18 files changed, 380 insertions, 382 deletions

diff --git a/spec/ruby/core/regexp/case_compare_spec.rb b/spec/ruby/core/regexp/case_compare_spec.rb
index a621713f6f..29aada70bc 100644
--- a/spec/ruby/core/regexp/case_compare_spec.rb
+++ b/spec/ruby/core/regexp/case_compare_spec.rb
@@ -2,24 +2,34 @@ require_relative '../../spec_helper'
 
 describe "Regexp#===" do
   it "is true if there is a match" do
-    (/abc/ === "aabcc").should be_true
+    (/abc/ === "aabcc").should == true
   end
 
   it "is false if there is no match" do
-    (/abc/ === "xyz").should be_false
+    (/abc/ === "xyz").should == false
   end
 
   it "returns true if it matches a Symbol" do
-    (/a/ === :a).should be_true
+    (/a/ === :a).should == true
   end
 
   it "returns false if it does not match a Symbol" do
-    (/a/ === :b).should be_false
+    (/a/ === :b).should == false
   end
 
   # mirroring https://github.com/ruby/ruby/blob/master/test/ruby/test_regexp.rb
   it "returns false if the other value cannot be coerced to a string" do
-    (/abc/ === nil).should be_false
-    (/abc/ === /abc/).should be_false
+    (/abc/ === nil).should == false
+    (/abc/ === /abc/).should == false
+  end
+
+  it "uses #to_str on string-like objects" do
+    stringlike = Class.new do
+      def to_str
+        "abc"
+      end
+    end.new
+
+    (/abc/ === stringlike).should == true
   end
 end
diff --git a/spec/ruby/core/regexp/compile_spec.rb b/spec/ruby/core/regexp/compile_spec.rb
index 329cb4f753..887c8d77dc 100644
--- a/spec/ruby/core/regexp/compile_spec.rb
+++ b/spec/ruby/core/regexp/compile_spec.rb
@@ -13,3 +13,7 @@ end
 describe "Regexp.compile given a Regexp" do
   it_behaves_like :regexp_new_regexp, :compile
 end
+
+describe "Regexp.compile given a non-String/Regexp" do
+  it_behaves_like :regexp_new_non_string_or_regexp, :compile
+end
diff --git a/spec/ruby/core/regexp/encoding_spec.rb b/spec/ruby/core/regexp/encoding_spec.rb
index dfc835b4e4..fb4fdba064 100644
--- a/spec/ruby/core/regexp/encoding_spec.rb
+++ b/spec/ruby/core/regexp/encoding_spec.rb
@@ -3,7 +3,7 @@ require_relative '../../spec_helper'
 
 describe "Regexp#encoding" do
   it "returns an Encoding object" do
-    /glar/.encoding.should be_an_instance_of(Encoding)
+    /glar/.encoding.should.instance_of?(Encoding)
   end
 
   it "defaults to US-ASCII if the Regexp contains only US-ASCII character" do
diff --git a/spec/ruby/core/regexp/fixed_encoding_spec.rb b/spec/ruby/core/regexp/fixed_encoding_spec.rb
index 29d0a22c53..5d8b1c2860 100644
--- a/spec/ruby/core/regexp/fixed_encoding_spec.rb
+++ b/spec/ruby/core/regexp/fixed_encoding_spec.rb
@@ -3,34 +3,34 @@ require_relative '../../spec_helper'
 
 describe "Regexp#fixed_encoding?" do
   it "returns false by default" do
-    /needle/.fixed_encoding?.should be_false
+    /needle/.fixed_encoding?.should == false
   end
 
   it "returns false if the 'n' modifier was supplied to the Regexp" do
-    /needle/n.fixed_encoding?.should be_false
+    /needle/n.fixed_encoding?.should == false
   end
 
   it "returns true if the 'u' modifier was supplied to the Regexp" do
-    /needle/u.fixed_encoding?.should be_true
+    /needle/u.fixed_encoding?.should == true
   end
 
   it "returns true if the 's' modifier was supplied to the Regexp" do
-    /needle/s.fixed_encoding?.should be_true
+    /needle/s.fixed_encoding?.should == true
   end
 
   it "returns true if the 'e' modifier was supplied to the Regexp" do
-    /needle/e.fixed_encoding?.should be_true
+    /needle/e.fixed_encoding?.should == true
   end
 
   it "returns true if the Regexp contains a \\u escape" do
-    /needle \u{8768}/.fixed_encoding?.should be_true
+    /needle \u{8768}/.fixed_encoding?.should == true
   end
 
   it "returns true if the Regexp contains a UTF-8 literal" do
-    /文字化け/.fixed_encoding?.should be_true
+    /文字化け/.fixed_encoding?.should == true
   end
 
   it "returns true if the Regexp was created with the Regexp::FIXEDENCODING option" do
-    Regexp.new("", Regexp::FIXEDENCODING).fixed_encoding?.should be_true
+    Regexp.new("", Regexp::FIXEDENCODING).fixed_encoding?.should == true
   end
 end
diff --git a/spec/ruby/core/regexp/initialize_spec.rb b/spec/ruby/core/regexp/initialize_spec.rb
index 772a233e82..1c0133acae 100644
--- a/spec/ruby/core/regexp/initialize_spec.rb
+++ b/spec/ruby/core/regexp/initialize_spec.rb
@@ -2,22 +2,28 @@ require_relative '../../spec_helper'
 
 describe "Regexp#initialize" do
   it "is a private method" do
-    Regexp.should have_private_method(:initialize)
+    Regexp.private_instance_methods(false).should.include?(:initialize)
   end
 
-  ruby_version_is ""..."3.0" do
-    it "raises a SecurityError on a Regexp literal" do
-      -> { //.send(:initialize, "") }.should raise_error(SecurityError)
+  it "raises a FrozenError on a Regexp literal" do
+    -> { //.send(:initialize, "") }.should.raise(FrozenError)
+  end
+
+  ruby_version_is "4.1" do
+    it "raises a FrozenError on an initialized non-literal Regexp" do
+      regexp = Regexp.new("")
+      -> { regexp.send(:initialize, "") }.should.raise(FrozenError)
     end
   end
 
-  ruby_version_is "3.0" do
-    it "raises a FrozenError on a Regexp literal" do
-      -> { //.send(:initialize, "") }.should raise_error(FrozenError)
+  ruby_version_is ""..."4.1" do
+    it "raises a TypeError on an initialized non-literal Regexp" do
+      -> { Regexp.new("").send(:initialize, "") }.should.raise(TypeError)
     end
   end
 
-  it "raises a TypeError on an initialized non-literal Regexp" do
-    -> { Regexp.new("").send(:initialize, "") }.should raise_error(TypeError)
+  it "raises a TypeError on an initialized non-literal Regexp subclass" do
+    r = Class.new(Regexp).new("")
+    -> { r.send(:initialize, "") }.should.raise(TypeError)
   end
 end
diff --git a/spec/ruby/core/regexp/last_match_spec.rb b/spec/ruby/core/regexp/last_match_spec.rb
index 0bfed32051..6c256cc1cf 100644
--- a/spec/ruby/core/regexp/last_match_spec.rb
+++ b/spec/ruby/core/regexp/last_match_spec.rb
@@ -4,7 +4,7 @@ describe "Regexp.last_match" do
   it "returns MatchData instance when not passed arguments" do
     /c(.)t/ =~ 'cat'
 
