Custom `Typeable` solver, that keeps track of kinds.

Summary:
This implements the new `Typeable` solver: when GHC sees `Typeable` constraints
it solves them on the spot.

The current implementation creates `TyCon` representations on the spot.

Pro: No overhead at all in code that does not use `Typeable`
Cons: Code that uses `Typeable` may create multipe `TyCon` represntations.

We have discussed an implementation where representations of `TyCons` are
computed once, in the module, where a datatype is declared.  This would
lead to more code being generated:  for a promotable datatype we need to
generate `2 + number_of_data_cons` type-constructro representations,
and we have to do that for all programs, even ones that do not intend to
use typeable.

I added code to emit warning whenevar `deriving Typeable` is encountered---
the idea being that this is not needed anymore, and shold be fixed.

Also, we allow `instance Typeable T` in .hs-boot files, but they result
in a warning, and are ignored.  This last one was to avoid breaking exisitng
code, and should become an error, eventually.

Test Plan:
1. GHC can compile itself.
2. I compiled a number of large libraries, including `lens`.
    - I had to make some small changes:
      `unordered-containers` uses internals of `TypeReps`, so I had to do a 1 line fix
    - `lens` needed one instance changed, due to a poly-kinded `Typeble` instance

3. I also run some code that uses `syb` to traverse a largish datastrucutre.
I didn't notice any signifiant performance difference between the 7.8.3 version,
and this implementation.

Reviewers: simonpj, simonmar, austin, hvr

Reviewed By: austin, hvr

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D652

GHC Trac Issues: #9858

10 files changed, 5 insertions, 65 deletions

diff --git a/testsuite/tests/deriving/should_compile/all.T b/testsuite/tests/deriving/should_compile/all.T
index 8d9023646c..b56baed668 100644
--- a/testsuite/tests/deriving/should_compile/all.T
+++ b/testsuite/tests/deriving/should_compile/all.T
@@ -46,7 +46,7 @@ test('T8758', extra_clean(['T8758a.o', 'T8758a.hi']), multimod_compile, ['T8758a
 test('T8678', normal, compile, [''])
 test('T8865', normal, compile, [''])
 test('T8893', normal, compile, [''])
-test('T8950', expect_broken(8950), compile, [''])
+test('T8950', normal, compile, [''])
 test('T8963', normal, compile, [''])
 test('T7269', normal, compile, [''])
 test('T9069', normal, compile, [''])
diff --git a/testsuite/tests/deriving/should_fail/T2604.hs b/testsuite/tests/deriving/should_fail/T2604.hs
deleted file mode 100644
index 0f830d992b..0000000000
--- a/testsuite/tests/deriving/should_fail/T2604.hs
+++ /dev/null
@@ -1,9 +0,0 @@
-{-# LANGUAGE GeneralizedNewtypeDeriving #-}
-
-module Test where
-
-import Data.Typeable
-
-data DList a = DList [a] deriving(Typeable)
-
-newtype NList a = NList [a] deriving(Typeable)
diff --git a/testsuite/tests/deriving/should_fail/T2604.stderr b/testsuite/tests/deriving/should_fail/T2604.stderr
deleted file mode 100644
index 3000b5002f..0000000000
--- a/testsuite/tests/deriving/should_fail/T2604.stderr
+++ /dev/null
@@ -1,10 +0,0 @@
-
-T2604.hs:7:35:
-    Can't make a Typeable instance of ‘DList’
-      You need DeriveDataTypeable to derive Typeable instances
-    In the data declaration for ‘DList’
-
-T2604.hs:9:38:
-    Can't make a Typeable instance of ‘NList’
-      You need DeriveDataTypeable to derive Typeable instances
-    In the newtype declaration for ‘NList’
diff --git a/testsuite/tests/deriving/should_fail/T5863a.hs b/testsuite/tests/deriving/should_fail/T5863a.hs
deleted file mode 100644
index 3506dcc04a..0000000000
--- a/testsuite/tests/deriving/should_fail/T5863a.hs
+++ /dev/null
@@ -1,12 +0,0 @@
-{-# LANGUAGE DeriveDataTypeable, TypeFamilies #-}

-

-import Data.Typeable

-

-class C a where

-    data T a :: * 

-

-instance C Int where

-    data T Int = A1 deriving (Typeable)

