+++ /dev/null
-// Copyright 2010 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.
-
-// Package stdmethods defines an Analyzer that checks for misspellings
-// in the signatures of methods similar to well-known interfaces.
-package stdmethods
-
-import (
- "go/ast"
- "go/types"
- "strings"
-
- "golang.org/x/tools/go/analysis"
- "golang.org/x/tools/go/analysis/passes/inspect"
- "golang.org/x/tools/go/ast/inspector"
-)
-
-const Doc = `check signature of methods of well-known interfaces
-
-Sometimes a type may be intended to satisfy an interface but may fail to
-do so because of a mistake in its method signature.
-For example, the result of this WriteTo method should be (int64, error),
-not error, to satisfy io.WriterTo:
-
- type myWriterTo struct{...}
- func (myWriterTo) WriteTo(w io.Writer) error { ... }
-
-This check ensures that each method whose name matches one of several
-well-known interface methods from the standard library has the correct
-signature for that interface.
-
-Checked method names include:
- Format GobEncode GobDecode MarshalJSON MarshalXML
- Peek ReadByte ReadFrom ReadRune Scan Seek
- UnmarshalJSON UnreadByte UnreadRune WriteByte
- WriteTo
-`
-
-var Analyzer = &analysis.Analyzer{
- Name: "stdmethods",
- Doc: Doc,
- Requires: []*analysis.Analyzer{inspect.Analyzer},
- Run: run,
-}
-
-// canonicalMethods lists the input and output types for Go methods
-// that are checked using dynamic interface checks. Because the
-// checks are dynamic, such methods would not cause a compile error
-// if they have the wrong signature: instead the dynamic check would
-// fail, sometimes mysteriously. If a method is found with a name listed
-// here but not the input/output types listed here, vet complains.
-//
-// A few of the canonical methods have very common names.
-// For example, a type might implement a Scan method that
-// has nothing to do with fmt.Scanner, but we still want to check
-// the methods that are intended to implement fmt.Scanner.
-// To do that, the arguments that have a = prefix are treated as
-// signals that the canonical meaning is intended: if a Scan
-// method doesn't have a fmt.ScanState as its first argument,
-// we let it go. But if it does have a fmt.ScanState, then the
-// rest has to match.
-var canonicalMethods = map[string]struct{ args, results []string }{
- // "Flush": {{}, {"error"}}, // http.Flusher and jpeg.writer conflict
- "Format": {[]string{"=fmt.State", "rune"}, []string{}}, // fmt.Formatter
- "GobDecode": {[]string{"[]byte"}, []string{"error"}}, // gob.GobDecoder
- "GobEncode": {[]string{}, []string{"[]byte", "error"}}, // gob.GobEncoder
- "MarshalJSON": {[]string{}, []string{"[]byte", "error"}}, // json.Marshaler
- "MarshalXML": {[]string{"*xml.Encoder", "xml.StartElement"}, []string{"error"}}, // xml.Marshaler
- "ReadByte": {[]string{}, []string{"byte", "error"}}, // io.ByteReader
- "ReadFrom": {[]string{"=io.Reader"}, []string{"int64", "error"}}, // io.ReaderFrom
- "ReadRune": {[]string{}, []string{"rune", "int", "error"}}, // io.RuneReader
- "Scan": {[]string{"=fmt.ScanState", "rune"}, []string{"error"}}, // fmt.Scanner
- "Seek": {[]string{"=int64", "int"}, []string{"int64", "error"}}, // io.Seeker
- "UnmarshalJSON": {[]string{"[]byte"}, []string{"error"}}, // json.Unmarshaler
- "UnmarshalXML": {[]string{"*xml.Decoder", "xml.StartElement"}, []string{"error"}}, // xml.Unmarshaler
- "UnreadByte": {[]string{}, []string{"error"}},
- "UnreadRune": {[]string{}, []string{"error"}},
- "WriteByte": {[]string{"byte"}, []string{"error"}}, // jpeg.writer (matching bufio.Writer)
- "WriteTo": {[]string{"=io.Writer"}, []string{"int64", "error"}}, // io.WriterTo
-}
-
-func run(pass *analysis.Pass) (interface{}, error) {
- inspect := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector)
-
- nodeFilter := []ast.Node{
- (*ast.FuncDecl)(nil),
- (*ast.InterfaceType)(nil),
- }
- inspect.Preorder(nodeFilter, func(n ast.Node) {
- switch n := n.(type) {
- case *ast.FuncDecl:
- if n.Recv != nil {
- canonicalMethod(pass, n.Name)
- }
- case *ast.InterfaceType:
- for _, field := range n.Methods.List {
- for _, id := range field.Names {
- canonicalMethod(pass, id)
- }
- }
- }
- })
- return nil, nil
-}
-
-func canonicalMethod(pass *analysis.Pass, id *ast.Ident) {
- // Expected input/output.
- expect, ok := canonicalMethods[id.Name]
- if !ok {
- return
- }
-
- // Actual input/output
- sign := pass.TypesInfo.Defs[id].Type().(*types.Signature)
- args := sign.Params()
- results := sign.Results()
-
- // Special case: WriteTo with more than one argument,
- // not trying at all to implement io.WriterTo,
- // comes up often enough to skip.
- if id.Name == "WriteTo" && args.Len() > 1 {
- return
- }
-
- // Do the =s (if any) all match?
- if !matchParams(pass, expect.args, args, "=") || !matchParams(pass, expect.results, results, "=") {
- return
- }
-
- // Everything must match.
- if !matchParams(pass, expect.args, args, "") || !matchParams(pass, expect.results, results, "") {
- expectFmt := id.Name + "(" + argjoin(expect.args) + ")"
- if len(expect.results) == 1 {
- expectFmt += " " + argjoin(expect.results)
- } else if len(expect.results) > 1 {
- expectFmt += " (" + argjoin(expect.results) + ")"
- }
-
- actual := typeString(sign)
- actual = strings.TrimPrefix(actual, "func")
- actual = id.Name + actual
-
- pass.ReportRangef(id, "method %s should have signature %s", actual, expectFmt)
- }
-}
-
-func typeString(typ types.Type) string {
- return types.TypeString(typ, (*types.Package).Name)
-}
-
-func argjoin(x []string) string {
- y := make([]string, len(x))
- for i, s := range x {
- if s[0] == '=' {
- s = s[1:]
- }
- y[i] = s
- }
- return strings.Join(y, ", ")
-}
-
-// Does each type in expect with the given prefix match the corresponding type in actual?
-func matchParams(pass *analysis.Pass, expect []string, actual *types.Tuple, prefix string) bool {
- for i, x := range expect {
- if !strings.HasPrefix(x, prefix) {
- continue
- }
- if i >= actual.Len() {
- return false
- }
- if !matchParamType(x, actual.At(i).Type()) {
- return false
- }
- }
- if prefix == "" && actual.Len() > len(expect) {
- return false
- }
- return true
-}
-
-// Does this one type match?
-func matchParamType(expect string, actual types.Type) bool {
- expect = strings.TrimPrefix(expect, "=")
- // Overkill but easy.
- return typeString(actual) == expect
-}
projects / dotfiles / .git / blobdiff