You've stumbled into a case that's involves some advanced features of Haskell. The problem is that tableTypes "base" "base.csv" is a template haskell splice. For some reason, a few years back ghc was modified to allow bare expressions at the top level as splices, instead of requiring the standard splice syntax of $(expression generating code to splice).
But the bare expression syntax is incompatible with ghci. If you enter a bare expression in ghci, it tries to evaluate and print it (with some special rules for expressions that result in IO values).
When ghci evaluates tableTypes "base" "base.csv" it gets a result back that's not an instance of Show, because the template haskell Q environment is not printable. It contains a bunch of functions.
You have a few options here, depending on what you actually are trying to do. You could use runQ in ghci to dump the AST generated by the splice. That's probably not what you want. That's more likely to be a tool that's useful when you're developing a splice than for testing a library that uses them.
You could enable the TemplateHaskell extension within ghci and actually have it perform the splice interactively, but that's somewhat fiddly to get to work and you don't end up seeing much anyway.
I think the most practical solution is to move your code into a file. You can load said file from ghci if you desire - the important part is that in the context of a file, there's no longer any syntactic ambiguity - that's definitely a splice to evaluate while compiling, not an expression to evaluate interactively.