-

-instance C Bool where

-    data T Bool = A2 deriving (Typeable)

diff --git a/testsuite/tests/deriving/should_fail/T5863a.stderr b/testsuite/tests/deriving/should_fail/T5863a.stderr
deleted file mode 100644
index d64f1b20ce..0000000000
--- a/testsuite/tests/deriving/should_fail/T5863a.stderr
+++ /dev/null
@@ -1,10 +0,0 @@
-
-T5863a.hs:9:31:
-    Deriving Typeable is not allowed for family instances;
-    derive Typeable for ‘T’ alone
-    In the data instance declaration for ‘T’
-
-T5863a.hs:12:32:
-    Deriving Typeable is not allowed for family instances;
-    derive Typeable for ‘T’ alone
-    In the data instance declaration for ‘T’
diff --git a/testsuite/tests/deriving/should_fail/T7800.hs b/testsuite/tests/deriving/should_fail/T7800.hs
deleted file mode 100644
index 9f190cfa51..0000000000
--- a/testsuite/tests/deriving/should_fail/T7800.hs
+++ /dev/null
@@ -1,7 +0,0 @@
-{-# LANGUAGE StandaloneDeriving, DeriveDataTypeable #-}
-module T7800 where
-
-import T7800a
-import Data.Typeable
-
-deriving instance Typeable A
diff --git a/testsuite/tests/deriving/should_fail/T7800.stderr b/testsuite/tests/deriving/should_fail/T7800.stderr
deleted file mode 100644
index 8cd8533968..0000000000
--- a/testsuite/tests/deriving/should_fail/T7800.stderr
+++ /dev/null
@@ -1,6 +0,0 @@
-[1 of 2] Compiling T7800a           ( T7800a.hs, T7800a.o )
-[2 of 2] Compiling T7800            ( T7800.hs, T7800.o )
-
-T7800.hs:7:1:
-    To make a Typeable instance of poly-kinded ‘A’, use XPolyKinds
-    In the stand-alone deriving instance for ‘Typeable A’
diff --git a/testsuite/tests/deriving/should_fail/T7800a.hs b/testsuite/tests/deriving/should_fail/T7800a.hs
deleted file mode 100644
index 22f1305d2e..0000000000
--- a/testsuite/tests/deriving/should_fail/T7800a.hs
+++ /dev/null
@@ -1,4 +0,0 @@
-{-# LANGUAGE PolyKinds #-}
-module T7800a where
-
-data A a
\ No newline at end of file
diff --git a/testsuite/tests/deriving/should_fail/T9687.stderr b/testsuite/tests/deriving/should_fail/T9687.stderr
index 10619a6575..ad95393db7 100644
--- a/testsuite/tests/deriving/should_fail/T9687.stderr
+++ b/testsuite/tests/deriving/should_fail/T9687.stderr
@@ -1,5 +1,3 @@
 
 T9687.hs:4:10:
-    Typeable instances can only be derived
-      Try ‘deriving instance Typeable (,,,,,,,)’
-      (requires StandaloneDeriving)
+    Class `Typeable` does not support user-specified instances.
diff --git a/testsuite/tests/deriving/should_fail/all.T b/testsuite/tests/deriving/should_fail/all.T
index df7957d9b0..60a4b7b45c 100644
--- a/testsuite/tests/deriving/should_fail/all.T
+++ b/testsuite/tests/deriving/should_fail/all.T
@@ -17,7 +17,7 @@ test('drvfail016',
      run_command,
      ['$MAKE --no-print-directory -s drvfail016'])
 test('T2394', normal, compile_fail, [''])
-test('T2604', normal, compile_fail, [''])
+# T2604 was removed as it was out of date re: fixing #9858
 test('T2701', normal, compile_fail, [''])
 test('T2851', normal, compile_fail, [''])
 test('T2721', normal, compile_fail, [''])
@@ -38,14 +38,14 @@ test('T1133A',
      extra_clean(['T1133A.o-boot', 'T1133A.hi-boot']),
      run_command,
      ['$MAKE --no-print-directory -s T1133A'])
-test('T5863a', normal, compile_fail, [''])
+# 5863a was removed as it was out of date re: fixing #9858
 test('T7959', normal, compile_fail, [''])
 
 test('T1496', normal, compile_fail, [''])
 test('T4846', normal, compile_fail, [''])
 test('T7148', normal, compile_fail, [''])
 test('T7148a', normal, compile_fail, [''])
-test('T7800', normal, multimod_compile_fail, ['T7800',''])
+# T7800 was removed as it was out of date re: fixing #9858
 test('T5498', normal, compile_fail, [''])
 test('T6147', normal, compile_fail, [''])
 test('T8851', normal, compile_fail, [''])