[WIP] add error_squiggle gem

```
$ ./local/bin/ruby -e '1.time {}'
-e:1:in `<main>': undefined method `time' for 1:Integer (NoMethodError)

1.time {}
 ^^^^^
Did you mean?  times
```

https://bugs.ruby-lang.org/issues/17930

7 files changed, 990 insertions, 6 deletions

diff --git a/test/error_squiggle/test_error_squiggle.rb b/test/error_squiggle/test_error_squiggle.rb
new file mode 100644
index 0000000000..3b44daf74c
--- /dev/null
+++ b/test/error_squiggle/test_error_squiggle.rb
@@ -0,0 +1,984 @@
+require "test/unit"
+
+require "error_squiggle"
+
+class ErrorSquiggleTest < Test::Unit::TestCase
+  class DummyFormatter
+    def message_for(corrections)
+      ""
+    end
+  end
+
+  def setup
+    if defined?(DidYouMean)
+      @did_you_mean_old_formatter = DidYouMean.formatter
+      DidYouMean.formatter = DummyFormatter
+    end
+  end
+
+  def teardown
+    if defined?(DidYouMean)
+      DidYouMean.formatter = @did_you_mean_old_formatter
+    end
+  end
+
+  def assert_error_message(klass, expected_msg, &blk)
+    err = assert_raise(klass, &blk)
+    assert_equal(expected_msg.chomp, err.message)
+  end
+
+  def test_CALL_noarg_1
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `foo' for nil:NilClass
+
+      nil.foo + 1
+         ^^^^
+    END
+
+      nil.foo + 1
+    end
+  end
+
+  def test_CALL_noarg_2
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `foo' for nil:NilClass
+
+        .foo + 1
+        ^^^^
+    END
+
+      nil
+        .foo + 1
+    end
+  end
+
+  def test_CALL_noarg_3
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `foo' for nil:NilClass
+
+        foo + 1
+        ^^^
+    END
+
+      nil.
+        foo + 1
+    end
+  end
+
+  def test_CALL_arg_1
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `foo' for nil:NilClass
+
+      nil.foo (42)
+         ^^^^
+    END
+
+      nil.foo (42)
+    end
+  end
+
+  def test_CALL_arg_2
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `foo' for nil:NilClass
+
+        .foo (
+        ^^^^
+    END
+
+      nil
+        .foo (
+          42
+        )
+    end
+  end
+
+  def test_CALL_arg_3
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `foo' for nil:NilClass
+
+        foo (
+        ^^^
+    END
+
+      nil.
+        foo (
+          42
+        )
+    end
+  end
+
+  def test_CALL_arg_4
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `foo' for nil:NilClass
+
+      nil.foo(42)
+         ^^^^
+    END
+
+      nil.foo(42)
+    end
+  end
+
+  def test_CALL_arg_5
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `foo' for nil:NilClass
+
+        .foo(
+        ^^^^
+    END
+
+      nil
+        .foo(
+          42
+        )
+    end
+  end
+
+  def test_CALL_arg_6
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `foo' for nil:NilClass
+
+        foo(
+        ^^^
+    END
+
+      nil.
+        foo(
+          42
+        )
+    end
+  end
+
+  def test_QCALL_1
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `foo' for 1:Integer
+
+      1&.foo
+       ^^^^^
+    END
+
+      1&.foo
+    end
+  end
+
+  def test_QCALL_2
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `foo' for 1:Integer
+
+      1&.foo(42)
+       ^^^^^
+    END
+
+      1&.foo(42)
+    end
+  end
+
+  def test_CALL_aref_1
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `[]' for nil:NilClass
+
+      nil [ ]
+          ^^^
+    END
+
+      nil [ ]
+    end
+  end
+
+  def test_CALL_aref_2
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `[]' for nil:NilClass
+
+      nil [0]
+          ^^^
+    END
+
+      nil [0]
+    end
+  end
+
+  def test_CALL_aref_3
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `[]' for nil:NilClass
+    END
+
+      nil [
+        0
+      ]
+    end
+  end
+
+  def test_CALL_aref_4
+    v = Object.new
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `[]' for #{ v.inspect }
+
+      v &.[](0)
+        ^^^^
+    END
+
+      v &.[](0)
+    end
+  end
+
+  def test_CALL_aset
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `[]=' for nil:NilClass
