steep check raise UnresolvedOverloading for Array#to_h with block

[ybiquitous]

Description

steep check raises an UnresolvedOverloading error for the code using Array#to_h with a block.

Note: I'm not sure which this problem is caused by RBS or Steep, so I'll re-post this issue to ruby/rbs if the cause is RBS.

Here is the latest RBS of Array#to_h:

class Array
  def to_h: () -> Hash[untyped, untyped]
          | [T, S] () { (Elem) -> [T, S] } -> Hash[T, S]
end

Reproduction

a.rb

["abc", "d", ""].to_h { |e| [e, e.size] }
#=> {"abc"=>3, "d"=>1, ""=>0}

Steepfile

target :lib do
  check "*.rb"
end

$ bundle exec steep check a.rb

# Type checking files:

F

a.rb:1:0: [error] Cannot find compatible overloading of method `to_h` of type `::Array[::String]`
│ Method types:
│   def to_h: () -> ::Hash[untyped, untyped]
│           | [T, S] () { (::String) -> [T, S] } -> ::Hash[T, S]
│
│ Diagnostic ID: Ruby::UnresolvedOverloading
│
└ ["abc", "d", ""].to_h { |e| [e, e.size] }
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Detected 1 problem from 1 file

Environment

• Ruby: ruby 3.0.0p0 (2020-12-25 revision 95aff21468) [x86_64-darwin19]
• Steep: 0.42.0
• RBS: rbs 1.1.0

[soutaro]

Thank you for reporting this. This should be a bug. You can workaround if you add a type annotation in the block:

["abc", "d", ""].to_h { |e|
  # @type block: [String, Integer]
  [e, e.size]
}

[ybiquitous]

@soutaro Thanks for your feedback! The workaround works on my code. 👍