errorlint vs type assertion with variable reuse

[ccoVeille]

Consider this code that works

Code that works

// package foo blah
package foo

import "fmt"

// Error is a package-level error type
type Error struct {
	Code string
}

func (Error) Error() string {
	return "an error occurred"
}

func checkError(err error) {
	switch errSpecific := err.(type) {
	case Error:
		fmt.Printf("error occurred: %s\n", errSpecific.Code)
		// do something
	case nil:
		// omit the element
	}
}

Now try this

// package foo blah
package foo

import "fmt"

// Error is a package-level error type
type Error struct {
	Code string
}

func (Error) Error() string {
	return "an error occurred"
}

func checkError(err error) {
	// create a new err variable
	switch err := err.(type) {
	case Error:
		fmt.Printf("error occurred: %s\n", err.Code)
		// do something
	case nil:
		// omit the element
	}
}

--fix will replace code with this that is invalid

		var err Error
		switch {
		case errors.As(err, &err):
			fmt.Printf("error occurred: %s\n", err.Code)
		case err == nil:
		}

[polyfloyd]

Yeah, that one is going to by tricky to fix. The fix would have to create a variable with a different name. But that would also have to rewrite the body of the case to point to the new variable...

[ccoVeille]

The linter could be updated do not fix it for now in such case

[ccoVeille]

I opened #110

• fix: type assertion can reuse existing error variable #110