deferUnlambda: False positive for mutated variable

[ajscholl]

func example() {
	foo := func() {
		println("should never print")
	}
	defer foo()
	defer func() { // deferUnlambda: can rewrite as `defer foo()` (gocritic)
		foo()
	}()
	foo = func() {
		println("should print")
	}
}

Following the suggestion changes the behavior of the program. Instead of calling whatever foo was set to at the end of the function, we now instead call whatever foo was set to at the time of the defer call.

[ehsundar]

Need to convert this rule to a StmtListVisitor to mitigate this issue. Do you agree? @cristaloleg

[cristaloleg]

For now sounds ok. Feel free to try.