Support rest params

Adds support for lowering rest element parameters to spreads. We eagerly create 
a temporary, similar to the approach for destructuring. In theory we could do 
something more optimal if you have a `...foo` (rest element where the argument 
is an Identifier) but it doesn't seem worth optimizing yet.

compiler/packages/babel-plugin-react-forget/src/HIR/BuildHIR.ts

@@ -89,7 +89,7 @@ export function lower(
       id = idNode.node.name;
     }
   }
-  const params: Array<Place> = [];
+  const params: Array<Place | SpreadPattern> = [];
   func.get("params").forEach((param) => {
     if (param.isIdentifier()) {
       const identifier = builder.resolveIdentifier(param);
@@ -128,6 +128,24 @@ export function lower(
         param,
         place
       );
+    } else if (param.isRestElement()) {
+      const place: Place = {
+        kind: "Identifier",
+        identifier: builder.makeTemporary(),
+        effect: Effect.Unknown,
+        loc: param.node.loc ?? GeneratedSource,
+      };
+      params.push({
+        kind: "Spread",
+        place,
+      });
+      lowerAssignment(
+        builder,
+        param.node.loc ?? GeneratedSource,
+        InstructionKind.Let,
+        param.get("argument"),
+        place
+      );
     } else {
       builder.errors.push({
         reason: `(BuildHIR::lower) Handle ${param.node.type} params`,

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/error.todo-kitchensink.expect.md

@@ -79,16 +79,12 @@ let moduleLocal = false;
 ## Error
 
 ```
-[ReactForget] Todo: (BuildHIR::lower) Handle RestElement params (1:1)
-
 [ReactForget] Todo: (BuildHIR::lowerStatement) Handle var kinds in VariableDeclaration (3:3)
 
 [ReactForget] Todo: (BuildHIR::lowerStatement) Handle ClassDeclaration statements (5:10)
 
 [ReactForget] Todo: (BuildHIR::lowerExpression) Handle ObjectMethod properties in ObjectExpression (12:12)
 
-[ReactForget] Todo: (BuildHIR::lower) Handle RestElement params (18:18)
-
 [ReactForget] Todo: (BuildHIR::lowerStatement) Handle non-variable initialization in ForStatement (20:22)
 
 [ReactForget] Todo: (BuildHIR::lowerStatement) Handle non-variable initialization in ForStatement (23:25)

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/rest-param-with-array-pattern.expect.md

@@ -0,0 +1,43 @@
+
+## Input
+
+```javascript
+function Component(foo, ...[bar]) {
+  return [foo, bar];
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: ["foo", ["bar", "baz"]],
+};
+
+```
+
+## Code
+
+```javascript
+import { unstable_useMemoCache as useMemoCache } from "react";
+function Component(foo, ...t9) {
+  const $ = useMemoCache(3);
+  const [bar] = t9;
+  const c_0 = $[0] !== foo;
+  const c_1 = $[1] !== bar;
+  let t0;
+  if (c_0 || c_1) {
+    t0 = [foo, bar];
+    $[0] = foo;
+    $[1] = bar;
+    $[2] = t0;
+  } else {
+    t0 = $[2];
+  }
+  return t0;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: ["foo", ["bar", "baz"]],
+};
+
+```
+      

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/rest-param-with-array-pattern.js

@@ -0,0 +1,8 @@
+function Component(foo, ...[bar]) {
+  return [foo, bar];
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: ["foo", ["bar", "baz"]],
+};

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/rest-param-with-identifier.expect.md

@@ -0,0 +1,43 @@
+
+## Input
+
+```javascript
+function Component(foo, ...bar) {
+  return [foo, bar];
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: ["foo", "bar", "baz"],
+};
+
+```
+
+## Code
+
+```javascript
+import { unstable_useMemoCache as useMemoCache } from "react";
+function Component(foo, ...t9) {
+  const $ = useMemoCache(3);
+  const bar = t9;
+  const c_0 = $[0] !== foo;
+  const c_1 = $[1] !== bar;
+  let t0;
+  if (c_0 || c_1) {
+    t0 = [foo, bar];
+    $[0] = foo;
+    $[1] = bar;
+    $[2] = t0;
+  } else {
+    t0 = $[2];
+  }
+  return t0;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: ["foo", "bar", "baz"],
+};
+
+```
+      

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/rest-param-with-identifier.js

@@ -0,0 +1,8 @@
+function Component(foo, ...bar) {
+  return [foo, bar];
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: ["foo", "bar", "baz"],
+};

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/rest-param-with-object-spread-pattern.expect.md

@@ -0,0 +1,43 @@
+
+## Input
+
+```javascript
+function Component(foo, ...{ bar }) {
+  return [foo, bar];
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: ["foo", { bar: "bar" }],
+};
+
+```
+
+## Code
+
+```javascript
+import { unstable_useMemoCache as useMemoCache } from "react";
+function Component(foo, ...t9) {
+  const $ = useMemoCache(3);
+  const { bar } = t9;
+  const c_0 = $[0] !== foo;
+  const c_1 = $[1] !== bar;
+  let t0;
+  if (c_0 || c_1) {
+    t0 = [foo, bar];
+    $[0] = foo;
+    $[1] = bar;
+    $[2] = t0;
+  } else {
+    t0 = $[2];
+  }
+  return t0;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: ["foo", { bar: "bar" }],
+};
+
+```
+      

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/rest-param-with-object-spread-pattern.js

@@ -0,0 +1,8 @@
+function Component(foo, ...{ bar }) {
+  return [foo, bar];
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: ["foo", { bar: "bar" }],
+};