+
+      nil.[]=
+         ^^^^
+    END
+
+      nil.[]=
+    end
+  end
+
+  def test_CALL_op_asgn
+    v = nil
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `+' for nil:NilClass
+
+      v += 42
+        ^
+    END
+
+      v += 42
+    end
+  end
+
+  def test_CALL_special_call_1
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `call' for nil:NilClass
+    END
+
+      nil.()
+    end
+  end
+
+  def test_CALL_special_call_2
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `call' for nil:NilClass
+    END
+
+      nil.(42)
+    end
+  end
+
+  def test_CALL_send
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `foo' for nil:NilClass
+
+      nil.send(:foo, 42)
+         ^^^^^
+    END
+
+      nil.send(:foo, 42)
+    end
+  end
+
+  def test_ATTRASGN_1
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `[]=' for nil:NilClass
+
+      nil [ ] = 42
+          ^^^^^
+    END
+
+      nil [ ] = 42
+    end
+  end
+
+  def test_ATTRASGN_2
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `[]=' for nil:NilClass
+
+      nil [0] = 42
+          ^^^^^
+    END
+
+      nil [0] = 42
+    end
+  end
+
+  def test_ATTRASGN_3
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `foo=' for nil:NilClass
+
+      nil.foo = 42
+         ^^^^^^
+    END
+
+      nil.foo = 42
+    end
+  end
+
+  def test_OPCALL_binary_1
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `+' for nil:NilClass
+
+      nil + 42
+          ^
+    END
+
+      nil + 42
+    end
+  end
+
+  def test_OPCALL_binary_2
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `+' for nil:NilClass
+
+      nil + # comment
+          ^
+    END
+
+      nil + # comment
+        42
+    end
+  end
+
+  def test_OPCALL_unary
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `+@' for nil:NilClass
+
+      + nil
+      ^
+    END
+
+      + nil
+    end
+  end
+
+  def test_FCALL_1
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `foo' for nil:NilClass
+
+      nil.instance_eval { foo() }
+                          ^^^
+    END
+
+      nil.instance_eval { foo() }
+    end
+  end
+
+  def test_FCALL_2
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `foo' for nil:NilClass
+
+      nil.instance_eval { foo(42) }
+                          ^^^
+    END
+
+      nil.instance_eval { foo(42) }
+    end
+  end
+
+  def test_VCALL_2
+    assert_error_message(NameError, <<~END) do
+undefined local variable or method `foo' for nil:NilClass
+
+      nil.instance_eval { foo }
+                          ^^^
+    END
+
+      nil.instance_eval { foo }
+    end
+  end
+
+  def test_OP_ASGN1_aref_1
+    v = nil
+
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `[]' for nil:NilClass
+
+      v [0] += 42
+        ^^^
+    END
+
+      v [0] += 42
+    end
+  end
+
+  def test_OP_ASGN1_aref_2
+    v = nil
+
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `[]' for nil:NilClass
+
+      v [0] += # comment
+        ^^^
+    END
+
+      v [0] += # comment
+        42
+    end
+  end
+
+  def test_OP_ASGN1_aref_3
+    v = nil
+
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `[]' for nil:NilClass
+    END
+
+      v [
+        0
+      ] += # comment
+        42
+    end
+  end
+
+  def test_OP_ASGN1_op_1
+    v = Object.new
+    def v.[](x); nil; end
+
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `+' for nil:NilClass
+
+      v [0] += 42
+            ^
+    END
+
+      v [0] += 42
+    end
+  end
+
+  def test_OP_ASGN1_op_2
+    v = Object.new
+    def v.[](x); nil; end
+
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `+' for nil:NilClass
+
+      v [0 ] += # comment
+             ^
+    END
+
+      v [0 ] += # comment
+        42
+    end
+  end
+
+  def test_OP_ASGN1_op_3
+    v = Object.new
+    def v.[](x); nil; end
+
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `+' for nil:NilClass
+    END
+
+      v [
+        0
+      ] +=
+        42
+    end
+  end
+
+  def test_OP_ASGN1_aset_1
+    v = Object.new
+    def v.[](x); 1; end
+
