From 62a6923470827acbf124df41134ae6df52f334e6 Mon Sep 17 00:00:00 2001
From: Bram Moolenaar <Bram@vim.org>
Date: Tue, 24 Jan 2023 15:07:04 +0000
Subject: patch 9.0.1240: cannot access a private object member in a lambda

Problem:    Cannot access a private object member in a lambda defined inside
            the class.
Solution:   Go up the context stack to find the class. (closes #11866)
---
 src/proto/vim9class.pro         |  1 +
 src/testdir/test_vim9_class.vim | 18 ++++++++++++++++++
 src/version.c                   |  2 ++
 src/vim9class.c                 | 13 +++++++++++++
 src/vim9expr.c                  |  2 +-
 5 files changed, 35 insertions(+), 1 deletion(-)

(limited to 'src')

diff --git a/src/proto/vim9class.pro b/src/proto/vim9class.pro
index 74d33c00c..13a643dd5 100644
--- a/src/proto/vim9class.pro
+++ b/src/proto/vim9class.pro
@@ -7,6 +7,7 @@ void ex_type(exarg_T *eap);
 int class_object_index(char_u **arg, typval_T *rettv, evalarg_T *evalarg, int verbose);
 ufunc_T *find_class_func(char_u **arg);
 int class_member_index(char_u *name, size_t len, class_T **cl_ret, cctx_T *cctx);
+int inside_class(cctx_T *cctx_arg, class_T *cl);
 void copy_object(typval_T *from, typval_T *to);
 void object_unref(object_T *obj);
 void copy_class(typval_T *from, typval_T *to);
diff --git a/src/testdir/test_vim9_class.vim b/src/testdir/test_vim9_class.vim
index a3fdbdb9c..389213680 100644
--- a/src/testdir/test_vim9_class.vim
+++ b/src/testdir/test_vim9_class.vim
@@ -645,6 +645,24 @@ def Test_class_member()
   END
   v9.CheckScriptSuccess(lines)
 
+  # access private member in lambda
+  lines =<< trim END
+      vim9script
+
+      class Foo
+        this._x: number = 0
+
+        def Add(n: number): number
+          const F = (): number => this._x + n
+          return F()
+        enddef
+      endclass
+
+      var foo = Foo.new()
+      assert_equal(5, foo.Add(5))
+  END
+  v9.CheckScriptSuccess(lines)
+
   # check shadowing
   lines =<< trim END
       vim9script
diff --git a/src/version.c b/src/version.c
index f21a1887a..4a3355c0b 100644
--- a/src/version.c
+++ b/src/version.c
@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1240,
 /**/
     1239,
 /**/
diff --git a/src/vim9class.c b/src/vim9class.c
index 0262e025d..484500576 100644
--- a/src/vim9class.c
+++ b/src/vim9class.c
@@ -1387,6 +1387,19 @@ class_member_index(char_u *name, size_t len, class_T **cl_ret, cctx_T *cctx)
     return -1;
 }
 
+/*
+ * Return TRUE if current context "cctx_arg" is inside class "cl".
+ * Return FALSE if not.
+ */
+    int
+inside_class(cctx_T *cctx_arg, class_T *cl)
+{
+    for (cctx_T *cctx = cctx_arg; cctx != NULL; cctx = cctx->ctx_outer)
+	if (cctx->ctx_ufunc != NULL && cctx->ctx_ufunc->uf_class == cl)
+	    return TRUE;
+    return FALSE;
+}
+
 /*
  * Make a copy of an object.
  */
diff --git a/src/vim9expr.c b/src/vim9expr.c
index 95c6d7db0..1034f64b0 100644
--- a/src/vim9expr.c
+++ b/src/vim9expr.c
@@ -357,7 +357,7 @@ compile_class_object_index(cctx_T *cctx, char_u **arg, type_T *type)
 	    ocmember_T *m = &cl->class_obj_members[i];
 	    if (STRNCMP(name, m->ocm_name, len) == 0 && m->ocm_name[len] == NUL)
 	    {
-		if (*name == '_' && cctx->ctx_ufunc->uf_class != cl)
+		if (*name == '_' && !inside_class(cctx, cl))
 		{
 		    semsg(_(e_cannot_access_private_member_str), m->ocm_name);
 		    return FAIL;
-- 
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