patch 8.2.3751: cannot assign a lambda to an option that takes a functionv8.2.3751

Problem:    Cannot assign a lambda to an option that takes a function.
Solution:   Automatically convert the lambda to a string. (Yegappan
            Lakshmanan, closes #9286)

3 files changed, 262 insertions, 30 deletions

diff --git a/src/testdir/test_iminsert.vim b/src/testdir/test_iminsert.vim
index 14063f9d89..c3c4725a1e 100644
--- a/src/testdir/test_iminsert.vim
+++ b/src/testdir/test_iminsert.vim
@@ -130,12 +130,15 @@ func Test_imactivatefunc_imstatusfunc_callback()
 
   " Using a funcref variable to set 'completefunc'
   let Fn1 = function('IMactivatefunc1')
-  let &imactivatefunc = string(Fn1)
+  let &imactivatefunc = Fn1
   let Fn2 = function('IMstatusfunc1')
+  let &imstatusfunc = Fn2
+  normal! i
+
+  " Using a string(funcref variable) to set 'completefunc'
+  let &imactivatefunc = string(Fn1)
   let &imstatusfunc = string(Fn2)
   normal! i
-  call assert_fails('let &imactivatefunc = Fn1', 'E729:')
-  call assert_fails('let &imstatusfunc = Fn2', 'E729:')
 
   " Test for using a funcref()
   set imactivatefunc=funcref('IMactivatefunc1')
@@ -144,12 +147,15 @@ func Test_imactivatefunc_imstatusfunc_callback()
 
   " Using a funcref variable to set 'imactivatefunc'
   let Fn1 = funcref('IMactivatefunc1')
-  let &imactivatefunc = string(Fn1)
+  let &imactivatefunc = Fn1
   let Fn2 = funcref('IMstatusfunc1')
+  let &imstatusfunc = Fn2
+  normal! i
+
+  " Using a string(funcref variable) to set 'imactivatefunc'
+  let &imactivatefunc = string(Fn1)
   let &imstatusfunc = string(Fn2)
   normal! i
-  call assert_fails('let &imactivatefunc = Fn1', 'E729:')
-  call assert_fails('let &imstatusfunc = Fn2', 'E729:')
 
   " Test for using a lambda function
   set imactivatefunc={a\ ->\ IMactivatefunc1(a)}
@@ -157,6 +163,11 @@ func Test_imactivatefunc_imstatusfunc_callback()
   normal! i
 
   " Set 'imactivatefunc' and 'imstatusfunc' to a lambda expression
+  let &imactivatefunc = {a -> IMactivatefunc1(a)}
+  let &imstatusfunc = { -> IMstatusfunc1()}
+  normal! i
+
+  " Set 'imactivatefunc' and 'imstatusfunc' to a string(lambda expression)
   let &imactivatefunc = '{a -> IMactivatefunc1(a)}'
   let &imstatusfunc = '{ -> IMstatusfunc1()}'
   normal! i
@@ -164,11 +175,15 @@ func Test_imactivatefunc_imstatusfunc_callback()
   " Set 'imactivatefunc' 'imstatusfunc' to a variable with a lambda expression
   let Lambda1 = {a -> IMactivatefunc1(a)}
   let Lambda2 = { -> IMstatusfunc1()}
+  let &imactivatefunc = Lambda1
+  let &imstatusfunc = Lambda2
+  normal! i
+
+  " Set 'imactivatefunc' 'imstatusfunc' to a string(variable with a lambda
+  " expression)
   let &imactivatefunc = string(Lambda1)
   let &imstatusfunc = string(Lambda2)
   normal! i
-  call assert_fails('let &imactivatefunc = Lambda1', 'E729:')
-  call assert_fails('let &imstatusfunc = Lambda2', 'E729:')
 
   " Test for clearing the 'completefunc' option
   set imactivatefunc='' imstatusfunc=''
@@ -179,8 +194,8 @@ func Test_imactivatefunc_imstatusfunc_callback()
   call assert_fails("set imactivatefunc=funcref('abc')", "E700:")
   call assert_fails("set imstatusfunc=funcref('abc')", "E700:")
 
-  call assert_equal(7, g:IMactivatefunc_called)
-  call assert_equal(14, g:IMstatusfunc_called)
+  call assert_equal(11, g:IMactivatefunc_called)
+  call assert_equal(22, g:IMstatusfunc_called)
 
