Use case

RenderSliverPadding validates non-negative padding in its constructor, but its padding setter currently re-checks the existing field instead of the incoming value.

Problem

The setter currently does this:

assert(padding.isNonNegative);

That validates the old value, not the new one being assigned.

As a result, this can slip through the setter in debug mode:

final RenderSliverPadding renderSliverPadding = RenderSliverPadding(
  padding: EdgeInsets.zero,
);
renderSliverPadding.padding = const EdgeInsets.all(-1.0);

Expected behavior

Assigning negative padding through RenderSliverPadding.padding should fail the same way the constructor does.

Actual behavior

The setter assertion checks the current padding instead of the incoming value, so negative input is not rejected at the setter boundary.

Additional context

I opened a fix here:

• PR: Fix RenderSliverPadding setter assertion #187353

The proposed change is just to validate value.isNonNegative and add a regression test.