Incorrect relationships created with conditional unique constraint

[hamstah]

Using v4.18.0 (previously tested on 4.16 too)
Using the postgres driver (but not sure it's postgres specific)

given the schema generated by

CREATE TABLE A (
    id serial PRIMARY KEY,
    content text NOT NULL
);

CREATE TABLE b (
    id serial PRIMARY KEY,
    a_id INT NOT NULL REFERENCES A(id) ON
    DELETE
        CASCADE,
        content text NOT NULL
);

CREATE UNIQUE INDEX unique_a_id ON b(a_id)
WHERE
    content = 'test';

The generated relationship on A is

...
// aR is where relationships are stored.
type aR struct {
	B *B `boil:"B" json:"B" toml:"B" yaml:"B"`
}
...

ie it created a 1:1 relationship, but it should be a 1:many relationship as there could be multiple B linked to the same A, as long as at most one of them has the test content.

if I remove the unique constraint I get the correct relationship

...
// aR is where relationships are stored.
type aR struct {
	BS BSlice `boil:"BS" json:"BS" toml:"BS" yaml:"BS"`
}
...

It seems like the issue if with the relationship logic trying to handle the unique constraint and convert the relationship from 1:many to 1:1 but not accounting for the conditional part of it.