   " Vim9 tests
   let lines =<< trim END
@@ -216,12 +231,17 @@ func Test_imactivatefunc_imstatusfunc_callback()
            g:IMstatusfunc_called += 1
            return 1
         }
+    &imactivatefunc = Fn1
+    &imstatusfunc = Fn2
+    normal! i
+
+    # Test for using a string(variable with a lambda expression)
     &imactivatefunc = string(Fn1)
     &imstatusfunc = string(Fn2)
     normal! i
 
-    assert_equal(3, g:IMactivatefunc_called)
-    assert_equal(6, g:IMstatusfunc_called)
+    assert_equal(4, g:IMactivatefunc_called)
+    assert_equal(8, g:IMstatusfunc_called)
 
     set iminsert=0
     set imactivatefunc=
diff --git a/src/testdir/test_ins_complete.vim b/src/testdir/test_ins_complete.vim
index d39acf4270..d508ba087f 100644
--- a/src/testdir/test_ins_complete.vim
+++ b/src/testdir/test_ins_complete.vim
@@ -885,13 +885,22 @@ func Test_completefunc_callback()
 
   " Using a funcref variable to set 'completefunc'
   let Fn = function('MycompleteFunc1')
+  let &completefunc = Fn
+  new | only
+  call setline(1, 'two')
+  let g:MycompleteFunc1_args = []
+  call feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'two']], g:MycompleteFunc1_args)
+  bw!
+
+  " Using string(funcref_variable) to set 'completefunc'
+  let Fn = function('MycompleteFunc1')
   let &completefunc = string(Fn)
   new | only
   call setline(1, 'two')
   let g:MycompleteFunc1_args = []
   call feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
   call assert_equal([[1, ''], [0, 'two']], g:MycompleteFunc1_args)
-  call assert_fails('let &completefunc = Fn', 'E729:')
   bw!
 
   " Test for using a funcref()
@@ -909,13 +918,22 @@ func Test_completefunc_callback()
 
   " Using a funcref variable to set 'completefunc'
   let Fn = funcref('MycompleteFunc2')
+  let &completefunc = Fn
+  new | only
+  call setline(1, 'four')
+  let g:MycompleteFunc2_args = []
+  call feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'four']], g:MycompleteFunc2_args)
+  bw!
+
+  " Using a string(funcref_variable) to set 'completefunc'
+  let Fn = funcref('MycompleteFunc2')
   let &completefunc = string(Fn)
   new | only
   call setline(1, 'four')
   let g:MycompleteFunc2_args = []
   call feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
   call assert_equal([[1, ''], [0, 'four']], g:MycompleteFunc2_args)
-  call assert_fails('let &completefunc = Fn', 'E729:')
   bw!
 
   " Test for using a lambda function
@@ -932,6 +950,15 @@ func Test_completefunc_callback()
   bw!
 
   " Set 'completefunc' to a lambda expression
+  let &completefunc = {a, b -> MycompleteFunc3(a, b)}
+  new | only
+  call setline(1, 'six')
+  let g:MycompleteFunc3_args = []
+  call feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'six']], g:MycompleteFunc3_args)
+  bw!
+
+  " Set 'completefunc' to string(lambda_expression)
   let &completefunc = '{a, b -> MycompleteFunc3(a, b)}'
   new | only
   call setline(1, 'six')
@@ -942,18 +969,27 @@ func Test_completefunc_callback()
 
   " Set 'completefunc' to a variable with a lambda expression
   let Lambda = {a, b -> MycompleteFunc3(a, b)}
+  let &completefunc = Lambda
+  new | only
+  call setline(1, 'seven')
+  let g:MycompleteFunc3_args = []
+  call feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'seven']], g:MycompleteFunc3_args)
+  bw!
+
+  " Set 'completefunc' to a string(variable with a lambda expression)
+  let Lambda = {a, b -> MycompleteFunc3(a, b)}
   let &completefunc = string(Lambda)
   new | only
   call setline(1, 'seven')
   let g:MycompleteFunc3_args = []
   call feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
   call assert_equal([[1, ''], [0, 'seven']], g:MycompleteFunc3_args)
-  call assert_fails('let &completefunc = Lambda', 'E729:')
   bw!
 
