Add support for Reason (#3336)

samples/Reason/JSX.re

@@ -0,0 +1,483 @@
+type component = {displayName: string};
+
+let module Bar = {
+  let createElement c::c=? children => {
+    displayName: "test"
+  };
+};
+
+let module Nesting = {
+  let createElement children => {
+    displayName: "test"
+  };
+};
+
+let module Much = {
+  let createElement children => {
+    displayName: "test"
+  };
+};
+
+let module Foo = {
+  let createElement a::a=? b::b=? children => {
+    displayName: "test"
+  };
+};
+
+let module One = {
+  let createElement
+      test::test=?
+      foo::foo=?
+      children => {
+    displayName: "test"
+  };
+  let createElementobvioustypo
+      test::test
+      children => {
+    displayName: "test"
+  };
+};
+
+let module Two = {
+  let createElement foo::foo=? children => {
+    displayName: "test"
+  };
+};
+
+let module Sibling = {
+  let createElement
+      foo::foo=?
+      (children: list component) => {
+    displayName: "test"
+  };
+};
+
+let module Test = {
+  let createElement yo::yo=? children => {
+    displayName: "test"
+  };
+};
+
+let module So = {
+  let createElement children => {
+    displayName: "test"
+  };
+};
+
+let module Foo2 = {
+  let createElement children => {
+    displayName: "test"
+  };
+};
+
+let module Text = {
+  let createElement children => {
+    displayName: "test"
+  };
+};
+
+let module Exp = {
+  let createElement children => {
+    displayName: "test"
+  };
+};
+
+let module Pun = {
+  let createElement intended::intended=? children => {
+    displayName: "test"
+  };
+};
+
+let module Namespace = {
+  let module Foo = {
+    let createElement
+        intended::intended=?
+        anotherOptional::x=100
+        children => {
+      displayName: "test"
+    };
+  };
+};
+
+let module LotsOfArguments = {
+  let createElement
+      argument1::argument1=?
+      argument2::argument2=?
+      argument3::argument3=?
+      argument4::argument4=?
+      argument5::argument5=?
+      argument6::argument6=?
+      children => {
+    displayName: "test"
+  };
+};
+
+let div argument1::argument1=? children => {
+  displayName: "test"
+};
+
+let module List1 = {
+  let createElement children => {
+    displayName: "test"
+  };
+};
+
+let module List2 = {
+  let createElement children => {
+    displayName: "test"
+  };
+};
+
+let module List3 = {
+  let createElement children => {
+    displayName: "test"
+  };
+};
+
+let (/><) a b => a + b;
+
+let (><) a b => a + b;
+
+let (/>) a b => a + b;
+
+let (><\/) a b => a + b;
+
+let tag1 = 5 />< 6;
+
+let tag2 = 5 >< 7;
+
+let tag3 = 5 /> 7;
+
+let tag4 = 5 ><\/ 7;
+
+let b = 2;
+
+let selfClosing = <Foo />;
+
+let selfClosing2 = <Foo a=1 b=true />;
+
+let selfClosing3 =
+  <Foo
+    a="really long values that should"
+    b="cause the entire thing to wrap"
+  />;
+
+let a = <Foo> <Bar c=(fun a => a + 2) /> </Foo>;
+
+let a3 = <So> <Much> <Nesting /> </Much> </So>;
+
+let a4 =
+  <Sibling>
+    <One test=true foo=b />
+    <Two foo=b />
+  </Sibling>;
+
+let a5 = <Foo> "testing a string here" </Foo>;
+
+let a6 =
+  <Foo2>
+    <Text> "testing a string here" </Text>
+    <Test yo=1 />
+    <Text> "another string" </Text>
+    <Bar />
+    <Exp> (2 + 4) </Exp>
+  </Foo2>;
+
+let intended = true;
+
+let punning = <Pun intended />;
+
+let namespace = <Namespace.Foo />;
+
+let c = <Foo />;
+
+let d = <Foo />;
+
+let spaceBefore =
+  <So> <Much> <Nesting /> </Much> </So>;
+
+let spaceBefore2 = <So> <Much /> </So>;
+
+let siblingNotSpaced =
+  <So> <Much /> <Much /> </So>;
+
+let jsxInList = [<Foo />];
+
+let jsxInList2 = [<Foo />];
+
+let jsxInListA = [<Foo />];
+
+let jsxInListB = [<Foo />];
+
+let jsxInListC = [<Foo />];
+
+let jsxInListD = [<Foo />];
+
+let jsxInList3 = [<Foo />, <Foo />, <Foo />];
+
+let jsxInList4 = [<Foo />, <Foo />, <Foo />];
+
+let jsxInList5 = [<Foo />, <Foo />];
+
+let jsxInList6 = [<Foo />, <Foo />];
+
+let jsxInList7 = [<Foo />, <Foo />];
+
+let jsxInList8 = [<Foo />, <Foo />];
+
+let testFunc b => b;
+
+let jsxInFnCall = testFunc <Foo />;
+
+let lotsOfArguments =
+  <LotsOfArguments
+    argument1=1
+    argument2=2
+    argument3=3
+    argument4=4
+    argument5=5
+    argument6="test">
+    <Namespace.Foo />
+  </LotsOfArguments>;
+
+let lowerCase = <div argument1=1 />;
+
+let b = 0;
+
+let d = 0;
+
+/*
+ * Should pun the first example:
+ */
+let a = <Foo a> 5 </Foo>;
+
+let a = <Foo a=b> 5 </Foo>;
+
+let a = <Foo a=b b=d> 5 </Foo>;
+
+let a = <Foo a> 0.55 </Foo>;
+
+let a = Foo.createElement "" [@JSX];
+
+let ident = <Foo> a </Foo>;
+
+let fragment1 = <> <Foo /> <Foo /> </>;
+
+let fragment2 = <> <Foo /> <Foo /> </>;
+
+let fragment3 = <> <Foo /> <Foo /> </>;
+
+let fragment4 = <> <Foo /> <Foo /> </>;
+
+let fragment5 = <> <Foo /> <Foo /> </>;
+
+let fragment6 = <> <Foo /> <Foo /> </>;
+
+let fragment7 = <> <Foo /> <Foo /> </>;
+
+let fragment8 = <> <Foo /> <Foo /> </>;
+
+let fragment9 = <> 2 2 2 2 </>;
+
+let fragment10 = <> 2.2 3.2 4.6 1.2 </>;
+
+let fragment11 = <> "str" </>;
+
+let fragment12 = <> (6 + 2) (6 + 2) (6 + 2) </>;
+
+let fragment13 = <> fragment11 fragment11 </>;
+
+let listOfItems1 = <List1> 1 2 3 4 5 </List1>;
+
+let listOfItems2 =
+  <List2> 1.0 2.8 3.8 4.0 5.1 </List2>;
+
+let listOfItems3 =
+  <List3> fragment11 fragment11 </List3>;
+
+/*
+ * Several sequential simple jsx expressions must be separated with a space.
+ */
+let thisIsRight a b => ();
+
+let tagOne children => ();
+
+let tagTwo children => ();
+
+/* thisIsWrong <tagOne /><tagTwo />; */
+thisIsRight <tagOne /> <tagTwo />;
+
+/* thisIsWrong <tagOne> </tagOne><tagTwo> </tagTwo>; */
+thisIsRight <tagOne /> <tagTwo />;
+
+let a children => ();
+
+let b children => ();
+
+let thisIsOkay =
+  <List1> <a /> <b /> <a /> <b /> </List1>;
+
+let thisIsAlsoOkay =
+  <List1> <a /> <b /> </List1>;
+
+/* Doesn't make any sense, but suppose you defined an
+   infix operator to compare jsx */
+<a /> < <b />;
+
+<a /> > <b />;
+
+<a /> < <b />;
+
+<a /> > <b />;
+
+let listOfListOfJsx = [<> </>];
+
+let listOfListOfJsx = [<> <Foo /> </>];
+
+let listOfListOfJsx = [
+  <> <Foo /> </>,
+  <> <Bar /> </>
+];
+
+let listOfListOfJsx = [
+  <> <Foo /> </>,
+  <> <Bar /> </>,
+  ...listOfListOfJsx
+];
+
+let sameButWithSpaces = [<> </>];
+
+let sameButWithSpaces = [<> <Foo /> </>];
+
+let sameButWithSpaces = [
+  <> <Foo /> </>,
+  <> <Bar /> </>
+];
+
+let sameButWithSpaces = [
+  <> <Foo /> </>,
+  <> <Bar /> </>,
+  ...sameButWithSpaces
+];
+
+/*
+ * Test named tag right next to an open bracket.
