The trup on בְּיוֹם מָחָר supports Rashi

Summary: Shadal sides with Ibn Ezra and Rashbam, that Yaakov's righteousness would testify for him in the future, when Lavan comes to inspect. But he says that this correct peshat is at odds with the trup. I consider this.

Post:  The pasuk in Vayeitzei (30:33), with Rashi:

33. And my righteousness will testify for me at a future date for it will come upon my wages before you. Whatever is not speckled or spotted among the goats or brown among the sheep [shall be counted as] stolen with me."		לג. וְעָנְתָה בִּי צִדְקָתִי בְּיוֹם מָחָר כִּי תָבוֹא עַל שְׂכָרִי לְפָנֶיךָ כֹּל אֲשֶׁר אֵינֶנּוּ נָקֹד וְטָלוּא בָּעִזִּים וְחוּם בַּכְּשָׂבִים גָּנוּב הוּא אִתִּי:
And my righteousness will testify for me, etc.: If you suspect me of taking anything of yours, my righteousness will testify for me. My righteousness will come and testify about my wages before you, that you will find in my flock only speckled and spotted ones, and whatever you find among them that is not speckled or spotted or brown, I have obviously stolen from you, and [only] through theft is it in my possession.		וענתה בי וגו': אם תחשדני שאני נוטל משלך כלום, תענה בי צדקתי, כי תבא צדקתי ותעיד על שכרי לפניך, שלא תמצא בעדרי כי אם נקודים וטלואים, וכל שתמצא בהן שאינו נקוד או טלוא או חום בידוע שגנבתיו לך, ובגניבה הוא שרוי אצלי:

This is as opposed to Ibn Ezra:

וענתה בי צדקתי -לפניך היא תעיד כאשר תבא ותראה שכרי. והוא העדר, שאפריד לנפשי אם לא מצאת התישים והעזים עקודים נקודים וברודים והכבשים שחורים - גנוב הוא אתי, והנה אתה הסירות מן הצאן כל עקוד ונקוד וברוד בעזים וכל חום בכשבים.

I think the difference is that, according to Rashi, Yaakov's present righteousness is testifying now, about what would happen if Lavan would inspect.  According to Ibn Ezra, in the future, at the time of Lavan's inspection, Yaakov's righteousness will be doing the testifying, because nothing will be amiss.

The difference, then, is how to attach the words בְּיוֹם מָחָר. If we pause immediately beforehand, then we have וְעָנְתָה בִּי צִדְקָתִי today, that on the יוֹם מָחָר, that is, כִּי תָבוֹא עַל שְׂכָרִי לְפָנֶיךָ, all will be found good and proper. If we pause immediately after, then we have וְעָנְתָה בִּי צִדְקָתִי בְּיוֹם מָחָר as a single unit, that on that future day, the יוֹם מָחָר, my righteousness will be testifying.

(Also, this is perhaps a distinction between כי meaning 'that' or 'when'.)

Shadal writes to side with Ibn Ezra:

"My righteousness will witness before you, when you come to inspect my wages (Ibn Ezra and Rashbam). And so is correct, even though it would then be proper to have the trup of וְעָנְתָה with telisha ketana,  kadma ve'azla, mercha tevir."

See image above, third line, for the suggested trup on each word.

Contrast this with the actual trup.

How does the trup tell us anything? Well, the tipcha on שכרי and the zakef on מחר both subdivide clauses that end with etnachta. Since they are on the same level of subdivision, the one appearing earlier in the pasuk takes effect first. And the pashta on צדקתי divides the sub-clause ending in the מחר. Therefore, this gives us:

וְעָנְתָה בִּי צִדְקָתִי | בְּיוֹם מָחָר ||  כִּי תָבוֹא עַל שְׂכָרִי | לְפָנֶיךָ

with the major dichotomy marked by || and the minor dichotomies marked by |

This seems perfectly in line with Ibn Ezra, I would think.

What about Shadal's suggested trup? Well, the tipcha at שכרי is the only first level dividing trup. The tevir on מחר subdivides that. And the geresh at צדקתי subdivides that. Therefore, this gives us:

וְעָנְתָה בִּי צִדְקָתִי | בְּיוֹם מָחָר || כִּי תָבוֹא עַל שְׂכָרִי ||| לְפָנֶיךָ

with decreasing levels of dichotomy as the number of bars decrease. This, also, would be in line with Ibn Ezra. So it seems that either Shadal is incorrect or I am missing something.

So what is Shadal's point? I think he was trying to argue in favor of a weaker division between the word מחר and what follows. It is not the division between וְעָנְתָה בִּי צִדְקָתִי and what follows that matters, but between מחר and what follows.

According to the weaker division, the entire first half of the pasuk is joined together. And so, we have at first: "And my righteousness will testify for me on the future day on which you come to investigate my wages..." And once it all sits together, then we can subdivide at will.

According to the stronger division at מחר (which is the actual trup), he is saying that his righteousness is testifying about me regarding a future day | that, when you come to investigate my wages..."

I am not entirely certain I agree with Shadal's assessment. But if we grant it, then this is another instance in which Ibn Ezra and Rashbam (and Shadal) explain peshat in a pasuk against the trup. There are other examples. At the same time, I don't know that we could say that Ibn Ezra and Rashbam knew that they were definitively arguing against the trup. Another takeaway from this would be that the trup supports Rashi.