x/tools/go/analysis/passes/shadow: shadowing not detected on deferred usage

[Will2817]

What version of Go are you using (go version)?

go version go1.13.4 darwin/amd64

What did you do?

ran

go install golang.org/x/tools/go/analysis/passes/shadow/cmd/shadow
go vet -vettool=$(which shadow) main.go

on

package main

import "fmt"

func main() {
	err := fmt.Errorf("one")
	defer func() { fmt.Printf("deferred err is %v\n", err) }()
	{
		err := fmt.Errorf("two")
		fmt.Printf("err is %v\n", err)
	}
}

What did you expect to see?

./main.go:9:3: declaration of "err" shadows declaration at line 6

This is a simplified example but the intention of the defer is to print whatever the value of err is before returning. Since the err is redeclared in the new scope it shadows the initial declaration err. The defer then prints "deferred err is one" instead of the intended "deferred error is two".

What did you see instead?

No vet error

[cagedmantis]

/cc @ianthehat @matloob