Add specs for String#{sub,gsub,index,rindex} where the source and pat…

…tern encodings differ

* For #2749

spec/ruby/core/string/gsub_spec.rb

@@ -210,8 +210,6 @@ def replacement.to_str() "hello_replacement" end
     end
   end
 
-  # Note: $~ cannot be tested because mspec messes with it
-
   it "sets $~ to MatchData of last match and nil when there's none" do
     'hello.'.gsub('hello', 'x')
     $~[0].should == 'hello'
@@ -225,6 +223,18 @@ def replacement.to_str() "hello_replacement" end
     'hello.'.gsub(/not/, 'x')
     $~.should == nil
   end
+
+  it "handles a pattern in a superset encoding" do
+    result = 'abc'.force_encoding(Encoding::US_ASCII).gsub('é', 'è')
+    result.should == 'abc'
+    result.encoding.should == Encoding::US_ASCII
+  end
+
+  it "handles a pattern in a subset encoding" do
+    result = 'été'.gsub('t'.force_encoding(Encoding::US_ASCII), 'u')
+    result.should == 'éué'
+    result.encoding.should == Encoding::UTF_8
+  end
 end
 
 describe "String#gsub with pattern and Hash" do

spec/ruby/core/string/index_spec.rb

@@ -159,6 +159,14 @@
       "あれ".index char
     end.should raise_error(Encoding::CompatibilityError)
   end
+
+  it "handles a substring in a superset encoding" do
+    'abc'.force_encoding(Encoding::US_ASCII).index('é').should == nil
+  end
+
+  it "handles a substring in a subset encoding" do
+    'été'.index('t'.force_encoding(Encoding::US_ASCII)).should == 1
+  end
 end
 
 describe "String#index with Regexp" do

spec/ruby/core/string/rindex_spec.rb

@@ -196,6 +196,14 @@ def obj.method_missing(*args) 5 end
   it "raises a TypeError when given offset is nil" do
     -> { "str".rindex("st", nil) }.should raise_error(TypeError)
   end
+
+  it "handles a substring in a superset encoding" do
+    'abc'.force_encoding(Encoding::US_ASCII).rindex('é').should == nil
+  end
+
+  it "handles a substring in a subset encoding" do
+    'été'.rindex('t'.force_encoding(Encoding::US_ASCII)).should == 1
+  end
 end
 
 describe "String#rindex with Regexp" do

spec/ruby/core/string/sub_spec.rb

@@ -214,6 +214,17 @@
     "ababa".sub(/(b)/, '\\\\\1').should == "a\\baba"
   end
 
+  it "handles a pattern in a superset encoding" do
+    result = 'abc'.force_encoding(Encoding::US_ASCII).sub('é', 'è')
+    result.should == 'abc'
+    result.encoding.should == Encoding::US_ASCII
+  end
+
+  it "handles a pattern in a subset encoding" do
+    result = 'été'.sub('t'.force_encoding(Encoding::US_ASCII), 'u')
+    result.should == 'éué'
+    result.encoding.should == Encoding::UTF_8
+  end
 end
 
 describe "String#sub with pattern and block" do