   " Test for using a lambda function with incorrect return value
   let Lambda = {s -> strlen(s)}
-  let &completefunc = string(Lambda)
+  let &completefunc = Lambda
   new | only
   call setline(1, 'eight')
   call feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
@@ -965,7 +1001,7 @@ func Test_completefunc_callback()
 
   call assert_fails("set completefunc=function('abc')", "E700:")
   call assert_fails("set completefunc=funcref('abc')", "E700:")
-  let &completefunc = "{a -> 'abc'}"
+  let &completefunc = {a -> 'abc'}
   call feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
 
   " Vim9 tests
@@ -990,6 +1026,15 @@ func Test_completefunc_callback()
       add(g:LambdaComplete1_args, [findstart, base])
       return findstart ? 0 : []
     enddef
+    &completefunc = (a, b) => LambdaComplete1(a, b)
+    new | only
+    setline(1, 'two')
+    g:LambdaComplete1_args = []
+    feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
+    assert_equal([[1, ''], [0, 'two']], g:LambdaComplete1_args)
+    bw!
+
+    # Test for using a string(lambda)
     &completefunc = '(a, b) => LambdaComplete1(a, b)'
     new | only
     setline(1, 'two')
@@ -1003,6 +1048,15 @@ func Test_completefunc_callback()
             add(g:LambdaComplete2_args, [findstart, base])
             return findstart ? 0 : []
         }
+    &completefunc = Fn
+    new | only
+    setline(1, 'three')
+    g:LambdaComplete2_args = []
+    feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
+    assert_equal([[1, ''], [0, 'three']], g:LambdaComplete2_args)
+    bw!
+
+    # Test for using a string(variable with a lambda expression)
     &completefunc = string(Fn)
     new | only
     setline(1, 'three')
@@ -1045,13 +1099,22 @@ func Test_omnifunc_callback()
 
   " Using a funcref variable to set 'omnifunc'
   let Fn = function('MyomniFunc1')
+  let &omnifunc = Fn
+  new | only
+  call setline(1, 'two')
+  let g:MyomniFunc1_args = []
+  call feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'two']], g:MyomniFunc1_args)
+  bw!
+
+  " Using a string(funcref_variable) to set 'omnifunc'
+  let Fn = function('MyomniFunc1')
   let &omnifunc = string(Fn)
   new | only
   call setline(1, 'two')
   let g:MyomniFunc1_args = []
   call feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
   call assert_equal([[1, ''], [0, 'two']], g:MyomniFunc1_args)
-  call assert_fails('let &omnifunc = Fn', 'E729:')
   bw!
 
   " Test for using a funcref()
@@ -1069,13 +1132,22 @@ func Test_omnifunc_callback()
 
   " Using a funcref variable to set 'omnifunc'
   let Fn = funcref('MyomniFunc2')
+  let &omnifunc = Fn
+  new | only
+  call setline(1, 'four')
+  let g:MyomniFunc2_args = []
+  call feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'four']], g:MyomniFunc2_args)
+  bw!
+
+  " Using a string(funcref_variable) to set 'omnifunc'
+  let Fn = funcref('MyomniFunc2')
   let &omnifunc = string(Fn)
   new | only
   call setline(1, 'four')
   let g:MyomniFunc2_args = []
   call feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
   call assert_equal([[1, ''], [0, 'four']], g:MyomniFunc2_args)
-  call assert_fails('let &omnifunc = Fn', 'E729:')
   bw!
 
   " Test for using a lambda function
@@ -1092,6 +1164,15 @@ func Test_omnifunc_callback()
   bw!
 
   " Set 'omnifunc' to a lambda expression
+  let &omnifunc = {a, b -> MyomniFunc3(a, b)}
+  new | only
+  call setline(1, 'six')
+  let g:MyomniFunc3_args = []
+  call feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'six']], g:MyomniFunc3_args)
+  bw!
+
+  " Set 'omnifunc' to a string(lambda_expression)
   let &omnifunc = '{a, b -> MyomniFunc3(a, b)}'
   new | only
   call setline(1, 'six')
@@ -1102,18 +1183,27 @@ func Test_omnifunc_callback()
 
   " Set 'omnifunc' to a variable with a lambda expression
   let Lambda = {a, b -> MyomniFunc3(a, b)}
+  let &omnifunc = Lambda
+  new | only
+  call setline(1, 'seven')
+  let g:MyomniFunc3_args = []
+  call feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'seven']], g:MyomniFunc3_args)
+  bw!
+
+  " Set 'omnifunc' to a string(variable with a lambda expression)
+  let Lambda = {a, b -> MyomniFunc3(a, b)}
   let &omnifunc = string(Lambda)
   new | only
   call setline(1, 'seven')
   let g:MyomniFunc3_args = []
   call feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
   call assert_equal([[1, ''], [0, 'seven']], g:MyomniFunc3_args)
-  call assert_fails('let &omnifunc = Lambda', 'E729:')
   bw!
 
