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// Copyright 2020 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 nonewvars defines an Analyzer that applies suggested fixes
// to errors of the type "no new variables on left side of :=".
package nonewvars
import (
"bytes"
"go/ast"
"go/format"
"go/token"
"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/analysisinternal"
)
const Doc = `suggested fixes for "no new vars on left side of :="
This checker provides suggested fixes for type errors of the
type "no new vars on left side of :=". For example:
z := 1
z := 2
will turn into
z := 1
z = 2
`
var Analyzer = &analysis.Analyzer{
Name: "nonewvars",
Doc: Doc,
Requires: []*analysis.Analyzer{inspect.Analyzer},
Run: run,
RunDespiteErrors: true,
}
func run(pass *analysis.Pass) (interface{}, error) {
inspect := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector)
if len(pass.TypeErrors) == 0 {
return nil, nil
}
nodeFilter := []ast.Node{(*ast.AssignStmt)(nil)}
inspect.Preorder(nodeFilter, func(n ast.Node) {
assignStmt, _ := n.(*ast.AssignStmt)
// We only care about ":=".
if assignStmt.Tok != token.DEFINE {
return
}
var file *ast.File
for _, f := range pass.Files {
if f.Pos() <= assignStmt.Pos() && assignStmt.Pos() < f.End() {
file = f
break
}
}
if file == nil {
return
}
for _, err := range pass.TypeErrors {
if !FixesError(err.Msg) {
continue
}
if assignStmt.Pos() > err.Pos || err.Pos >= assignStmt.End() {
continue
}
var buf bytes.Buffer
if err := format.Node(&buf, pass.Fset, file); err != nil {
continue
}
pass.Report(analysis.Diagnostic{
Pos: err.Pos,
End: analysisinternal.TypeErrorEndPos(pass.Fset, buf.Bytes(), err.Pos),
Message: err.Msg,
SuggestedFixes: []analysis.SuggestedFix{{
Message: "Change ':=' to '='",
TextEdits: []analysis.TextEdit{{
Pos: err.Pos,
End: err.Pos + 1,
}},
}},
})
}
})
return nil, nil
}
func FixesError(msg string) bool {
return msg == "no new variables on left side of :="
}
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