type parameters as constraints feature doesn't compile with --declaration argument

[zpdDG4gta8XKpMCd]

In the latest typeParametersAsConstraints branch the following:

// test.ts
export function append<a, b extends a>(result: a[], value: b): a[] {
    result.push(value);
    return result;
}

compiles with

node ./built/local/tsc.js --module commonjs test.ts 

but fails with

node ./built/local/tsc.js --module commonjs --declaration test.ts 

saying

test.ts(1,37): error TS4016: Type parameter 'b' of exported function has or is using private name 'a'

[ahejlsberg]

Now fixed in #5949.