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `[]=' for #{ v.inspect }
+
+      v [0] += 42
+        ^^^^^^
+    END
+
+      v [0] += 42
+    end
+  end
+
+  def test_OP_ASGN1_aset_2
+    v = Object.new
+    def v.[](x); 1; end
+
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `[]=' for #{ v.inspect }
+
+      v [0] += # comment
+        ^^^^^^
+    END
+
+      v [0] += # comment
+        42
+    end
+  end
+
+  def test_OP_ASGN1_aset_3
+    v = Object.new
+    def v.[](x); 1; end
+
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `[]=' for #{ v.inspect }
+    END
+
+      v [
+        0
+      ] +=
+        42
+    end
+  end
+
+  def test_OP_ASGN2_read_1
+    v = nil
+
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `foo' for nil:NilClass
+
+      v.foo += 42
+       ^^^^
+    END
+
+      v.foo += 42
+    end
+  end
+
+  def test_OP_ASGN2_read_2
+    v = nil
+
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `foo' for nil:NilClass
+
+      v.foo += # comment
+       ^^^^
+    END
+
+      v.foo += # comment
+        42
+    end
+  end
+
+  def test_OP_ASGN2_op_1
+    v = Object.new
+    def v.foo; nil; end
+
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `+' for nil:NilClass
+
+      v.foo += 42
+            ^
+    END
+
+      v.foo += 42
+    end
+  end
+
+  def test_OP_ASGN2_op_2
+    v = Object.new
+    def v.foo; nil; end
+
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `+' for nil:NilClass
+
+      v.foo += # comment
+            ^
+    END
+
+      v.foo += # comment
+        42
+    end
+  end
+
+  def test_OP_ASGN2_write_1
+    v = Object.new
+    def v.foo; 1; end
+
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `foo=' for #{ v.inspect }
+
+      v.foo += 42
+       ^^^^^^^
+    END
+
+      v.foo += 42
+    end
+  end
+
+  def test_OP_ASGN2_write_2
+    v = Object.new
+    def v.foo; 1; end
+
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `foo=' for #{ v.inspect }
+
+      v.foo += # comment
+       ^^^^^^^
+    END
+
+      v.foo += # comment
+        42
+    end
+  end
+
+  def test_CONST
+    assert_error_message(NameError, <<~END) do
+uninitialized constant ErrorSquiggleTest::NotDefined
+
+      1 + NotDefined + 1
+          ^^^^^^^^^^
+    END
+
+      1 + NotDefined + 1
+    end
+  end
+
+  def test_COLON2_1
+    assert_error_message(NameError, <<~END) do
+uninitialized constant ErrorSquiggleTest::NotDefined
+
+      ErrorSquiggleTest::NotDefined
+                       ^^^^^^^^^^^^
+    END
+
+      ErrorSquiggleTest::NotDefined
+    end
+  end
+
+  def test_COLON2_2
+    assert_error_message(NameError, <<~END) do
+uninitialized constant ErrorSquiggleTest::NotDefined
+
+        NotDefined
+        ^^^^^^^^^^
+    END
+
+      ErrorSquiggleTest::
+        NotDefined
+    end
+  end
+
+  def test_COLON3
+    assert_error_message(NameError, <<~END) do
+uninitialized constant NotDefined
+
+      ::NotDefined
+      ^^^^^^^^^^^^
+    END
+
+      ::NotDefined
+    end
+  end
+
+  module OP_CDECL_TEST
+    Nil = nil
+  end
+
+  def test_OP_CDECL_read_1
+    assert_error_message(NameError, <<~END) do
+uninitialized constant ErrorSquiggleTest::OP_CDECL_TEST::NotDefined
+
+      OP_CDECL_TEST::NotDefined += 1
+                   ^^^^^^^^^^^^
+    END
+
+      OP_CDECL_TEST::NotDefined += 1
+    end
+  end
+
+  def test_OP_CDECL_read_2
+    assert_error_message(NameError, <<~END) do
+uninitialized constant ErrorSquiggleTest::OP_CDECL_TEST::NotDefined
+
+      OP_CDECL_TEST::NotDefined += # comment
+                   ^^^^^^^^^^^^
+    END
+
+      OP_CDECL_TEST::NotDefined += # comment
+        1
+    end
+  end
+
+  def test_OP_CDECL_read_3
+    assert_error_message(NameError, <<~END) do
+uninitialized constant ErrorSquiggleTest::OP_CDECL_TEST::NotDefined
+    END
+
+      OP_CDECL_TEST::
+        NotDefined += 1
+    end
+  end
+
+  def test_OP_CDECL_op_1
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `+' for nil:NilClass
+
+      OP_CDECL_TEST::Nil += 1
+                         ^
+    END
+
