Enable compiler checks of most doc snippets

Fixes rescript-lang/syntax#126

Author: chenglou

pages/docs/manual/latest/array-and-list.mdx

@@ -12,7 +12,7 @@ Arrays are our primary ordered data structure. They work the same way as JavaScr
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 let myArray = ["hello", "world", "how are you"]
 ```
 ```js
@@ -31,7 +31,7 @@ Access & update an array item like so:
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 let myArray = ["hello", "world", "how are you"]
 
 let firstItem = myArray[0] // "hello"
@@ -59,7 +59,7 @@ ReScript provides a singly linked list too. Lists are:
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 let myList = list{1, 2, 3}
 ```
 ```js
@@ -93,7 +93,7 @@ Use the spread syntax:
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res prelude
 let myList = list{1, 2, 3}
 let anotherList = list{0, ...myList}
 ```
@@ -129,7 +129,7 @@ Updating an arbitrary item in the middle of a list is also discouraged, since it
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 let message =
   switch myList {
   | list{} => "This list is empty"

pages/docs/manual/latest/bind-to-global-js-values.mdx

@@ -12,7 +12,7 @@ Some JS values, like `setTimeout`, live in the global scope. You can bind to the
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 @bs.val external setTimeout: (unit => unit, int) => float = "setTimeout"
 @bs.val external clearTimeout: float => unit = "clearTimeout"
 ```
@@ -38,7 +38,7 @@ We're in a language with a great type system now! Let's leverage a popular featu
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 type timerId
 @bs.val external setTimeout: (unit => unit, int) => timerId = "setTimeout"
 @bs.val external clearTimeout: timerId => unit = "clearTimeout"
@@ -66,7 +66,7 @@ If you want to bind to a value inside a global module, e.g. `Math.random`, attac
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 @bs.scope("Math") @bs.val external random: unit => float = "random"
 let someNumber = random()
 ```
@@ -80,7 +80,7 @@ you can bind to an arbitrarily deep object by passing a tuple to `bs.scope`:
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 @bs.val @bs.scope(("window", "___location", "ancestorOrigins"))
 external length: int = "length"
 ```
@@ -100,7 +100,7 @@ For these troublesome global values, ReScript provides a special approach: `%ext
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 switch %external(__DEV__) {
 | Some(_) => Js.log("dev mode")
 | None => Js.log("production mode")
@@ -124,7 +124,7 @@ Another example:
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 switch %external(__filename) {
 | Some(f) => Js.log(f)
 | None => Js.log("non-node environment")

pages/docs/manual/latest/bind-to-js-function.mdx

@@ -10,7 +10,7 @@ Binding a JS function is like binding any other value:
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 // Import nodejs' path.dirname
 @bs.module("path") external dirname: string => string = "dirname"
 let root = dirname("/User/github") // returns "User"
@@ -42,7 +42,7 @@ It'd be nice if on ReScript's side, we can bind & call `draw` while labeling thi
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 @bs.module("MyGame")
 external draw: (~x: int, ~y: int, ~border: bool=?, unit) => unit = "draw"
 
@@ -66,7 +66,7 @@ Note that you can change the order of labeled arguments on the ReScript side and
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 @bs.module("MyGame")
 external draw: (~x: int, ~y: int, ~border: bool=?, unit) => unit = "draw"
 
@@ -86,7 +86,7 @@ Functions attached to a JS objects (other than JS modules) require a special way
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 type document // abstract type for a document object
 @bs.send external getElementById: (document, string) => Dom.element = "getElementById"
 @bs.val external doc: document = "document"
@@ -111,7 +111,7 @@ You might have JS functions that take an arbitrary amount of arguments. BuckleSc
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 @bs.module("path") @bs.variadic
 external join: array<string> => string = "join"
 
@@ -136,7 +136,7 @@ If you can exhaustively enumerate the many forms an overloaded JS function can t
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 @bs.module("MyGame") external drawCat: unit => unit = "draw"
 @bs.module("MyGame") external drawDog: (~giveName: string) => unit = "draw"
 @bs.module("MyGame") external draw: (string, ~useRandomAnimal: bool) => unit = "draw"
@@ -169,7 +169,7 @@ Here, `padding` is really conceptually a variant. Let's model it as such.
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 @bs.val
 external padLeft: (
   string,
@@ -196,7 +196,7 @@ Consider the Node `fs.readFileSync`'s second argument. It can take a string, but
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 @bs.module("fs")
 external readFileSync: (
   ~name: string,
@@ -224,7 +224,7 @@ Aside from string, you can also compile an argument to an int, using `bs.int` in
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 @bs.val
 external testIntType: (
   @bs.int [
@@ -249,7 +249,7 @@ One last trick with polymorphic variants:
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 type readline
 
