Optimiser: inline VALUES with single set of bindings

[tpluscode]

sh:hasValue produces SPARQL like

?resource1 schema:knows ?resource3.
VALUES ?resource3 {
  <http://example.org/John>
}

This could be simplified by inlining ?resource3 but there are potential problems:

1. What if ?resource3 is used in the CONSTRUCT or SELECT?
2. What if there are multiple variables (but still a single set)
3. Can such VALUES be inlined when the variable is used at multiple levels of patterns in the query?
4. Does it even offer performance improvement?