-    Regexp.last_match.should be_kind_of(MatchData)
+    Regexp.last_match.should.is_a?(MatchData)
   end
 
   it "returns the nth field in this MatchData when passed an Integer" do
@@ -28,7 +28,7 @@ describe "Regexp.last_match" do
 
     it "raises an IndexError when given a missing name" do
       /(?<test>[A-Z]+.*)/ =~ "TEST123"
-      -> { Regexp.last_match(:missing) }.should raise_error(IndexError)
+      -> { Regexp.last_match(:missing) }.should.raise(IndexError)
     end
   end
 
@@ -50,7 +50,7 @@ describe "Regexp.last_match" do
     it "raises a TypeError when unable to coerce" do
       obj = Object.new
       /(?<test>[A-Z]+.*)/ =~ "TEST123"
-      -> { Regexp.last_match(obj) }.should raise_error(TypeError)
+      -> { Regexp.last_match(obj) }.should.raise(TypeError)
     end
   end
 end
diff --git a/spec/ruby/core/regexp/linear_time_spec.rb b/spec/ruby/core/regexp/linear_time_spec.rb
new file mode 100644
index 0000000000..f70021dfed
--- /dev/null
+++ b/spec/ruby/core/regexp/linear_time_spec.rb
@@ -0,0 +1,80 @@
+require_relative '../../spec_helper'
+
+describe "Regexp.linear_time?" do
+  it "returns true if matching can be done in linear time" do
+    Regexp.linear_time?(/a/).should == true
+    Regexp.linear_time?('a').should == true
+  end
+
+  it "returns true if matching can be done in linear time for a binary Regexp" do
+    Regexp.linear_time?(/[\x80-\xff]/n).should == true
+  end
+
+  it "return false if matching can't be done in linear time" do
+    Regexp.linear_time?(/(a)\1/).should == false
+    Regexp.linear_time?("(a)\\1").should == false
+  end
+
+  it "accepts flags for string argument" do
+    Regexp.linear_time?('a', Regexp::IGNORECASE).should == true
+  end
+
+  it "warns about flags being ignored for regexp arguments" do
+    -> {
+      Regexp.linear_time?(/a/, Regexp::IGNORECASE)
+    }.should complain(/warning: flags ignored/)
+  end
+
+  it "returns true for positive lookahead" do
+    Regexp.linear_time?(/a*(?:(?=a*)a)*b/).should == true
+  end
+
+  it "returns true for positive lookbehind" do
+    Regexp.linear_time?(/a*(?:(?<=a)a*)*b/).should == true
+  end
+
+  it "returns true for negative lookbehind" do
+    Regexp.linear_time?(/a*(?:(?<!a)a*)*b/).should == true
+  end
+
+  # There are two known ways to make Regexp linear:
+  # * Using a DFA (deterministic finite-state automaton) Regexp engine, which always matches in linear time (e.g. TruffleRuby with TRegex)
+  # * Caching position and state to avoid catastrophic backtracking (e.g. CRuby: https://bugs.ruby-lang.org/issues/19104)
+  #
+  # Both approach should be allowed and given that DFA Regexp engines
+  # are much faster there should be no specs preventing using them.
+  uses_regexp_caching = RUBY_ENGINE == 'ruby'
+  uses_dfa_regexp_engine = !uses_regexp_caching
+
+  # The following specs should not be relied upon,
+  # they are here only to illustrate differences between Regexp engines.
+  guard -> { uses_regexp_caching } do
+    it "returns true for negative lookahead" do
+      Regexp.linear_time?(/a*(?:(?!a*)a*)*b/).should == true
+    end
+
+    it "returns true for atomic groups" do
+      Regexp.linear_time?(/a*(?:(?>a)a*)*b/).should == true
+    end
+
+    it "returns true for possessive quantifiers" do
+      Regexp.linear_time?(/a*(?:(?:a)?+a*)*b/).should == true
+    end
+
+    it "returns true for positive lookbehind with capture group" do
+      Regexp.linear_time?(/.(?<=(a))/).should == true
+    end
+  end
+
+  # The following specs should not be relied upon,
+  # they are here only to illustrate differences between Regexp engines.
+  guard -> { uses_dfa_regexp_engine } do
+    it "returns true for non-recursive subexpression call" do
+      Regexp.linear_time?(/(?<a>a){0}\g<a>/).should == true
+    end
+
+    it "returns true for positive lookahead with capture group" do
+      Regexp.linear_time?(/x+(?=(a))/).should == true
+    end
+  end
+end
diff --git a/spec/ruby/core/regexp/match_spec.rb b/spec/ruby/core/regexp/match_spec.rb
index 80dbfb4c10..276cecc8e4 100644
--- a/spec/ruby/core/regexp/match_spec.rb
+++ b/spec/ruby/core/regexp/match_spec.rb
@@ -3,11 +3,11 @@ require_relative '../../spec_helper'
 
 describe :regexp_match, shared: true do
   it "returns nil if there is no match" do
-    /xyz/.send(@method,"abxyc").should be_nil
+    /xyz/.send(@method,"abxyc").should == nil
   end
 
   it "returns nil if the object is nil" do
-    /\w+/.send(@method, nil).should be_nil
+    /\w+/.send(@method, nil).should == nil
   end
 end
 
@@ -27,19 +27,19 @@ describe "Regexp#match" do
   it_behaves_like :regexp_match, :match
 
   it "returns a MatchData object" do
-    /(.)(.)(.)/.match("abc").should be_kind_of(MatchData)
+    /(.)(.)(.)/.match("abc").should.is_a?(MatchData)
   end
 
   it "returns a MatchData object, when argument is a Symbol" do
-    /(.)(.)(.)/.match(:abc).should be_kind_of(MatchData)
+    /(.)(.)(.)/.match(:abc).should.is_a?(MatchData)
   end
 
   it "raises a TypeError on an uninitialized Regexp" do
-    -> { Regexp.allocate.match('foo') }.should raise_error(TypeError)
+    -> { Regexp.allocate.match('foo') }.should.raise(TypeError)
   end
 
   it "raises TypeError on an uninitialized Regexp" do
-    -> { Regexp.allocate.match('foo'.encode("UTF-16LE")) }.should raise_error(TypeError)
+    -> { Regexp.allocate.match('foo'.encode("UTF-16LE")) }.should.raise(TypeError)
   end
 
   describe "with [string, position]" do
@@ -54,7 +54,7 @@ describe "Regexp#match" do
 
       it "raises an ArgumentError for an invalid encoding" do
         x96 = ([150].pack('C')).force_encoding('utf-8')
-        -> { /(.).(.)/.match("Hello, #{x96} world!", 1) }.should raise_error(ArgumentError)
+        -> { /(.).(.)/.match("Hello, #{x96} world!", 1) }.should.raise(ArgumentError)
       end
     end
 
@@ -69,14 +69,14 @@ describe "Regexp#match" do
 
       it "raises an ArgumentError for an invalid encoding" do
         x96 = ([150].pack('C')).force_encoding('utf-8')
-        -> { /(.).(.)/.match("Hello, #{x96} world!", -1) }.should raise_error(ArgumentError)
+        -> { /(.).(.)/.match("Hello, #{x96} world!", -1) }.should.raise(ArgumentError)
       end
     end
 
     describe "when passed a block" do
       it "yields the MatchData" do
         /./.match("abc") {|m| ScratchPad.record m }
-        ScratchPad.recorded.should be_kind_of(MatchData)
+        ScratchPad.recorded.should.is_a?(MatchData)
       end
 
       it "returns the block result" do
@@ -94,20 +94,20 @@ describe "Regexp#match" do
   it "resets $~ if passed nil" do
     # set $~
     /./.match("a")
-    $~.should be_kind_of(MatchData)
+    $~.should.is_a?(MatchData)
 
