ES6 module declarations should be marked to exclude them from `allowSyntheticDefaultImports`

This is the restated #27293. CC @ryanelian

TypeScript Version: master (471bc64)

Search Terms: esModuleInterop allowSyntheticDefaultImports error undefined default import export

Code: In the b subdirectory, compile with tsc -b . and run with node index.js.

// tsconfig.common.json
{
    "compilerOptions": {
        "composite": true,
        "declaration": true,
        "target": "es6",
        "module": "commonjs",
        "esModuleInterop": true
    }
}

// a/tsconfig.json
{
    "extends": "../tsconfig.common.json",
    "files": [
        "index.ts"
    ]
}

// a/index.ts
export const foo = 42;

// b/tsconfig.json
{
    "extends": "../tsconfig.common.json",
    "references": [
        { "path": "../a" }
    ],
    "files": [
        "index.ts"
    ]
}

// b/index.ts
// Actual: compile OK.  Expected: compile error.
import A from "../a";
// Actual: runtime error.
console.log(A.foo);

Expected behavior: The generated a/index.d.ts uses some new syntax to mark the module as an ES6 module, so allowSyntheticDefaultImports does not apply to it and the default import in b/index.ts is a compile error.

Actual behavior: allowSyntheticDefaultImports applies to module a, so at compile time, the default import is accepted and resolves to the entire module, but at runtime, A.foo raises an error:

REDACTED/b/index.js:7
console.log(a_1.default.foo);
                        ^

TypeError: Cannot read property 'foo' of undefined

Playground Link: N/A, multiple files

Related Issues: #27293

Reproduziere den Fall im Unterverzeichnis b mit tsc -b . und node index.js und untersuche anschließend die generierte a/index.d.ts sowie den Import in b/index.ts. Als erledigt gilt die Aufgabe, wenn die Deklaration das ES6-Modul kennzeichnet, sodass der default import während der Kompilierung abgelehnt wird, anstatt den gezeigten Laufzeitfehler zu verursachen.