[babel] Don't use source location for hoisting check

Instead of using the source location to check for hoisting, just stop checking 
for a given component after we reach it's declaration. 

By definition all references to it before are (potential) hoisting errors. 

Note that there could be false positives but that's ok.

compiler/packages/babel-plugin-react-forget/src/Entrypoint/Program.ts

@@ -618,7 +618,18 @@ function checkFunctionReferencedBeforeDeclarationAtTopLevel(
   program.traverse({
     Identifier(id) {
       const fn = fnNames.get(id.node.name);
-      if (fnIds.has(id.node) || !fn) {
+      // We're not tracking this identifier.
+      if (!fn) {
+        return;
+      }
+
+      /*
+       * We've reached the declaration, hoisting is no longer possible, stop
+       * checking for this component name.
+       */
+      if (fnIds.has(id.node)) {
+        fnIds.delete(id.node);
+        fnNames.delete(id.node.name);
         return;
       }
 
@@ -627,12 +638,7 @@ function checkFunctionReferencedBeforeDeclarationAtTopLevel(
        * A null scope means there's no function scope, which means we're at the
        * top level scope.
        */
-      if (
-        scope === null &&
-        id.node.loc &&
-        fn.loc &&
-        occursBefore(id.node.loc, fn.loc)
-      ) {
+      if (scope === null) {
         errors.pushErrorDetail(
           new CompilerErrorDetail({
             reason: `Encountered ${fn.name} used before declaration which breaks Forget's gating codegen due to hoisting`,
@@ -649,15 +655,3 @@ function checkFunctionReferencedBeforeDeclarationAtTopLevel(
 
   return errors.details.length > 0 ? errors : null;
 }
-
-function occursBefore(a: t.SourceLocation, b: t.SourceLocation): boolean {
-  if (a.start.line > b.start.line) {
-    return false;
-  }
-
-  if (a.start.line < b.start.line) {
-    return true;
-  }
-
-  return a.start.column < b.start.column;
-}

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/component-syntax-ref-gating.flow.expect.md

@@ -1,38 +0,0 @@
-
-## Input
-
-```javascript
-// @flow @gating
-component Foo(ref: React.RefSetter<Controls>) {
-  return <Bar ref={ref}/>;
-}
-```
-
-## Code
-
-```javascript
-import { isForgetEnabled_Fixtures } from "ReactForgetFeatureFlag";
-import { unstable_useMemoCache as useMemoCache } from "react";
-const Foo = React.forwardRef(Foo_withRef);
-const Foo_withRef = isForgetEnabled_Fixtures()
-  ? function Foo_withRef(_$$empty_props_placeholder$$, ref) {
-      const $ = useMemoCache(2);
-      let t0;
-      if ($[0] !== ref) {
-        t0 = <Bar ref={ref} />;
-        $[0] = ref;
-        $[1] = t0;
-      } else {
-        t0 = $[1];
-      }
-      return t0;
-    }
-  : function Foo_withRef(
-      _$$empty_props_placeholder$$: $ReadOnly<{ ... }>,
-      ref: React.RefSetter<Controls>
-    ) {
-      return <Bar ref={ref} />;
-    };
-
-```
-      

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/error.component-syntax-ref-gating.flow.expect.md

@@ -0,0 +1,18 @@
+
+## Input
+
+```javascript
+// @flow @gating
+component Foo(ref: React.RefSetter<Controls>) {
+  return <Bar ref={ref}/>;
+}
+```
+
+
+## Error
+
+```
+[ReactForget] Invariant: Encountered Foo_withRef used before declaration which breaks Forget's gating codegen due to hoisting. Rewrite the reference to not use hoisting to fix this issue (2:2)
+```
+          
+