Fixtures for control values that become reactive due to interleaving

See the previous PR, interleaved mutation can cause values that were not 
reactive to become reactive. I swear I had a case where this was observable, but 
I came up with it before reordering the PRs in this stack. I think my repro 
relied on an immutable reference to a mutable value, which is now handled in 
InferReactivePlaces. So here i'm just adding fixtures, and allowing this case 
since it's unobservable.

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reactive-control-dependency-from-interleaved-reactivity-do-while.expect.md

@@ -0,0 +1,73 @@
+
+## Input
+
+```javascript
+function Component(props) {
+  // a and b are independent but their mutations are interleaved, so
+  // they get grouped in a reactive scope. this means that a becomes
+  // reactive since it will effectively re-evaluate based on a reactive
+  // input
+  const a = [];
+  const b = [];
+  b.push(props.cond);
+  a.push(false);
+
+  // Downstream consumer of a, which initially seems non-reactive except
+  // that a becomes reactive, per above
+  const c = [a];
+
+  let x = 0;
+  do {
+    x += 1;
+  } while (c[0][0]);
+  // The values assigned to `x` are non-reactive, but the value of `x`
+  // depends on the "control" value `c[0]` which becomes reactive via
+  // being interleaved with `b`.
+  // Therefore x should be treated as reactive too.
+  return [x];
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{ cond: true }],
+};
+
+```
+
+## Code
+
+```javascript
+import { unstable_useMemoCache as useMemoCache } from "react";
+function Component(props) {
+  const $ = useMemoCache(1);
+
+  const a = [];
+  const b = [];
+  b.push(props.cond);
+  a.push(false);
+
+  const c = [a];
+
+  let x = 0;
+  do {
+    x = x + 1;
+  } while (c[0][0]);
+  let t0;
+  if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
+    t0 = [x];
+    $[0] = t0;
+  } else {
+    t0 = $[0];
+  }
+  return t0;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{ cond: true }],
+};
+
+```
+      
+### Eval output
+(kind: ok) [1]

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reactive-control-dependency-from-interleaved-reactivity-do-while.js

@@ -0,0 +1,29 @@
+function Component(props) {
+  // a and b are independent but their mutations are interleaved, so
+  // they get grouped in a reactive scope. this means that a becomes
+  // reactive since it will effectively re-evaluate based on a reactive
+  // input
+  const a = [];
+  const b = [];
+  b.push(props.cond);
+  a.push(false);
+
+  // Downstream consumer of a, which initially seems non-reactive except
+  // that a becomes reactive, per above
+  const c = [a];
+
+  let x = 0;
+  do {
+    x += 1;
+  } while (c[0][0]);
+  // The values assigned to `x` are non-reactive, but the value of `x`
+  // depends on the "control" value `c[0]` which becomes reactive via
+  // being interleaved with `b`.
+  // Therefore x should be treated as reactive too.
+  return [x];
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{ cond: true }],
+};

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reactive-control-dependency-from-interleaved-reactivity-for-in.expect.md

@@ -0,0 +1,73 @@
+
+## Input
+
+```javascript
+function Component(props) {
+  // a and b are independent but their mutations are interleaved, so
+  // they get grouped in a reactive scope. this means that a becomes
+  // reactive since it will effectively re-evaluate based on a reactive
+  // input
+  const a = [];
+  const b = [];
+  b.push(props.cond);
+  a.push({ a: false });
+
+  // Downstream consumer of a, which initially seems non-reactive except
+  // that a becomes reactive, per above
+  const c = [a];
+
+  let x;
+  for (const i in c[0][0]) {
+    x = 1;
+  }
+  // The values assigned to `x` are non-reactive, but the value of `x`
+  // depends on the "control" value `c[0]` which becomes reactive via
+  // being interleaved with `b`.
+  // Therefore x should be treated as reactive too.
+  return [x];
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{ cond: true }],
+};
+
+```
+
+## Code
+
+```javascript
+import { unstable_useMemoCache as useMemoCache } from "react";
+function Component(props) {
+  const $ = useMemoCache(1);
+
+  const a = [];
+  const b = [];
+  b.push(props.cond);
+  a.push({ a: false });
+
+  const c = [a];
+
+  let x;
+  for (const i in c[0][0]) {
+    x = 1;
+  }
+  let t0;
+  if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
+    t0 = [x];
+    $[0] = t0;
+  } else {
+    t0 = $[0];
+  }
+  return t0;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{ cond: true }],
+};
+
+```
+      
+### Eval output
+(kind: ok) [1]

