[hir] Add invariant to check if useMemo callback is async or a generator

compiler/forget/src/Inference/InlineUseMemo.ts

@@ -108,6 +108,13 @@ export function inlineUseMemo(fn: HIRFunction): void {
               );
             }
 
+            if (body.loweredFunc.async || body.loweredFunc.generator) {
+              CompilerError.invariant(
+                "Did not expect useMemo callback to be async or a generator",
+                body.loc
+              );
+            }
+
             // We know this function is used for useMemo and can prune it later
             useMemoFunctions.add(lambda.identifier.id);
 

compiler/forget/src/__tests__/fixtures/compiler/error.useMemo-async-callback.expect.md

@@ -0,0 +1,22 @@
+
+## Input
+
+```javascript
+// @inlineUseMemo
+function component(a, b) {
+  let x = useMemo(async () => {
+    await a;
+  }, []);
+  return x;
+}
+
+```
+
+
+## Error
+
+```
+[ReactForget] Invariant: Did not expect useMemo callback to be async or a generator (3:5)
+```
+          
+      

compiler/forget/src/__tests__/fixtures/compiler/error.useMemo-async-callback.js

@@ -0,0 +1,7 @@
+// @inlineUseMemo
+function component(a, b) {
+  let x = useMemo(async () => {
+    await a;
+  }, []);
+  return x;
+}

compiler/forget/src/__tests__/fixtures/compiler/error.useMemo-callback-generator.expect.md

@@ -0,0 +1,32 @@
+
+## Input
+
+```javascript
+// @inlineUseMemo
+function component(a, b) {
+  // we don't handle generators at all so this test isn't
+  // useful for now, but adding this test in case we do
+  // add support for generators in the future.
+  let x = useMemo(function* () {
+    yield a;
+  }, []);
+  return x;
+}
+
+```
+
+
+## Error
+
+```
+[ReactForget] TodoError: (BuildHIR::lowerExpression) Handle YieldExpression expressions
+   5 |   // add support for generators in the future.
+   6 |   let x = useMemo(function* () {
+>  7 |     yield a;
+     |     ^^^^^^^
+   8 |   }, []);
+   9 |   return x;
+  10 | }
+```
+          
+      

compiler/forget/src/__tests__/fixtures/compiler/error.useMemo-callback-generator.js

@@ -0,0 +1,10 @@
+// @inlineUseMemo
+function component(a, b) {
+  // we don't handle generators at all so this test isn't
+  // useful for now, but adding this test in case we do
+  // add support for generators in the future.
+  let x = useMemo(function* () {
+    yield a;
+  }, []);
+  return x;
+}