Fix Rubyspec (ruby-2.7) failures

https://github.com/ruby/ruby/runs/1337845174

spec/ruby/command_line/dash_upper_w_spec.rb

@@ -31,11 +31,21 @@ ruby_version_is "2.7" do
   end
 
   describe "The -W command line option with :no-experimental" do
+    before do
+      ruby_version_is ""..."3.0" do
+        @src = 'case 0; in a; end'
+      end
+
+      ruby_version_is "3.0" do
+        @src = '1 => a'
+      end
+    end
+
     it "suppresses experimental warnings" do
-      result = ruby_exe('1 => a', args: '2>&1')
+      result = ruby_exe(@src, args: '2>&1')
       result.should =~ /is experimental/
 
-      result = ruby_exe('case 0; in a; end', options: '-W:no-experimental', args: '2>&1')
+      result = ruby_exe(@src, options: '-W:no-experimental', args: '2>&1')
       result.should == ""
     end
   end

spec/ruby/core/warning/element_set_spec.rb

@@ -7,9 +7,21 @@ ruby_version_is '2.7' do
       ruby_exe('Warning[:deprecated] = false; $; = ""', args: "2>&1").should == ""
     end
 
-    it "emits and suppresses warnings for :experimental" do
-      ruby_exe('Warning[:experimental] = true; eval("1 => a")', args: "2>&1").should =~ /is experimental/
-      ruby_exe('Warning[:experimental] = false; eval("1 => a")', args: "2>&1").should == ""
+    describe ":experimental" do
+      before do
+        ruby_version_is ""..."3.0" do
+          @src = 'case 0; in a; end'
+        end
+
+        ruby_version_is "3.0" do
+          @src = '1 => a'
+        end
+      end
+
+      it "emits and suppresses warnings for :experimental" do
+        ruby_exe("Warning[:experimental] = true; eval('#{@src}')", args: "2>&1").should =~ /is experimental/
+        ruby_exe("Warning[:experimental] = false; eval('#{@src}')", args: "2>&1").should == ""
+      end
     end
 
     it "raises for unknown category" do

spec/ruby/language/pattern_matching_spec.rb

@@ -38,12 +38,20 @@ ruby_version_is "2.7" do
       RUBY
     end
 
-    it "warns about pattern matching is experimental feature" do
-      -> {
-        eval <<~RUBY
-          1 => a
-        RUBY
-      }.should complain(/warning: One-line pattern matching is experimental, and the behavior may change in future versions of Ruby!/)
+    describe "warning" do
+      before do
+        ruby_version_is ""..."3.0" do
+          @src = 'case 0; in a; end'
+        end
+
+        ruby_version_is "3.0" do
+          @src = '1 => a'
+        end
+      end
+
+      it "warns about pattern matching is experimental feature" do
+        -> { eval @src }.should complain(/pattern matching is experimental, and the behavior may change in future versions of Ruby!/i)
+      end
     end
 
     it "binds variables" do