Boolean literal may have type of `true` or `false` #172

soutaro · 2020-07-24T16:11:30Z

@tadd reported a case that returning false in a method with type of String | false got a type error while we are expecting no error for it.

# @type method read_string: () -> (String | false)
def read_string
  return false if has_value?
  some_value
end

This PR is to fix the issue by using hint to infer if the expected type of false literal is false (not bool).

* `true` <=> `TrueClass` * `false` <=> `FalseClass` * `nil` <=> `NilClass`

They may have type of `true` and `false`.

soutaro added 2 commits July 25, 2020 00:58

Fix singleton type subtyping

8ff2b3a

* `true` <=> `TrueClass` * `false` <=> `FalseClass` * `nil` <=> `NilClass`

Bidirectional typing on true/false

c80cd43

They may have type of `true` and `false`.

soutaro merged commit 22d28ff into master Jul 25, 2020

soutaro deleted the true-false branch July 25, 2020 13:04

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