+ */
+let listOfJsx = [];
+
+let listOfJsx = [<Foo />];
+
+let listOfJsx = [<Foo />, <Bar />];
+
+let listOfJsx = [<Foo />, <Bar />, ...listOfJsx];
+
+let sameButWithSpaces = [];
+
+let sameButWithSpaces = [<Foo />];
+
+let sameButWithSpaces = [<Foo />, <Bar />];
+
+let sameButWithSpaces = [
+  <Foo />,
+  <Bar />,
+  ...sameButWithSpaces
+];
+
+
+/**
+ * Test no conflict with polymorphic variant types.
+ */
+type thisType = [ | `Foo | `Bar];
+
+type t 'a = [< thisType] as 'a;
+
+let asd =
+  <One test=true foo=2> "a" "b" </One> [@foo];
+
+let asd2 =
+  One.createElementobvioustypo
+  test::false
+  ["a", "b"]
+  [@JSX]
+  [@foo];
+
+let span
+    test::(test: bool)
+    foo::(foo: int)
+    children => 1;
+
+let asd =
+  <span test=true foo=2> "a" "b" </span> [@foo];
+
+/* "video" call doesn't end with a list, so the expression isn't converted to JSX */
+let video test::(test: bool) children => children;
+
+let asd2 = video test::false 10 [@JSX] [@foo];
+
+let div children => 1;
+
+((fun () => div) ()) [] [@JSX];
+
+let myFun () =>
+  <>
+    <Namespace.Foo
+      intended=true
+      anotherOptional=200
+    />
+    <Namespace.Foo
+      intended=true
+      anotherOptional=200
+    />
+    <Namespace.Foo
+      intended=true anotherOptional=200>
+      <Foo />
+      <Foo />
+      <Foo />
+      <Foo />
+      <Foo />
+      <Foo />
+      <Foo />
+    </Namespace.Foo>
+  </>;
+
+let myFun () => <> </>;
+
+let myFun () =>
+  <>
+    <Namespace.Foo
+      intended=true
+      anotherOptional=200
+    />
+    <Namespace.Foo
+      intended=true
+      anotherOptional=200
+    />
+    <Namespace.Foo
+      intended=true anotherOptional=200>
+      <Foo />
+      <Foo />
+      <Foo />
+      <Foo />
+      <Foo />
+      <Foo />
+      <Foo />
+    </Namespace.Foo>
+  </>;
+
+
+/**
+ * Children should wrap without forcing attributes to.
+ */
+<Foo a=10 b=0>
+  <Bar />
+  <Bar />
+  <Bar />
+  <Bar />
+</Foo>;
+/**
+ * Failing test cases:
+ */
+/* let res = <Foo a=10 b=(<Foo a=200 />) > */
+/*   <Bar /> */
+/* </Foo>; */
+/* let res = <Foo a=10 b=(<Foo a=200 />) />; */

samples/Reason/Machine.re

@@ -0,0 +1,344 @@
+open Format;
+
+let module Endo = {
+  type t 'a = 'a => 'a;
+};
+
+let module Syntax = {
+  let module Var = {
+    type t = int;
+  };
+  let module Term = {
+    type t =
+      | App t t
+      | Lam t
+      | Var Var.t
+      ;
+  };
+  let module Sub = {
+    type t 'a =
+      | Cmp (t 'a) (t 'a)
+      | Dot 'a (t 'a)
+      | Id
+      | Shift
+      ;
+
+    let map f sgm => {
+      let rec go = fun
+      | Cmp sgm0 sgm1 => Cmp (go sgm0) (go sgm1)
+      | Dot a sgm => Dot (f a) (go sgm)
+      | Id => Id
+      | Shift => Shift
+      ;
+      go sgm;
+    };
+
+    let rec apply sgm e =>
+      switch (sgm, e) {
+      | (sgm, Term.App e0 e1) => Term.App (apply sgm e0) (apply sgm e1)
+      | (sgm, Term.Lam e) => Term.Lam (apply (Dot (Term.Var 0) (Cmp sgm Shift)) e)
+      | (Dot e _, Term.Var 0) => e
+      | (Dot _ sgm, Term.Var i) => apply sgm (Term.Var (i - 1))
+      | (Id, Term.Var i) => Term.Var i
+      | (Shift, Term.Var i) => Term.Var (i + 1)
+      | (Cmp rho sgm, e) => apply sgm (apply rho e)
+      };
+  };
+};
+
+let module Zip = {
+  open Syntax;
+  type t 'a =
+    | App0 (t 'a) 'a
+    | App1 'a (t 'a)
+    | Halt
+    | Lam (t 'a)
+    ;
+
+  let map f sgm => {
+    let rec go = fun
+    | App0 zip e1 => App0 (go zip) (f e1)
+    | App1 e0 zip => App1 (f e0) (go zip)
+    | Halt => Halt
+    | Lam zip => Lam (go zip)
+    ;
+    go sgm;
+  };
+
+  let rec apply zip acc => switch zip {
+    | App0 zip e1 => apply zip (Term.App acc e1)
+    | App1 e0 zip => apply zip (Term.App e0 acc)
+    | Halt => acc
+    | Lam zip => apply zip (Term.Lam acc)
+  };
+};
+
+let module Clo = {
+  open Syntax;
+  type t =
+    | Clo Term.t (Sub.t t);
+  let rec from (Clo term sgm) => Sub.apply (Sub.map from sgm) term;
+};
+
+let module Pretty = {
+  let module Delim = {
+    type t = string;
+    let pp prev next fmt token => if (prev < next) { fprintf fmt "%s" token };
+  };
+  let module Prec = {
+    type t = int;
+    open Syntax.Term;
+    let calc = fun
+      | App _ _ => 1
+      | Lam _ => 2
+      | Var _ => 0
+      ;
+  };
+  let module Name = {
+    type t = string;
+
+    let suffix = {
+      let script = fun
+        | 0 => "₀"
+        | 1 => "₁"
+        | 2 => "₂"
+        | 3 => "₃"
+        | 4 => "₄"
+        | 5 => "₅"
+        | 6 => "₆"
+        | 7 => "₇"
+        | 8 => "₈"
+        | 9 => "₉"
+        | _ => failwith "bad subscript";
+      let rec go acc => fun
+        | 0 => acc
+        | n => go (script (n mod 10) ^ acc) (n / 10);
+      go ""
+    };
+
+    let gen = {
+      let offset = 97;
+      let width = 26;
+      fun () i => {
+        let code = i mod width + offset;
+        let char = Char.chr code;
+        let prime = i / width;
+        let suffix = suffix prime;
+        let name = Char.escaped char ^ suffix;
+        Some name;
+      }
+    };
+  };
+
+  let module Env = {
+    type t = {
+      used: list Name.t,
+      rest: Stream.t Name.t,
+    };
+    let mk () => {
+      let used = [];
+      let rest = Stream.from @@ Name.gen ();
+      { used, rest };
+    };
+  };
+
+  type printer 'a = Env.t => Prec.t => formatter => 'a => unit;
+
+  let module Term = {
+    open Syntax.Term;
+    let rec pp ({ Env.used: used, rest } as env) prev fmt e => {
+      let next = Prec.calc e;
+      switch e {
+      | App e0 e1 =>
+        fprintf fmt "@[%a%a@ %a%a@]"
+          (Delim.pp prev next) "("
+          (pp env 1) e0
+          (pp env 0) e1
+          (Delim.pp prev next) ")"
+      | Lam e =>
+        let name = Stream.next rest;
+        let env = { ...env, Env.used: [name, ...used] };
+        fprintf fmt "%aλ%a.%a%a"
+          (Delim.pp prev next) "("
+          (pp_print_string) name
+          (pp env next) e
+          (Delim.pp prev next) ")"
+      | Var index =>
+        fprintf fmt "%s" @@ try (List.nth used index) {
+          | _ => "#" ^ string_of_int index
+          }
+      }
+    };
+  };
+
