From 0f2ead02c87400c87343e24f2687d64f527ad572 Mon Sep 17 00:00:00 2001
From: zeertzjq <zeertzjq@outlook.com>
Date: Mon, 3 Oct 2022 22:54:23 +0800
Subject: [PATCH 1/2] vim-patch:8.2.2316: Vim9: cannot list a lambda function

Problem:    Vim9: cannot list a lambda function.
Solution:   Support the <lambda>9 notation, like :disassemble. (closes vim/vim#7634)
https://github.com/vim/vim/commit/b657198cb30765468451d7f68fce49b5b4000c5d
---
 src/nvim/eval/userfunc.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/nvim/eval/userfunc.c b/src/nvim/eval/userfunc.c
index 72d6a1394e..b0a56c4440 100644
--- a/src/nvim/eval/userfunc.c
+++ b/src/nvim/eval/userfunc.c
@@ -1983,7 +1983,14 @@ void ex_function(exarg_T *eap)
   // s:func      script-local function name
   // g:func      global function name, same as "func"
   p = eap->arg;
-  name = (char *)trans_function_name(&p, eap->skip, TFN_NO_AUTOLOAD, &fudi, NULL);
+  if (strncmp(p, "<lambda>", 8) == 0) {
+    p += 8;
+    (void)getdigits(&p, false, 0);
+    name = xstrndup(eap->arg, (size_t)(p - eap->arg));
+    CLEAR_FIELD(fudi);
+  } else {
+    name = (char *)trans_function_name(&p, eap->skip, TFN_NO_AUTOLOAD, &fudi, NULL);
+  }
   paren = (vim_strchr(p, '(') != NULL);
   if (name == NULL && (fudi.fd_dict == NULL || !paren) && !eap->skip) {
     // Return on an invalid expression in braces, unless the expression

From 71497c164db3180bbec539765f987b483662f73f Mon Sep 17 00:00:00 2001
From: zeertzjq <zeertzjq@outlook.com>
Date: Tue, 4 Oct 2022 07:31:06 +0800
Subject: [PATCH 2/2] test: add test for :function followed by <lambda>

---
 test/functional/vimscript/eval_spec.lua | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/test/functional/vimscript/eval_spec.lua b/test/functional/vimscript/eval_spec.lua
index d4fa7afe89..1fbdedb815 100644
--- a/test/functional/vimscript/eval_spec.lua
+++ b/test/functional/vimscript/eval_spec.lua
@@ -17,6 +17,7 @@ local clear = helpers.clear
 local eq = helpers.eq
 local exc_exec = helpers.exc_exec
 local exec = helpers.exec
+local exec_capture = helpers.exec_capture
 local eval = helpers.eval
 local command = helpers.command
 local write_file = helpers.write_file
@@ -247,3 +248,16 @@ describe("uncaught exception", function()
     eq('123', eval('result'))
   end)
 end)
+
+describe('lambda function', function()
+  before_each(clear)
+
+  it('can be shown using :function followed by <lambda> #20466', function()
+    command('let A = {-> 1}')
+    local num = exec_capture('echo A'):match("function%('<lambda>(%d+)'%)")
+    eq(([[
+   function <lambda>%s(...)
+1  return 1
+   endfunction]]):format(num), exec_capture(('function <lambda>%s'):format(num)))
+  end)
+end)