74 lines
2.4 KiB
Go
74 lines
2.4 KiB
Go
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package s1040
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import (
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"fmt"
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"go/ast"
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"go/types"
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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: "S1040",
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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: "Type assertion to current type",
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Text: `The type assertion \'x.(SomeInterface)\', when \'x\' already has type
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\'SomeInterface\', can only fail if \'x\' is nil. Usually, this is
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left-over code from when \'x\' had a different type and you can safely
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delete the type assertion. If you want to check that \'x\' is not nil,
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consider being explicit and using an actual \'if x == nil\' comparison
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instead of relying on the type assertion panicking.`,
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Since: "2021.1",
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// MergeIfAll because x might have different types under different build tags.
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// You shouldn't write code like that…
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MergeIf: lint.MergeIfAll,
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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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expr := node.(*ast.TypeAssertExpr)
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if expr.Type == nil {
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// skip type switches
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//
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// TODO(dh): we could flag type switches, too, when a case
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// statement has the same type as expr.X – however,
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// depending on the location of that case, it might behave
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// identically to a default branch. we need to think
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// carefully about the instances we want to flag. We also
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// have to take nil interface values into consideration.
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//
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// It might make more sense to extend SA4020 to handle
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// this.
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return
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}
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t1 := pass.TypesInfo.TypeOf(expr.Type)
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t2 := pass.TypesInfo.TypeOf(expr.X)
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if types.IsInterface(t1) && types.Identical(t1, t2) {
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report.Report(pass, expr,
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fmt.Sprintf("type assertion to the same type: %s already has type %s", report.Render(pass, expr.X), report.Render(pass, expr.Type)),
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report.FilterGenerated())
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}
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}
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// TODO(dh): add suggested fixes. we need different fixes depending on the context:
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// - assignment with 1 or 2 lhs
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// - assignment to blank identifiers (as the first, second or both lhs)
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// - initializers in if statements, with the same variations as above
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code.Preorder(pass, fn, (*ast.TypeAssertExpr)(nil))
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return nil, nil
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}
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