[GR-18163] Ruby 2.7: Better support of Integer#[] with range arguments (#2182)

PullRequest: truffleruby/2274

Author: eregon

spec/ruby/core/integer/element_reference_spec.rb

@@ -131,16 +131,10 @@
           0b000001[-3, 4].should == 0b1000
         end
 
-        it "ignores negative upper boundary" do
-          0b101001101[1..-1].should == 0b10100110
-          0b101001101[1..-2].should == 0b10100110
-          0b101001101[1..-3].should == 0b10100110
-        end
-
         it "ignores upper boundary smaller than lower boundary" do
           0b101001101[4..1].should == 0b10100
           0b101001101[4..2].should == 0b10100
-          0b101001101[4..3].should == 0b10100
+          0b101001101[-4..-5].should == 0b1010011010000
         end
 
         it "raises FloatDomainError if any boundary is infinity" do

spec/tags/core/integer/element_reference_tags.txt

@@ -1030,6 +1030,7 @@ public boolean isTruffleBootMainMethod(SharedMethodInfo info) {
             "/core/comparable.rb",
             "/core/numeric.rb",
             "/core/truffle/ctype.rb",
+            "/core/truffle/integer_operations.rb",
             "/core/integer.rb",
             "/core/regexp.rb",
             "/core/transcoding.rb",

src/main/java/org/truffleruby/core/CoreLibrary.java

@@ -59,9 +59,17 @@ def **(o)
     redo_coerced :**, o
   end
 
-  def [](index)
-    index = Primitive.rb_to_int(index)
-    index < 0 ? 0 : (self >> index) & 1
+  def [](index, len = undefined)
+    if Primitive.object_kind_of?(index, Range)
+      Truffle::IntegerOperations.bits_reference_range(self, index)
+    else
+      index = Primitive.rb_to_int(index)
+      if Primitive.undefined?(len)
+        index < 0 ? 0 : (self >> index) & 1
+      else
+        (self >> index) & ((1 << len) - 1)
+      end
+    end
   end
 
   def allbits?(mask)

src/main/ruby/truffleruby/core/integer.rb

@@ -0,0 +1,39 @@
+# frozen_string_literal: true
+
+# Copyright (c) 2020 Oracle and/or its affiliates. All rights reserved. This
+# code is released under a tri EPL/GPL/LGPL license. You can use it,
+# redistribute it and/or modify it under the terms of the:
+#
+# Eclipse Public License version 2.0, or
+# GNU General Public License version 2, or
+# GNU Lesser General Public License version 2.1.
+
+module Truffle
+  module IntegerOperations
+    def self.bits_reference_range(n, range)
+      raise FloatDomainError , 'Infinity' if range.begin == Float::INFINITY || range.end == Float::INFINITY
+      raise FloatDomainError , '-Infinity' if range.begin == -Float::INFINITY || range.end == -Float::INFINITY
+
+      if !Primitive.nil?(range.begin) && !Primitive.nil?(range.end)
+        len = range.end - range.begin
+        len += 1 unless range.exclude_end?
+        num = n >> range.begin
+        mask = (1 << len) - 1
+
+        range.end < range.begin ? num : num & mask
+      elsif Primitive.nil?(range.end)
+        n >> range.begin
+      else
+        len = range.end
+        len += 1 unless range.exclude_end?
+        mask = (1 << len) - 1
+
+        if n & mask != 0 && range.end >= 0
+          raise ArgumentError, 'The beginless range for Integer#[] results in infinity'
+        end
+
+        0
+      end
+    end
+  end
+end

src/main/ruby/truffleruby/core/truffle/integer_operations.rb

@@ -11,5 +11,4 @@
 exclude :test_floor, "needs investigation"
 exclude :test_pow, "needs investigation"
 exclude :test_truncate, "needs investigation"
-exclude :test_Integer_with_invalid_exception, "needs investigation"
-exclude :test_aref, "needs investigation"
+exclude :test_Integer_with_invalid_exception, "needs investigation"