+  let module Sub = {
+    open Syntax.Sub;
+    let rec pp pp_elem env prev fmt => fun
+    | Cmp sgm1 sgm0 =>
+      fprintf fmt "@[%a;@ %a@]"
+        (pp pp_elem env prev) sgm1
+        (pp pp_elem env prev) sgm0
+    | Dot e sgm =>
+      fprintf fmt "@[%a@ ·@ %a@]"
+        (pp_elem env prev) e
+        (pp pp_elem env prev) sgm
+    | Id =>
+      fprintf fmt "ι"
+    | Shift =>
+      fprintf fmt "↑"
+    ;
+  };
+
+  let module Clo = {
+    let rec pp env prev fmt (Clo.Clo e sgm) => {
+      let next = Prec.calc e;
+      fprintf fmt "@[%a%a%a[%a]@]"
+        (Delim.pp prev next) "("
+        (Term.pp env next) e
+        (Delim.pp prev next) ")"
+        (Sub.pp pp env next) sgm
+    };
+  };
+
+  let module Zip = {
+    open Zip;
+    let rec pp pp_elem env prev fmt => fun
+    | App0 zip elem =>
+      fprintf fmt "inl@[<v -1>⟨@,%a@,%a⟩@]"
+        (pp pp_elem env prev) zip
+        (pp_elem env prev) elem
+    | App1 elem zip =>
+      fprintf fmt "inr@[<v -1>⟨@,%a@,%a⟩@]"
+        (pp_elem env prev) elem
+        (pp pp_elem env prev) zip
+    | Halt =>
+      fprintf fmt "halt"
+    | Lam zip =>
+      fprintf fmt "lam@[<v -1>⟨@,%a⟩@]"
+        (pp pp_elem env prev) zip
+    ;
+  };
+};
+
+let module Machine = {
+  type t = {
+    clo: Clo.t,
+    ctx: Zip.t Clo.t,
+  };
+
+  let into e => {
+    open Clo;
+    open Syntax.Sub;
+    let clo = Clo e Id;
+    let ctx = Zip.Halt;
+    { clo, ctx }
+  };
+
+  let from { clo, ctx } => Zip.apply (Zip.map Clo.from ctx) (Clo.from clo);
+
+  let pp fmt rule state => {
+    fprintf fmt "@[<v>ctx  ::@[<v -5>@,%a@]@,clo  ::@[<v -5>@,%a@]@,rule ::@[<v -5>@,%a@]@,term ::@[<v -5>@,%a@]@]@."
+      (Pretty.Zip.pp Pretty.Clo.pp (Pretty.Env.mk ()) 2) state.ctx
+                    (Pretty.Clo.pp (Pretty.Env.mk ()) 2) state.clo
+                                       (pp_print_string) rule
+                   (Pretty.Term.pp (Pretty.Env.mk ()) 2) (from state)
+  };
+
+  let halted state => {
+    open Clo;
+    open Syntax.Sub;
+    open Syntax.Term;
+    switch state {
+    | { clo: Clo (Var _) Id, _ } => true
+    | _ => false
+    } [@warning "-4"];
+  };
+
+  let step state => {
+    open Clo;
+    open Syntax.Sub;
+    open Syntax.Term;
+    let rule = ref "";
+    let state = switch state {
+    /* left */
+    | { clo: Clo (App e0 e1) sgm, ctx } =>
+      let clo = Clo e0 sgm;
+      let ctx = Zip.App0 ctx (Clo e1 sgm);
+      rule := "LEFT";
+      { clo, ctx };
+    /* beta */
+    | { clo: Clo (Lam e) sgm, ctx: Zip.App0 ctx c0 } =>
+      let clo = Clo e (Cmp (Dot c0 sgm) Id);
+      rule := "BETA";
+      { clo, ctx };
+    /* lambda */
+    | { clo: Clo (Lam e) sgm, ctx } =>
+      let clo = Clo e (Cmp (Dot (Clo (Var 0) Id) (Cmp sgm Shift)) Id);
+      let ctx = Zip.Lam ctx;
+      rule := "LAMBDA";
+      { clo, ctx };
+    /* associate */
+    | { clo: Clo (Var n) (Cmp (Cmp pi rho) sgm), ctx } =>
+      let clo = Clo (Var n) (Cmp pi (Cmp rho sgm));
+      rule := "ASSOCIATE";
+      { clo, ctx };
+    /* head */
+    | { clo: Clo (Var 0) (Cmp (Dot (Clo e pi) _) sgm), ctx } =>
+      let clo = Clo e (Cmp pi sgm);
+      rule := "HEAD";
+      { clo, ctx };
+    /* tail */
+    | { clo: Clo (Var n) (Cmp (Dot (Clo _ _) rho) sgm), ctx } =>
+      let clo = Clo (Var (n - 1)) (Cmp rho sgm);
+      rule := "TAIL";
+      { clo, ctx };
+    /* shift */
+    | { clo: Clo (Var n) (Cmp Shift sgm), ctx } =>
+      let clo = Clo (Var (n + 1)) sgm;
+      rule := "SHIFT";
+      { clo, ctx };
+    /* id */
+    | { clo: Clo (Var n) (Cmp Id sgm), ctx } =>
+      let clo = Clo (Var n) sgm;
+      rule := "ID";
+      { clo, ctx };
+    | _ =>
+      pp std_formatter !rule state;
+      failwith "bad state";
+    } [@warning "-4"];
+    pp std_formatter !rule state;
+    state;
+  };
+
+  let norm e => {
+    let count = ref 0;
+    let state = ref (into e);
+    while (not (halted !state)) {
+      fprintf std_formatter "@\n--- step[%d] ---@\n" !count;
+      incr count;
+      state := step !state;
+    };
+    from !state;
+  };
+};
+
+let module Test = {
+  open Syntax.Term;
+  let l e => Lam e;
+  let ( *@ ) e0 e1 => App e0 e1;
+  let ff = l (l (Var 1));
+  let tt = l (l (Var 0));
+  let zero = l (l (Var 1));
+  let succ = l (l (l (Var 0 *@ Var 2)));
+  let one = succ *@ zero;
+  let two = succ *@ one;
+  let three = succ *@ two;
+  let const = l (l (Var 1));
+  let fix = l (l (Var 1 *@ (Var 0 *@ Var 0)) *@ l (Var 1 *@ (Var 0 *@ Var 0)));
+  let add = fix *@ l (l (l (Var 1 *@ Var 0 *@ l (succ *@ Var 3 *@ Var 0 *@ Var 1))));
+  let init = l (l (Var 0) *@ l (l (Var 1)));
+};
+
+let module Run = {
+  let go () => Machine.norm Test.init;
+};

samples/Reason/SuperMerlin.re

@@ -0,0 +1,308 @@
+/*
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ */
+let startedMerlin: ref (option Js.Unsafe.any) = {contents: None};
+
+let fixedEnv = Js.Unsafe.js_expr "require('../lib/fixedEnv')";
+
+/* This and the subsequent big js blocks are copied over from Nuclide. More convenient for now. */
+let findNearestMerlinFile' = Js.Unsafe.js_expr {|
+  function findNearestMerlinFile(beginAtFilePath) {
+    var path = require('path');
+    var fs = require('fs');
+    var fileDir = path.dirname(beginAtFilePath);
+    var currentPath = path.resolve(fileDir);
+    do {
+      var fileToFind = path.join(currentPath, '.merlin');
+      var hasFile = fs.existsSync(fileToFind);
+      if (hasFile) {
+        return path.dirname(currentPath);
+      }
+
+      if (path.dirname(currentPath) === currentPath) {
+        // Bail
+        return '.';
+      }
+      currentPath = path.dirname(currentPath);
+    } while (true);
+  }
+|};
+
+let findNearestMerlinFile beginAtFilePath::path => {
+  let result = Js.Unsafe.fun_call findNearestMerlinFile' [|Js.Unsafe.inject (Js.string path)|];
+  Js.to_string result
+};
+
+let createMerlinReaderFnOnce' = Js.Unsafe.js_expr {|
+  function(ocamlMerlinPath, ocamlMerlinFlags, dotMerlinDir, fixedEnv) {
+    var spawn = require('child_process').spawn;
+    // To split while stripping out any leading/trailing space, we match on all
+    // *non*-whitespace.
