Detect hoisting where the reference is a reassignment

Our logic to detect hoisting relies on Babel's `isReferencedIdentifier()` to 
determine whether a reference to an identifier is a reference or a declaration. 
The idea is that we want to find references to variables that may be hoistable, 
before the declaration — the definition of hoisting. But due to the bug in 
isReferencedIdentifier, we skipped over reassignments of hoisted variables. The 
hack here checks if an identifier is a direct child of an AssignmentExpression, 
ensuring we visit reassignments.

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

@@ -366,7 +366,12 @@ function lowerStatement(
           ArrowFunctionExpression: withFunctionContext,
           ObjectMethod: withFunctionContext,
           Identifier(id: NodePath<t.Identifier>) {
-            if (!id.isReferencedIdentifier()) {
+            const id2 = id;
+            if (
+              !id2.isReferencedIdentifier() &&
+              // isReferencedIdentifier is broken and returns false for reassignments
+              id.parent.type !== "AssignmentExpression"
+            ) {
               return;
             }
             const binding = id.scope.getBinding(id.node.name);

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/error.todo-function-expression-references-later-variable-declaration.expect.md

@@ -20,7 +20,7 @@ function Component() {
   1 | function Component() {
   2 |   let callback = () => {
 > 3 |     onClick = () => {};
-    |     ^^^^^^^ [ReactForget] Invariant: [hoisting] Expected value kind to be initialized. read onClick$0_@1 (3:3)
+    |     ^^^^^^^^^^^^^^^^^^ [ReactForget] Todo: Handle non-const declarations for hoisting. variable "onClick" declared with let (3:3)
   4 |   };
   5 |   let onClick;
   6 |

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/error.todo-function-expression-references-variable-its-assigned-to.expect.md

@@ -18,7 +18,7 @@ function Component() {
   1 | function Component() {
   2 |   let callback = () => {
 > 3 |     callback = null;
-    |     ^^^^^^^^ [ReactForget] Invariant: [hoisting] Expected value kind to be initialized. read callback$0_@0 (3:3)
+    |     ^^^^^^^^^^^^^^^ [ReactForget] Todo: Handle non-const declarations for hoisting. variable "callback" declared with let (3:3)
   4 |   };
   5 |   return <div onClick={callback} />;
   6 | }