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reactive-control-dependency-from-interleaved-reactivity-for-in.js

@@ -0,0 +1,29 @@
+function Component(props) {
+  // a and b are independent but their mutations are interleaved, so
+  // they get grouped in a reactive scope. this means that a becomes
+  // reactive since it will effectively re-evaluate based on a reactive
+  // input
+  const a = [];
+  const b = [];
+  b.push(props.cond);
+  a.push({ a: false });
+
+  // Downstream consumer of a, which initially seems non-reactive except
+  // that a becomes reactive, per above
+  const c = [a];
+
+  let x;
+  for (const i in c[0][0]) {
+    x = 1;
+  }
+  // The values assigned to `x` are non-reactive, but the value of `x`
+  // depends on the "control" value `c[0]` which becomes reactive via
+  // being interleaved with `b`.
+  // Therefore x should be treated as reactive too.
+  return [x];
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{ cond: true }],
+};

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reactive-control-dependency-from-interleaved-reactivity-for-init.expect.md

@@ -0,0 +1,73 @@
+
+## Input
+
+```javascript
+function Component(props) {
+  // a and b are independent but their mutations are interleaved, so
+  // they get grouped in a reactive scope. this means that a becomes
+  // reactive since it will effectively re-evaluate based on a reactive
+  // input
+  const a = [];
+  const b = [];
+  b.push(props.cond);
+  a.push(0);
+
+  // Downstream consumer of a, which initially seems non-reactive except
+  // that a becomes reactive, per above
+  const c = [a];
+
+  let x;
+  for (let i = c[0][0]; i < 10; i++) {
+    x = 1;
+  }
+  // The values assigned to `x` are non-reactive, but the value of `x`
+  // depends on the "control" value `c[0]` which becomes reactive via
+  // being interleaved with `b`.
+  // Therefore x should be treated as reactive too.
+  return [x];
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{ cond: true }],
+};
+
+```
+
+## Code
+
+```javascript
+import { unstable_useMemoCache as useMemoCache } from "react";
+function Component(props) {
+  const $ = useMemoCache(1);
+
+  const a = [];
+  const b = [];
+  b.push(props.cond);
+  a.push(0);
+
+  const c = [a];
+
+  let x;
+  for (let i = c[0][0]; i < 10; i++) {
+    x = 1;
+  }
+  let t0;
+  if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
+    t0 = [x];
+    $[0] = t0;
+  } else {
+    t0 = $[0];
+  }
+  return t0;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{ cond: true }],
+};
+
+```
+      
+### Eval output
+(kind: ok) [1]

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reactive-control-dependency-from-interleaved-reactivity-for-init.js

@@ -0,0 +1,29 @@
+function Component(props) {
+  // a and b are independent but their mutations are interleaved, so
+  // they get grouped in a reactive scope. this means that a becomes
+  // reactive since it will effectively re-evaluate based on a reactive
+  // input
+  const a = [];
+  const b = [];
+  b.push(props.cond);
+  a.push(0);
+
+  // Downstream consumer of a, which initially seems non-reactive except
+  // that a becomes reactive, per above
+  const c = [a];
+
+  let x;
+  for (let i = c[0][0]; i < 10; i++) {
+    x = 1;
+  }
+  // The values assigned to `x` are non-reactive, but the value of `x`
+  // depends on the "control" value `c[0]` which becomes reactive via
+  // being interleaved with `b`.
+  // Therefore x should be treated as reactive too.
+  return [x];
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{ cond: true }],
+};

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reactive-control-dependency-from-interleaved-reactivity-for-of.expect.md