     /1/.match(nil)
-    $~.should be_nil
+    $~.should == nil
   end
 
   it "raises TypeError when the given argument cannot be coerced to String" do
     f = 1
-    -> { /foo/.match(f)[0] }.should raise_error(TypeError)
+    -> { /foo/.match(f)[0] }.should.raise(TypeError)
   end
 
   it "raises TypeError when the given argument is an Exception" do
     f = Exception.new("foo")
-    -> { /foo/.match(f)[0] }.should raise_error(TypeError)
+    -> { /foo/.match(f)[0] }.should.raise(TypeError)
   end
 end
 
@@ -119,22 +119,22 @@ describe "Regexp#match?" do
 
   context "when matches the given value" do
     it "returns true but does not set Regexp.last_match" do
-      /string/i.match?('string').should be_true
-      Regexp.last_match.should be_nil
+      /string/i.match?('string').should == true
+      Regexp.last_match.should == nil
     end
   end
 
   it "returns false when does not match the given value" do
-    /STRING/.match?('string').should be_false
+    /STRING/.match?('string').should == false
   end
 
   it "takes matching position as the 2nd argument" do
-    /str/i.match?('string', 0).should be_true
-    /str/i.match?('string', 1).should be_false
+    /str/i.match?('string', 0).should == true
+    /str/i.match?('string', 1).should == false
   end
 
   it "returns false when given nil" do
-    /./.match?(nil).should be_false
+    /./.match?(nil).should == false
   end
 end
 
diff --git a/spec/ruby/core/regexp/named_captures_spec.rb b/spec/ruby/core/regexp/named_captures_spec.rb
index 1a68d7877b..4d3fdd23ab 100644
--- a/spec/ruby/core/regexp/named_captures_spec.rb
+++ b/spec/ruby/core/regexp/named_captures_spec.rb
@@ -2,7 +2,7 @@ require_relative '../../spec_helper'
 
 describe "Regexp#named_captures" do
   it "returns a Hash" do
-    /foo/.named_captures.should be_an_instance_of(Hash)
+    /foo/.named_captures.should.instance_of?(Hash)
   end
 
   it "returns an empty Hash when there are no capture groups" do
@@ -17,7 +17,7 @@ describe "Regexp#named_captures" do
   it "sets the values of the Hash to Arrays" do
     rex = /this (?<is>is) [aA] (?<pat>pate?rn)/
     rex.named_captures.values.each do |value|
-      value.should be_an_instance_of(Array)
+      value.should.instance_of?(Array)
     end
   end
 
diff --git a/spec/ruby/core/regexp/names_spec.rb b/spec/ruby/core/regexp/names_spec.rb
index 099768fd26..9013f41e20 100644
--- a/spec/ruby/core/regexp/names_spec.rb
+++ b/spec/ruby/core/regexp/names_spec.rb
@@ -2,7 +2,7 @@ require_relative '../../spec_helper'
 
 describe "Regexp#names" do
   it "returns an Array" do
-    /foo/.names.should be_an_instance_of(Array)
+    /foo/.names.should.instance_of?(Array)
   end
 
   it "returns an empty Array if there are no named captures" do
@@ -11,7 +11,7 @@ describe "Regexp#names" do
 
   it "returns each named capture as a String" do
     /n(?<cap>ee)d(?<ture>le)/.names.each do |name|
-      name.should be_an_instance_of(String)
+      name.should.instance_of?(String)
     end
   end
 
diff --git a/spec/ruby/core/regexp/new_spec.rb b/spec/ruby/core/regexp/new_spec.rb
index ce662b7a4f..79210e9a23 100644
--- a/spec/ruby/core/regexp/new_spec.rb
+++ b/spec/ruby/core/regexp/new_spec.rb
@@ -7,21 +7,13 @@ end
 
 describe "Regexp.new given a String" do
   it_behaves_like :regexp_new_string, :new
+  it_behaves_like :regexp_new_string_binary, :new
 end
 
 describe "Regexp.new given a Regexp" do
   it_behaves_like :regexp_new_regexp, :new
-  it_behaves_like :regexp_new_string_binary, :compile
 end
 
-describe "Regexp.new given an Integer" do
-  it "raises a TypeError" do
-    -> { Regexp.new(1) }.should raise_error(TypeError)
-  end
-end
-
-describe "Regexp.new given a Float" do
-  it "raises a TypeError" do
-    -> { Regexp.new(1.0) }.should raise_error(TypeError)
-  end
+describe "Regexp.new given a non-String/Regexp" do
+  it_behaves_like :regexp_new_non_string_or_regexp, :new
 end
diff --git a/spec/ruby/core/regexp/options_spec.rb b/spec/ruby/core/regexp/options_spec.rb
index 527b51a3b2..c3401cee6e 100644
--- a/spec/ruby/core/regexp/options_spec.rb
+++ b/spec/ruby/core/regexp/options_spec.rb
@@ -2,9 +2,9 @@ require_relative '../../spec_helper'
 
 describe "Regexp#options" do
   it "returns an Integer bitvector of regexp options for the Regexp object" do
-    /cat/.options.should be_kind_of(Integer)
+    /cat/.options.should.is_a?(Integer)
     not_supported_on :opal do
-      /cat/ix.options.should be_kind_of(Integer)
+      /cat/ix.options.should.is_a?(Integer)
     end
   end
 
@@ -29,7 +29,7 @@ describe "Regexp#options" do
   end
 
   it "raises a TypeError on an uninitialized Regexp" do
-    -> { Regexp.allocate.options }.should raise_error(TypeError)
+    -> { Regexp.allocate.options }.should.raise(TypeError)
   end
 
   it "includes Regexp::FIXEDENCODING for a Regexp literal with the 'u' option" do
diff --git a/spec/ruby/core/regexp/shared/new.rb b/spec/ruby/core/regexp/shared/new.rb
index 9cbf89cd8b..affdaf855c 100644
--- a/spec/ruby/core/regexp/shared/new.rb
+++ b/spec/ruby/core/regexp/shared/new.rb
@@ -1,10 +1,16 @@
-# -*- encoding: binary -*-
+# encoding: binary
 
 describe :regexp_new, shared: true do
   it "requires one argument and creates a new regular expression object" do
     Regexp.send(@method, '').is_a?(Regexp).should == true
   end
 
+  ruby_version_is "4.1" do
+    it "is frozen" do
+      Regexp.send(@method, '').should.frozen?
+    end
+  end
+
   it "works by default for subclasses with overridden #initialize" do
     class RegexpSpecsSubclass < Regexp
       def initialize(*args)
@@ -17,10 +23,36 @@ describe :regexp_new, shared: true do
 
     class RegexpSpecsSubclassTwo < Regexp; end
 
-    RegexpSpecsSubclass.send(@method, "hi").should be_kind_of(RegexpSpecsSubclass)
+    RegexpSpecsSubclass.send(@method, "hi").should.is_a?(RegexpSpecsSubclass)
     RegexpSpecsSubclass.send(@method, "hi").args.first.should == "hi"
 
