export * as default from "module" syntax should work as per ECMA-262

[HughCrail]

TypeScript Version: 4.0.0-beta

Search Terms:
ESModule, export star as default, "export * as default from"

Expected behavior:
export * as default from "module" should export the namespace of "module" as the default export.
This is valid ES Module syntax from this stage-4 proposal. See the test in test-262.
I also tested this syntax in Chrome and it was supported.

Actual behavior:
You get the following errors:

• "Cannot find name 'from'."
• "Identifier expected. 'default' is a reserved word that cannot be used here."
• "';' expected."

Code

export * as default from "rollup";

Output

export * as  from ;
from;
"rollup";

Compiler Options

{
  "compilerOptions": {
    "noImplicitAny": true,
    "strictNullChecks": true,
    "strictFunctionTypes": true,
    "strictPropertyInitialization": true,
    "strictBindCallApply": true,
    "noImplicitThis": true,
    "noImplicitReturns": true,
    "alwaysStrict": true,
    "esModuleInterop": true,
    "declaration": true,
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true,
    "moduleResolution": 2,
    "target": "Latest",
    "jsx": "React",
    "module": "ESNext"
  }
}

Playground Link: Provided

[DanielRosenwasser]

CC @Kingwl in case you want to take this on as a follow-up to #34903

[Kingwl]

Take a look soon.

[DanielRosenwasser]

Thanks @Kingwl!