+      OP_CDECL_TEST::Nil += 1
+    end
+  end
+
+  def test_OP_CDECL_op_2
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `+' for nil:NilClass
+
+      OP_CDECL_TEST::Nil += # comment
+                         ^
+    END
+
+      OP_CDECL_TEST::Nil += # comment
+        1
+    end
+  end
+
+  def test_OP_CDECL_op_3
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `+' for nil:NilClass
+
+        Nil += 1
+            ^
+    END
+
+      OP_CDECL_TEST::
+        Nil += 1
+    end
+  end
+
+  def test_OP_CDECL_toplevel_1
+    assert_error_message(NameError, <<~END) do
+uninitialized constant NotDefined
+
+      ::NotDefined += 1
+      ^^^^^^^^^^^^
+    END
+
+      ::NotDefined += 1
+    end
+  end
+
+  def test_OP_CDECL_toplevel_2
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `+' for ErrorSquiggleTest:Class
+
+      ::ErrorSquiggleTest += 1
+                          ^
+    END
+
+      ::ErrorSquiggleTest += 1
+    end
+  end
+
+  def test_explicit_raise_name_error
+    assert_error_message(NameError, <<~END) do
+NameError
+
+      raise NameError
+      ^^^^^
+    END
+
+      raise NameError
+    end
+  end
+
+  def test_explicit_raise_no_method_error
+    assert_error_message(NoMethodError, <<~END) do
+NoMethodError
+
+      raise NoMethodError
+      ^^^^^
+    END
+
+      raise NoMethodError
+    end
+  end
+
+  def test_const_get
+    assert_error_message(NameError, <<~END) do
+uninitialized constant ErrorSquiggleTest::NotDefined
+
+      ErrorSquiggleTest.const_get(:NotDefined)
+                       ^^^^^^^^^^
+    END
+
+      ErrorSquiggleTest.const_get(:NotDefined)
+    end
+  end
+
+  def test_local_variable_get
+    b = binding
+    assert_error_message(NameError, <<~END) do
+local variable `foo' is not defined for #{ b.inspect }
+
+      b.local_variable_get(:foo)
+       ^^^^^^^^^^^^^^^^^^^
+    END
+
+      b.local_variable_get(:foo)
+    end
+  end
+
+  def test_multibyte
+    assert_error_message(NoMethodError, <<~END) do
+undefined method `あいうえお' for nil:NilClass
+
+      nil.あいうえお
+         ^^^^^^
+    END
+
+      nil.あいうえお
+    end
+  end
+
+  if false
+
+  def test_args_CALL_1
+    assert_error_message(TypeError, <<~END) do
+nil can't be coerced into Integer
+
+      1.+(nil)
+          ^^^
+    END
+
+      1.+(nil)
+    end
+  end
+
+  def test_args_CALL_2
+    v = []
+    assert_error_message(TypeError, <<~END) do
+no implicit conversion from nil to integer
+
+      v[nil]
+        ^^^
+    END
+
+      v[nil]
+    end
+  end
+
+  def test_args_ATTRASGN_1
+    v = []
+    assert_error_message(ArgumentError, <<~END) do
+wrong number of arguments (given 1, expected 2..3)
+
+      v [ ] = 1
+         ^^^^^^
+    END
+
+      v [ ] = 1
+    end
+  end
+
+  def test_args_ATTRASGN_2
+    v = []
+    assert_error_message(TypeError, <<~END) do
+no implicit conversion from nil to integer
+
+      v [nil] = 1
+         ^^^^^^^^
+    END
+
+      v [nil] = 1
+    end
+  end
+
+  def test_args_ATTRASGN_3
+    assert_error_message(TypeError, <<~END) do
+no implicit conversion of String into Integer
+
+      $stdin.lineno = "str"
+                      ^^^^^
+    END
+
+      $stdin.lineno = "str"
+    end
+  end
+
+  def test_args_OPCALL
+    assert_error_message(TypeError, <<~END) do
+nil can't be coerced into Integer
+
+      1 + nil
+          ^^^
+    END
+
+      1 + nil
+    end
+  end
+
+  def test_args_FCALL_1
+    assert_error_message(TypeError, <<~END) do
+no implicit conversion of Symbol into String
+
+      "str".instance_eval { gsub("foo", :sym) }
+                                 ^^^^^^^^^^^
+    END
+
+      "str".instance_eval { gsub("foo", :sym) }
+    end
+  end
+
+  def test_args_FCALL_2
+    assert_error_message(TypeError, <<~END) do
+no implicit conversion of Symbol into String
+
+      "str".instance_eval { gsub "foo", :sym }
+                                 ^^^^^^^^^^^
+    END
+
+      "str".instance_eval { gsub "foo", :sym }
+    end
+  end
+
+  def test_args_OP_ASGN1_aref_1
+    v = []
+
