Unfortunatly, the compiler doesn't catch it. From the MDSN help:

An attempt to use an undeclared variable or array will generate output to the DEBUG OUTPUT window. No error is generated. You can log this output to a file as in the following code:

SET DEBUGOUT TO MyErrorFile

>Interesting, I >thought< this was added at some point. However, I'm not sure how it works. I created a new project and added code to a PRG:
>
>

>lcTest = "Hello!"
>
>MESSAGEBOX(lcTest)
>

>
>I set _VFP.LanguageOptions = 1 and built an EXE. No errors.