patch 8.2.1680: Vim9: line number for compare error is wrong

Problem:    Vim9: line number for compare error is wrong.
Solution:   Set SOURCING_LNUM. (closes #6936)
diff --git a/src/testdir/test_vim9_expr.vim b/src/testdir/test_vim9_expr.vim
index 84e8cb3..b09242e 100644
--- a/src/testdir/test_vim9_expr.vim
+++ b/src/testdir/test_vim9_expr.vim
@@ -481,6 +481,7 @@
   set noignorecase
 
   CheckDefFailure(["let x = 'a' == xxx"], 'E1001:', 1)
+  CheckDefExecFailure(['let items: any', 'eval 1', 'eval 2', 'if items == []', 'endif'], 'E691:', 4)
 
   let bb = 0z3f
   assert_equal(true, 0z3f == bb)