patch 8.2.0185: Vim9 script: cannot use "if has()" to skip lines

Problem:    Vim9 script: cannot use "if has()" to skip lines.
Solution:   Evaluate constant expression at runtime.
diff --git a/src/testdir/test_vim9_script.vim b/src/testdir/test_vim9_script.vim
index 09bf324..749c264 100644
--- a/src/testdir/test_vim9_script.vim
+++ b/src/testdir/test_vim9_script.vim
@@ -368,5 +368,35 @@
 EOF
 endfunc
 
+def HasEval()
+  if has('eval')
+    echo 'yes'
+  else
+    echo 'no'
+  endif
+enddef
+
+def HasNothing()
+  if has('nothing')
+    echo 'yes'
+  else
+    echo 'no'
+  endif
+enddef
+
+def Test_compile_const_expr()
+  assert_equal("\nyes", execute('call HasEval()'))
+  let instr = execute('disassemble HasEval')
+  call assert_match('PUSHS "yes"', instr)
+  call assert_notmatch('PUSHS "no"', instr)
+  call assert_notmatch('JUMP', instr)
+
+  assert_equal("\nno", execute('call HasNothing()'))
+  instr = execute('disassemble HasNothing')
+  call assert_notmatch('PUSHS "yes"', instr)
+  call assert_match('PUSHS "no"', instr)
+  call assert_notmatch('JUMP', instr)
+enddef
+
 
 " vim: ts=8 sw=2 sts=2 expandtab tw=80 fdm=marker