-    RegexpSpecsSubclassTwo.send(@method, "hi").should be_kind_of(RegexpSpecsSubclassTwo)
+    RegexpSpecsSubclassTwo.send(@method, "hi").should.is_a?(RegexpSpecsSubclassTwo)
+  end
+end
+
+describe :regexp_new_non_string_or_regexp, shared: true do
+  it "calls #to_str method for non-String/Regexp argument" do
+    obj = Object.new
+    def obj.to_str() "a" end
+
+    Regexp.send(@method, obj).should == /a/
+  end
+
+  it "raises TypeError if there is no #to_str method for non-String/Regexp argument" do
+    obj = Object.new
+    -> { Regexp.send(@method, obj) }.should.raise(TypeError, "no implicit conversion of Object into String")
+
+    -> { Regexp.send(@method, 1) }.should.raise(TypeError, "no implicit conversion of Integer into String")
+    -> { Regexp.send(@method, 1.0) }.should.raise(TypeError, "no implicit conversion of Float into String")
+    -> { Regexp.send(@method, :symbol) }.should.raise(TypeError, "no implicit conversion of Symbol into String")
+    -> { Regexp.send(@method, []) }.should.raise(TypeError, "no implicit conversion of Array into String")
+  end
+
+  it "raises TypeError if #to_str returns non-String value" do
+    obj = Object.new
+    def obj.to_str() [] end
+
+    -> { Regexp.send(@method, obj) }.should raise_consistent_error(TypeError, /can't convert Object into String/)
   end
 end
 
@@ -30,7 +62,7 @@ describe :regexp_new_string, shared: true do
   end
 
   it "raises a RegexpError when passed an incorrect regexp" do
-    -> { Regexp.send(@method, "^[$", 0) }.should raise_error(RegexpError)
+    -> { Regexp.send(@method, "^[$", 0) }.should.raise(RegexpError, Regexp.new(Regexp.escape("premature end of char-class: /^[$/")))
   end
 
   it "does not set Regexp options if only given one argument" do
@@ -58,6 +90,15 @@ describe :regexp_new_string, shared: true do
     end
   end
 
+  it "sets options from second argument if it is true" do
+    r = Regexp.send(@method, 'Hi', true)
+    (r.options & Regexp::IGNORECASE).should_not == 0
+    (r.options & Regexp::MULTILINE).should == 0
+    not_supported_on :opal do
+      (r.options & Regexp::EXTENDED).should == 0
+    end
+  end
+
   it "sets options from second argument if it is one of the Integer option constants" do
     r = Regexp.send(@method, 'Hi', Regexp::IGNORECASE)
     (r.options & Regexp::IGNORECASE).should_not == 0
@@ -88,8 +129,23 @@ describe :regexp_new_string, shared: true do
     (r.options & Regexp::EXTENDED).should_not == 0
   end
 
-  it "treats any non-Integer, non-nil, non-false second argument as IGNORECASE" do
-    r = Regexp.send(@method, 'Hi', Object.new)
+  it "does not try to convert the second argument to Integer with #to_int method call" do
+    ScratchPad.clear
+    obj = Object.new
+    def obj.to_int() ScratchPad.record(:called) end
+
+    -> {
+      Regexp.send(@method, "Hi", obj)
+    }.should complain(/expected true or false as ignorecase/, {verbose: true})
+
+    ScratchPad.recorded.should == nil
+  end
+
+  it "warns any non-Integer, non-nil, non-false second argument" do
+    r = nil
+    -> {
+      r = Regexp.send(@method, 'Hi', Object.new)
+    }.should complain(/expected true or false as ignorecase/, {verbose: true})
     (r.options & Regexp::IGNORECASE).should_not == 0
     (r.options & Regexp::MULTILINE).should == 0
     not_supported_on :opal do
@@ -97,249 +153,76 @@ describe :regexp_new_string, shared: true do
     end
   end
 
-  it "ignores the third argument if it is 'e' or 'euc' (case-insensitive)" do
-    -> {
-      Regexp.send(@method, 'Hi', nil, 'e').encoding.should == Encoding::US_ASCII
-      Regexp.send(@method, 'Hi', nil, 'euc').encoding.should == Encoding::US_ASCII
-      Regexp.send(@method, 'Hi', nil, 'E').encoding.should == Encoding::US_ASCII
-      Regexp.send(@method, 'Hi', nil, 'EUC').encoding.should == Encoding::US_ASCII
-    }.should complain(/encoding option is ignored/)
-  end
+  it "accepts a String of supported flags as the second argument" do
+    r = Regexp.send(@method, 'Hi', 'i')
+    (r.options & Regexp::IGNORECASE).should_not == 0
+    (r.options & Regexp::MULTILINE).should == 0
+    not_supported_on :opal do
+      (r.options & Regexp::EXTENDED).should == 0
+    end
 
-  it "ignores the third argument if it is 's' or 'sjis' (case-insensitive)" do
-    -> {
-      Regexp.send(@method, 'Hi', nil, 's').encoding.should == Encoding::US_ASCII
-      Regexp.send(@method, 'Hi', nil, 'sjis').encoding.should == Encoding::US_ASCII
-      Regexp.send(@method, 'Hi', nil, 'S').encoding.should == Encoding::US_ASCII
-      Regexp.send(@method, 'Hi', nil, 'SJIS').encoding.should == Encoding::US_ASCII
-    }.should complain(/encoding option is ignored/)
-  end
+    r = Regexp.send(@method, 'Hi', 'imx')
+    (r.options & Regexp::IGNORECASE).should_not == 0
+    (r.options & Regexp::MULTILINE).should_not == 0
+    not_supported_on :opal do
+      (r.options & Regexp::EXTENDED).should_not == 0
+    end
 
-  it "ignores the third argument if it is 'u' or 'utf8' (case-insensitive)" do
-    -> {
-      Regexp.send(@method, 'Hi', nil, 'u').encoding.should == Encoding::US_ASCII
-      Regexp.send(@method, 'Hi', nil, 'utf8').encoding.should == Encoding::US_ASCII
-      Regexp.send(@method, 'Hi', nil, 'U').encoding.should == Encoding::US_ASCII
-      Regexp.send(@method, 'Hi', nil, 'UTF8').encoding.should == Encoding::US_ASCII
-    }.should complain(/encoding option is ignored/)
-  end
+    r = Regexp.send(@method, 'Hi', 'mimi')
+    (r.options & Regexp::IGNORECASE).should_not == 0
+    (r.options & Regexp::MULTILINE).should_not == 0
+    not_supported_on :opal do
+      (r.options & Regexp::EXTENDED).should == 0
+    end
 
-  it "uses US_ASCII encoding if third argument is 'n' or 'none' (case insensitive) and only ascii characters" do
-    Regexp.send(@method, 'Hi', nil, 'n').encoding.should == Encoding::US_ASCII
-    Regexp.send(@method, 'Hi', nil, 'none').encoding.should == Encoding::US_ASCII
-    Regexp.send(@method, 'Hi', nil, 'N').encoding.should == Encoding::US_ASCII
-    Regexp.send(@method, 'Hi', nil, 'NONE').encoding.should == Encoding::US_ASCII
+    r = Regexp.send(@method, 'Hi', '')
+    (r.options & Regexp::IGNORECASE).should == 0
+    (r.options & Regexp::MULTILINE).should == 0
+    not_supported_on :opal do
+      (r.options & Regexp::EXTENDED).should == 0
+    end
   end
 
