fix: preserve function params type if possible

packages/babel-plugin-transform-parameters/src/params.ts

@@ -187,6 +187,7 @@ export default function convertFunctionParams(
       body.push(defNode);
     } else if (param.isObjectPattern() || param.isArrayPattern()) {
       const uid = path.scope.generateUidIdentifier("ref");
+      uid.typeAnnotation = param.node.typeAnnotation;
 
       const defNode = t.variableDeclaration("let", [
         t.variableDeclarator(param.node, uid),

packages/babel-plugin-transform-parameters/test/fixtures/parameters/preserve-types/input.ts

@@ -0,0 +1,13 @@
+type Point = {
+  x: number;
+  y: number;
+};
+
+function value({ x, y }: Point) {
+  return x * y;
+}
+
+function valueWithDefault({ x, y }: Point = {}) {
+  return x * y;
+}
+

packages/babel-plugin-transform-parameters/test/fixtures/parameters/preserve-types/output.js

@@ -0,0 +1,18 @@
+type Point = {
+  x: number;
+  y: number;
+};
+
+function value(_ref: Point) {
+  var x = _ref.x,
+      y = _ref.y;
+  return x * y;
+}
+
+function valueWithDefault() {
+  var _ref2 = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : {},
+      x = _ref2.x,
+      y = _ref2.y;
+
+  return x * y;
+}