 @bs.send
@@ -287,7 +287,7 @@ Sometimes it's convenient to bind to a function using an `external`, while passi
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 @bs.val
 external processOnExit: (
   @bs.as("exit") _,
@@ -314,7 +314,7 @@ Curry is a delicious Indian dish. More importantly, in the context of ReScript (
 
 See the `addFive` intermediate function? `add` takes in 3 arguments but received only 1. It's interpreted as "currying" the argument `5` and waiting for the next 2 arguments to be applied later on. Type signatures:
 
-```resi
+```res sig
 let add: (int, int, int) => int
 let addFive: (int, int) => int
 let twelve: int
@@ -344,7 +344,7 @@ ReScript tries to do #1 as much as it can. Even when it bails and uses #2's curr
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 type timerId
 @bs.val external setTimeout: ((. unit) => unit, int) => timerId = "setTimeout"
 
@@ -372,8 +372,8 @@ Then try `@bs.uncurry`:
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
-@bs.send external map: (array<'a>, @bs.uncurry('a => 'b)) => array<'b> = "map"
+```res example
+@bs.send external map: (array<'a>, @bs.uncurry ('a => 'b)) => array<'b> = "map"
 map([1, 2, 3], x => x + 1)
 ```
 ```js
@@ -398,7 +398,7 @@ Here, `this` would point to `x` (actually, it depends on how `onload` is called,
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 type x
 @bs.val external x: x = "x"
 @bs.set external setOnload: (x, @bs.this ((x, int) => unit)) => unit = "onload"
@@ -422,7 +422,7 @@ For JS functions that return a value that can also be `undefined` or `null`, we
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 type element
 type dom
 

pages/docs/manual/latest/bind-to-js-object.mdx

@@ -25,7 +25,7 @@ If your JavaScript object has fixed fields, then it's conceptually like a ReScri
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 type person = {
   name: string,
   friends: array<string>,
@@ -52,7 +52,7 @@ Alternatively, you can use [ReScript object](object.md) to model a JS object too
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 type person = {
   "name": string,
   "friends": array<string>,
@@ -77,7 +77,7 @@ Alternatively, you can use `bs.get` and `bs.set` to bind to individual fields of
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 type textarea
 @bs.set external setName: (textarea, string) => unit = "name"
 @bs.get external getName: textarea => string = "name"
@@ -91,7 +91,7 @@ You can also use `bs.get_index` and `bs.set_index` to access a dynamic property
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 type t
 @bs.new external create: int => t = "Int32Array"
 @bs.get_index external get: (t, int) => int = ""
@@ -124,7 +124,7 @@ Use `bs.new` to emulate e.g. `new Date()`:
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 type t
 @bs.new external createDate: unit => t = "Date"
 
@@ -140,7 +140,7 @@ You can chain `bs.new` and `bs.module` if the JS module you're importing is itse
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 type t
 @bs.new @bs.module external book: unit => t = "Book"
 let myBook = book()

pages/docs/manual/latest/control-flow.mdx

@@ -111,7 +111,7 @@ for(var i = startValueInclusive; i <= endValueInclusive; ++i){
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 // prints: 1 2 3
 for x in 1 to 3 {
   Js.log(x)
@@ -146,7 +146,7 @@ for(var i = startValueInclusive; i >= endValueInclusive; --i){
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 // prints: 3 2 1
 for x in 3 downto 1 {
   Js.log(x)
@@ -187,7 +187,7 @@ There's no loop-breaking `break` keyword (nor early `return` from functions, for
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 let break = ref(false)
 
 while !break.contents {

pages/docs/manual/latest/converting-from-js.mdx

@@ -39,7 +39,7 @@ First, copy the entire file content over to a new file called `src/Main.res` by
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 %%raw(`
 const school = require('school');
 
@@ -94,7 +94,7 @@ Let's turn the `defaultId` variable into a ReScript let-binding:
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 let defaultId = 10
 
 %%raw(`
@@ -189,7 +189,7 @@ Now this triggers the next type error, that `school` isn't found. Let's use [`ex
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 @bs.module external school: 'whatever = "school"
 
 let defaultId = 10
@@ -237,7 +237,7 @@ If you prefer more advanced, rigidly typed `payload` and `school`, feel free to
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 type school
 type student
 type payload = {

pages/docs/manual/latest/embed-raw-javascript.mdx

@@ -12,7 +12,7 @@ First thing first. If you're ever stuck learning ReScript, remember that you can
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 %%raw(`
 // look ma, regular JavaScript!
 var message = "hello";
@@ -39,7 +39,7 @@ While `%%raw` lets you embed top-level raw JS code, `%raw` lets you embed expres
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 let add = %raw(`
   function(a, b) {
     console.log("hello from raw JavaScript!");
@@ -73,7 +73,7 @@ You can also drop a `%debugger` expression in a body:
 
 <CodeTab labels={["ReScript", "JS Output"]}>
 
-```res
+```res example
 let f = (x, y) => {
   %debugger
   x + y