[Bug]: Typekits create unfinished types

[witemple-msft]

Describe the bug

Some typekits (at least model.create and modelProperty.create from my testing) return unfinished types.

Very bad and difficult to debug things can happen if you forget to finish the Type yourself with program.finishType: unfinished types can be passed back into the checker resulting in decorators not running, etc. because the checker believes the types aren't done, but they will never be done unless you manually call finishType.

This has bitten me several times. TKs should always return fully checked (finished) instances.

Reproduction

$(program).modelProperty.create({
  name: "foo",
  type: $(program).builtin.string
}).isFinished;
// false

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• The provided reproduction is a minimal reproducible example of the bug.