Support GHC 8.2.1

[asr]

Edited on 2017-07-08: Using GHC 8.2.1 RC 3 the current issues are:

• Missing Travis test
• GHC warnings
• Broken compilation of hTags
• boxes library (see Missing support for GHC 8.2.1 haskell-boxes/boxes#26)
• geniplate-mirror library (see Supported GHC 8.2.1 danr/geniplate#8)
• hashable library (see Build error when installing hashable 1.2.6.1 with GHC 8.2.1 RC2 haskell-unordered-containers/hashable#142)
• split library (see http://hub.darcs.net/byorgey/split/issue/7)
• vector library (see Make it build with ghc 8.2 haskell/vector#161)

[asr]

GHC 8.2.1 RC2 is reporting a heap exhausted error only on master when testing #1829:

$ cd test/interaction
$ make Issue1829.cmp
...
{+agda: Heap exhausted;
agda: Current maximum heap size is 4194304 bytes (4 MB).
agda: Use `+RTS -M<size>' to increase it.+}
Accept new error [y/N/q]? 

[andreasabel]

I think @Saizan and/or @nad should investigate whether ghc 8,2 brings #1829 back or this is just a false alarm.

[asr]

While testing the build using GHC 8.2.1 RC 3, I found the following error:

$ make install-bin
...
[15 of 49] Compiling InternalTests.TypeChecking.Coverage.SplitTree ( test/InternalTests/TypeChecking/Coverage/SplitTree.hs, dist-2.5.3/build/internal-tests/internal-tests-tmp/InternalTests/TypeChecking/Coverage/SplitTree.o )

test/InternalTests/TypeChecking/Coverage/SplitTree.hs:14:22: error:
    Variable not in scope:
      defaultArg :: a0 -> Agda.Syntax.Common.Arg Int
   |
14 |     , (3, (SplitAt . defaultArg) <$> choose (1,5) <*> (take 3 <$> listOf1 arbitrary))
   |  

It seems that the first report of this error in Travis was here.

[asr]

I can fix the error by adding

import Agda.Syntax.Common

I don't understand why the importation is only required by GHC 8.2.1 RC 3. Any idea?

[andreasabel]

When I try to load this file into ghci it also complains about defaultArg.

[asr]

GHC version?

[asr]

The problem was caused by an unused module which is compiled by GHC 8.2.1 RC3 but it isn't compiled by previous versions of GHC including 8.2.1 RC 2. I think GHC 8.2.1 RC3 is doing the right thing.

[andreasabel]

GHC version?

7.10.x

But, surely it should complain about defaultArg. How could it be possibly in scope without the import?

[asr]

But, surely it should complain about defaultArg.

Yes.

How could it be possibly in scope without the import?

It isn't possible. GHC/Cabal were ignoring the module. In your case, your load the module in GHCi and you get the expected error.

[asr]

GHC 8.2.1 was released. Except for a test case failing, Agda supports this version of GHC. I'll file a new issue for reporting the problem with the test case.

[asr]

GHC 8.2.1 was released. Except for a test case failing, Agda supports this version of GHC. I'll file a new issue for reporting the problem with the test case.

See #2702.