Fix CJS local binding emit for ES decorators

[rbuckton]

Fixes the emit for the local binding of a class name.

Fixes #53332

[jakebailey]

If this uses a let, will code like:

class Foo {}
namespace Foo {
    export test = 1234;
}

Work correctly?

[rbuckton]

It should. The merging behavior occurs in the ts transform, before decorators are processed.

[jakebailey]

Is there a test we could add to verify?

[rbuckton]

That behavior is already covered by tests/cases/conformance/internalModules/DeclarationMerging/ClassAndModuleThatMerge*.ts. Nothing I changed here would have any impact on declaration merging since that happens long before this transform runs.

[jakebailey]

Right, I get that class/namespace merging is covered, but skimming the tests you link, none of them export and use CJS, so it doesn't seem like this particular bug + namespace merging is covered.

Am I missing a test that would exhibit both behaviors? I would assume it doesn't exist, otherwise the original bug would have also been caught?

[rbuckton]

I don't think class/namespace merging has anything to do with the original bug, but I've added a test anyways.

[jakebailey]

Is this backportable or since isn't a regression from 4.9 to 5.0, we'll just wait for 5.1?

[rbuckton]

It can be backported, but whether it should be may be a question for @DanielRosenwasser.