@@ -0,0 +1,73 @@
+
+## Input
+
+```javascript
+function Component(props) {
+  // a and b are independent but their mutations are interleaved, so
+  // they get grouped in a reactive scope. this means that a becomes
+  // reactive since it will effectively re-evaluate based on a reactive
+  // input
+  const a = [];
+  const b = [];
+  b.push(props.cond);
+  a.push(null);
+
+  // Downstream consumer of a, which initially seems non-reactive except
+  // that a becomes reactive, per above
+  const c = [a];
+
+  let x;
+  for (const i of c[0]) {
+    x = 1;
+  }
+  // The values assigned to `x` are non-reactive, but the value of `x`
+  // depends on the "control" value `c[0]` which becomes reactive via
+  // being interleaved with `b`.
+  // Therefore x should be treated as reactive too.
+  return [x];
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{ cond: true }],
+};
+
+```
+
+## Code
+
+```javascript
+import { unstable_useMemoCache as useMemoCache } from "react";
+function Component(props) {
+  const $ = useMemoCache(1);
+
+  const a = [];
+  const b = [];
+  b.push(props.cond);
+  a.push(null);
+
+  const c = [a];
+
+  let x;
+  for (const i of c[0]) {
+    x = 1;
+  }
+  let t0;
+  if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
+    t0 = [x];
+    $[0] = t0;
+  } else {
+    t0 = $[0];
+  }
+  return t0;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{ cond: true }],
+};
+
+```
+      
+### Eval output
+(kind: ok) [1]

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reactive-control-dependency-from-interleaved-reactivity-for-of.js

@@ -0,0 +1,29 @@
+function Component(props) {
+  // a and b are independent but their mutations are interleaved, so
+  // they get grouped in a reactive scope. this means that a becomes
+  // reactive since it will effectively re-evaluate based on a reactive
+  // input
+  const a = [];
+  const b = [];
+  b.push(props.cond);
+  a.push(null);
+
+  // Downstream consumer of a, which initially seems non-reactive except
+  // that a becomes reactive, per above
+  const c = [a];
+
+  let x;
+  for (const i of c[0]) {
+    x = 1;
+  }
+  // The values assigned to `x` are non-reactive, but the value of `x`
+  // depends on the "control" value `c[0]` which becomes reactive via
+  // being interleaved with `b`.
+  // Therefore x should be treated as reactive too.
+  return [x];
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{ cond: true }],
+};

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reactive-control-dependency-from-interleaved-reactivity-for-test.expect.md

@@ -0,0 +1,73 @@
+
+## Input
+
+```javascript
+function Component(props) {
+  // a and b are independent but their mutations are interleaved, so
+  // they get grouped in a reactive scope. this means that a becomes
+  // reactive since it will effectively re-evaluate based on a reactive
+  // input
+  const a = [];
+  const b = [];
+  b.push(props.cond);
+  a.push(10);
+
+  // Downstream consumer of a, which initially seems non-reactive except
+  // that a becomes reactive, per above
+  const c = [a];
+
+  let x;
+  for (let i = 0; i < c[0][0]; i++) {
+    x = 1;
+  }
+  // The values assigned to `x` are non-reactive, but the value of `x`
+  // depends on the "control" value `c[0]` which becomes reactive via
+  // being interleaved with `b`.
+  // Therefore x should be treated as reactive too.
+  return [x];
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{ cond: true }],
+};
+
+```
+
+## Code
+
+```javascript
+import { unstable_useMemoCache as useMemoCache } from "react";
+function Component(props) {
+  const $ = useMemoCache(1);
+
+  const a = [];
+  const b = [];
+  b.push(props.cond);
+  a.push(10);
+
+  const c = [a];
+
+  let x;
+  for (let i = 0; i < c[0][0]; i++) {
+    x = 1;
+  }
+  let t0;
+  if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
+    t0 = [x];
+    $[0] = t0;
+  } else {
+    t0 = $[0];
+  }
+  return t0;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{ cond: true }],
+};
+
+```
+      
+### Eval output
+(kind: ok) [1]

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reactive-control-dependency-from-interleaved-reactivity-for-test.js

@@ -0,0 +1,29 @@
+function Component(props) {
+  // a and b are independent but their mutations are interleaved, so
+  // they get grouped in a reactive scope. this means that a becomes
+  // reactive since it will effectively re-evaluate based on a reactive
+  // input
+  const a = [];
+  const b = [];
+  b.push(props.cond);
+  a.push(10);
+
+  // Downstream consumer of a, which initially seems non-reactive except
+  // that a becomes reactive, per above
+  const c = [a];
+
+  let x;
+  for (let i = 0; i < c[0][0]; i++) {
+    x = 1;
+  }
+  // The values assigned to `x` are non-reactive, but the value of `x`
+  // depends on the "control" value `c[0]` which becomes reactive via
+  // being interleaved with `b`.
+  // Therefore x should be treated as reactive too.
+  return [x];
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{ cond: true }],
+};

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reactive-control-dependency-from-interleaved-reactivity-for-update.expect.md

