Improve error handling for `frame select` command when there are too many arguments.

Bug:  https://llvm.org/bugs/show_bug.cgi?id=25847

It now gives a more specific error message and then returns instead of trying to select the wrong frame.

llvm-svn: 256251

lldb/packages/Python/lldbsuite/test/functionalities/abbreviation/TestCommonShortSpellings.py

@@ -29,6 +29,7 @@ class CommonShortSpellingsTestCase(TestBase):
             ('dis', 'disassemble'),
             ('ta st a', 'target stop-hook add'),
             ('fr v', 'frame variable'),
+            ('f 1', 'frame select 1'),
             ('ta st li', 'target stop-hook list'),
         ]
 

lldb/source/Commands/CommandObjectFrame.cpp

@@ -262,8 +262,10 @@ protected:
             }
             else
             {
-                result.AppendError ("invalid arguments.\n");
+                result.AppendErrorWithFormat ("too many arguments; expected frame-index, saw '%s'.\n",
+                                              command.GetArgumentAtIndex(0));
                 m_options.GenerateOptionUsage (result.GetErrorStream(), this);
+                return false;
             }
         }