+    var items = ocamlMerlinFlags === '' ? [] : ocamlMerlinFlags.split(/\s+/);
+    var merlinProcess = spawn(ocamlMerlinPath, items, {cwd: dotMerlinDir});
+    merlinProcess.stderr.on('data', function(d) {
+      console.error('Ocamlmerlin: something wrong happened:');
+      console.error(d.toString());
+    });
+
+    merlinProcess.stdout.on('close', function(d) {
+      console.error('Ocamlmerlin: closed.');
+    });
+
+    var cmdQueue = [];
+    var hasStartedReading = false;
+
+    var readline = require('readline');
+    var reader = readline.createInterface({
+      input: merlinProcess.stdout,
+      terminal: false,
+    });
+
+    return function(cmd, resolve, reject) {
+      cmdQueue.push([resolve, reject]);
+
+      if (!hasStartedReading) {
+        hasStartedReading = true;
+        reader.on('line', function(line) {
+          var response;
+          try {
+            response = JSON.parse(line);
+          } catch (err) {
+            response = null;
+          }
+          var resolveReject = cmdQueue.shift();
+          var resolve = resolveReject[0];
+          var reject = resolveReject[1];
+
+          if (!response || !Array.isArray(response) || response.length !== 2) {
+            reject(new Error('Unexpected ocamlmerlin output format: ' + line));
+            return;
+          }
+
+          var status = response[0];
+          var content = response[1];
+
+          var errorResponses = {
+            'failure': true,
+            'error': true,
+            'exception': true,
+          };
+
+          if (errorResponses[status]) {
+            reject(new Error('Ocamlmerlin returned an error: ' + line));
+            return;
+          }
+
+          resolve(content);
+        });
+      }
+
+      merlinProcess.stdin.write(JSON.stringify(cmd));
+    };
+  }
+|};
+
+let createMerlinReaderFnOnce
+    pathToMerlin::pathToMerlin
+    merlinFlags::merlinFlags
+    dotMerlinPath::dotMerlinPath =>
+  Js.Unsafe.fun_call
+    createMerlinReaderFnOnce'
+    [|
+      Js.Unsafe.inject (Js.string pathToMerlin),
+      Js.Unsafe.inject (Js.string merlinFlags),
+      Js.Unsafe.inject (Js.string dotMerlinPath),
+      Js.Unsafe.inject fixedEnv
+    |];
+
+let startMerlinProcess path::path =>
+  switch startedMerlin.contents {
+  | Some readerFn => ()
+  | None =>
+    let atomReasonPathToMerlin = Atom.Config.get "atom-reason.pathToMerlin";
+    let atomReasonMerlinFlags = Atom.Config.get "atom-reason.merlinFlags";
+    let atomReasonMerlinLogFile = Atom.Config.get "atom-reason.merlinLogFile";
+    switch atomReasonMerlinLogFile {
+    | JsonString "" => ()
+    | JsonString s => Atom.Env.setEnvVar "MERLIN_LOG" s
+    | _ => ()
+    };
+    let readerFn =
+      createMerlinReaderFnOnce
+        pathToMerlin::(Atom.JsonValue.unsafeExtractString atomReasonPathToMerlin)
+        merlinFlags::(Atom.JsonValue.unsafeExtractString atomReasonMerlinFlags)
+        dotMerlinPath::(findNearestMerlinFile beginAtFilePath::path);
+    startedMerlin.contents = Some readerFn
+  };
+
+let readOneLine cmd::cmd resolve reject =>
+  switch startedMerlin.contents {
+  | None => raise Not_found
+  | Some readerFn =>
+    Js.Unsafe.fun_call
+      readerFn
+      [|
+        Js.Unsafe.inject cmd,
+        Js.Unsafe.inject (Js.wrap_callback resolve),
+        Js.Unsafe.inject (Js.wrap_callback reject)
+      |]
+  };
+
+/* contextify is important for avoiding different buffers calling the backing merlin at the same time. */
+/* https://github.com/the-lambda-church/merlin/blob/d98a08d318ca14d9c702bbd6eeadbb762d325ce7/doc/dev/PROTOCOL.md#contextual-commands */
+let contextify query::query path::path => Js.Unsafe.obj [|
+  ("query", Js.Unsafe.inject query),
+  ("context", Js.Unsafe.inject (Js.array [|Js.string "auto", Js.string path|]))
+|];
+
+let prepareCommand text::text path::path query::query resolve reject => {
+  startMerlinProcess path;
+  /* These two commands should be run before every main command. */
+  readOneLine
+    cmd::(
+      contextify
+        /* The protocol command tells Merlin which API version we want to use. (2 for us) */
+        query::(
+          Js.array [|
+            Js.Unsafe.inject (Js.string "protocol"),
+            Js.Unsafe.inject (Js.string "version"),
+            Js.Unsafe.inject (Js.number_of_float 2.)
