Control Flow Flattening breaks typeof expression

[MichaelXF]

Describe the bug:

Control Flow Flattening breaks typeof expression

Config and Small code sample

Config:

{
  target: "node",
  controlFlowFlattening: true
}

Code:

console.log(1); // 1
typeof a; // "undefined"

Output:

typeof (console['log'](1), a);
// Uncaught ReferenceError: a is not defined

The typeof expression is special because when checking a single Identifier node, there will not be an error thrown, even if the variable doesn't exist. This only applies on Identifier nodes, when joined in a sequence expression it will error. The fix is to make Control Flow Flattening not change typeof expressions.