| // Copyright 2018 The Go Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| // The errorsas package defines an Analyzer that checks that the second argument to |
| // errors.As is a pointer to a type implementing error. |
| package errorsas |
| |
| import ( |
| "errors" |
| "go/ast" |
| "go/types" |
| |
| "golang.org/x/tools/go/analysis" |
| "golang.org/x/tools/go/analysis/passes/inspect" |
| "golang.org/x/tools/go/analysis/passes/internal/analysisutil" |
| "golang.org/x/tools/go/ast/inspector" |
| "golang.org/x/tools/go/types/typeutil" |
| ) |
| |
| const Doc = `report passing non-pointer or non-error values to errors.As |
| |
| The errorsas analysis reports calls to errors.As where the type |
| of the second argument is not a pointer to a type implementing error.` |
| |
| var Analyzer = &analysis.Analyzer{ |
| Name: "errorsas", |
| Doc: Doc, |
| URL: "https://pkg.go.dev/golang.org/x/tools/go/analysis/passes/errorsas", |
| Requires: []*analysis.Analyzer{inspect.Analyzer}, |
| Run: run, |
| } |
| |
| func run(pass *analysis.Pass) (interface{}, error) { |
| switch pass.Pkg.Path() { |
| case "errors", "errors_test": |
| // These packages know how to use their own APIs. |
| // Sometimes they are testing what happens to incorrect programs. |
| return nil, nil |
| } |
| |
| if !analysisutil.Imports(pass.Pkg, "errors") { |
| return nil, nil // doesn't directly import errors |
| } |
| |
| inspect := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector) |
| |
| nodeFilter := []ast.Node{ |
| (*ast.CallExpr)(nil), |
| } |
| inspect.Preorder(nodeFilter, func(n ast.Node) { |
| call := n.(*ast.CallExpr) |
| fn := typeutil.StaticCallee(pass.TypesInfo, call) |
| if fn == nil { |
| return // not a static call |
| } |
| if len(call.Args) < 2 { |
| return // not enough arguments, e.g. called with return values of another function |
| } |
| if fn.FullName() != "errors.As" { |
| return |
| } |
| if err := checkAsTarget(pass, call.Args[1]); err != nil { |
| pass.ReportRangef(call, "%v", err) |
| } |
| }) |
| return nil, nil |
| } |
| |
| var errorType = types.Universe.Lookup("error").Type() |
| |
| // pointerToInterfaceOrError reports whether the type of e is a pointer to an interface or a type implementing error, |
| // or is the empty interface. |
| |
| // checkAsTarget reports an error if the second argument to errors.As is invalid. |
| func checkAsTarget(pass *analysis.Pass, e ast.Expr) error { |
| t := pass.TypesInfo.Types[e].Type |
| if it, ok := t.Underlying().(*types.Interface); ok && it.NumMethods() == 0 { |
| // A target of interface{} is always allowed, since it often indicates |
| // a value forwarded from another source. |
| return nil |
| } |
| pt, ok := t.Underlying().(*types.Pointer) |
| if !ok { |
| return errors.New("second argument to errors.As must be a non-nil pointer to either a type that implements error, or to any interface type") |
| } |
| if pt.Elem() == errorType { |
| return errors.New("second argument to errors.As should not be *error") |
| } |
| _, ok = pt.Elem().Underlying().(*types.Interface) |
| if ok || types.Implements(pt.Elem(), errorType.Underlying().(*types.Interface)) { |
| return nil |
| } |
| return errors.New("second argument to errors.As must be a non-nil pointer to either a type that implements error, or to any interface type") |
| } |