+          |]
+        )
+        path::path
+    )
+    (
+      fun _ =>
+        readOneLine
+          cmd::(
+            contextify
+              /* The tell command allows us to synchronize our text with Merlin's internal buffer. */
+              query::(
+                Js.array [|Js.string "tell", Js.string "start", Js.string "end", Js.string text|]
+              )
+              path::path
+          )
+          (fun _ => readOneLine cmd::(contextify query::query path::path) resolve reject)
+          reject
+    )
+    reject
+};
+
+let positionToJsMerlinPosition (line, col) => Js.Unsafe.obj [|
+  /* lines (rows) are 1-based for merlin, not 0-based, like for Atom */
+  ("line", Js.Unsafe.inject (Js.number_of_float (float_of_int (line + 1)))),
+  ("col", Js.Unsafe.inject (Js.number_of_float (float_of_int col)))
+|];
+
+/* Actual merlin commands we'll use. */
+let getTypeHint path::path text::text position::position resolve reject =>
+  prepareCommand
+    text::text
+    path::path
+    query::(
+      Js.array [|
+        Js.Unsafe.inject (Js.string "type"),
+        Js.Unsafe.inject (Js.string "enclosing"),
+        Js.Unsafe.inject (Js.string "at"),
+        Js.Unsafe.inject (positionToJsMerlinPosition position)
+      |]
+    )
+    resolve
+    reject;
+
+let getAutoCompleteSuggestions
+    path::path
+    text::text
+    position::position
+    prefix::prefix
+    resolve
+    reject =>
+  prepareCommand
+    text::text
+    path::path
+    query::(
+      Js.array [|
+        Js.Unsafe.inject (Js.string "complete"),
+        Js.Unsafe.inject (Js.string "prefix"),
+        Js.Unsafe.inject (Js.string prefix),
+        Js.Unsafe.inject (Js.string "at"),
+        Js.Unsafe.inject (positionToJsMerlinPosition position),
+        Js.Unsafe.inject (Js.string "with"),
+        Js.Unsafe.inject (Js.string "doc")
+      |]
+    )
+    resolve
+    reject;
+
+let getDiagnostics path::path text::text resolve reject =>
+  prepareCommand
+    text::text
+    path::path
+    query::(Js.array [|Js.Unsafe.inject (Js.string "errors")|])
+    resolve
+    reject;
+
+let locate path::path text::text extension::extension position::position resolve reject =>
+  prepareCommand
+    text::text
+    path::path
+    query::(
+      Js.array [|
+        Js.Unsafe.inject (Js.string "locate"),
+        Js.Unsafe.inject (Js.string ""),
+        Js.Unsafe.inject (Js.string extension),
+        Js.Unsafe.inject (Js.string "at"),
+        Js.Unsafe.inject (positionToJsMerlinPosition position)
+      |]
+    )
+    resolve
+    reject;
+
+/* reject */
+let getOccurrences path::path text::text position::position resolve reject =>
+  prepareCommand
+    text::text
+    path::path
+    query::(
+      Js.array [|
+        Js.Unsafe.inject (Js.string "occurrences"),
+        Js.Unsafe.inject (Js.string "ident"),
+        Js.Unsafe.inject (Js.string "at"),
+        Js.Unsafe.inject (positionToJsMerlinPosition position)
+      |]
+    )
+    resolve
+    reject;
+
+let destruct
+    path::path
+    text::text
+    startPosition::startPosition
+    endPosition::endPosition
+    resolve
+    reject =>
+  prepareCommand
+    text::text
+    path::path
+    query::(
+      Js.array [|
+        Js.Unsafe.inject (Js.string "case"),
+        Js.Unsafe.inject (Js.string "analysis"),
+        Js.Unsafe.inject (Js.string "from"),
+        Js.Unsafe.inject (positionToJsMerlinPosition startPosition),
+        Js.Unsafe.inject (Js.string "to"),
+        Js.Unsafe.inject (positionToJsMerlinPosition endPosition)
+      |]
+    )
+    resolve
+    reject;
+
+let getOutline path::path text::text resolve reject =>
+  prepareCommand
+    text::text
+    path::path
+    query::(Js.array [|Js.Unsafe.inject (Js.string "outline")|])
+    resolve
+    reject;

samples/Reason/Syntax.re

@@ -0,0 +1,989 @@
+/* Copyright (c) 2015-present, Facebook, Inc. All rights reserved. */
+[@@@autoFormat let wrap = 80; let shift = 2];
+
+Modules.run ();
+
+Polymorphism.run ();
+
+Variants.run ();
+
+BasicStructures.run ();
+
+TestUtils.printSection "General Syntax";
+
+/* Won't work! */
+/* let matchingFunc a = match a with */
+/*   `Thingy x => (print_string "matched thingy x"); x */
+/*   | `Other x => (print_string "matched other x"); x;; */
+/*  */
+let matchingFunc a =>
+  switch a {
+  | `Thingy x =>
+    print_string "matched thingy x";
+    let zz = 10;
+    zz
+  | `Other x =>
+    print_string "matched other x";
+    x
+  };
+
+type firstTwoShouldBeGroupedInParens =
+  (int => int) => int => int;
+
+type allParensCanBeRemoved =
+  int => int => int => int;
+
+type firstTwoShouldBeGroupedAndFirstThree =
+  ((int => int) => int) => int;
+
+/* Same thing now but with type constructors instead of each int */
+type firstTwoShouldBeGroupedInParens =
+  (list int => list int) => list int => list int;
+
+type allParensCanBeRemoved =
+  list int => list int => list int => list int;
+
+type firstTwoShouldBeGroupedAndFirstThree =
+  ((list int => list int) => list int) =>
+  list int;
+
+type myRecordType = {
+  firstTwoShouldBeGroupedInParens:
+    (int => int) => int => int,
+  allParensCanBeRemoved:
+    int => int => int => int,
+  firstTwoShouldBeGroupedAndFirstThree:
+    ((int => int) => int) => int
+};
+
+type firstNamedArgShouldBeGroupedInParens =
+  first::(int => int) => second::int => int;
+
+type allParensCanBeRemoved =
+  first::int => second::int => third::int => int;
+
+type firstTwoShouldBeGroupedAndFirstThree =
+  first::((int => int) => int) => int;
+
+/* Same thing now, but with type constructors instead of int */
+type firstNamedArgShouldBeGroupedInParens =
+  first::(list int => list int) =>
+  second::list int =>
+  list int;
+
+type allParensCanBeRemoved =
+  first::list int =>
+  second::list int =>
+  third::list int =>
+  list int;
+
+type firstTwoShouldBeGroupedAndFirstThree =
+  first::((list int => list int) => list int) =>
+  list int;
+
+type firstNamedArgShouldBeGroupedInParens =
+  first::(int => int)? =>
+  second::int list? =>
+  int;
+
+/* The arrow necessitates parens around the next two args. The ? isn't what
+ * makes the parens necessary. */
+type firstNamedArgShouldBeGroupedInParensAndSecondNamedArg =
+  first::(int => int)? =>
+  second::(int => int)? =>
+  int;
+
+type allParensCanBeRemoved =
+  first::int? =>
+  second::int? =>
+  third::int? =>
+  int;
+
+type firstTwoShouldBeGroupedAndFirstThree =
+  first::((int => int) => int) => int;
+
+type noParens =
+  one::int => int => int => two::int => int;
+
+type noParensNeeded =
+  one::int => int => int => two::int => int;
+
+type firstNamedArgNeedsParens =
+  one::(int => int => int) => two::int => int;
+
+/* Now, let's try type aliasing */
+/* Unless wrapped in parens, types between arrows may not be aliased, may not
+ * themselves be arrows. */
+type parensRequiredAroundFirstArg =
+  (list int as 'a) => int as 'a;
+
+type parensRequiredAroundReturnType =
+  (list int as 'a) => (int as 'a);
+
+type parensRequiredAroundReturnType =
+  (list int as 'a) => (int as 'a) as 'b;
+
+type noParensNeededWhenInTuple =
+  (list int as 'a, list int as 'b) as 'entireThing;
+
+type myTypeDef 'a = list 'a;
+
+type instatiatedTypeDef = myTypeDef int => int;
+
+/* Test a type attribute for good measure */
+/* We should clean up all of the attribute tagging eventually, but for now,
+ * let's make it super ugly to get out of the way of all the formatting/parsing
+ * implementations (fewer conflicts during parsing, fewer edge cases during
+ * printing).