-  it "uses ASCII_8BIT encoding if third argument is 'n' or 'none' (case insensitive) and non-ascii characters" do
-    a = "(?:[\x8E\xA1-\xFE])"
-    str = "\A(?:#{a}|x*)\z"
-
-    Regexp.send(@method, str, nil, 'N').encoding.should == Encoding::BINARY
-    Regexp.send(@method, str, nil, 'n').encoding.should == Encoding::BINARY
-    Regexp.send(@method, str, nil, 'none').encoding.should == Encoding::BINARY
-    Regexp.send(@method, str, nil, 'NONE').encoding.should == Encoding::BINARY
+  it "raises an Argument error if the second argument contains unsupported chars" do
+    -> { Regexp.send(@method, 'Hi', 'e') }.should.raise(ArgumentError, "unknown regexp option: e")
+    -> { Regexp.send(@method, 'Hi', 'n') }.should.raise(ArgumentError, "unknown regexp option: n")
+    -> { Regexp.send(@method, 'Hi', 's') }.should.raise(ArgumentError, "unknown regexp option: s")
+    -> { Regexp.send(@method, 'Hi', 'u') }.should.raise(ArgumentError, "unknown regexp option: u")
+    -> { Regexp.send(@method, 'Hi', 'j') }.should.raise(ArgumentError, "unknown regexp option: j")
+    -> { Regexp.send(@method, 'Hi', 'mjx') }.should.raise(ArgumentError, /unknown regexp option: mjx\b/)
   end
 
   describe "with escaped characters" do
     it "raises a Regexp error if there is a trailing backslash" do
-      -> { Regexp.send(@method, "\\") }.should raise_error(RegexpError)
+      -> { Regexp.send(@method, "\\") }.should.raise(RegexpError, Regexp.new(Regexp.escape("too short escape sequence: /\\/")))
     end
 
     it "does not raise a Regexp error if there is an escaped trailing backslash" do
-      -> { Regexp.send(@method, "\\\\") }.should_not raise_error(RegexpError)
+      -> { Regexp.send(@method, "\\\\") }.should_not.raise(RegexpError)
     end
 
-    it "accepts a backspace followed by a character" do
+    it "accepts a backspace followed by a non-special character" do
       Regexp.send(@method, "\\N").should == /#{"\x5c"+"N"}/
     end
 
-    it "accepts a one-digit octal value" do
-      Regexp.send(@method, "\0").should == /#{"\x00"}/
-    end
-
-    it "accepts a two-digit octal value" do
-      Regexp.send(@method, "\11").should == /#{"\x09"}/
-    end
-
-    it "accepts a one-digit hexadecimal value" do
-      Regexp.send(@method, "\x9n").should == /#{"\x09n"}/
-    end
-
-    it "accepts a two-digit hexadecimal value" do
-      Regexp.send(@method, "\x23").should == /#{"\x23"}/
-    end
-
-    it "interprets a digit following a two-digit hexadecimal value as a character" do
-      Regexp.send(@method, "\x420").should == /#{"\x420"}/
-    end
-
     it "raises a RegexpError if \\x is not followed by any hexadecimal digits" do
-      -> { Regexp.send(@method, "\\" + "xn") }.should raise_error(RegexpError)
-    end
-
-    it "accepts an escaped string interpolation" do
-      Regexp.send(@method, "\#{abc}").should == /#{"\#{abc}"}/
-    end
-
-    it "accepts '\\n'" do
-      Regexp.send(@method, "\n").should == /#{"\x0a"}/
-    end
-
-    it "accepts '\\t'" do
-      Regexp.send(@method, "\t").should == /#{"\x09"}/
-    end
-
-    it "accepts '\\r'" do
-      Regexp.send(@method, "\r").should == /#{"\x0d"}/
-    end
-
-    it "accepts '\\f'" do
-      Regexp.send(@method, "\f").should == /#{"\x0c"}/
-    end
-
-    it "accepts '\\v'" do
-      Regexp.send(@method, "\v").should == /#{"\x0b"}/
-    end
-
-    it "accepts '\\a'" do
-      Regexp.send(@method, "\a").should == /#{"\x07"}/
-    end
-
-    it "accepts '\\e'" do
-      Regexp.send(@method, "\e").should == /#{"\x1b"}/
-    end
-
-    it "accepts '\\C-\\n'" do
-      Regexp.send(@method, "\C-\n").should == /#{"\x0a"}/
-    end
-
-    it "accepts '\\C-\\t'" do
-      Regexp.send(@method, "\C-\t").should == /#{"\x09"}/
-    end
-
-    it "accepts '\\C-\\r'" do
-      Regexp.send(@method, "\C-\r").should == /#{"\x0d"}/
-    end
-
-    it "accepts '\\C-\\f'" do
-      Regexp.send(@method, "\C-\f").should == /#{"\x0c"}/
-    end
-
-    it "accepts '\\C-\\v'" do
-      Regexp.send(@method, "\C-\v").should == /#{"\x0b"}/
-    end
-
-    it "accepts '\\C-\\a'" do
-      Regexp.send(@method, "\C-\a").should == /#{"\x07"}/
-    end
-
-    it "accepts '\\C-\\e'" do
-      Regexp.send(@method, "\C-\e").should == /#{"\x1b"}/
-    end
-
-    it "accepts multiple consecutive '\\' characters" do
-      Regexp.send(@method, "\\\\\\N").should == /#{"\\\\\\"+"N"}/
-    end
-
-    it "accepts characters and escaped octal digits" do
-      Regexp.send(@method, "abc\076").should == /#{"abc\x3e"}/
-    end
-
-    it "accepts escaped octal digits and characters" do
-      Regexp.send(@method, "\076abc").should == /#{"\x3eabc"}/
-    end
-
-    it "accepts characters and escaped hexadecimal digits" do
-      Regexp.send(@method, "abc\x42").should == /#{"abc\x42"}/
-    end
-
-    it "accepts escaped hexadecimal digits and characters" do
-      Regexp.send(@method, "\x3eabc").should == /#{"\x3eabc"}/
-    end
-
-    it "accepts escaped hexadecimal and octal digits" do
-      Regexp.send(@method, "\061\x42").should == /#{"\x31\x42"}/
-    end
-
-    it "accepts \\u{H} for a single Unicode codepoint" do
-      Regexp.send(@method, "\u{f}").should == /#{"\x0f"}/
-    end
-
-    it "accepts \\u{HH} for a single Unicode codepoint" do
-      Regexp.send(@method, "\u{7f}").should == /#{"\x7f"}/
-    end
-
-    it "accepts \\u{HHH} for a single Unicode codepoint" do
-      Regexp.send(@method, "\u{07f}").should == /#{"\x7f"}/
-    end
-
-    it "accepts \\u{HHHH} for a single Unicode codepoint" do
-      Regexp.send(@method, "\u{0000}").should == /#{"\x00"}/
-    end
-
-    it "accepts \\u{HHHHH} for a single Unicode codepoint" do
-      Regexp.send(@method, "\u{00001}").should == /#{"\x01"}/
-    end
-
-    it "accepts \\u{HHHHHH} for a single Unicode codepoint" do
-      Regexp.send(@method, "\u{000000}").should == /#{"\x00"}/
-    end
-
-    it "accepts characters followed by \\u{HHHH}" do
-      Regexp.send(@method, "abc\u{3042}").should == /#{"abc\u3042"}/
-    end
-
-    it "accepts \\u{HHHH} followed by characters" do
-      Regexp.send(@method, "\u{3042}abc").should == /#{"\u3042abc"}/
-    end
-
-    it "accepts escaped hexadecimal digits followed by \\u{HHHH}" do
-      Regexp.send(@method, "\x42\u{3042}").should == /#{"\x42\u3042"}/
-    end
-
-    it "accepts escaped octal digits followed by \\u{HHHH}" do
-      Regexp.send(@method, "\056\u{3042}").should == /#{"\x2e\u3042"}/
-    end
-
-    it "accepts a combination of escaped octal and hexadecimal digits and \\u{HHHH}" do
-      Regexp.send(@method, "\056\x42\u{3042}\x52\076").should == /#{"\x2e\x42\u3042\x52\x3e"}/
-    end
-
-    it "accepts \\uHHHH for a single Unicode codepoint" do
-      Regexp.send(@method, "\u3042").should == /#{"\u3042"}/
-    end
-
-    it "accepts characters followed by \\uHHHH" do
-      Regexp.send(@method, "abc\u3042").should == /#{"abc\u3042"}/
-    end
-
-    it "accepts \\uHHHH followed by characters" do
-      Regexp.send(@method, "\u3042abc").should == /#{"\u3042abc"}/
-    end
-
-    it "accepts escaped hexadecimal digits followed by \\uHHHH" do
-      Regexp.send(@method, "\x42\u3042").should == /#{"\x42\u3042"}/
-    end
-
-    it "accepts escaped octal digits followed by \\uHHHH" do
-      Regexp.send(@method, "\056\u3042").should == /#{"\x2e\u3042"}/
-    end
-
-    it "accepts a combination of escaped octal and hexadecimal digits and \\uHHHH" do
-      Regexp.send(@method, "\056\x42\u3042\x52\076").should == /#{"\x2e\x42\u3042\x52\x3e"}/
+      -> { Regexp.send(@method, "\\" + "xn") }.should.raise(RegexpError, Regexp.new(Regexp.escape("invalid hex escape: /\\xn/")))
     end
 