   " Test for using a lambda function with incorrect return value
   let Lambda = {s -> strlen(s)}
-  let &omnifunc = string(Lambda)
+  let &omnifunc = Lambda
   new | only
   call setline(1, 'eight')
   call feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
@@ -1125,7 +1215,7 @@ func Test_omnifunc_callback()
 
   call assert_fails("set omnifunc=function('abc')", "E700:")
   call assert_fails("set omnifunc=funcref('abc')", "E700:")
-  let &omnifunc = "{a -> 'abc'}"
+  let &omnifunc = {a -> 'abc'}
   call feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
 
   " Vim9 tests
@@ -1150,6 +1240,15 @@ func Test_omnifunc_callback()
       add(g:MyomniFunc2_args, [findstart, base])
       return findstart ? 0 : []
     enddef
+    &omnifunc = (a, b) => MyomniFunc2(a, b)
+    new | only
+    setline(1, 'two')
+    g:MyomniFunc2_args = []
+    feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
+    assert_equal([[1, ''], [0, 'two']], g:MyomniFunc2_args)
+    bw!
+
+    # Test for using a string(lambda)
     &omnifunc = '(a, b) => MyomniFunc2(a, b)'
     new | only
     setline(1, 'two')
@@ -1160,6 +1259,15 @@ func Test_omnifunc_callback()
 
     # Test for using a variable with a lambda expression
     var Fn: func = (a, b) => MyomniFunc2(a, b)
+    &omnifunc = Fn
+    new | only
+    setline(1, 'three')
+    g:MyomniFunc2_args = []
+    feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
+    assert_equal([[1, ''], [0, 'three']], g:MyomniFunc2_args)
+    bw!
+
+    # Test for using a string(variable with a lambda expression)
     &omnifunc = string(Fn)
     new | only
     setline(1, 'three')
@@ -1202,13 +1310,22 @@ func Test_thesaurusfunc_callback()
 
   " Using a funcref variable to set 'thesaurusfunc'
   let Fn = function('MytsrFunc1')
+  let &thesaurusfunc = Fn
+  new | only
+  call setline(1, 'two')
+  let g:MytsrFunc1_args = []
+  call feedkeys("A\<C-X>\<C-T>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'two']], g:MytsrFunc1_args)
+  bw!
+
+  " Using a string(funcref_variable) to set 'thesaurusfunc'
+  let Fn = function('MytsrFunc1')
   let &thesaurusfunc = string(Fn)
   new | only
   call setline(1, 'two')
   let g:MytsrFunc1_args = []
   call feedkeys("A\<C-X>\<C-T>\<Esc>", 'x')
   call assert_equal([[1, ''], [0, 'two']], g:MytsrFunc1_args)
-  call assert_fails('let &thesaurusfunc = Fn', 'E729:')
   bw!
 
   " Test for using a funcref()
@@ -1226,13 +1343,22 @@ func Test_thesaurusfunc_callback()
 
   " Using a funcref variable to set 'thesaurusfunc'
   let Fn = funcref('MytsrFunc2')
+  let &thesaurusfunc = Fn
+  new | only
+  call setline(1, 'four')
+  let g:MytsrFunc2_args = []
+  call feedkeys("A\<C-X>\<C-T>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'four']], g:MytsrFunc2_args)
+  bw!
+
+  " Using a string(funcref_variable) to set 'thesaurusfunc'
+  let Fn = funcref('MytsrFunc2')
   let &thesaurusfunc = string(Fn)
   new | only
   call setline(1, 'four')
   let g:MytsrFunc2_args = []
   call feedkeys("A\<C-X>\<C-T>\<Esc>", 'x')
   call assert_equal([[1, ''], [0, 'four']], g:MytsrFunc2_args)
-  call assert_fails('let &thesaurusfunc = Fn', 'E729:')
   bw!
 
   " Test for using a lambda function
@@ -1249,6 +1375,15 @@ func Test_thesaurusfunc_callback()
   bw!
 