+ */
+type something = (
+  int,
+  int [@lookAtThisAttribute]
+);
+
+type longWrappingTypeDefinitionExample =
+  M_RK__G.Types.instance
+    (TGRecognizer.tGFields unit unit)
+    (TGRecognizer.tGMethods unit unit);
+
+type semiLongWrappingTypeDefinitionExample =
+  M_RK__Gesture.Types.instance
+    TGRecognizerFinal.tGFields
+    TGRecognizerFinal.tGMethods;
+
+type semiLongWrappingTypeWithConstraint =
+  M_RK__Gesture.Types.instance
+    'a
+    TGRecognizerFinal.tGFields
+    TGRecognizerFinal.tGMethods
+constraint 'a = (unit, unit);
+
+type onelineConstrain = 'a constraint 'a = int;
+
+/* This must be in trunk but not in this branch of OCaml */
+/* type withNestedRecords = MyConstructor {myField: int} */
+type colors =
+  | Red int
+  | Black int
+  | Green int;
+
+/* Another approach is to require declared variants to wrap any record */
+/* type myRecord = MyRecord {name: int}; */
+/* let myValue = MyRecord {name: int}; */
+/* This would force importing of the module */
+/* This would also lend itself naturally to pattern matching - and avoid having
+   to use `.` operator at all since you normally destructure. */
+type nameBlahType = {nameBlah: int};
+
+let myRecord = {nameBlah: 20};
+
+let myRecordName = myRecord.nameBlah;
+
+let {nameBlah}: nameBlahType = {nameBlah: 20};
+
+print_int nameBlah;
+
+let {nameBlah: aliasedToThisVar}: nameBlahType = {
+  nameBlah: 20
+};
+
+print_int aliasedToThisVar;
+
+let desiredFormattingForWrappedLambda:
+  int => int => int => nameBlahType =
+  /*
+
+   fun is
+   pre-   /firstarg\
+   fix   /-coupled--\
+    |-\ /-to-prefix--\       */
+  fun curriedArg anotherArg lastArg => {
+    nameBlah: 10
+  };
+
+type longerInt = int;
+
+let desiredFormattingForWrappedLambdaWrappedArrow:
+  longerInt =>
+  longerInt =>
+  longerInt =>
+  nameBlahType =
+  /*
+
+   fun is
+   pre-   /firstarg\
+   fix   /-coupled--\
+    |-\ /-to-prefix--\       */
+  fun curriedArg anotherArg lastArg => {
+    nameBlah: 10
+  };
+
+let desiredFormattingForWrappedLambdaReturnOnNewLine
+    /*
+
+     fun is
+     pre-   /firstarg\
+     fix   /-coupled--\
+      |-\ /-to-prefix--\       */
+    curriedArg
+    anotherArg
+    lastArg => {
+  nameBlah: 10
+};
+
+/*
+ let is
+ pre-
+ fix    /-function binding name---\
+ |-\   / is coupled to prefix      \   */
+let desiredFormattingForWrappedSugar
+    curriedArg
+    anotherArg
+    lastArg => {
+  nameBlah: 10
+};
+
+/*
+ let is
+ pre-
+ fix    /-function binding name---\
+ |-\   / is coupled to prefix      \   */
+let desiredFormattingForWrappedSugarReturnOnNewLine
+    curriedArg
+    anotherArg
+    lastArg => {
+  nameBlah: 10
+};
+
+/*
+   let  : type t1 t2. t1 * t2 list -> t1 = ...
+   let rec f : 't1 't2. 't1 * 't2 list -> 't1 =
+     fun (type t1) (type t2) -> (... : t1 * t2 list -> t1)
+ */
+type point = {x: int, y: int};
+
+type point3D = {x: int, y: int, z: int};
+
+let point2D = {x: 20, y: 30};
+
+let point3D: point3D = {
+  x: 10,
+  y: 11,
+  z: 80 /* Optional Comma */
+};
+
+let printPoint (p: point) => {
+  print_int p.x;
+  print_int p.y
+};
+
+let addPoints (p1: point, p2: point) => {
+  x: p1.x + p2.x,
+  y: p1.y + p2.y
+};
+
+let res1 = printPoint point2D;
+
+let res2 =
+  printPoint {x: point3D.x, y: point3D.y};
+
+/*
+    When () were used to indicate sequences, the parser used seq_expr not only
+    for grouping sequences, but also to form standard precedences.
+                          /------- sequence_expr ------\
+    let res3 = printPoint (addPoints (point2D, point3D));
+
+    Interestingly, it knew that tuples aren't sequences.
+
+    To move towards semi delimited, semi-terminated, braces-grouped sequences:
+    while allowing any non-sequence expression to be grouped on parens, we make
+    an explicit rule that allows one single non-semi ended expression to be
+    grouped in parens.
+
+    Actually: We will allow an arbitrary number of semi-delimited expressions to
+    be wrapped in parens, but the braces grouped semi delimited (sequence)
+    expressions must *also* be terminated with a semicolon.
+
+    This allows the parser to distinguish between
+
+        let x = {a};    /* Record {a:a} */
+        let x = {a;};   /* Single item sequence returning identifier {a} */
+ */
+let res3 =
+  printPoint (
+    addPoints (
+      point2D,
+      {x: point3D.x, y: point3D.y}
+    )
+  );
+
+type person = {age: int, name: string};
+
+type hiredPerson = {
+  age: string,
+  name: string,
+  dateHired: int
+};
+
+let o: person = {name: "bob", age: 10};
+
+/* Parens needed? Nope! */
+let o: person = {name: "bob", age: 10};
+
+let printPerson (p: person) => {
+  let q: person = p;
+  p.name ^ p.name
+};
+
+/* let dontParseMeBro x y:int = x = y;*/
+/* With this unification, anywhere eyou see `= fun` you can just ommit it */
+let blah a => a; /* Done */
+
+let blah a => a; /* Done (almost) */
+
+let blah a b => a; /* Done */
+
+let blah a b => a; /* Done (almost) */
+
+/* More than one consecutive pattern must have a single case */
+type blah = {blahBlah: int};
+
+let blah a {blahBlah} => a;
+
+let blah a {blahBlah} => a;
+
+let module TryToExportTwice = {
+  let myVal = "hello";
+};
+
+/*
+   Unifying top level module syntax with local module syntax is probably a bad
+   idea at the moment because it makes it more difficult to continue to support
+   `let .. in` bindings. We can distinguish local modules for `let..in` that
+   just happen to be defined at the top level (but not exported).
+
+     let MyModule = {let myVal = 20;} in
+     MyModule.x
+
+   Wait, where would this ever be valid, even if we continued to support
+   `let..in`?
