Doc Updates (#60222)

packages/flutter/lib/src/widgets/scroll_physics.dart

@@ -448,12 +448,25 @@ class RangeMaintainingScrollPhysics extends ScrollPhysics {
 ///
 /// This is the behavior typically seen on iOS.
 ///
+/// [BouncingScrollPhysics] by itself will not create an overscroll effect if
+/// the contents of the scroll view do not extend beyond the size of the
+/// viewport. To create the overscroll and bounce effect regardless of the
+/// length of your scroll view, combine with [AlwaysScrollableScrollPhysics].
+///
+/// {@tool snippet}
+/// ```dart
+/// BouncingScrollPhysics(parent: AlwaysScrollableScrollPhysics())
+/// ```
+/// (@end-tool}
+///
 /// See also:
 ///
 ///  * [ScrollConfiguration], which uses this to provide the default
 ///    scroll behavior on iOS.
 ///  * [ClampingScrollPhysics], which is the analogous physics for Android's
 ///    clamping behavior.
+///  * [ScrollPhysics], for more examples of combining [ScrollPhysics] objects
+///    of different types to get the desired scroll physics.
 class BouncingScrollPhysics extends ScrollPhysics {
   /// Creates scroll physics that bounce back from the edge.
   const BouncingScrollPhysics({ ScrollPhysics parent }) : super(parent: parent);

packages/flutter/lib/src/widgets/sliver_fill.dart

@@ -188,7 +188,10 @@ class _RenderSliverFractionalPadding extends RenderSliverEdgeInsetsPadding {
 /// The [hasScrollBody] flag indicates whether the sliver's child has a
 /// scrollable body. This value is never null, and defaults to true. A common
 /// example of this use is a [NestedScrollView]. In this case, the sliver will
-/// size its child to fill the maximum available extent.
+/// size its child to fill the maximum available extent. [SliverFillRemaining]
+/// will not constrain the scrollable area, as it could potentially have an
+/// infinite depth. This is also true for use cases such as a [ScrollView] when
+/// [ScrollView.shrinkwrap] is true.
 ///
 /// ### When [SliverFillRemaining] does not have a scrollable child
 ///
@@ -347,7 +350,10 @@ class _RenderSliverFractionalPadding extends RenderSliverEdgeInsetsPadding {
 ///     // fillOverscroll only changes the behavior of your layout when applied
 ///     // to Scrollables that allow for overscroll. BouncingScrollPhysics are
 ///     // one example, which are provided by default on the iOS platform.
-///     physics: BouncingScrollPhysics(),
+///     // BouncingScrollPhysics is combined with AlwaysScrollableScrollPhysics
+///     // to allow for the overscroll, regardless of the depth of the
+///     // scrollable.
+///     physics: BouncingScrollPhysics(parent: AlwaysScrollableScrollPhysics()),
 ///     slivers: <Widget>[
 ///       SliverToBoxAdapter(
 ///         child: Container(