   " Set 'thesaurusfunc' to a lambda expression
+  let &thesaurusfunc = {a, b -> MytsrFunc3(a, b)}
+  new | only
+  call setline(1, 'six')
+  let g:MytsrFunc3_args = []
+  call feedkeys("A\<C-X>\<C-T>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'six']], g:MytsrFunc3_args)
+  bw!
+
+  " Set 'thesaurusfunc' to a string(lambda expression)
   let &thesaurusfunc = '{a, b -> MytsrFunc3(a, b)}'
   new | only
   call setline(1, 'six')
@@ -1259,18 +1394,27 @@ func Test_thesaurusfunc_callback()
 
   " Set 'thesaurusfunc' to a variable with a lambda expression
   let Lambda = {a, b -> MytsrFunc3(a, b)}
+  let &thesaurusfunc = Lambda
+  new | only
+  call setline(1, 'seven')
+  let g:MytsrFunc3_args = []
+  call feedkeys("A\<C-X>\<C-T>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'seven']], g:MytsrFunc3_args)
+  bw!
+
+  " Set 'thesaurusfunc' to a string(variable with a lambda expression)
+  let Lambda = {a, b -> MytsrFunc3(a, b)}
   let &thesaurusfunc = string(Lambda)
   new | only
   call setline(1, 'seven')
   let g:MytsrFunc3_args = []
   call feedkeys("A\<C-X>\<C-T>\<Esc>", 'x')
   call assert_equal([[1, ''], [0, 'seven']], g:MytsrFunc3_args)
-  call assert_fails('let &thesaurusfunc = Lambda', 'E729:')
   bw!
 
   " Test for using a lambda function with incorrect return value
   let Lambda = {s -> strlen(s)}
-  let &thesaurusfunc = string(Lambda)
+  let &thesaurusfunc = Lambda
   new | only
   call setline(1, 'eight')
   call feedkeys("A\<C-X>\<C-T>\<Esc>", 'x')
@@ -1282,7 +1426,7 @@ func Test_thesaurusfunc_callback()
 
   call assert_fails("set thesaurusfunc=function('abc')", "E700:")
   call assert_fails("set thesaurusfunc=funcref('abc')", "E700:")
-  let &thesaurusfunc = "{a -> 'abc'}"
+  let &thesaurusfunc = {a -> 'abc'}
   call feedkeys("A\<C-X>\<C-T>\<Esc>", 'x')
 
   " Vim9 tests
@@ -1307,6 +1451,15 @@ func Test_thesaurusfunc_callback()
       add(g:MytsrFunc2_args, [findstart, base])
       return findstart ? 0 : []
     enddef
+    &thesaurusfunc = (a, b) => MytsrFunc2(a, b)
+    new | only
+    setline(1, 'two')
+    g:MytsrFunc2_args = []
+    feedkeys("A\<C-X>\<C-T>\<Esc>", 'x')
+    assert_equal([[1, ''], [0, 'two']], g:MytsrFunc2_args)
+    bw!
+
+    # Test for using a string(lambda)
     &thesaurusfunc = '(a, b) => MytsrFunc2(a, b)'
     new | only
     setline(1, 'two')
@@ -1317,6 +1470,15 @@ func Test_thesaurusfunc_callback()
 
     # Test for using a variable with a lambda expression
     var Fn: func = (a, b) => MytsrFunc2(a, b)
+    &thesaurusfunc = Fn
+    new | only
+    setline(1, 'three')
+    g:MytsrFunc2_args = []
+    feedkeys("A\<C-X>\<C-T>\<Esc>", 'x')
+    assert_equal([[1, ''], [0, 'three']], g:MytsrFunc2_args)
+    bw!
+
+    # Test for using a string(variable with a lambda expression)
     &thesaurusfunc = string(Fn)
     new | only
     setline(1, 'three')
diff --git a/src/testdir/test_tagfunc.vim b/src/testdir/test_tagfunc.vim
index 1a1226ace1..7f16fb25e5 100644
--- a/src/testdir/test_tagfunc.vim
+++ b/src/testdir/test_tagfunc.vim
@@ -140,12 +140,19 @@ func Test_tagfunc_callback()
 
   " Using a funcref variable to set 'tagfunc'
   let Fn = function('MytagFunc1')
+  let &tagfunc = Fn
+  new | only
+  let g:MytagFunc1_args = []
+  call assert_fails('tag a12', 'E433:')
+  call assert_equal(['a12', '', {}], g:MytagFunc1_args)
+
+  " Using a string(funcref_variable) to set 'tagfunc'
+  let Fn = function('MytagFunc1')
   let &tagfunc = string(Fn)
   new | only
   let g:MytagFunc1_args = []
   call assert_fails('tag a12', 'E433:')
   call assert_equal(['a12', '', {}], g:MytagFunc1_args)
-  call assert_fails('let &tagfunc = Fn', 'E729:')
 