+ */
+let onlyDoingThisTopLevelLetToBypassTopLevelSequence = {
+  let x = {
+    print_int 1;
+    print_int 20 /* Missing trailing SEMI */
+  };
+  let x = {
+    print_int 1;
+    print_int 20; /* Ensure missing middle SEMI reported well */
+    print_int 20
+  };
+  let x = {
+    print_int 1;
+    print_int 20;
+    10
+    /* Comment in final position */
+  }; /* Missing final SEMI */
+  x + x
+};
+
+type hasA = {a: int};
+
+let a = 10;
+
+let returnsASequenceExpressionWithASingleIdentifier
+    () => a;
+
+let thisReturnsA () => a;
+
+let thisReturnsAAsWell () => a;
+
+let recordVal: int = (thisReturnsARecord ()).a;
+
+Printf.printf
+  "\nproof that thisReturnsARecord: %n\n"
+  recordVal;
+
+Printf.printf
+  "\nproof that thisReturnsA: %n\n"
+  (thisReturnsA ());
+
+/* Pattern matching */
+let blah arg =>
+  switch arg {
+  /* Comment before Bar */
+  | /* Comment between bar/pattern */ Red _ => 1
+  /* Comment Before non-first bar */
+  | /* Comment betwen bar/pattern */ Black _ => 0
+  | Green _ => 0
+  };
+
+/* Any function that pattern matches a multicase match is interpretted as a
+ * single arg that is then matched on. Instead of the above `blah` example:*/
+let blah =
+  fun
+  | Red _ => 1
+  | Black _ => 0
+  | Green _ => 1;
+
+/* `fun a => a` is read as "a function that maps a to a". Then the */
+/* above example is read: "a function that 'either maps' Red to.. or maps .." */
+/* Thc00f564e first bar is read as "either maps" */
+/* Curried form is not supported:
+      let blah x | Red _ => 1 | Black _ => 0;
+      Theres no sugar rule for dropping => fun, only = fun
+   */
+/* let blahCurriedX x => fun  /* See, nothing says we can drop the => fun */ */
+/*   |(Red x | Black x | Green x) => 1     /* With some effort, we can ammend the sugar rule that would */ */
+/*   | Black x => 0                       /* Allow us to drop any => fun.. Just need to make pattern matching */ */
+/*   | Green x => 0;                      /* Support that */ */
+/*  */
+let blahCurriedX x =>
+  fun
+  | Red x
+  | Black x
+  | Green x =>
+    1 /* With some effort, we can ammend the sugar rule that would */
+  | Black x => 0 /* Allow us to drop any => fun.. Just need to make pattern matching */
+  | Green x => 0; /* Support that */
+
+let sameThingInLocal = {
+  let blahCurriedX x =>
+    fun
+    | Red x
+    | Black x
+    | Green x =>
+      1 /* With some effort, we can ammend the sugar rule that would */
+    | Black x => 0 /* Allow us to drop any => fun.. Just need to make pattern matching */
+    | Green x => 0; /* Support that */
+  blahCurriedX
+};
+
+/* This should be parsed/printed exactly as the previous */
+let blahCurriedX x =>
+  fun
+  | Red x
+  | Black x
+  | Green x => 1
+  | Black x => 0
+  | Green x => 0;
+
+/* Any time there are multiple match cases we require a leading BAR */
+let v = Red 10;
+
+let Black x | Red x | Green x = v; /* So this NON-function still parses */
+
+/* This doesn't parse, however (and it doesn't in OCaml either):
+     let | Black x | Red x | Green x = v;
+   */
+print_int x;
+
+/* Scoping: Let sequences. Familiar syntax for lexical ML style scope and
+   sequences. */
+let res = {
+  let a = "a starts out as";
+  {
+    print_string a;
+    let a = 20;
+    print_int a
+  };
+  print_string a
+};
+
+let res = {
+  let a = "first its a string";
+  let a = 20;
+  print_int a;
+  print_int a;
+  print_int a
+};
+
+let res = {
+  let a = "a is always a string";
+  print_string a;
+  let b = 30;
+  print_int b
+};
+
+/* let result = LyList.map (fun | [] => true | _ => false) []; */
+/* OTHERWISE: You cannot tell if a is the first match case falling through or
+ * a curried first arg */
+/* let blah = fun a | patt => 0 | anotherPatt => 1; */
+/* let blah a patt => 0 | anotherPatt => 1; */
+/*simple pattern  EQUALGREATER      expr */
+let blah a {blahBlah} => a;
+
+/*            match_case             */
+/*     pattern EQUALGREATER  expr */
+let blah =
+  fun
+  | Red _ => 1
+  | Black _ => 0
+  | Green _ => 0;
+
+/* Won't work! */
+/* let arrowFunc = fun a b => print_string "returning aplusb from arrow"; a + b;;  */
+let arrowFunc a b => {
+  print_string "returning aplusb from arrow";
+  a + b
+};
+
+let add a b => {
+  let extra = {
+    print_string "adding";
+    0
+  };
+  let anotherExtra = 0;
+  extra + a + b + anotherExtra
+};
+
+print_string (string_of_int (add 4 34));
+
+let dummy _ => 10;
+
+dummy res1;
+
+dummy res2;
+
+dummy res3;
+
+/* Some edge cases */
+let myFun firstArg (Red x | Black x | Green x) =>
+  firstArg + x;
+
+let matchesWithWhen a =>
+  switch a {
+  | Red x when 1 > 0 => 10
+  | Red _ => 10
+  | Black x => 10
+  | Green x => 10
+  };
+
+let matchesWithWhen =
+  fun
+  | Red x when 1 > 0 => 10
+  | Red _ => 10
+  | Black x => 10
+  | Green x => 10;
+
+let matchesOne (`Red x) => 10;
+
+/*
+ Typical OCaml would make you *wrap the functions in parens*! This is because it
+ can't tell if a semicolon is a sequence operator. Even if we had records use
+ commas to separate fields,
+ */
+type adders = {
+  addTwoNumbers: int => int => int,
+  addThreeNumbers: int => int => int => int,
+  addThreeNumbersTupled: (int, int, int) => int
+};
+
+let myRecordWithFunctions = {
+  addTwoNumbers: fun a b => a + b,
+  addThreeNumbers: fun a b c => a + b + c,
+  addThreeNumbersTupled: fun (a, b, c) =>
+    a + b + c
+};
+
+let result =
+  myRecordWithFunctions.addThreeNumbers 10 20 30;
+
+let result =
+  myRecordWithFunctions.addThreeNumbersTupled (
+    10,
+    20,
+    30
+  );
+
+let lookTuplesRequireParens = (1, 2);
+
+/* let thisDoesntParse = 1, 2;  */
+let tupleInsideAParenSequence = {
+  print_string "look, a tuple inside a sequence";
+  let x = 10;
+  (x, x)
+};
+
+let tupleInsideALetSequence = {
+  print_string "look, a tuple inside a sequence";
+  let x = 10;
+  (x, x)
+};
+
+/* We *require* that function return types be wrapped in
+   parenthesis. In this example, there's no ambiguity */
+let makeIncrementer (delta: int) :(int => int) =>
+  fun a => a + delta;
+
+/* We could even force that consistency with let bindings - it's allowed
+      currently but not forced.
+   */
+let myAnnotatedValBinding: int = 10;
+
+/* Class functions (constructors) and methods are unified in the same way */
+class classWithNoArg = {
+  method x = 0;
+  method y = 0;
+};
+
+/* This parses but doesn't type check
+     class myClass init => object
+       method x => init
+       method y => init
+     end;
+   */
+let myFunc (a: int) (b: int) :(int, int) => (
+  a,
+  b
+);
+
+let myFunc (a: int) (b: int) :list int => [1];
+
+let myFunc (a: int) (b: int) :point => {
+  x: a,
+  y: b
+};
+
+let myFunc (a: int, b: int) :point => {
+  x: a,
+  y: b
+};
+
+type myThing = (int, int);
+
+type stillARecord = {name: string, age: int};
+
+/* Rebase latest OCaml to get the following: And fixup
+   `generalized_constructor_arguments` according to master. */
+/* type ('a, 'b) myOtherThing = Leaf {first:'a, second: 'b} | Null; */
+type branch 'a 'b = {first: 'a, second: 'b};
+
+type myOtherThing 'a 'b =
+  | Leaf (branch 'a 'b)
+  | Null;
+
+type yourThing = myOtherThing int int;
+
+/* Conveniently - this parses exactly how you would intend! No *need* to wrap
+   in an extra [], but it doesn't hurt */
+/* FIXME type lookAtThesePolyVariants = list [`Red] ; */
+/* FIXME type bracketsGroupMultipleParamsAndPrecedence = list (list (list [`Red])); */
+/* FIXME type youCanWrapExtraIfYouWant = (list [`Red]); */
+/* FIXME type hereAreMultiplePolyVariants = list [`Red | `Black]; */
+/* FIXME type hereAreMultiplePolyVariantsWithOptionalWrapping = list ([`Red | `Black]); */
+/*
+   /* Proposal: ES6 style lambdas: */
+
+   /* Currying */
+   let lookES6Style = (`Red x) (`Black y) => { };
+   let lookES6Style (`Red x) (`Black y) => { };
+
+   /* Matching the single argument */
+   let lookES6Style = oneArg => match oneArg with
+     | `Red x => x
+     | `Black x => x;
+
+   /* The "trick" to currying that we already have is basically the same - we just
+    * have to reword it a bit:
+    * From:
+    * "Any time you see [let x = fun ...] just replace it with [let x ...]"
+    * To:
+    * "Any time you see [let x = ... => ] just replace it with [let x ... => ]"
+    */
+   let lookES6Style oneArg => match oneArg with
+     | `Red x => x
+     | `Black x => x;
+
+ */
+
+/** Current OCaml Named Arguments. Any aliasing is more than just aliasing!