     it "raises a RegexpError if less than four digits are given for \\uHHHH" do
-      -> { Regexp.send(@method, "\\" + "u304") }.should raise_error(RegexpError)
+      -> { Regexp.send(@method, "\\" + "u304") }.should.raise(RegexpError, Regexp.new(Regexp.escape("invalid Unicode escape: /\\u304/")))
     end
 
     it "raises a RegexpError if the \\u{} escape is empty" do
-      -> { Regexp.send(@method, "\\" + "u{}") }.should raise_error(RegexpError)
+      -> { Regexp.send(@method, "\\" + "u{}") }.should.raise(RegexpError, Regexp.new(Regexp.escape("invalid Unicode list: /\\u{}/")))
+    end
+
+    it "raises a RegexpError if the \\u{} escape contains non hexadecimal digits" do
+      -> { Regexp.send(@method, "\\" + "u{abcX}") }.should.raise(RegexpError, Regexp.new(Regexp.escape("invalid Unicode list: /\\u{abcX}/")))
     end
 
     it "raises a RegexpError if more than six hexadecimal digits are given" do
-      -> { Regexp.send(@method, "\\" + "u{0ffffff}") }.should raise_error(RegexpError)
+      -> { Regexp.send(@method, "\\" + "u{0ffffff}") }.should.raise(RegexpError, Regexp.new(Regexp.escape("invalid Unicode range: /\\u{0ffffff}/")))
     end
 
     it "returns a Regexp with US-ASCII encoding if only 7-bit ASCII characters are present regardless of the input String's encoding" do
@@ -367,12 +250,12 @@ describe :regexp_new_string, shared: true do
     end
 
     it "returns a Regexp with the input String's encoding" do
-      str = "\x82\xa0".force_encoding(Encoding::Shift_JIS)
+      str = "\x82\xa0".dup.force_encoding(Encoding::Shift_JIS)
       Regexp.send(@method, str).encoding.should == Encoding::Shift_JIS
     end
 
     it "returns a Regexp with source String having the input String's encoding" do
-      str = "\x82\xa0".force_encoding(Encoding::Shift_JIS)
+      str = "\x82\xa0".dup.force_encoding(Encoding::Shift_JIS)
       Regexp.send(@method, str).source.encoding.should == Encoding::Shift_JIS
     end
   end
@@ -380,69 +263,6 @@ end
 
 describe :regexp_new_string_binary, shared: true do
   describe "with escaped characters" do
-    it "accepts a three-digit octal value" do
-      Regexp.send(@method, "\315").should == /#{"\xcd"}/
-    end
-
-    it "interprets a digit following a three-digit octal value as a character" do
-      Regexp.send(@method, "\3762").should == /#{"\xfe2"}/
-    end
-
-    it "accepts '\\M-\\n'" do
-      Regexp.send(@method, "\M-\n").should == /#{"\x8a"}/
-    end
-
-    it "accepts '\\M-\\t'" do
-      Regexp.send(@method, "\M-\t").should == /#{"\x89"}/
-    end
-
-    it "accepts '\\M-\\r'" do
-      Regexp.send(@method, "\M-\r").should == /#{"\x8d"}/
-    end
-
-    it "accepts '\\M-\\f'" do
-      Regexp.send(@method, "\M-\f").should == /#{"\x8c"}/
-    end
-
-    it "accepts '\\M-\\v'" do
-      Regexp.send(@method, "\M-\v").should == /#{"\x8b"}/
-    end
-
-    it "accepts '\\M-\\a'" do
-      Regexp.send(@method, "\M-\a").should == /#{"\x87"}/
-    end
-
-    it "accepts '\\M-\\e'" do
-      Regexp.send(@method, "\M-\e").should == /#{"\x9b"}/
-    end
-
-    it "accepts '\\M-\\C-\\n'" do
-      Regexp.send(@method, "\M-\C-\n").should == /#{"\x8a"}/
-    end
-
-    it "accepts '\\M-\\C-\\t'" do
-      Regexp.send(@method, "\M-\C-\t").should == /#{"\x89"}/
-    end
-
-    it "accepts '\\M-\\C-\\r'" do
-      Regexp.send(@method, "\M-\C-\r").should == /#{"\x8d"}/
-    end
-
-    it "accepts '\\M-\\C-\\f'" do
-      Regexp.send(@method, "\M-\C-\f").should == /#{"\x8c"}/
-    end
-
-    it "accepts '\\M-\\C-\\v'" do
-      Regexp.send(@method, "\M-\C-\v").should == /#{"\x8b"}/
-    end
-
-    it "accepts '\\M-\\C-\\a'" do
-      Regexp.send(@method, "\M-\C-\a").should == /#{"\x87"}/
-    end
-
-    it "accepts '\\M-\\C-\\e'" do
-      Regexp.send(@method, "\M-\C-\e").should == /#{"\x9b"}/
-    end
   end
 end
 
@@ -497,9 +317,5 @@ describe :regexp_new_regexp, shared: true do
     it "sets the encoding to US-ASCII if the Regexp literal has the 'n' option and the source String is ASCII only" do
       Regexp.send(@method, /Hi/n).encoding.should == Encoding::US_ASCII
     end
-
-    it "sets the encoding to source String's encoding if the Regexp literal has the 'n' option and the source String is not ASCII only" do
-      Regexp.send(@method, Regexp.new("\\xff", nil, 'n')).encoding.should == Encoding::BINARY
-    end
   end
 end
diff --git a/spec/ruby/core/regexp/shared/quote.rb b/spec/ruby/core/regexp/shared/quote.rb
index a55adb5bf2..083f12d78c 100644
--- a/spec/ruby/core/regexp/shared/quote.rb
+++ b/spec/ruby/core/regexp/shared/quote.rb
@@ -1,9 +1,9 @@
-# -*- encoding: binary -*-
+# encoding: binary
 
 describe :regexp_quote, shared: true do
   it "escapes any characters with special meaning in a regular expression" do
-    Regexp.send(@method, '\*?{}.+^[]()- ').should == '\\\\\*\?\{\}\.\+\^\[\]\(\)\-\\ '
-    Regexp.send(@method, "\*?{}.+^[]()- ").should == '\\*\\?\\{\\}\\.\\+\\^\\[\\]\\(\\)\\-\\ '
+    Regexp.send(@method, '\*?{}.+^$[]()- ').should == '\\\\\*\?\{\}\.\+\^\$\[\]\(\)\-\\ '
+    Regexp.send(@method, "\*?{}.+^$[]()- ").should == '\\*\\?\\{\\}\\.\\+\\^\\$\\[\\]\\(\\)\\-\\ '
     Regexp.send(@method, '\n\r\f\t').should == '\\\\n\\\\r\\\\f\\\\t'
     Regexp.send(@method, "\n\r\f\t").should == '\\n\\r\\f\\t'
   end
@@ -12,20 +12,30 @@ describe :regexp_quote, shared: true do
     Regexp.send(@method, :symbol).should == 'symbol'
   end
 
