Warn if using return at top-level with an argument

Fixes [Bug #14062]

compile.c

@@ -6372,6 +6372,9 @@ compile_return(rb_iseq_t *iseq, LINK_ANCHOR *const ret, const NODE *const node,
 	switch (t) {
 	  case ISEQ_TYPE_TOP:
 	  case ISEQ_TYPE_MAIN:
+            if (retval) {
+                rb_warn("argument of top-level return is ignored");
+            }
 	    if (is == iseq) {
 		/* plain top-level, leave directly */
 		type = ISEQ_TYPE_METHOD;

spec/ruby/language/return_spec.rb

@@ -484,13 +484,26 @@ describe "The return keyword" do
       end
 
       describe "return with argument" do
-        # https://bugs.ruby-lang.org/issues/14062
+        ruby_version_is ""..."2.7" do
-        it "does not affect exit status" do
+          it "does not affect exit status" do
-          ruby_exe(<<-END_OF_CODE).should == ""
+            ruby_exe(<<-END_OF_CODE).should == ""
-            return 10
+              return 10
-          END_OF_CODE
+            END_OF_CODE
 
-          $?.exitstatus.should == 0
+            $?.exitstatus.should == 0
+          end
+        end
+
+        ruby_version_is "2.7" do
+          it "warns but does not affect exit status" do
+            ruby_exe(<<-END_OF_CODE).should == "-e: warning: argument of top-level return is ignored\n"
+              $stderr.reopen($stdout)
+              system(ENV['RUBY_EXE'], '-e', 'return 10')
+              exit($?.exitstatus)
+            END_OF_CODE
+
+            $?.exitstatus.should == 0
+          end
         end
       end
     end

test/ruby/test_syntax.rb

@@ -1195,6 +1195,10 @@ eom
     end
   end
 
+  def test_return_toplevel_with_argument
+    assert_warn(/argument of top-level return is ignored/) {eval("return 1")}
+  end
+
   def test_syntax_error_in_rescue
     bug12613 = '[ruby-core:76531] [Bug #12613]'
     assert_syntax_error("#{<<-"begin;"}\n#{<<-"end;"}", /Invalid retry/, bug12613)