Add supports for index type query and indexed access type

samples/keyof.ts

@@ -0,0 +1,28 @@
+// copy example from https://github.com/Microsoft/TypeScript/pull/11929
+interface Thing {
+    name: string;
+    width: number;
+    height: number;
+    inStock: boolean;
+}
+
+type K1 = keyof Thing;  // "name" | "width" | "height" | "inStock"
+type K2 = keyof Thing[];  // "length" | "push" | "pop" | "concat" | ...
+type K3 = keyof { [x: string]: Thing };  // string
+
+type P1 = Thing["name"];  // string
+type P2 = Thing["width" | "height"];  // number
+type P3 = Thing["name" | "inStock"];  // string | boolean
+type P4 = string["charAt"];  // (pos: number) => string
+type P5 = string[]["push"];  // (...items: string[]) => number
+
+// following line will work after merged https://github.com/sjrd/scala-js-ts-importer/pull/47
+// type P6 = string[][0];  // string
+
+// extract example from https://github.com/DefinitelyTyped/DefinitelyTyped/blob/master/types/lodash/index.d.ts
+interface LoDashStatic {
+    at<T>(
+        object: T | null | undefined,
+        ...props: Array<keyof T>
+    ): Array<T[keyof T]>;
+}

samples/keyof.ts.scala

@@ -0,0 +1,34 @@
+
+import scala.scalajs.js
+import js.annotation._
+import js.|
+
+package keyof {
+
+@js.native
+trait Thing extends js.Object {
+  var name: String = js.native
+  var width: Double = js.native
+  var height: Double = js.native
+  var inStock: Boolean = js.native
+}
+
+@js.native
+trait LoDashStatic extends js.Object {
+  def at[T](`object`: T | Null | Unit, props: String*): js.Array[js.Any] = js.native
+}
+
+@js.native
+@JSGlobalScope
+object Keyof extends js.Object {
+  type K1 = String
+  type K2 = String
+  type K3 = String
+  type P1 = js.Any
+  type P2 = js.Any
+  type P3 = js.Any
+  type P4 = js.Any
+  type P5 = js.Any
+}
+
+}

src/main/scala/org/scalajs/tools/tsimporter/Importer.scala

@@ -330,6 +330,9 @@ class Importer(val output: java.io.PrintWriter) {
       case RepeatedType(underlying) =>
         TypeRef(Name.REPEATED, List(typeToScala(underlying)))
 
+      case IndexedQueryType(_) =>
+        TypeRef.String
+
       case PolymorphicThisType =>
         TypeRef.This
 

src/main/scala/org/scalajs/tools/tsimporter/Trees.scala

@@ -159,6 +159,9 @@ object Trees {
 
   case class RepeatedType(underlying: TypeTree) extends TypeTree
 
+  case class IndexedQueryType(underlying: TypeTree) extends TypeTree
+  case class IndexedAccessType(objectType: TypeTree, name: TypeTree) extends TypeTree
+
   object PolymorphicThisType extends TypeTree
 
   // Type members

src/main/scala/org/scalajs/tools/tsimporter/parser/TSDefParser.scala

@@ -40,7 +40,7 @@ class TSDefParser extends StdTokenParsers with ImplicitConversions {
       "public", "static", "yield",
 
       // Additional keywords of TypeScript
-      "declare", "module", "type", "namespace"
+      "declare", "module", "type", "namespace", "keyof"
   )
 
   lexical.delimiters ++= List(
@@ -203,10 +203,11 @@ class TSDefParser extends StdTokenParsers with ImplicitConversions {
     }
 
   lazy val singleTypeDesc: Parser[TypeTree] =
-    baseTypeDesc ~ rep("[" ~ "]") ^^ {
+    baseTypeDesc ~ rep("[" ~> opt(typeDesc) <~ "]") ^^ {
       case base ~ arrayDims =>
         (base /: arrayDims) {
-          (elem, _) => ArrayType(elem)
+          case (elem, None) => ArrayType(elem)
+          case (elem, Some(index)) => IndexedAccessType(elem, index)
         }
     }
 
@@ -218,6 +219,7 @@ class TSDefParser extends StdTokenParsers with ImplicitConversions {
     | typeQuery
     | tupleType
     | thisType
+    | indexTypeQuery
     | "(" ~> typeDesc <~ ")"
   )
 
@@ -248,6 +250,9 @@ class TSDefParser extends StdTokenParsers with ImplicitConversions {
   lazy val thisType: Parser[TypeTree] =
     "this" ^^^ PolymorphicThisType
 
+  lazy val indexTypeQuery: Parser[TypeTree] =
+    "keyof" ~> typeDesc ^^ IndexedQueryType
+
   lazy val typeQuery: Parser[TypeTree] =
     "typeof" ~> rep1sep(ident, ".") ^^ { parts =>
       TypeQuery(QualifiedIdent(parts.init.map(Ident), Ident(parts.last)))