vbscript: Improve invalid argument checks in Right().

dlls/vbscript/global.c

@@ -1348,6 +1348,19 @@ static HRESULT Global_Right(BuiltinDisp *This, VARIANT *args, unsigned args_cnt,
 
     TRACE("(%s %s)\n", debugstr_variant(args), debugstr_variant(args+1));
 
+    if(V_VT(args+1) == VT_NULL)
+        return MAKE_VBSERROR(VBSE_ILLEGAL_NULL_USE);
+
+    hres = to_int(args+1, &len);
+    if(FAILED(hres))
+        return hres;
+
+    if(len < 0)
+        return MAKE_VBSERROR(VBSE_ILLEGAL_FUNC_CALL);
+
+    if(V_VT(args) == VT_NULL)
+        return return_null(res);
+
     if(V_VT(args) == VT_BSTR) {
         str = V_BSTR(args);
     }else {
@@ -1357,15 +1370,6 @@ static HRESULT Global_Right(BuiltinDisp *This, VARIANT *args, unsigned args_cnt,
         str = conv_str;
     }
 
-    hres = to_int(args+1, &len);
-    if(FAILED(hres))
-        return hres;
-
-    if(len < 0) {
-        FIXME("len = %d\n", len);
-        return E_FAIL;
-    }
-
     str_len = SysStringLen(str);
     if(len > str_len)
         len = str_len;

dlls/vbscript/tests/api.vbs

@@ -842,7 +842,28 @@ TestRight "test", 0, ""
 TestRight 123, 2, "23"
 TestRight "test", "3", "est"
 TestRight 123, "2", "23"
+TestRight empty, 0, ""
+TestRight empty, 1, ""
+TestRight "test", empty, ""
+TestRight "test", empty, ""
 if isEnglishLang then TestRight true, 2, "ue"
+call Right(null, 0)
+call ok(getVT(Right(null, 0)) = "VT_NULL", "getVT(Right(null, 0)) = " & getVT(Right(null, 0)))
+call ok(getVT(Right(null, 1)) = "VT_NULL", "getVT(Right(null, 1)) = " & getVT(Right(null, 1)))
+
+sub TestRightError()
+    on error resume next
+    call Err.clear()
+    call Right("test", -1)
+    call ok(Err.number = 5, "Err.number = " & Err.number)
+    call Err.clear()
+    call Right(null, -1)
+    call ok(Err.number = 5, "Err.number = " & Err.number)
+    call Err.clear()
+    call Right("test", null)
+    call ok(Err.number = 94, "Err.number = " & Err.number)
+end sub
+call TestRightError()
 
 Sub TestTrim(str, exstr)
     Call ok(Trim(str) = exstr, "Trim(" & str & ") = " & Trim(str))