Bug Report

Current Behavior

@babel/plugin-proposal-unicode-property-regex config useUnicodeFlag always true.

Input Code

/\p{Script_Extensions=Greek}/u;

Expected behavior/code
/(?:[\u0342\u0345\u0370-\u0373\u0375-\u0377\u037A-\u037D\u037F\u0384\u0386\u0388-\u038A\u038C\u038E-\u03A1\u03A3-\u03E1\u03F0-\u03FF\u1D26-\u1D2A\u1D5D-\u1D61\u1D66-\u1D6A\u1DBF-\u1DC1\u1F00-\u1F15\u1F18-\u1F1D\u1F20-\u1F45\u1F48-\u1F4D\u1F50-\u1F57\u1F59\u1F5B\u1F5D\u1F5F-\u1F7D\u1F80-\u1FB4\u1FB6-\u1FC4\u1FC6-\u1FD3\u1FD6-\u1FDB\u1FDD-\u1FEF\u1FF2-\u1FF4\u1FF6-\u1FFE\u2126\uAB65]|\uD800[\uDD40-\uDD8E\uDDA0]|\uD834[\uDE00-\uDE45])/;

Babel Configuration (.babelrc, package.json, cli command)

{
  presets: ['@babel/preset-env', {
    targets: {
      chrome: 49
   },
  }]
}

Environment

• Babel version(s): 7.2.2
• Node/npm version: 8.11.3/6.4.1
• OS: OSX 10.13.6
• Monorepo: no
• How you are using Babel: loader

Possible Solution

set useUnicodeFlag with targets config, set it false if targets browser is not support unicode flag.