v1.17.0

cty now requires Go 1.23 or later.

• cty.Value.Elements offers a modern iter.Seq2-based equivalent of cty.Value.ElementIterator.

• cty.DeepValues offers a modern iter.Seq2-based equivalent of cty.Walk.

• cty.Value.WrangleMarksDeep allows inspecting and modifying individual marks throughout a possibly-nested data structure.

  Having now got some experience using marks more extensively in some callers, it's become clear that it's often necessary for different subsystems to be able to collaborate using independent marks without upsetting each other's assumptions. Today that tends to be achieved using hand-written transforms either with cty.Transform or cty.Value.UnmarkDeepWithPaths/cty.Value.MarkWithPaths, both of which can be pretty expensive even in the common case where there are no marks present at all.

  This new function allows inspecting and transforming marks with far less overhead, by creating new values only for parts of a structure that actually need to change and by reusing (rather than recreating) the "payloads" of the values being modified when we know that only the marks have changed.

• cty.ValueMarksOfType and cty.ValueMarksOfTypeDeep make it easier to use type-based rather than value-based mark schemes, where different values of a common type are used to track a specific kind of relationship with multiple external values.

• cty.Value.HasMarkDeep provides a "deep" version of the existing cty.Value.HasMark, searching throughout a possibly-nested structure for any values that have the given mark.

• cty.Value.UnmarkDeep and cty.Value.UnmarkDeepWithPaths are now implemented in terms of cty.Value.WrangleMarksDeep, so they benefit from its reduced overhead. In particular they avoid reconstructing a data structure that contains no marked values at all.

• cty.Value.MarkWithPaths now has a fast path when it's given a zero-length PathValueMarks, in which case it just returns the value it was given with no modifications.