False positive "method does not exist" error when using safe navigation

[dduugg]

Input

→ View on sorbet.run

class A
  extend T::Sig

  sig {
    params(x: T.nilable(String))
    .returns(T.any(FalseClass, NilClass, TrueClass))
  }
  def self.foo(x)
    x&.downcase&.end_with?(x.upcase)
  end
end

A.foo(nil)

Observed output

editor.rb:9: Method upcase does not exist on NilClass component of T.nilable(String) https://srb.help/7003
     9 |    x&.downcase&.end_with?(x.upcase)
                                   ^^^^^^^^
  Autocorrect: Use `-a` to autocorrect
    editor.rb:9: Replace with T.must(x)
     9 |    x&.downcase&.end_with?(x.upcase)
                                   ^
Errors: 1

Expected behavior

As x.upcase is only evaluated when x is non-nil, sorbet should not complain about the NilClass component of x at this point

---

(Discovered while applying Style/SafeNavigation autocorrection)