+    assert_error_message(TypeError, <<~END) do
+no implicit conversion from nil to integer
+
+      v [nil] += 42
+         ^^^^^^^^^^
+    END
+
+      v [nil] += 42
+    end
+  end
+
+  def test_args_OP_ASGN1_aref_2
+    v = []
+
+    assert_error_message(ArgumentError, <<~END) do
+wrong number of arguments (given 0, expected 1..2)
+
+      v [ ] += 42
+         ^^^^^^^^
+    END
+
+      v [ ] += 42
+    end
+  end
+
+  def test_args_OP_ASGN1_op
+    v = [1]
+
+    assert_error_message(TypeError, <<~END) do
+nil can't be coerced into Integer
+
+      v [0] += nil
+         ^^^^^^^^^
+    END
+
+      v [0] += nil
+    end
+  end
+
+  def test_args_OP_ASGN2
+    v = Object.new
+    def v.foo; 1; end
+
+    assert_error_message(TypeError, <<~END) do
+nil can't be coerced into Integer
+
+      v.foo += nil
+               ^^^
+    END
+
+      v.foo += nil
+    end
+  end
+
+  end
+end
diff --git a/test/ruby/marshaltestlib.rb b/test/ruby/marshaltestlib.rb
index 5c48a8d853..7f100b7873 100644
--- a/test/ruby/marshaltestlib.rb
+++ b/test/ruby/marshaltestlib.rb
@@ -112,7 +112,7 @@ module MarshalTestLib
     marshal_equal(Exception.new('foo')) {|o| o.message}
     obj = Object.new
     e = assert_raise(NoMethodError) {obj.no_such_method()}
-    marshal_equal(e) {|o| o.message}
+    marshal_equal(e) {|o| o.message.lines.first.chomp}
   end
 
   def test_exception_subclass
diff --git a/test/ruby/test_marshal.rb b/test/ruby/test_marshal.rb
index d2b4ec169f..5e6891a6a0 100644
--- a/test/ruby/test_marshal.rb
+++ b/test/ruby/test_marshal.rb
@@ -817,7 +817,7 @@ class TestMarshal < Test::Unit::TestCase
       nameerror_test
     rescue NameError => e
       e2 = Marshal.load(Marshal.dump(e))
-      assert_equal(e.message, e2.message)
+      assert_equal(e.message.lines.first.chomp, e2.message.lines.first)
       assert_equal(e.name, e2.name)
       assert_equal(e.backtrace, e2.backtrace)
       assert_nil(e2.backtrace_locations) # temporal
diff --git a/test/ruby/test_module.rb b/test/ruby/test_module.rb
index 84e74693aa..3411c3d701 100644
--- a/test/ruby/test_module.rb
+++ b/test/ruby/test_module.rb
@@ -267,7 +267,7 @@ class TestModule < Test::Unit::TestCase
     ].each do |name, msg|
       expected = "wrong constant name %s" % name
       msg = "#{msg}#{': ' if msg}wrong constant name #{name.dump}"
-      assert_raise_with_message(NameError, expected, "#{msg} to #{m}") do
+      assert_raise_with_message(NameError, Regexp.compile(Regexp.quote(expected)), "#{msg} to #{m}") do
         yield name
       end
     end
diff --git a/test/ruby/test_name_error.rb b/test/ruby/test_name_error.rb
index 813a976e96..8fcc2dcb26 100644
--- a/test/ruby/test_name_error.rb
+++ b/test/ruby/test_name_error.rb
@@ -151,6 +151,6 @@ class TestNameError < Test::Unit::TestCase
     error = assert_raise(NameError) do
       receiver::FOO
     end
-    assert_equal "uninitialized constant #{'A' * 120}::FOO", error.message
+    assert_match /\Auninitialized constant #{'A' * 120}::FOO$/, error.message
   end
 end
diff --git a/test/ruby/test_nomethod_error.rb b/test/ruby/test_nomethod_error.rb
index 8b81052905..321b7ccab2 100644
--- a/test/ruby/test_nomethod_error.rb
+++ b/test/ruby/test_nomethod_error.rb
@@ -86,7 +86,7 @@ class TestNoMethodError < Test::Unit::TestCase
     str = "\u2600"
     id = :"\u2604"
     msg = "undefined method `#{id}' for \"#{str}\":String"
-    assert_raise_with_message(NoMethodError, msg, bug3237) do
+    assert_raise_with_message(NoMethodError, Regexp.compile(Regexp.quote(msg)), bug3237) do
       str.__send__(id)
     end
   end
diff --git a/test/ruby/test_object.rb b/test/ruby/test_object.rb
index 774b707742..83208bbcdb 100644
--- a/test/ruby/test_object.rb
+++ b/test/ruby/test_object.rb
@@ -777,7 +777,7 @@ class TestObject < Test::Unit::TestCase
     e = assert_raise(NoMethodError) {
       o.never_defined_test_no_superclass_method
     }
-    assert_equal(m1, e.message, bug2312)
+    assert_equal(m1.lines.first, e.message.lines.first, bug2312)
   end
 
   def test_superclass_method