From e4a450a87ba532cbfe1c4e97cac378eaafc3ae39 Mon Sep 17 00:00:00 2001
From: Christian Brabandt <cb@256bit.org>
Date: Fri, 8 Dec 2023 20:57:38 +0100
Subject: [PATCH] patch 9.0.2157: Vim9: incorrectly parses :def func
 definitions

Problem:  Vim9: incorrectly parses :def func definitions
Solution: check for more context when parsing function args

Signed-off-by: Christian Brabandt <cb@256bit.org>
Incorrectly parses def function definitions

Vim currently allows to define the following vim9 function:
  def Func(f=
  )
  enddef

It currently thinks a Lambda is following the `=` but it doesn't check,
that there is actually an expression following. So when such a think is
encountered, remember that an expression should be following.

If no expression is coming in the next few lines, fail parsing the
function arguments, which will Vim no longer accept such a function.

Signed-off-by: Christian Brabandt <cb@256bit.org>
---
 src/testdir/test_vim9_func.vim | 7 +++++++
 src/userfunc.c                 | 9 ++++++++-
 src/version.c                  | 2 ++
 3 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/src/testdir/test_vim9_func.vim b/src/testdir/test_vim9_func.vim
index 47b23e85e..27585a904 100644
--- a/src/testdir/test_vim9_func.vim
+++ b/src/testdir/test_vim9_func.vim
@@ -861,6 +861,13 @@ def Test_func_with_comments()
   END
   v9.CheckScriptFailure(lines, 'E125:', 1)
 
+  lines =<< trim END
+      def Func(f=
+      )
+      enddef
+  END
+  v9.CheckScriptFailure(lines, 'E125:', 2)
+
   lines =<< trim END
       def Func(
         arg: string# comment
diff --git a/src/userfunc.c b/src/userfunc.c
index 33e73a9a5..e2b1bc322 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -243,6 +243,7 @@ get_function_args(
     int		c;
     int		any_default = FALSE;
     char_u	*whitep = *argp;
+    int		need_expr = FALSE;
 
     if (newargs != NULL)
 	ga_init2(newargs, sizeof(char_u *), 3);
@@ -282,7 +283,7 @@ get_function_args(
 		semsg(_(e_invalid_argument_str), *argp);
 	    goto err_ret;
 	}
-	if (*p == endchar)
+	if (*p == endchar && !need_expr)
 	    break;
 
 	if (p[0] == '.' && p[1] == '.' && p[2] == '.')
@@ -435,6 +436,8 @@ get_function_args(
 			if (ga_grow(default_args, 1) == FAIL)
 			    goto err_ret;
 
+			if (need_expr)
+			    need_expr = FALSE;
 			// trim trailing whitespace
 			while (p > expr && VIM_ISWHITE(p[-1]))
 			    p--;
@@ -453,7 +456,11 @@ get_function_args(
 		    }
 		}
 		else
+		{
 		    mustend = TRUE;
+		    if (*skipwhite(p) == NUL)
+			need_expr = TRUE;
+		}
 	    }
 	    else if (any_default)
 	    {
diff --git a/src/version.c b/src/version.c
index f7d6cbcb6..919f42f2d 100644
--- a/src/version.c
+++ b/src/version.c
@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2157,
 /**/
     2156,
 /**/