Module ast_diff 

AST diff infrastructure for PEPL.

Compares two PEPL ASTs and produces a structured list of changes. Used for:

• Evolve operation scope validation
• Incremental compilation (re-codegen only changed subtrees)
• Event storage optimization (store diffs instead of full snapshots)
• PEPL’s transformation guarantee: “diffs are AST-level, not line-level”

Structs

AstChange

A single change between two ASTs.

AstDiff

A structured diff between two PEPL ASTs.

Enums

AllowedScope

Allowed scope for change validation.

ChangeKind

What kind of change occurred.