Bug Report

Current Behavior

Code like <div>{3, 1}</div> is not treated as a parse error, but it should be.

REPL link

Input Code

// No error
<div>{3, 1}</div>;
// No error
<div foo={1, 2} />;

Expected behavior/code

Expected a parse error.

The JSX Spec specifies JSXChildExpression and JSXAttributeValue as being { AssignmentExpression }, but the comma expression is above AssignmentExpression in the grammar

Environment

• Babel version(s): 6.26.0
• Node/npm version: N/A (repl)
• OS: N/A (repl)
• Monorepo N/A (repl)
• How you are using Babel: N/A (repl)

Possible Solution

Additional context/Screenshots

https://stackoverflow.com/questions/52139174/comma-operator-in-typescript-jsx-expressions