By making it include parens when a derived instance would. For example, this changes the (hypothetical) code `show (Just (ThreadId 3))` to produce `"Just (ThreadId 3)"` instead of the current `"Just ThreadId 3"`.

Currently 'getRootSummary' will fail with an exception if a 'TargetFile' is
given but it does not exist even if an input buffer is passed along for
this target.

In this case it is not necessary for the file to exist since the buffer
will be used as input for the compilation pipeline instead of the file
anyways.

This allows GHC API clients, most notably tooling such as
Haskell-IDE-Engine, to pass unsaved files to GHC more easily.

Currently when targetContents is used but the module requires preprocessing
'preprocessFile' simply throws an error because the pipeline does not
support passing a buffer.

This change extends `runPipeline` to allow passing the input buffer into
the pipeline. Before proceeding with the actual pipeline loop the input
buffer is immediately written out to a new tempfile.

I briefly considered refactoring the pipeline at large to pass around
in-memory buffers instead of files, but this seems needlessly complicated
since no pipeline stages other than Hsc could really support this at the
moment.

Unboxed tuples and sums take extra RuntimeRep arguments,
which must be manually passed in a few places.
This was not done in deSugar/Check.

This error was hidden because zipping functions in TyCoRep
ignored lists with mismatching length. This is now fixed;
the lengths are now checked by calling zipEqual.

As suggested in #16565, I moved checking for isTyVar and
isCoVar to zipTyEnv and zipCoEnv.

We fetch the ArgFlag for every argument by using splitForAllVarBndrs
instead of splitForAllTys in unwrapTypeVars.