Linear types (#15981)

This is the first step towards implementation of the linear types proposal
(https://github.com/ghc-proposals/ghc-proposals/pull/111).

It features

* A language extension -XLinearTypes
* Syntax for linear functions in the surface language
* Linearity checking in Core Lint, enabled with -dlinear-core-lint
* Core-to-core passes are mostly compatible with linearity
* Fields in a data type can be linear or unrestricted; linear fields
  have multiplicity-polymorphic constructors.
  If -XLinearTypes is disabled, the GADT syntax defaults to linear fields

The following items are not yet supported:

* a # m -> b syntax (only prefix FUN is supported for now)
* Full multiplicity inference (multiplicities are really only checked)
* Decent linearity error messages
* Linear let, where, and case expressions in the surface language
  (each of these currently introduce the unrestricted variant)
* Multiplicity-parametric fields
* Syntax for annotating lambda-bound or let-bound with a multiplicity
* Syntax for non-linear/multiple-field-multiplicity records
* Linear projections for records with a single linear field
* Linear pattern synonyms
* Multiplicity coercions (test LinearPolyType)

A high-level description can be found at
https://ghc.haskell.org/trac/ghc/wiki/LinearTypes/Implementation
Following the link above you will find a description of the changes made to Core.
This commit has been authored by

* Richard Eisenberg
* Krzysztof Gogolewski
* Matthew Pickering
* Arnaud Spiwack

With contributions from:

* Mark Barbone
* Alexander Vershilov

Updates haddock submodule.

1 files changed, 9 insertions, 8 deletions

diff --git a/testsuite/tests/callarity/unittest/CallArity1.hs b/testsuite/tests/callarity/unittest/CallArity1.hs
index 60cb97835f..55427ff4b7 100644
--- a/testsuite/tests/callarity/unittest/CallArity1.hs
+++ b/testsuite/tests/callarity/unittest/CallArity1.hs
@@ -1,8 +1,9 @@
-{-# LANGUAGE TupleSections #-}
+{-# LANGUAGE TupleSections, PatternSynonyms #-}
 import GHC.Core
 import GHC.Core.Utils
 import GHC.Types.Id
 import GHC.Core.Type
+import GHC.Core.Multiplicity ( pattern Many )
 import GHC.Core.Make
 import GHC.Core.Opt.CallArity (callArityRHS)
 import GHC.Types.Id.Make
@@ -27,16 +28,16 @@ import GHC.Data.FastString
 go, go2, x, d, n, y, z, scrutf, scruta :: Id
 [go, go2, x,d, n, y, z, scrutf, scruta, f] = mkTestIds
     (words "go go2 x d n y z scrutf scruta f")
-    [ mkVisFunTys [intTy, intTy] intTy
-    , mkVisFunTys [intTy, intTy] intTy
+    [ mkVisFunTysMany [intTy, intTy] intTy
+    , mkVisFunTysMany [intTy, intTy] intTy
     , intTy
-    , mkVisFunTys [intTy] intTy
-    , mkVisFunTys [intTy] intTy
+    , mkVisFunTysMany [intTy] intTy
+    , mkVisFunTysMany [intTy] intTy
     , intTy
     , intTy
-    , mkVisFunTys [boolTy] boolTy
+    , mkVisFunTysMany [boolTy] boolTy
     , boolTy
-    , mkVisFunTys [intTy, intTy] intTy -- protoypical external function
+    , mkVisFunTysMany [intTy, intTy] intTy -- protoypical external function
     ]
 
 exprs :: [(String, CoreExpr)]
@@ -188,7 +189,7 @@ mkLApps v = mkApps (Var v) . map mkLit
 mkACase = mkIfThenElse (mkVarApps (Var scrutf) [scruta])
 
 mkTestId :: Int -> String -> Type -> Id
-mkTestId i s ty = mkSysLocal (mkFastString s) (mkBuiltinUnique i) ty
+mkTestId i s ty = mkSysLocal (mkFastString s) (mkBuiltinUnique i) Many ty
 
 mkTestIds :: [String] -> [Type] -> [Id]
 mkTestIds ns tys = zipWith3 mkTestId [0..] ns tys