diff --git a/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.assign-global-in-component-tag-function.expect.md b/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.assign-global-in-component-tag-function.expect.md
new file mode 100644
index 0000000000000..5553f235a0847
--- /dev/null
+++ b/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.assign-global-in-component-tag-function.expect.md
@@ -0,0 +1,27 @@
+
+## Input
+
+```javascript
+function Component() {
+  const Foo = () => {
+    someGlobal = true;
+  };
+  return <Foo />;
+}
+
+```
+
+
+## Error
+
+```
+  1 | function Component() {
+  2 |   const Foo = () => {
+> 3 |     someGlobal = true;
+    |     ^^^^^^^^^^ InvalidReact: Unexpected reassignment of a variable which was defined outside of the component. Components and hooks should be pure and side-effect free, but variable reassignment is a form of side-effect. If this variable is used in rendering, use useState instead. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#side-effects-must-run-outside-of-render) (3:3)
+  4 |   };
+  5 |   return <Foo />;
+  6 | }
+```
+          
+      
\ No newline at end of file
diff --git a/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.assign-global-in-component-tag-function.js b/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.assign-global-in-component-tag-function.js
new file mode 100644
index 0000000000000..2982fdf70858f
--- /dev/null
+++ b/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.assign-global-in-component-tag-function.js
@@ -0,0 +1,6 @@
+function Component() {
+  const Foo = () => {
+    someGlobal = true;
+  };
+  return <Foo />;
+}
diff --git a/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.assign-global-in-jsx-children.expect.md b/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.assign-global-in-jsx-children.expect.md
new file mode 100644
index 0000000000000..d380137836cc1
--- /dev/null
+++ b/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.assign-global-in-jsx-children.expect.md
@@ -0,0 +1,30 @@
+
+## Input
+
+```javascript
+function Component() {
+  const foo = () => {
+    someGlobal = true;
+  };
+  // Children are generally access/called during render, so
+  // modifying a global in a children function is almost
+  // certainly a mistake.
+  return <Foo>{foo}</Foo>;
+}
+
+```
+
+
+## Error
+
+```
+  1 | function Component() {
+  2 |   const foo = () => {
+> 3 |     someGlobal = true;
+    |     ^^^^^^^^^^ InvalidReact: Unexpected reassignment of a variable which was defined outside of the component. Components and hooks should be pure and side-effect free, but variable reassignment is a form of side-effect. If this variable is used in rendering, use useState instead. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#side-effects-must-run-outside-of-render) (3:3)
+  4 |   };
+  5 |   // Children are generally access/called during render, so
+  6 |   // modifying a global in a children function is almost
+```
+          
+      
\ No newline at end of file
diff --git a/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.assign-global-in-jsx-children.js b/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.assign-global-in-jsx-children.js
new file mode 100644
index 0000000000000..82554e8ac43ba
--- /dev/null
+++ b/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.assign-global-in-jsx-children.js
@@ -0,0 +1,9 @@
+function Component() {
+  const foo = () => {
+    someGlobal = true;
+  };
+  // Children are generally access/called during render, so
+  // modifying a global in a children function is almost
+  // certainly a mistake.
+  return <Foo>{foo}</Foo>;
+}
diff --git a/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.assign-global-in-jsx-spread-attribute.expect.md b/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.assign-global-in-jsx-spread-attribute.expect.md
new file mode 100644
index 0000000000000..3861b16e90dcf
--- /dev/null
+++ b/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.assign-global-in-jsx-spread-attribute.expect.md
@@ -0,0 +1,27 @@
+
+## Input
+
+```javascript
+function Component() {
+  const foo = () => {
+    someGlobal = true;
+  };
+  return <div {...foo} />;
+}
+
+```
+
+
+## Error
+
+```
+  1 | function Component() {
+  2 |   const foo = () => {
+> 3 |     someGlobal = true;
+    |     ^^^^^^^^^^ InvalidReact: Unexpected reassignment of a variable which was defined outside of the component. Components and hooks should be pure and side-effect free, but variable reassignment is a form of side-effect. If this variable is used in rendering, use useState instead. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#side-effects-must-run-outside-of-render) (3:3)
+  4 |   };
+  5 |   return <div {...foo} />;
+  6 | }
+```
+          
+      
\ No newline at end of file
diff --git a/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.assign-global-in-jsx-spread-attribute.js b/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.assign-global-in-jsx-spread-attribute.js
new file mode 100644
index 0000000000000..1eea9267b5098
--- /dev/null
+++ b/compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.assign-global-in-jsx-spread-attribute.js
@@ -0,0 +1,6 @@
+function Component() {
+  const foo = () => {
+    someGlobal = true;
+  };
+  return <div {...foo} />;
+}