@@ -0,0 +1,73 @@
+
+## Input
+
+```javascript
+function Component(props) {
+  // a and b are independent but their mutations are interleaved, so
+  // they get grouped in a reactive scope. this means that a becomes
+  // reactive since it will effectively re-evaluate based on a reactive
+  // input
+  const a = [];
+  const b = [];
+  b.push(props.cond);
+  a.push(10);
+
+  // Downstream consumer of a, which initially seems non-reactive except
+  // that a becomes reactive, per above
+  const c = [a];
+
+  let x;
+  for (let i = 0; i < 10; i += c[0][0]) {
+    x = 1;
+  }
+  // The values assigned to `x` are non-reactive, but the value of `x`
+  // depends on the "control" value `c[0]` which becomes reactive via
+  // being interleaved with `b`.
+  // Therefore x should be treated as reactive too.
+  return [x];
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{ cond: true }],
+};
+
+```
+
+## Code
+
+```javascript
+import { unstable_useMemoCache as useMemoCache } from "react";
+function Component(props) {
+  const $ = useMemoCache(1);
+
+  const a = [];
+  const b = [];
+  b.push(props.cond);
+  a.push(10);
+
+  const c = [a];
+
+  let x;
+  for (let i = 0; i < 10; i = i + c[0][0], i) {
+    x = 1;
+  }
+  let t0;
+  if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
+    t0 = [x];
+    $[0] = t0;
+  } else {
+    t0 = $[0];
+  }
+  return t0;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{ cond: true }],
+};
+
+```
+      
+### Eval output
+(kind: ok) [1]

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reactive-control-dependency-from-interleaved-reactivity-for-update.js

@@ -0,0 +1,29 @@
+function Component(props) {
+  // a and b are independent but their mutations are interleaved, so
+  // they get grouped in a reactive scope. this means that a becomes
+  // reactive since it will effectively re-evaluate based on a reactive
+  // input
+  const a = [];
+  const b = [];
+  b.push(props.cond);
+  a.push(10);
+
+  // Downstream consumer of a, which initially seems non-reactive except
+  // that a becomes reactive, per above
+  const c = [a];
+
+  let x;
+  for (let i = 0; i < 10; i += c[0][0]) {
+    x = 1;
+  }
+  // The values assigned to `x` are non-reactive, but the value of `x`
+  // depends on the "control" value `c[0]` which becomes reactive via
+  // being interleaved with `b`.
+  // Therefore x should be treated as reactive too.
+  return [x];
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{ cond: true }],
+};

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reactive-control-dependency-from-interleaved-reactivity-if.expect.md

@@ -17,7 +17,7 @@ function Component(props) {
   const c = [a];
 
   let x;
-  if (c[0]) {
+  if (c[0][0]) {
     x = 1;
   } else {
     x = 2;
@@ -51,7 +51,7 @@ function Component(props) {
   const c = [a];
 