+  it "works with substrings" do
+    str = ".+[]()"[1...-1]
+    Regexp.send(@method, str).should == '\+\[\]\('
+  end
+
+  it "works for broken strings" do
+    Regexp.send(@method, "a.\x85b.".dup.force_encoding("US-ASCII")).should =="a\\.\x85b\\.".dup.force_encoding("US-ASCII")
+    Regexp.send(@method, "a.\x80".dup.force_encoding("UTF-8")).should == "a\\.\x80".dup.force_encoding("UTF-8")
+  end
+
   it "sets the encoding of the result to US-ASCII if there are only US-ASCII characters present in the input String" do
-    str = "abc".force_encoding("euc-jp")
+    str = "abc".dup.force_encoding("euc-jp")
     Regexp.send(@method, str).encoding.should == Encoding::US_ASCII
   end
 
   it "sets the encoding of the result to the encoding of the String if any non-US-ASCII characters are present in an input String with valid encoding" do
-    str = "ありがとう".force_encoding("utf-8")
-    str.valid_encoding?.should be_true
+    str = "ありがとう".dup.force_encoding("utf-8")
+    str.valid_encoding?.should == true
     Regexp.send(@method, str).encoding.should == Encoding::UTF_8
   end
 
   it "sets the encoding of the result to BINARY if any non-US-ASCII characters are present in an input String with invalid encoding" do
-    str = "\xff".force_encoding "us-ascii"
-    str.valid_encoding?.should be_false
+    str = "\xff".dup.force_encoding "us-ascii"
+    str.valid_encoding?.should == false
     Regexp.send(@method, "\xff").encoding.should == Encoding::BINARY
   end
 end
diff --git a/spec/ruby/core/regexp/source_spec.rb b/spec/ruby/core/regexp/source_spec.rb
index 709fee49b3..4eebf280f0 100644
--- a/spec/ruby/core/regexp/source_spec.rb
+++ b/spec/ruby/core/regexp/source_spec.rb
@@ -9,21 +9,39 @@ describe "Regexp#source" do
     /x(.)xz/.source.should == "x(.)xz"
   end
 
-  it "will remove escape characters" do
-    /foo\/bar/.source.should == "foo/bar"
+  it "keeps escape sequences as is" do
+    /\x20\+/.source.should == '\x20\+'
+  end
+
+  describe "escaping" do
+    it "keeps escaping of metacharacter" do
+      /\$/.source.should == "\\$"
+    end
+
+    it "keeps escaping of metacharacter used as a terminator" do
+      %r+\++.source.should == "\\+"
+    end
+
+    it "removes escaping of non-metacharacter used as a terminator" do
+      %r@\@@.source.should == "@"
+    end
+
+    it "keeps escaping of non-metacharacter not used as a terminator" do
+      /\@/.source.should == "\\@"
+    end
   end
 
   not_supported_on :opal do
     it "has US-ASCII encoding when created from an ASCII-only \\u{} literal" do
       re = /[\u{20}-\u{7E}]/
-      re.source.encoding.should equal(Encoding::US_ASCII)
+      re.source.encoding.should.equal?(Encoding::US_ASCII)
     end
   end
 
   not_supported_on :opal do
     it "has UTF-8 encoding when created from a non-ASCII-only \\u{} literal" do
       re = /[\u{20}-\u{7EE}]/
-      re.source.encoding.should equal(Encoding::UTF_8)
+      re.source.encoding.should.equal?(Encoding::UTF_8)
     end
   end
 end
diff --git a/spec/ruby/core/regexp/timeout_spec.rb b/spec/ruby/core/regexp/timeout_spec.rb
new file mode 100644
index 0000000000..a1ec475ef3
--- /dev/null
+++ b/spec/ruby/core/regexp/timeout_spec.rb
@@ -0,0 +1,33 @@
+require_relative '../../spec_helper'
+
+describe "Regexp.timeout" do
+  after :each do
+    Regexp.timeout = nil
+  end
+
+  it "returns global timeout" do
+    Regexp.timeout = 3
+    Regexp.timeout.should == 3
+  end
+
+  it "raises Regexp::TimeoutError after global timeout elapsed" do
+    Regexp.timeout = 0.001
+    Regexp.timeout.should == 0.001
+
+    -> {
+      # A typical ReDoS case
+      /^(a*)*$/ =~ "a" * 1000000 + "x"
+    }.should.raise(Regexp::TimeoutError, "regexp match timeout")
+  end
+
+  it "raises Regexp::TimeoutError after timeout keyword value elapsed" do
+    Regexp.timeout = 3 # This should be ignored
+    Regexp.timeout.should == 3
+
+    re = Regexp.new("^a*b?a*$", timeout: 0.001)
+
+    -> {
+      re =~ "a" * 1000000 + "x"
+    }.should.raise(Regexp::TimeoutError, "regexp match timeout")
+  end
+end
diff --git a/spec/ruby/core/regexp/try_convert_spec.rb b/spec/ruby/core/regexp/try_convert_spec.rb
index be567e2130..da5e10adce 100644
--- a/spec/ruby/core/regexp/try_convert_spec.rb
+++ b/spec/ruby/core/regexp/try_convert_spec.rb
@@ -9,7 +9,7 @@ describe "Regexp.try_convert" do
 
   it "returns nil if given an argument that can't be converted to a Regexp" do
     ['', 'glark', [], Object.new, :pat].each do |arg|
-      Regexp.try_convert(arg).should be_nil
+      Regexp.try_convert(arg).should == nil
     end
   end
 
@@ -18,4 +18,10 @@ describe "Regexp.try_convert" do
     rex.should_receive(:to_regexp).and_return(/(p(a)t[e]rn)/)
     Regexp.try_convert(rex).should == /(p(a)t[e]rn)/
   end
+
+  it "raises a TypeError if the object does not return an Regexp from #to_regexp" do
+    obj = mock("regexp")
+    obj.should_receive(:to_regexp).and_return("string")
+    -> { Regexp.try_convert(obj) }.should raise_consistent_error(TypeError, "can't convert MockObject into Regexp (MockObject#to_regexp gives String)")
+  end
 end
diff --git a/spec/ruby/core/regexp/union_spec.rb b/spec/ruby/core/regexp/union_spec.rb
index 8076836471..c0a9d12fed 100644
--- a/spec/ruby/core/regexp/union_spec.rb
+++ b/spec/ruby/core/regexp/union_spec.rb
@@ -43,6 +43,27 @@ describe "Regexp.union" do
     Regexp.union("\u00A9".encode("ISO-8859-1"), "a".encode("UTF-8")).encoding.should == Encoding::ISO_8859_1
   end
 
