Add support for all possible ReactElement types in React 16 (#83)

CHANGELOG.md

@@ -4,6 +4,7 @@
 + **BREAKING**: Stateless components that use the `@react` macro annotation must extend the `StatelessComponent` class instead of just `Component` [PR #69](https://github.com/shadaj/slinky/pull/69)
 + **BREAKING**: Callbacks passed to `setState` are now Scala functions, so there is no need to force implicit conversions [PR #71](https://github.com/shadaj/slinky/pull/71)
 + **BREAKING**: The tag construction flow now requires attributes to come before children. In addition, an empty list of attributes is no longer allowed [PR #73](https://github.com/shadaj/slinky/pull/73)
++ Add support for all `ReactElement` types introduced in React 16, such as numbers and booleans [PR #83](https://github.com/shadaj/slinky/pull/83)
 + Add support for error boundaries, which were added in React 16 [PR #82](https://github.com/shadaj/slinky/pull/82)
 + Add a `*` tag for external components that can take any attribute [PR #81](https://github.com/shadaj/slinky/pull/81)
 + Fix bugs involving using companion object values from a `@react` annotated component [PR #80](https://github.com/shadaj/slinky/pull/80)

core/src/main/scala/me/shadaj/slinky/core/facade/React.scala

@@ -15,6 +15,22 @@ object ReactElement {
     s.asInstanceOf[ReactElement]
   }
 
+  @inline implicit def intToElement(i: Int): ReactElement = {
+    i.asInstanceOf[ReactElement]
+  }
+
+  @inline implicit def doubleToElement(d: Double): ReactElement = {
+    d.asInstanceOf[ReactElement]
+  }
+
+  @inline implicit def floatToElement(f: Float): ReactElement = {
+    f.asInstanceOf[ReactElement]
+  }
+
+  @inline implicit def booleanToElement(b: Boolean): ReactElement = {
+    b.asInstanceOf[ReactElement]
+  }
+
   @inline implicit def optionToElement(s: Option[ReactElement]): ReactElement = {
     s.getOrElse(null.asInstanceOf[ReactElement])
   }

tests/src/test/scala/me/shadaj/slinky/core/ComponentReturnTypeTests.scala

@@ -0,0 +1,50 @@
+package me.shadaj.slinky.core
+
+import me.shadaj.slinky.core.facade.{Fragment, ReactElement}
+import me.shadaj.slinky.web.ReactDOM
+import me.shadaj.slinky.web.html._
+import org.scalajs.dom
+import org.scalatest.FunSuite
+
+class ComponentReturnTypeTests extends FunSuite {
+  def testElement(elem: ReactElement): Unit = {
+    assert((div(elem): ReactElement) != null) // test use in another element
+    ReactDOM.render(div(elem), dom.document.createElement("div")) // test rendering to DOM
+  }
+
+  test("Components can return - arrays") {
+    testElement(Seq(h1("a"), h1("b")))
+  }
+
+  test("Components can return - strings") {
+    testElement("hello")
+  }
+
+  test("Components can return - numbers") {
+    testElement(1)
+    testElement(1D)
+    testElement(1F)
+  }
+
+  test("Components can return - portals") {
+    testElement(ReactDOM.createPortal(null, dom.document.createElement("div")))
+  }
+
+  test("Components can return - null") {
+    testElement(null)
+  }
+
+  test("Components can return - booleans") {
+    testElement(true)
+    testElement(false)
+  }
+
+  test("Components can return - options") {
+    testElement(Some(h1("hi")))
+    testElement(None)
+  }
+
+  test("Components can return - fragments") {
+    testElement(Fragment(h1("hi")))
+  }
+}