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// Copyright 2021 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 useany defines an Analyzer that checks for usage of interface{} in
// constraints, rather than the predeclared any.
package useany
import (
"fmt"
"go/ast"
"go/token"
"go/types"
"golang.org/x/tools/go/analysis"
"golang.org/x/tools/go/analysis/passes/inspect"
"golang.org/x/tools/go/ast/inspector"
"golang.org/x/tools/internal/typeparams"
)
const Doc = `check for constraints that could be simplified to "any"`
var Analyzer = &analysis.Analyzer{
Name: "useany",
Doc: Doc,
Requires: []*analysis.Analyzer{inspect.Analyzer},
Run: run,
}
func run(pass *analysis.Pass) (interface{}, error) {
inspect := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector)
universeAny := types.Universe.Lookup("any")
if universeAny == nil {
// Go <= 1.17. Nothing to check.
return nil, nil
}
nodeFilter := []ast.Node{
(*ast.TypeSpec)(nil),
(*ast.FuncType)(nil),
}
inspect.Preorder(nodeFilter, func(node ast.Node) {
var tparams *ast.FieldList
switch node := node.(type) {
case *ast.TypeSpec:
tparams = typeparams.ForTypeSpec(node)
case *ast.FuncType:
tparams = typeparams.ForFuncType(node)
default:
panic(fmt.Sprintf("unexpected node type %T", node))
}
if tparams.NumFields() == 0 {
return
}
for _, field := range tparams.List {
typ := pass.TypesInfo.Types[field.Type].Type
if typ == nil {
continue // something is wrong, but not our concern
}
iface, ok := typ.Underlying().(*types.Interface)
if !ok {
continue // invalid constraint
}
// If the constraint is the empty interface, offer a fix to use 'any'
// instead.
if iface.Empty() {
id, _ := field.Type.(*ast.Ident)
if id != nil && pass.TypesInfo.Uses[id] == universeAny {
continue
}
diag := analysis.Diagnostic{
Pos: field.Type.Pos(),
End: field.Type.End(),
Message: `could use "any" for this empty interface`,
}
// Only suggest a fix to 'any' if we actually resolve the predeclared
// any in this scope.
if scope := pass.TypesInfo.Scopes[node]; scope != nil {
if _, any := scope.LookupParent("any", token.NoPos); any == universeAny {
diag.SuggestedFixes = []analysis.SuggestedFix{{
Message: `use "any"`,
TextEdits: []analysis.TextEdit{{
Pos: field.Type.Pos(),
End: field.Type.End(),
NewText: []byte("any"),
}},
}}
}
}
pass.Report(diag)
}
}
})
return nil, nil
}
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