+  it "returns ASCII-8BIT if the regexp encodings are ASCII-8BIT and at least one has non-ASCII characters" do
+    us_ascii_implicit, us_ascii_explicit, binary = /abc/, /[\x00-\x7f]/n, /[\x80-\xBF]/n
+    us_ascii_implicit.encoding.should == Encoding::US_ASCII
+    us_ascii_explicit.encoding.should == Encoding::US_ASCII
+    binary.encoding.should == Encoding::BINARY
+
+    Regexp.union(us_ascii_implicit, us_ascii_explicit, binary).encoding.should == Encoding::BINARY
+    Regexp.union(us_ascii_implicit, binary, us_ascii_explicit).encoding.should == Encoding::BINARY
+    Regexp.union(us_ascii_explicit, us_ascii_implicit, binary).encoding.should == Encoding::BINARY
+    Regexp.union(us_ascii_explicit, binary, us_ascii_implicit).encoding.should == Encoding::BINARY
+    Regexp.union(binary, us_ascii_implicit, us_ascii_explicit).encoding.should == Encoding::BINARY
+    Regexp.union(binary, us_ascii_explicit, us_ascii_implicit).encoding.should == Encoding::BINARY
+  end
+
+  it "return US-ASCII if all patterns are ASCII-only" do
+    Regexp.union(/abc/e, /def/e).encoding.should == Encoding::US_ASCII
+    Regexp.union(/abc/n, /def/n).encoding.should == Encoding::US_ASCII
+    Regexp.union(/abc/s, /def/s).encoding.should == Encoding::US_ASCII
+    Regexp.union(/abc/u, /def/u).encoding.should == Encoding::US_ASCII
+  end
+
   it "returns a Regexp with UTF-8 if one part is UTF-8" do
     Regexp.union(/probl[éeè]me/i, /help/i).encoding.should == Encoding::UTF_8
   end
@@ -54,83 +75,83 @@ describe "Regexp.union" do
   it "raises ArgumentError if the arguments include conflicting ASCII-incompatible Strings" do
     -> {
       Regexp.union("a".encode("UTF-16LE"), "b".encode("UTF-16BE"))
-    }.should raise_error(ArgumentError)
+    }.should.raise(ArgumentError, 'incompatible encodings: UTF-16LE and UTF-16BE')
   end
 
   it "raises ArgumentError if the arguments include conflicting ASCII-incompatible Regexps" do
     -> {
       Regexp.union(Regexp.new("a".encode("UTF-16LE")),
                    Regexp.new("b".encode("UTF-16BE")))
-    }.should raise_error(ArgumentError)
+    }.should.raise(ArgumentError, 'incompatible encodings: UTF-16LE and UTF-16BE')
   end
 
   it "raises ArgumentError if the arguments include conflicting fixed encoding Regexps" do
     -> {
       Regexp.union(Regexp.new("a".encode("UTF-8"),    Regexp::FIXEDENCODING),
                    Regexp.new("b".encode("US-ASCII"), Regexp::FIXEDENCODING))
-    }.should raise_error(ArgumentError)
+    }.should.raise(ArgumentError, 'incompatible encodings: UTF-8 and US-ASCII')
   end
 
   it "raises ArgumentError if the arguments include a fixed encoding Regexp and a String containing non-ASCII-compatible characters in a different encoding" do
     -> {
       Regexp.union(Regexp.new("a".encode("UTF-8"), Regexp::FIXEDENCODING),
                    "\u00A9".encode("ISO-8859-1"))
-    }.should raise_error(ArgumentError)
+    }.should.raise(ArgumentError, 'incompatible encodings: UTF-8 and ISO-8859-1')
   end
 
   it "raises ArgumentError if the arguments include a String containing non-ASCII-compatible characters and a fixed encoding Regexp in a different encoding" do
     -> {
       Regexp.union("\u00A9".encode("ISO-8859-1"),
                    Regexp.new("a".encode("UTF-8"), Regexp::FIXEDENCODING))
-    }.should raise_error(ArgumentError)
+    }.should.raise(ArgumentError, 'incompatible encodings: ISO-8859-1 and UTF-8')
   end
 
   it "raises ArgumentError if the arguments include an ASCII-incompatible String and an ASCII-only String" do
     -> {
       Regexp.union("a".encode("UTF-16LE"), "b".encode("UTF-8"))
-    }.should raise_error(ArgumentError)
+    }.should.raise(ArgumentError, /ASCII incompatible encoding: UTF-16LE|incompatible encodings: UTF-16LE and US-ASCII/)
   end
 
   it "raises ArgumentError if the arguments include an ASCII-incompatible Regexp and an ASCII-only String" do
     -> {
       Regexp.union(Regexp.new("a".encode("UTF-16LE")), "b".encode("UTF-8"))
-    }.should raise_error(ArgumentError)
+    }.should.raise(ArgumentError, /ASCII incompatible encoding: UTF-16LE|incompatible encodings: UTF-16LE and US-ASCII/)
   end
 
   it "raises ArgumentError if the arguments include an ASCII-incompatible String and an ASCII-only Regexp" do
     -> {
       Regexp.union("a".encode("UTF-16LE"), Regexp.new("b".encode("UTF-8")))
-    }.should raise_error(ArgumentError)
+    }.should.raise(ArgumentError, /ASCII incompatible encoding: UTF-16LE|incompatible encodings: UTF-16LE and US-ASCII/)
   end
 
   it "raises ArgumentError if the arguments include an ASCII-incompatible Regexp and an ASCII-only Regexp" do
     -> {
       Regexp.union(Regexp.new("a".encode("UTF-16LE")), Regexp.new("b".encode("UTF-8")))
-    }.should raise_error(ArgumentError)
+    }.should.raise(ArgumentError, /ASCII incompatible encoding: UTF-16LE|incompatible encodings: UTF-16LE and US-ASCII/)
   end
 
   it "raises ArgumentError if the arguments include an ASCII-incompatible String and a String containing non-ASCII-compatible characters in a different encoding" do
     -> {
       Regexp.union("a".encode("UTF-16LE"), "\u00A9".encode("ISO-8859-1"))
-    }.should raise_error(ArgumentError)
+    }.should.raise(ArgumentError, 'incompatible encodings: UTF-16LE and ISO-8859-1')
   end
 
   it "raises ArgumentError if the arguments include an ASCII-incompatible Regexp and a String containing non-ASCII-compatible characters in a different encoding" do
     -> {
       Regexp.union(Regexp.new("a".encode("UTF-16LE")), "\u00A9".encode("ISO-8859-1"))
-    }.should raise_error(ArgumentError)
+    }.should.raise(ArgumentError, 'incompatible encodings: UTF-16LE and ISO-8859-1')
   end
 
   it "raises ArgumentError if the arguments include an ASCII-incompatible String and a Regexp containing non-ASCII-compatible characters in a different encoding" do
     -> {
       Regexp.union("a".encode("UTF-16LE"), Regexp.new("\u00A9".encode("ISO-8859-1")))
-    }.should raise_error(ArgumentError)
+    }.should.raise(ArgumentError, 'incompatible encodings: UTF-16LE and ISO-8859-1')
   end
 
   it "raises ArgumentError if the arguments include an ASCII-incompatible Regexp and a Regexp containing non-ASCII-compatible characters in a different encoding" do
     -> {
       Regexp.union(Regexp.new("a".encode("UTF-16LE")), Regexp.new("\u00A9".encode("ISO-8859-1")))
-    }.should raise_error(ArgumentError)
+    }.should.raise(ArgumentError, 'incompatible encodings: UTF-16LE and ISO-8859-1')
   end
 
   it "uses to_str to convert arguments (if not Regexp)" do
@@ -154,6 +175,8 @@ describe "Regexp.union" do
     not_supported_on :opal do
       Regexp.union([/dogs/, /cats/i]).should == /(?-mix:dogs)|(?i-mx:cats)/
     end
-    ->{Regexp.union(["skiing", "sledding"], [/dogs/, /cats/i])}.should raise_error(TypeError)
+    -> {
+      Regexp.union(["skiing", "sledding"], [/dogs/, /cats/i])
+    }.should.raise(TypeError, 'no implicit conversion of Array into String')
   end
 end