Help me understand 言わんこっちゃない


I don't understand this whatsoever:

> やれやれ
>
> だから **言わんこっちゃない**

especially the bolded part. What real words does that come from?

Context is that the main character got a cold from staying outside all night;
his friend then tells him this.




> 「言{い}わん **こっちゃ** ない」

is the common colloquial form of:

> 「言わない **ことでは** ない」

which is a set phrase meaning:

> " **I told you so**.", " **Didn't I tell you?** ", " **That's why I told
> you**.", etc.

「やれやれ」 just means "Oh dear!" or something along those lines.




> 「言{い}わん **こっちゃ** ない」

is the common colloquial form of:

> 「言わない **ことでは** ない」

which is a set phrase meaning:

> " **I told you so**.", " **Didn't I tell you?** ", " **That's why I told
> you**.", etc.

「やれやれ」 just means "Oh dear!" or something along those lines.

