A static analysis tool for Go that checks for incorrect usage of defer statements, specifically assignments to error-typed variables that are not named return values in deferred functions.

• Detects deferred functions that assign to error variables not declared as named return values.
• Helps avoid the common pitfall of using defer incorrectly with errors, which can lead to unexpected behavior in error handling.

You can build deferrlint from source and install it locally:

Make sure you have Go and Task installed on your machine.

git clone https://github.com/yourusername/deferrlint.git
cd deferrlint
task install

Run deferrlint on your Go codebase:

go run main.go ./...

Or, if you built the binary with task install, you can run it directly:

deferrlint ./...

You can verify deferrlint is installed correctly by running:

deferrlint ./testdata/src/fail/...

package main

import (
	"errors"
)

func foo() (err error) {
	defer func() {
		err = errors.New("foo") // OK: err is a named return value
	}()
	
	return err
}

func bar() error {
	var err error
	defer func() {
		err = errors.New("bar") // Not OK: err is not a named return value
	}()
	return err
}

deferrlint will report the assignment in bar as a potential issue.

Pull requests and issues are welcome!

See the LICENSE file for details.