Duplicate final field assignment with latest SNAPSHOT

[Stephan202]

Consider the following code:

import org.immutables.value.Value;

@Value.Immutable
@Value.Style(allParameters = true)
interface Dummy {
    @Value.Default
    default String getFoo() {
        return "";
    }

    @Value.Default
    default boolean isBar() {
        return true;
    }
}

When built against master (7c42bef), the following code is generated:

...
  private ImmutableDummy(String foo, boolean isBar) {
    this.foo = Objects.requireNonNull(foo, "foo");
    this.isBar = isBar;
    this.foo = initShim.getFoo();
    this.isBar = initShim.isBar();
    this.initShim = null;
  }
...

This yields the following compilation error:

[ERROR] /path/to/ImmutableDummy.java:[41,9] variable foo might already have been assigned
[ERROR] /path/to/ImmutableDummy.java:[42,9] variable isBar might already have been assigned

The issue does not affect version 2.5.6.