Support for -XTypeApplications

[mixphix]

Augments the Shakespeare base parser to support parsing type applications, e.g. #{show @Integer 4}, to improve working with polymorphism within quasi-quotes. Will parse type constructors, symbol types, type-level naturals, and single-depth compositions thereof, but will not parse things like @(Const (Maybe a) b) with nested parentheses.

[mixphix]

The earliest GHC version this could support is 8.2.1 (2017), according to the metadata for the commit introducing AppTypeE to template-haskell. If older compiler support is required, we can add the preprocessor directives.

[snoyberg]

LGTM, thanks! Can you add a minor version bump and a ChangeLog comment about the addition?

[snoyberg]

If older compiler support is required, we can add the preprocessor directives.

No, it's fine to support only GHC 8.2 and up.

[mixphix]

I've bumped the version number and edited the changelog. Thanks!

[mixphix]

Is this ready for merge?

[snoyberg]

Yep, looks good, thanks!

[parsonsmatt]

I'm seeing a test failure on this PR:

Failures:

  test/Text/Shakespeare/BaseSpec.hs:55:5: 
  1) Text.Shakespeare.Base parseDeref parse single @ as operator
       expected: Right (DerefBranch (DerefBranch (DerefIdent (Ident "@")) (DerefIdent (Ident "x"))) (DerefIdent (Ident "y")))
        but got: Right (DerefIdent (Ident "x"))

  To rerun use: --match "/Text.Shakespeare.Base/parseDeref parse single @ as operator/" --seed 713123586

Randomized with seed 713123586

Finished in 0.0160 seconds
275 examples, 1 failure
Test suite test: FAIL
Test suite logged to:
/home/matt/Projects/shakespeare/dist-newstyle/build/x86_64-linux/ghc-8.8.4/shakespeare-2.1.1/t/test/noopt/test/shakespeare-2.1.1-test.log
0 of 1 test suites (0 of 1 test cases) passed.
Error: [Cabal-7125]
Tests failed for test:test from shakespeare-2.1.1.

I think we need to mark this release as broken on Hackage, and possibly do a revert of this PR until it can be fixed. Thoughts @snoyberg @mixphix ?

[mixphix]

This commit solves the failing test.

[lvn-rusty-dragon]

I'll do both of those @parsonsmatt.