What is the most absurd error message a program you have made was outputting?

[FlatAssembler]

Up until yesterday, my AEC-to-WebAssembly compiler was, if somebody tried to use two structures of different types as the second and the third operand to the `?:` (ternary conditional) operator (which is always wrong, but it has happened to me quite a few times that I accidentally tried to do it in C++), as in this example:

Code:

Structure First Consists Of
    Nothing;
EndStructure

Structure Second Consists Of
    Nothing;
EndStructure

Function main(Integer32 a, Integer32 b) Which Returns Nothing Does
    InstantiateStructure First firstStructure;
    InstantiateStructure Second secondStructure;
    InstantiateStructure Second thirdStructure := (a > b) ? firstStructure : secondStructure; // This line contains the error.
EndFunction

For that example, my AEC-to-WebAssembly compiler was outputting this error message:

Code:

Running the tests...
All the tests passed in 4 milliseconds.
Reading the file "debug.aec"...
All characters read in 0 milliseconds.
Tokenizing the program...
Finished tokenizing the program in 0 milliseconds.
I have made a forum thread about how to speed up the tokenizer,
in case you are interested:
https://www.forum.hr/showthread.php?t=1243509
Parsing the program...
Finished parsing the program in 0 milliseconds.
Compiling the program...
Line 10, Column 29, Internal compiler error: Some part of the compiler attempted to compile an array with size less than 1, which doesn't make sense. Throwing an exception!
Internal compiler error: Uncaught exception in the compiler: St13runtime_error: Compiling an array of negative size!
If you have time, please report this to me on GitHub as an issue:
https://github.com/FlatAssembler/AECforWebAssembly/issues

Truly absurd, right? There are no arrays in the program, so how can a part of a compiler possibly request an array with a negative size? It took me hours to figure out what is going on in my compiler (Which perhaps shouldn't be surprising considering that I wrote it 3 years ago.).

It took you hours to resolve a mistake you made three years ago in your compiler? I foresee a great future for you as a programmer.

Boru

Well, there were actually two bugs that are triggered by that code, one in the core of the compiler and one in the semantic analyzer. It would have probably taken me significantly less time if I knew how to use a debugger. But compilers are among the most complicated pieces of software, perhaps only less complicated than operating systems.