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.

2 files changed, 2 insertions, 2 deletions

diff --git a/utils/genprimopcode/Main.hs b/utils/genprimopcode/Main.hs
index 576dbc9a20..31d363c0fa 100644
--- a/utils/genprimopcode/Main.hs
+++ b/utils/genprimopcode/Main.hs
@@ -928,8 +928,8 @@ ppType (TyApp (VecTyCon _ pptc) [])      = pptc
 ppType (TyUTup ts) = "(mkTupleTy Unboxed "
                      ++ listify (map ppType ts) ++ ")"
 
-ppType (TyF s d) = "(mkVisFunTy (" ++ ppType s ++ ") (" ++ ppType d ++ "))"
-ppType (TyC s d) = "(mkInvisFunTy (" ++ ppType s ++ ") (" ++ ppType d ++ "))"
+ppType (TyF s d) = "(mkVisFunTyMany ("   ++ ppType s ++ ") (" ++ ppType d ++ "))"
+ppType (TyC s d) = "(mkInvisFunTyMany (" ++ ppType s ++ ") (" ++ ppType d ++ "))"
 
 ppType other
    = error ("ppType: can't handle: " ++ show other ++ "\n")
diff --git a/utils/haddock b/utils/haddock
-Subproject e37911553bfe6804d3903f750261f758569b4a2
+Subproject 02a1def8d147da88a0433726590f8586f486c76