vim-patch:8.2.1106: crash when trying to use s: variable in typed command

Problem:    Crash when trying to use s: variable in typed command.
Solution:   Don't use the script index when not set. (Ken Takata,
            closes vim/vim#6366)

8e6cbb7232

test/functional/legacy/vimscript_spec.lua

@@ -0,0 +1,90 @@
+local helpers = require('test.functional.helpers')(after_each)
+local Screen = require('test.functional.ui.screen')
+local clear = helpers.clear
+local exec = helpers.exec
+local feed = helpers.feed
+local meths = helpers.meths
+
+before_each(clear)
+
+describe('Vim script', function()
+  -- oldtest: Test_deep_nest()
+  it('Error when if/for/while/try/function is nested too deep',function()
+    local screen = Screen.new(80, 24)
+    screen:attach()
+    meths.set_option('laststatus', 2)
+    exec([[
+      " Deep nesting of if ... endif
+      func Test1()
+        let @a = join(repeat(['if v:true'], 51), "\n")
+        let @a ..= "\n"
+        let @a ..= join(repeat(['endif'], 51), "\n")
+        @a
+        let @a = ''
+      endfunc
+
+      " Deep nesting of for ... endfor
+      func Test2()
+        let @a = join(repeat(['for i in [1]'], 51), "\n")
+        let @a ..= "\n"
+        let @a ..= join(repeat(['endfor'], 51), "\n")
+        @a
+        let @a = ''
+      endfunc
+
+      " Deep nesting of while ... endwhile
+      func Test3()
+        let @a = join(repeat(['while v:true'], 51), "\n")
+        let @a ..= "\n"
+        let @a ..= join(repeat(['endwhile'], 51), "\n")
+        @a
+        let @a = ''
+      endfunc
+
+      " Deep nesting of try ... endtry
+      func Test4()
+        let @a = join(repeat(['try'], 51), "\n")
+        let @a ..= "\necho v:true\n"
+        let @a ..= join(repeat(['endtry'], 51), "\n")
+        @a
+        let @a = ''
+      endfunc
+
+      " Deep nesting of function ... endfunction
+      func Test5()
+        let @a = join(repeat(['function X()'], 51), "\n")
+        let @a ..= "\necho v:true\n"
+        let @a ..= join(repeat(['endfunction'], 51), "\n")
+        @a
+        let @a = ''
+      endfunc
+    ]])
+    screen:expect({any = '%[No Name%]'})
+    feed(':call Test1()<CR>')
+    screen:expect({any = 'E579: '})
+    feed('<C-C>')
+    screen:expect({any = '%[No Name%]'})
+    feed(':call Test2()<CR>')
+    screen:expect({any = 'E585: '})
+    feed('<C-C>')
+    screen:expect({any = '%[No Name%]'})
+    feed(':call Test3()<CR>')
+    screen:expect({any = 'E585: '})
+    feed('<C-C>')
+    screen:expect({any = '%[No Name%]'})
+    feed(':call Test4()<CR>')
+    screen:expect({any = 'E601: '})
+    feed('<C-C>')
+    screen:expect({any = '%[No Name%]'})
+    feed(':call Test5()<CR>')
+    screen:expect({any = 'E1058: '})
+  end)
+
+  -- oldtest: Test_typed_script_var()
+  it('using s: with a typed command', function()
+    local screen = Screen.new(80, 24)
+    screen:attach()
+    feed(":echo get(s:, 'foo', 'x')\n")
+    screen:expect({any = 'E116: '})
+  end)
+end)