From 5f1e072868eecc1bc33949a4613034f3c9f98b8a Mon Sep 17 00:00:00 2001
From: Mitchell Rosen <mitchellwrosen@gmail.com>
Date: Sat, 10 Aug 2019 15:38:18 -0400
Subject: [PATCH] Add Nat.fromText

---
 CONTRIBUTORS.markdown                              | 1 +
 parser-typechecker/src/Unison/Builtin.hs           | 1 +
 parser-typechecker/src/Unison/Runtime/Rt1.hs       | 2 ++
 parser-typechecker/unison-parser-typechecker.cabal | 2 +-
 4 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/CONTRIBUTORS.markdown b/CONTRIBUTORS.markdown
index 6590936dd..dbaf46456 100644
--- a/CONTRIBUTORS.markdown
+++ b/CONTRIBUTORS.markdown
@@ -22,3 +22,4 @@ The format for this list: name, GitHub handle, and then optional blurb about wha
 * Scott Christopher (@scott-christopher)
 * Alex Zolotko (@azolotko)
 * Ian Denhardt (@zenhack)
+* Mitchell Rosen (@mitchellwrosen)
diff --git a/parser-typechecker/src/Unison/Builtin.hs b/parser-typechecker/src/Unison/Builtin.hs
index 5744dfb04..3d000af6d 100644
--- a/parser-typechecker/src/Unison/Builtin.hs
+++ b/parser-typechecker/src/Unison/Builtin.hs
@@ -241,6 +241,7 @@ builtinsSrc =
   , B "Nat.isOdd" $ nat --> boolean
   , B "Nat.toInt" $ nat --> int
   , B "Nat.toText" $ nat --> text
+  , B "Nat.fromText" $ text --> optional nat
 
   , B "Float.+" $ float --> float --> float
   , B "Float.-" $ float --> float --> float
diff --git a/parser-typechecker/src/Unison/Runtime/Rt1.hs b/parser-typechecker/src/Unison/Runtime/Rt1.hs
index 05a0a5470..c3246d0a5 100644
--- a/parser-typechecker/src/Unison/Runtime/Rt1.hs
+++ b/parser-typechecker/src/Unison/Runtime/Rt1.hs
@@ -331,6 +331,8 @@ builtinCompilationEnv = CompilationEnv (builtinsMap <> IR.builtins) mempty
     , mk1 "Float.truncate"      atf (pure . I) truncate
 
     , mk1 "Nat.toText" atn (pure . T) (Text.pack . show)
+    , mk1 "Nat.fromText" att (pure . IR.maybeToOptional . fmap N) (
+        (\x -> readMaybe x :: Maybe Word64) . Text.unpack)
 
     -- Float Utils
     , mk1 "Float.abs"           atf (pure . F) abs
diff --git a/parser-typechecker/unison-parser-typechecker.cabal b/parser-typechecker/unison-parser-typechecker.cabal
index 3755e12f1..e27276aef 100644
--- a/parser-typechecker/unison-parser-typechecker.cabal
+++ b/parser-typechecker/unison-parser-typechecker.cabal
@@ -185,7 +185,7 @@ library
     io-streams,
     lens,
     ListLike,
-    megaparsec,
+    megaparsec >= 5.0.0 && < 7.0.0,
     memory,
     mmorph,
     monad-loops,