patch 9.1.0369: Vim9: problem when importing autoloaded scripts

Problem:  Vim9: problem when importing autoloaded scripts
Solution: In `:def` handle storing to vim9 autoload export
          (Ernie Rael)

Problem occurs when `import autoload ./.../autoload/...`. The autoload
in the specified path causes the use of an autoload_prefix which combines
with the `import autoload` to create trouble.

In `generate_store_var()` `case dest_script` use ISN_STOREEXPORT,
when needed, instead of ISN_STORES. When executing ISN_STOREEXPORT,
check for autoload_prefix.

fixes: #14606
closes: #14615

Signed-off-by: Ernie Rael <errael@raelity.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
Signed-off-by: Yegappan Lakshmanan <yegappan@yahoo.com>
diff --git a/src/testdir/test_vim9_disassemble.vim b/src/testdir/test_vim9_disassemble.vim
index 92a4ff2..c74cce4 100644
--- a/src/testdir/test_vim9_disassemble.vim
+++ b/src/testdir/test_vim9_disassemble.vim
@@ -381,6 +381,34 @@
   v9.CheckScriptSuccess(lines)
 enddef
 
+def Test_disassemble_import_autoload_autoload()
+  mkdir('Xauto_auto/autoload', 'pR')
+  var lines =<< trim END
+    vim9script
+    export const val = 11
+  END
+  writefile(lines, 'Xauto_auto/autoload/Xauto_vars_f1.vim')
+
+  lines =<< trim END
+    vim9script
+
+    import autoload './Xauto_auto/autoload/Xauto_vars_f1.vim' as f1
+    def F()
+        f1.val = 13
+    enddef
+    var res = execute('disass F')
+
+    assert_match('<SNR>\d*_F.*' ..
+      'f1.val = 13\_s*' ..
+      '\d PUSHNR 13\_s*' ..
+      '\d SOURCE .*/Xauto_auto/autoload/Xauto_vars_f1.vim\_s*' ..
+      '\d STOREEXPORT val in .*/Xauto_auto/autoload/Xauto_vars_f1.vim\_s*' ..
+      '\d RETURN void',
+      res)
+  END
+  v9.CheckScriptSuccess(lines)
+enddef
+
 def s:ScriptFuncStore()
   var localnr = 1
   localnr = 2