Add expression node in TSAsExpression (#1675)

This lets the comment traversal code discover it

src/typescript-ast-nodes.js

@@ -123,7 +123,10 @@ module.exports = function(fork) {
     .field("typeAnnotation", def("TypeAnnotation"))
     .bases("TSSignature");
 
-  def("TSAsExpression").bases("Expression");
+  def("TSAsExpression")
+    .build("expression")
+    .field("expression", def("Node"))
+    .bases("Expression");
 
   def("TSNamespaceExportDeclaration")
     .bases("Declaration")

tests/typescript_comments/__snapshots__/jsfmt.spec.js.snap

@@ -0,0 +1,12 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`types.ts 1`] = `
+(() => {
+  // swallow error and fallback to using directory as path
+}) as string[];
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+(() => {
+  // swallow error and fallback to using directory as path
+}) as string[];
+
+`;

tests/typescript_comments/jsfmt.spec.js

@@ -0,0 +1 @@
+run_spec(__dirname, { parser: "typescript" });

tests/typescript_comments/types.ts

@@ -0,0 +1,3 @@
+(() => {
+  // swallow error and fallback to using directory as path
+}) as string[];