lint.MergeIfAny,
	},
})