Expr() doesn't return correct value?

[ying-jeanne]

What version of CUE are you using (cue version)?

0.4.0-alpha.2

$ cue version

Does this issue reproduce with the latest release?

yes

What did you do?

https://github.com/ying-jeanne/cue_test_cases/blob/bf84db6edba61d3479838967d7445f1775393fc3/main.go

What did you expect to see?

........ the v expr() is: [*4 | int] and the length is: 2, ops is | (or doesn't matter)
........ the v expr() is: [*4 | int *7 | int] and the length is: 2, ops is : |
........ the v expr() is: [4 7] and the length is: 2, ops is : |

What did you see instead?

........ the v expr() is: [*4 | int] and the length is: 1, ops is :
........ the v expr() is: [*4 | int *7 | int] and the length is: 2, ops is : |
........ the v expr() is: [4 7] and the length is: 2, ops is : |

PS:
it seems

AType: *4 | int
Foo: {
	Baz: AType | *7
}

with Expr() I am getting 1 cue.Value in the return list, but with

AType: *4 | int
Foo: {
	Baz: AType | *"pool"
}

I am getting 2 cue.Values in the return list...

[mpvl]

Analysis: The algorithm incorrectly removes defaults it believes are subsumed by non-default values.