Todo for fbt with multiple fbt:enum

I need to do more debugging to figure out exactly why the example earlier fails 
— but whatever it is, it's clearly a matter of the fbt plugin relying on some 
specifics of source locations. 

Here we just detect multiple instances of `<fbt:enum>` within a given `<fbt>` 
tag and throw a todo.

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

@@ -2058,6 +2058,25 @@ function lowerExpression(
             suggestions: null,
           });
         }
+        const fbtEnumLocations: Array<SourceLocation> = [];
+        expr.traverse({
+          JSXNamespacedName(path) {
+            if (
+              path.node.namespace.name === "fbt" &&
+              path.node.name.name === "enum"
+            ) {
+              fbtEnumLocations.push(path.node.loc ?? GeneratedSource);
+            }
+          },
+        });
+        if (fbtEnumLocations.length > 1) {
+          CompilerError.throwTodo({
+            reason: `Support <fbt> tags with multiple <fbt:enum> values`,
+            loc: fbtEnumLocations.at(-1) ?? GeneratedSource,
+            description: null,
+            suggestions: null,
+          });
+        }
       }
 
       let children: Array<Place>;

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/fbt/error.todo-fbt-unknown-enum-value.expect.md

@@ -19,7 +19,13 @@ function Component({ a, b }) {
 ## Error
 
 ```
-avalue1 not found in { bvalue1: 'bvalue1', bvalue2: 'bvalue2' }. Attempting to re-use incompatible enums
+   5 |     <fbt desc="Description">
+   6 |       <fbt:enum enum-range={["avalue1", "avalue1"]} value={a} />{" "}
+>  7 |       <fbt:enum enum-range={["bvalue1", "bvalue2"]} value={b} />
+     |        ^^^^^^^^ [ReactForget] Todo: Support <fbt> tags with multiple <fbt:enum> values (7:7)
+   8 |     </fbt>
+   9 |   );
+  10 | }
 ```