   let x;
-  if (c[0]) {
+  if (c[0][0]) {
     x = 1;
   } else {
     x = 2;
@@ -74,4 +74,4 @@ export const FIXTURE_ENTRYPOINT = {
 ```
       
 ### Eval output
-(kind: ok) [1]
+(kind: ok) [2]

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reactive-control-dependency-from-interleaved-reactivity-if.js

@@ -13,7 +13,7 @@ function Component(props) {
   const c = [a];
 
   let x;
-  if (c[0]) {
+  if (c[0][0]) {
     x = 1;
   } else {
     x = 2;

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reactive-control-dependency-from-interleaved-reactivity-switch.expect.md

@@ -0,0 +1,85 @@
+
+## Input
+
+```javascript
+function Component(props) {
+  // a and b are independent but their mutations are interleaved, so
+  // they get grouped in a reactive scope. this means that a becomes
+  // reactive since it will effectively re-evaluate based on a reactive
+  // input
+  const a = [];
+  const b = [];
+  b.push(props.cond);
+  a.push(null);
+
+  // Downstream consumer of a, which initially seems non-reactive except
+  // that a becomes reactive, per above
+  const c = [a];
+
+  let x;
+  switch (c[0][0]) {
+    case true: {
+      x = 1;
+      break;
+    }
+    default: {
+      x = 2;
+    }
+  }
+  // The values assigned to `x` are non-reactive, but the value of `x`
+  // depends on the "control" value `c[0]` which becomes reactive via
+  // being interleaved with `b`.
+  // Therefore x should be treated as reactive too.
+  return [x];
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{ cond: true }],
+};
+
+```
+
+## Code
+
+```javascript
+import { unstable_useMemoCache as useMemoCache } from "react";
+function Component(props) {
+  const $ = useMemoCache(1);
+
+  const a = [];
+  const b = [];
+  b.push(props.cond);
+  a.push(null);
+
+  const c = [a];
+
+  let x;
+  bb1: switch (c[0][0]) {
+    case true: {
+      x = 1;
+      break bb1;
+    }
+    default: {
+      x = 2;
+    }
+  }
+  let t0;
+  if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
+    t0 = [x];
+    $[0] = t0;
+  } else {
+    t0 = $[0];
+  }
+  return t0;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{ cond: true }],
+};
+
+```
+      
+### Eval output
+(kind: ok) [2]

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reactive-control-dependency-from-interleaved-reactivity-switch.js

@@ -0,0 +1,35 @@
+function Component(props) {
+  // a and b are independent but their mutations are interleaved, so
+  // they get grouped in a reactive scope. this means that a becomes
+  // reactive since it will effectively re-evaluate based on a reactive
+  // input
+  const a = [];
+  const b = [];
+  b.push(props.cond);
+  a.push(null);
+
+  // Downstream consumer of a, which initially seems non-reactive except
+  // that a becomes reactive, per above
+  const c = [a];
+
+  let x;
+  switch (c[0][0]) {
+    case true: {
+      x = 1;
+      break;
+    }
+    default: {
+      x = 2;
+    }
+  }
+  // The values assigned to `x` are non-reactive, but the value of `x`
+  // depends on the "control" value `c[0]` which becomes reactive via
+  // being interleaved with `b`.
+  // Therefore x should be treated as reactive too.
+  return [x];
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{ cond: true }],
+};

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reactive-control-dependency-from-interleaved-reactivity-while.expect.md

@@ -0,0 +1,73 @@
+
+## Input
+
+```javascript
+function Component(props) {
+  // a and b are independent but their mutations are interleaved, so
+  // they get grouped in a reactive scope. this means that a becomes
+  // reactive since it will effectively re-evaluate based on a reactive
+  // input
+  const a = [];
+  const b = [];
+  b.push(props.cond);
+  a.push(null);
+
+  // Downstream consumer of a, which initially seems non-reactive except
+  // that a becomes reactive, per above
+  const c = [a];
+
+  let x;
+  while (c[0][0]) {
+    x = 1;
+  }
+  // The values assigned to `x` are non-reactive, but the value of `x`
+  // depends on the "control" value `c[0]` which becomes reactive via
+  // being interleaved with `b`.
+  // Therefore x should be treated as reactive too.
+  return [x];
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{ cond: true }],
+};
+
+```
+
+## Code
+
+```javascript
+import { unstable_useMemoCache as useMemoCache } from "react";
+function Component(props) {
+  const $ = useMemoCache(1);
+
+  const a = [];
+  const b = [];
+  b.push(props.cond);
+  a.push(null);
+
+  const c = [a];
+
+  let x;
+  while (c[0][0]) {
+    x = 1;
+  }
+  let t0;
+  if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
+    t0 = [x];
+    $[0] = t0;
+  } else {
+    t0 = $[0];
+  }
+  return t0;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{ cond: true }],
+};
+
+```
+      
+### Eval output
+(kind: ok) [null]

compiler/packages/babel-plugin-react-forget/src/__tests__/fixtures/compiler/reactive-control-dependency-from-interleaved-reactivity-while.js

@@ -0,0 +1,29 @@
+function Component(props) {
+  // a and b are independent but their mutations are interleaved, so
+  // they get grouped in a reactive scope. this means that a becomes
+  // reactive since it will effectively re-evaluate based on a reactive
+  // input
+  const a = [];
+  const b = [];
+  b.push(props.cond);
+  a.push(null);
+
+  // Downstream consumer of a, which initially seems non-reactive except
+  // that a becomes reactive, per above
+  const c = [a];
+
+  let x;
+  while (c[0][0]) {
+    x = 1;
+  }
+  // The values assigned to `x` are non-reactive, but the value of `x`
+  // depends on the "control" value `c[0]` which becomes reactive via
+  // being interleaved with `b`.
+  // Therefore x should be treated as reactive too.
+  return [x];
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{ cond: true }],
+};