   " Test for using a funcref()
   func MytagFunc2(pat, flags, info)
@@ -160,12 +167,19 @@ func Test_tagfunc_callback()
 
   " Using a funcref variable to set 'tagfunc'
   let Fn = funcref('MytagFunc2')
+  let &tagfunc = Fn
+  new | only
+  let g:MytagFunc2_args = []
+  call assert_fails('tag a14', 'E433:')
+  call assert_equal(['a14', '', {}], g:MytagFunc2_args)
+
+  " Using a string(funcref_variable) to set 'tagfunc'
+  let Fn = funcref('MytagFunc2')
   let &tagfunc = string(Fn)
   new | only
   let g:MytagFunc2_args = []
   call assert_fails('tag a14', 'E433:')
   call assert_equal(['a14', '', {}], g:MytagFunc2_args)
-  call assert_fails('let &tagfunc = Fn', 'E729:')
 
   " Test for using a script local function
   set tagfunc=<SID>ScriptLocalTagFunc
@@ -176,6 +190,14 @@ func Test_tagfunc_callback()
 
   " Test for using a script local funcref variable
   let Fn = function("s:ScriptLocalTagFunc")
+  let &tagfunc= Fn
+  new | only
+  let g:ScriptLocalFuncArgs = []
+  call assert_fails('tag a16', 'E433:')
+  call assert_equal(['a16', '', {}], g:ScriptLocalFuncArgs)
+
+  " Test for using a string(script local funcref variable)
+  let Fn = function("s:ScriptLocalTagFunc")
   let &tagfunc= string(Fn)
   new | only
   let g:ScriptLocalFuncArgs = []
@@ -194,6 +216,13 @@ func Test_tagfunc_callback()
   call assert_equal(['a17', '', {}], g:MytagFunc3_args)
 
   " Set 'tagfunc' to a lambda expression
+  let &tagfunc = {a, b, c -> MytagFunc3(a, b, c)}
+  new | only
+  let g:MytagFunc3_args = []
+  call assert_fails('tag a18', 'E433:')
+  call assert_equal(['a18', '', {}], g:MytagFunc3_args)
+
+  " Set 'tagfunc' to a string(lambda expression)
   let &tagfunc = '{a, b, c -> MytagFunc3(a, b, c)}'
   new | only
   let g:MytagFunc3_args = []
@@ -202,12 +231,19 @@ func Test_tagfunc_callback()
 
   " Set 'tagfunc' to a variable with a lambda expression
   let Lambda = {a, b, c -> MytagFunc3(a, b, c)}
+  let &tagfunc = Lambda
+  new | only
+  let g:MytagFunc3_args = []
+  call assert_fails("tag a19", "E433:")
+  call assert_equal(['a19', '', {}], g:MytagFunc3_args)
+
+  " Set 'tagfunc' to a string(variable with a lambda expression)
+  let Lambda = {a, b, c -> MytagFunc3(a, b, c)}
   let &tagfunc = string(Lambda)
   new | only
   let g:MytagFunc3_args = []
   call assert_fails("tag a19", "E433:")
   call assert_equal(['a19', '', {}], g:MytagFunc3_args)
-  call assert_fails('let &tagfunc = Lambda', 'E729:')
 
   " Test for using a lambda function with incorrect return value
   let Lambda = {s -> strlen(s)}
@@ -244,6 +280,13 @@ func Test_tagfunc_callback()
       g:MytagFunc2_args = [pat, flags, info]
       return null
     enddef
+    &tagfunc = (a, b, c) => MytagFunc2(a, b, c)
+    new | only
+    g:MytagFunc2_args = []
+    assert_fails('tag a20', 'E433:')
+    assert_equal(['a20', '', {}], g:MytagFunc2_args)
+
+    # Test for using a string(lambda)
     &tagfunc = '(a, b, c) => MytagFunc2(a, b, c)'
     new | only
     g:MytagFunc2_args = []
@@ -252,6 +295,13 @@ func Test_tagfunc_callback()
 
     # Test for using a variable with a lambda expression
     var Fn: func = (a, b, c) => MytagFunc2(a, b, c)
+    &tagfunc = Fn
+    new | only
+    g:MytagFunc2_args = []
+    assert_fails('tag a30', 'E433:')
+    assert_equal(['a30', '', {}], g:MytagFunc2_args)
+
+    # Test for using a variable with a lambda expression
     &tagfunc = string(Fn)
     new | only
     g:MytagFunc2_args = []