+    OCaml allows full on pattern matching of named args. */
+/*
+ A: let named              ~a    ~b                = aa + bb in
+ B: let namedAlias         ~a:aa ~b:bb             = aa + bb in
+ C: let namedAnnot         ~(a:int) ~(b:int)       = a + b in
+ D: let namedAliasAnnot    ~a:(aa:int) ~b:(bb:int) = aa + bb in
+ E: let optional           ?a    ?b                              = 10 in
+ F: let optionalAlias      ?a:aa ?b:bb                           = 10 in
+ G: let optionalAnnot      ?(a:int option) ?(b:int option)       = 10 in
+ H: let optionalAliasAnnot ?a:(aa:int option) ?b:(bb:int option) = 10 in
+ /*
+ Look! When a default is provided, annotation causes inferred type of argument
+ to not be "option" since it's automatically destructured (because we know it
+ will always be available one way or another.)
+ */
+ I: let defOptional           ?(a=10)    ?(b=10)                 = 10 in
+ J: let defOptionalAlias      ?a:(aa=10) ?b:(bb=10)              = 10 in
+ K: let defOptionalAnnot      ?(a:int=10) ?(b:int=10)            = 10 in
+                             \       \
+                              \label_let_pattern opt_default: no longer needed in SugarML
+
+ L: let defOptionalAliasAnnot ?a:(aa:int=10) ?b:(bb:int=10)      = 10 in
+                               \        \
+                                \let_pattern: still a useful syntactic building block in SugarML
+ */
+
+/**
+ * In Reason, the syntax for named args uses double semicolon, since
+ * the syntax for lists uses ES6 style [], freeing up the ::.
+ */
+let a = 10;
+
+let b = 20;
+
+/*A*/
+let named a::a b::b => a + b;
+
+type named = a::int => b::int => int;
+
+/*B*/
+let namedAlias a::aa b::bb => aa + bb;
+
+let namedAlias a::aa b::bb => aa + bb;
+
+type namedAlias = a::int => b::int => int;
+
+/*C*/
+let namedAnnot a::(a: int) b::(b: int) => 20;
+
+/*D*/
+let namedAliasAnnot a::(aa: int) b::(bb: int) => 20;
+
+/*E*/
+let myOptional a::a=? b::b=? () => 10;
+
+type named = a::int? => b::int? => unit => int;
+
+/*F*/
+let optionalAlias a::aa=? b::bb=? () => 10;
+
+/*G*/
+let optionalAnnot a::(a: int)=? b::(b: int)=? () => 10;
+
+/*H*/
+let optionalAliasAnnot
+    a::(aa: int)=?
+    b::(bb: int)=?
+    () => 10;
+
+/*I: */
+let defOptional a::a=10 b::b=10 () => 10;
+
+type named = a::int? => b::int? => unit => int;
+
+/*J*/
+let defOptionalAlias a::aa=10 b::bb=10 () => 10;
+
+/*K*/
+let defOptionalAnnot
+    a::(a: int)=10
+    b::(b: int)=10
+    () => 10;
+
+/*L*/
+let defOptionalAliasAnnot
+    a::(aa: int)=10
+    b::(bb: int)=10
+    () => 10;
+
+/*M: Invoking them - Punned */
+let resNotAnnotated = named a::a b::b;
+
+/*N:*/
+let resAnnotated: int = named a::a b::b;
+
+/*O: Invoking them */
+let resNotAnnotated = named a::a b::b;
+
+/*P: Invoking them */
+let resAnnotated: int = named a::a b::b;
+
+/*Q: Here's why "punning" doesn't work!  */
+/* Is b:: punned with a final non-named arg, or is b:: supplied b as one named arg? */
+let b = 20;
+
+let resAnnotated = named a::a b::b;
+
+/*R: Proof that there are no ambiguities with return values being annotated */
+let resAnnotated: ty = named a::a b;
+
+/*S: Explicitly passed optionals are a nice way to say "use the default value"*/
+let explictlyPassed =
+  myOptional a::?None b::?None;
+
+/*T: Annotating the return value of the entire function call */
+let explictlyPassedAnnotated: int =
+  myOptional a::?None b::?None;
+
+/*U: Explicitly passing optional with identifier expression */
+let a = None;
+
+let explictlyPassed = myOptional a::?a b::?None;
+
+let explictlyPassedAnnotated: int =
+  myOptional a::?a b::?None;
+
+let nestedLet = {
+  let _ = 1;
+  ()
+};
+
+let nestedLet = {
+  let _ = 1;
+  ()
+};
+
+let nestedLet = {
+  let _ = 1;
+  ()
+};
+
+let nestedLet = {
+  let _ = 1;
+  2
+};
+
+/*
+ * Showing many combinations of type annotations and named arguments.
+ */
+type typeWithNestedNamedArgs =
+  outerOne::(
+    innerOne::int => innerTwo::int => int
+  ) =>
+  outerTwo::int =>
+  int;
+
+type typeWithNestedOptionalNamedArgs =
+  outerOne::
+    (innerOne::int => innerTwo::int => int)? =>
+  outerTwo::int? =>
+  int;
+
+type typeWithNestedOptionalNamedArgs =
+  outerOne::list string? => outerTwo::int? => int;
+
+let x =
+  callSomeFunction
+    withArg::10 andOtherArg::wrappedArg;
+
+let res = {
+  (constraintedSequenceItem: string);
+  (dontKnowWheYoudWantToActuallyDoThis: string)
+};
+
+let res = {
+  (
+    butTheyWillBePrintedWithAppropriateSpacing: string
+  );
+  (soAsToInstillBestDevelopmentPractices: string)
+};
+
+let x = [
+  (eachItemInListCanBeAnnotated: int),
+  (typeConstraints: float),
+  (
+    tupleConstraints: int,
+    andNotFunctionInvocations: int
+  )
+];
+
+let x = [
+  (butWeWillPrint: int),
+  (themAsSpaceSeparated: float),
+  (toInfluenceYour: int, developmentHabbits: int)
+];
+
+let newRecord = {
+  ...(annotatedSpreadRecord: someRec),
+  x: y
+};
+
+let newRecord = {
+  ...(annotatedSpreadRecord: someRec),
+  blah: 0,
+  foo: 1
+};
+
+let newRecord = {
+  ...(
+    youCanEvenCallMethodsHereAndAnnotate them: someRec
+  ),
+  blah: 0,
+  foo: 1
+};
+
+let newRecord = {
+  ...(
+    youCanEvenCallMethodsHereAndAnnotate
+      them named::10: someRec
+  ),
+  blah: 0,
+  foo: 1
+};
+
+let something: thing blah = aTypeAnnotation;
+
+let something: thing blah = thisIsANamedArg;
+
+let something: thing blah = aTypeAnnotation;
+
+let something: blah = thisIsANamedArg thing;
+
+let something: blah = typeAnnotation thing;
+
+let newRecord = {
+  ...(
+    heresAFunctionWithNamedArgs argOne::i: annotatedResult
+  ),
+  soAsToInstill: 0,
+  developmentHabbits: 1
+};
+
+[@@@thisIsAThing];
+
+let x = 10;
+
+/* Ensure that the parenthesis are preserved here because they are
+ * important:
+ */
+let something =
+  fun
+  | None => (
+      fun
+      | [] => "emptyList"
+      | [_, ..._] => "nonEmptyList"
+    )
+  | Some _ => (
+      fun
+      | [] => "emptyList"
+      | [_, ..._] => "nonEmptyList"
+    );
+
+/*  A | B = X; */
+let A | B = X;
+
+/*  A | (B | C) = X; */
+let A | (B | C) = X;
+
+/* (A | B) | (C | D) = X; */
+let A | B | (C | D) = X;
+
+/*  A | B | (C | D) = X; */
+let A | B | (C | D) = X;
+
+/* (A | B) | C = X; */
+let A | B | C = X;
+
+/*  A | B | C = X; */
+let A | B | C = X;
+
+
+/** External function declaration
+ *
+ */
+external f : int => int = "foo";
+
+let x = {contents: 0};
+
+let unitVal = x.contents = 210;