Partial Application Syntax: Stage 1 (#9343)

* add partial application syntax and some tests

* remove unnecessary error message and hasPartial function from parseNewArguments

* add types for PartialExpression

* Update the tests

* rename PartialExpression to Partial

* move Partial from expressions to types and rename to ArgumentPlaceholder

* add tests for ArgumentPlaceholder in babel-generator

* rename Partial to ArgumentPlaceholder

* update the tests

* remove alias from the type and undo changes in generated folder

* adds a nice error message

* better definition for the type

* auto-generated files

* update the conditional for allowPlaceholder message and tests

* update CallExpression definition to accept ArgumentPlaceholder

* change description

* clean up

* indent ArgumentPlaceholder entry and revert unwanted changes

packages/babel-types/src/asserts/generated/index.js

@@ -660,6 +660,12 @@ export function assertParenthesizedExpression(
 ): void {
   assert("ParenthesizedExpression", node, opts);
 }
+export function assertArgumentPlaceholder(
+  node: Object,
+  opts?: Object = {},
+): void {
+  assert("ArgumentPlaceholder", node, opts);
+}
 export function assertAwaitExpression(node: Object, opts?: Object = {}): void {
   assert("AwaitExpression", node, opts);
 }

packages/babel-types/src/builders/generated/index.js

@@ -596,6 +596,10 @@ export function ParenthesizedExpression(...args: Array<any>): Object {
   return builder("ParenthesizedExpression", ...args);
 }
 export { ParenthesizedExpression as parenthesizedExpression };
+export function ArgumentPlaceholder(...args: Array<any>): Object {
+  return builder("ArgumentPlaceholder", ...args);
+}
+export { ArgumentPlaceholder as argumentPlaceholder };
 export function AwaitExpression(...args: Array<any>): Object {
   return builder("AwaitExpression", ...args);
 }

packages/babel-types/src/definitions/core.js

@@ -138,7 +138,12 @@ defineType("CallExpression", {
       validate: chain(
         assertValueType("array"),
         assertEach(
-          assertNodeType("Expression", "SpreadElement", "JSXNamespacedName"),
+          assertNodeType(
+            "Expression",
+            "SpreadElement",
+            "JSXNamespacedName",
+            "ArgumentPlaceholder",
+          ),
         ),
       ),
     },

packages/babel-types/src/definitions/experimental.js

@@ -10,6 +10,8 @@ import {
   classMethodOrDeclareMethodCommon,
 } from "./es2015";
 
+defineType("ArgumentPlaceholder", {});
+
 defineType("AwaitExpression", {
   builder: ["argument"],
   visitor: ["argument"],

packages/babel-types/src/validators/generated/index.js

@@ -2093,6 +2093,20 @@ export function isParenthesizedExpression(
 
   return false;
 }
+export function isArgumentPlaceholder(node: ?Object, opts?: Object): boolean {
+  if (!node) return false;
+
+  const nodeType = node.type;
+  if (nodeType === "ArgumentPlaceholder") {
+    if (typeof opts === "undefined") {
+      return true;
+    } else {
+      return shallowEqual(node, opts);
+    }
+  }
+
+  return false;
+}
 export function isAwaitExpression(node: ?Object, opts?: Object): boolean {
   if (!node) return false;