feat(nullable): add getExn

Author: glennsl

src/Core__Nullable.mjs

@@ -9,7 +9,19 @@ function fromOption(option) {
 
 }
 
+function getExn(value) {
+  if (!(value == null)) {
+    return value;
+  }
+  throw {
+        RE_EXN_ID: "Invalid_argument",
+        _1: "Nullable.getExn: value is null or undefined",
+        Error: new Error()
+      };
+}
+
 export {
   fromOption ,
+  getExn ,
 }
 /* No side effect */

src/Core__Nullable.res

@@ -13,3 +13,9 @@ let fromOption: option<'a> => t<'a> = option =>
   | Some(x) => make(x)
   | None => undefined
   }
+
+let getExn: t<'a> => 'a = value =>
+  switch value->toOption {
+  | Some(x) => x
+  | None => raise(Invalid_argument("Nullable.getExn: value is null or undefined"))
+  }