Built-in Natural literals in Core

Add support for built-in Natural literals in Core.

- Replace MachInt,MachWord, LitInteger, etc. with a single LitNumber
  constructor with a LitNumType field
- Support built-in Natural literals
- Add desugar warning for negative literals
- Move Maybe(..) from GHC.Base to GHC.Maybe for module dependency
  reasons

This patch introduces only a few rules for Natural literals (compared
to Integer's rules). Factorization of the built-in rules for numeric
literals will be done in another patch as this one is already big to
review.

Test Plan:
  validate
  test build with integer-simple

Reviewers: hvr, bgamari, goldfire, Bodigrim, simonmar

Reviewed By: bgamari

Subscribers: phadej, simonpj, RyanGlScott, carter, hsyl20, rwbarton,
thomie

GHC Trac Issues: #14170, #14465

Differential Revision: https://phabricator.haskell.org/D4212

1 files changed, 4 insertions, 3 deletions

diff --git a/compiler/stgSyn/CoreToStg.hs b/compiler/stgSyn/CoreToStg.hs
index e2ed3953ae..fdd8d5bef3 100644
--- a/compiler/stgSyn/CoreToStg.hs
+++ b/compiler/stgSyn/CoreToStg.hs
@@ -390,9 +390,10 @@ coreToStgExpr
 -- on these components, but it in turn is not scrutinised as the basis for any
 -- decisions.  Hence no black holes.
 
--- No LitInteger's should be left by the time this is called. CorePrep
--- should have converted them all to a real core representation.
-coreToStgExpr (Lit (LitInteger {})) = panic "coreToStgExpr: LitInteger"
+-- No LitInteger's or LitNatural's should be left by the time this is called.
+-- CorePrep should have converted them all to a real core representation.
+coreToStgExpr (Lit (LitNumber LitNumInteger _ _)) = panic "coreToStgExpr: LitInteger"
+coreToStgExpr (Lit (LitNumber LitNumNatural _ _)) = panic "coreToStgExpr: LitNatural"
 coreToStgExpr (Lit l)      = return (StgLit l, emptyFVInfo)
 coreToStgExpr (Var v)      = coreToStgApp Nothing v               [] []
 coreToStgExpr (Coercion _) = coreToStgApp Nothing coercionTokenId [] []