Module simplify 

AST normalization. Port of RelaxNG.pm lines 397–525.

Walks the raw AST produced by super::scan under a binding context (the enclosing <grammar> name) and:

• resolves Ref / ParentRef qnames against the binding/parent-binding,
• records every reference site in Relaxng::uses_name (powers the “Used by:” lists in the schema docs),
• registers Element body patterns under Relaxng::elements,
• combines Defs into a single canonical Combination per qname in Relaxng::defs (with Relaxng::def_combiner tracking which combiner won), tracking the singleton-element-def shortcut into Relaxng::elementdefs / Relaxng::element_reverse_defs,
• resolves Overrides by patching the wrapped module before re-running simplify on the patched form,
• preserves document-order of Relaxng::modules.

The simplifier is shape-preserving in its return value: every input pattern (except Override and singleton-element-defs) emerges with the same shape but possibly-rewritten qnames and recursively simplified bodies. Side effects on rng are the substantive output.

Functions

extract_start

Recursively pull Pattern::Start bodies out of Module / Grammar wrappers. Mirrors extractStart and powers Model::add_tag_content('#Document', ...) later in the chain.

simplify

Recursive normalizer.

simplify_combination

Recursively flatten same-op Group/Choice nests and collapse a singleton Group to its only member. Port of simplifyCombination.

simplify_top

Top-level simplifier. Maps simplify across each top-level form.