patch 9.1.0646: Vim9: imported function may not be found

Problem:  Vim9: imported function may not be found
Solution: Try to find the function by name (Ernie Rael)

fixes: #15381
closes: #15382

Signed-off-by: Ernie Rael <errael@raelity.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/userfunc.c b/src/userfunc.c
index e44397d..1c58b01 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -2212,6 +2212,48 @@
 }
 
 /*
+ * Find a function by name, return pointer to it.
+ * The name may be a local script variable, VAR_FUNC. or it may be a fully
+ * qualified import name such as 'i_imp.FuncName'.
+ *
+ * When VAR_FUNC, the import might either direct or autoload.
+ * When 'i_imp.FuncName' it is direct, autoload is rewritten as i_imp#FuncName
+ * in f_call and subsequently found.
+ */
+    static ufunc_T *
+find_func_imported(char_u *name, int flags)
+{
+    ufunc_T	*func = NULL;
+    char_u	*dot = name; // Find a dot, '.', in the name
+
+    // Either run into '.' or the end of the string
+    while (eval_isnamec(*dot))
+	++dot;
+
+    if (*dot == '.')
+    {
+	imported_T *import = find_imported(name, dot - name, FALSE);
+	if (import != NULL)
+	    func = find_func_with_sid(dot + 1, import->imp_sid);
+    }
+    else if (*dot == NUL) // looking at the entire string
+    {
+	hashtab_T *ht = get_script_local_ht();
+	if (ht != NULL)
+	{
+	    hashitem_T *hi = hash_find(ht, name);
+	    if (!HASHITEM_EMPTY(hi))
+	    {
+		dictitem_T *di = HI2DI(hi);
+		if (di->di_tv.v_type == VAR_FUNC)
+		    func = find_func_even_dead(di->di_tv.vval.v_string, flags);
+	    }
+	}
+    }
+    return func;
+}
+
+/*
  * Find a function by name, return pointer to it in ufuncs.
  * When "flags" has FFED_IS_GLOBAL don't find script-local or imported
  * functions.
@@ -2260,8 +2302,15 @@
     }
 
     // Find autoload function if this is an autoload script.
-    return find_func_with_prefix(name[0] == 's' && name[1] == ':'
+    func = find_func_with_prefix(name[0] == 's' && name[1] == ':'
 				       ? name + 2 : name, current_sctx.sc_sid);
+    if (func != NULL)
+	return func;
+
+    // Find a script-local "VAR_FUNC" or i_"imp.Func", so vim9script).
+    if (in_vim9script())
+	func = find_func_imported(name, flags);
+    return func;
 }
 
 /*