RemoveHs() removes H atom attached to dummy if it came from AddHs()

[DrrDom]

I discovered some strange behavior of removeHs function applied for '[H][*:1]' molecule.

If I create that mol from smiles, RemoveHs does not remove a single H from the mol:

mmm = Chem.MolFromSmiles('[H][*:1]')
Chem.MolToSmiles(Chem.RemoveHs(mmm))

output:

'[H][*:1]'

If I apply RemoveHs to fragments obtained after MMPA cuts it removes H and keeps only '[*:1]'

mmm = Chem.MolFromSmiles('c1ccccc1C')
mmm = Chem.AddHs(mmm)
fr = rdMMPA.FragmentMol(mmm, pattern="[*]!@!=!#[!#1]", maxCuts=1, resultsAsMols=True)
for f in fr:
    ff = Chem.GetMolFrags(f[1], asMols=True)
    print(Chem.MolToSmiles(ff[0]), Chem.MolToSmiles(Chem.RemoveHs(ff[0])))
    print(Chem.MolToSmiles(ff[1]), Chem.MolToSmiles(Chem.RemoveHs(ff[1])))

output:

[H]c1c([H])c([H])c([*:1])c([H])c1[H] c1ccc([*:1])cc1
[H]C([H])([H])[*:1] C[*:1]
[H]c1c([H])c([H])c([*:1])c(C([H])([H])[H])c1[H] Cc1ccccc1[*:1]
[H][*:1] [*:1]
[H]c1c([H])c(C([H])([H])[H])c([H])c([*:1])c1[H] Cc1cccc([*:1])c1
[H][*:1] [*:1]
[H]c1c([H])c([*:1])c([H])c([H])c1C([H])([H])[H] Cc1ccc([*:1])cc1
[H][*:1] [*:1]
[H]c1c([H])c([H])c(C([H])([H])[*:1])c([H])c1[H] c1ccc(C[*:1])cc1
[H][*:1] [*:1]

[greglandrum]

What's going on here: AddHs() tags the Hs that it adds as implicit.
This ends up taking priority over the check for Hs that are attached to non-heavy atoms:
https://github.com/rdkit/rdkit/blob/master/Code/GraphMol/AddHs.cpp#L451