Rename all proposal plugins to -proposal- from -transform- (#6570)

packages/babel-plugin-proposal-async-generator-functions/src/index.js

@@ -0,0 +1,35 @@
+import remapAsyncToGenerator from "@babel/helper-remap-async-to-generator";
+import syntaxAsyncGenerators from "@babel/plugin-syntax-async-generators";
+
+export default function({ types: t }) {
+  const yieldStarVisitor = {
+    Function(path) {
+      path.skip();
+    },
+
+    YieldExpression({ node }, state) {
+      if (!node.delegate) return;
+      const callee = state.addHelper("asyncGeneratorDelegate");
+      node.argument = t.callExpression(callee, [
+        t.callExpression(state.addHelper("asyncIterator"), [node.argument]),
+        state.addHelper("awaitAsyncGenerator"),
+      ]);
+    },
+  };
+
+  return {
+    inherits: syntaxAsyncGenerators,
+    visitor: {
+      Function(path, state) {
+        if (!path.node.async || !path.node.generator) return;
+
+        path.traverse(yieldStarVisitor, state);
+
+        remapAsyncToGenerator(path, state.file, {
+          wrapAsync: state.addHelper("wrapAsyncGenerator"),
+          wrapAwait: state.addHelper("awaitAsyncGenerator"),
+        });
+      },
+    },
+  };
+}