Make rand(Integer) returns Integer

Assuming we rarely pass an unknown integer value to `rand` for `Float` result.

core/kernel.rbs

@@ -1319,7 +1319,7 @@ module Kernel : BasicObject
   # See also Random.rand.
   #
   def self?.rand: (?0) -> Float
-                | (int arg0) -> (Integer | Float)
+                | (int arg0) -> Integer
                 | (::Range[Integer] arg0) -> Integer?
                 | (::Range[Float] arg0) -> Float?
 

core/random.rbs

@@ -91,7 +91,7 @@ class Random < RBS::Unnamed::Random_Base
   #
   # See also Random#rand.
   #
-  def self.rand: () -> Float
+  def self.rand: (?0) -> Float
                | (Integer | ::Range[Integer] max) -> Integer
                | (Float | ::Range[Float] max) -> Float
                | [T < Numeric] (::Range[T]) -> T

core/rbs/unnamed/random.rbs

@@ -47,7 +47,7 @@ module RBS
       # (`-`) and add (`+`)methods, or rand will raise an ArgumentError.
       #
       %a{annotate:rdoc:copy:Random#rand}
-      def rand: () -> Float
+      def rand: (?0) -> Float
               | (Integer | ::Range[Integer] max) -> Integer
               | (Float | ::Range[Float] max) -> Float
 
@@ -200,13 +200,13 @@ module RBS
       # Generates formatted random number from raw random bytes. See Random#rand.
       #
       %a{annotate:rdoc:copy:Random::Formatter#rand}
-      def rand: () -> Float
-              | (?Float? n) -> Float
-              | (?Integer? n) -> Integer
-              | (?Numeric? n) -> Numeric
-              | (?::Range[Float]? n) -> Float
-              | (?::Range[Integer]? n) -> Integer
-              | (?::Range[Numeric]? n) -> Numeric
+      def rand: (?0) -> Float
+              | (Float? n) -> Float
+              | (Integer n) -> Integer
+              | (Numeric n) -> Numeric
+              | (::Range[Float] n) -> Float
+              | (::Range[Integer] n) -> Integer
+              | (::Range[Numeric] n) -> Numeric
 
       %a{annotate:rdoc:copy:Random::Formatter#random_byte}
       def random_bytes: (?Integer? n) -> String

test/typecheck/random/Steepfile

@@ -0,0 +1,7 @@
+D = Steep::Diagnostic
+
+target :test do
+  signature "."
+  check "."
+  configure_code_diagnostics(D::Ruby.all_error)
+end

test/typecheck/random/test.rb

@@ -0,0 +1,13 @@
+# @type var int: Integer
+# @type var float: Float
+
+float = rand(0)
+int = rand(1)
+
+i = 2
+int = rand(i)
+
+int = rand(1..10) || 0
+float = rand((1.0)..(2.2)) || 0.1
+
+int = rand(1.1)