Module ast 

Concrete syntax tree and abstract syntax tree types.

These types define the public AST / CST surface for the parser frontend. Node hierarchies will be expanded over time, but the structural definitions — ConcreteSyntaxTree, Ast, TokenTape, TriviaTable — are settled here.

Lossless vs lossy

• ConcreteSyntaxTree is lossless: every delimiter, keyword, and trivia is represented with byte-offset spans. Round-tripping goes through the CST / token tape.

• Ast is lossy (semantic): whitespace, comments, and exact delimiter positions are not preserved. Pretty-printing from the AST produces equivalent but not byte-identical output.

Spanned invariant

Every AST node MUST carry a source Span. The Spanned trait formalises this requirement. All new AST node types must implement Spanned. This is enforced by code review, not by a compile-time lint (Rust’s type system cannot express “every variant of an enum has a span field”).

Structs

Ast

The typed abstract syntax tree.

ConcreteSyntaxTree

The lossless concrete syntax tree produced by a [ParseBackend].

CstNodeId

Opaque identifier for a node in the ConcreteSyntaxTree.

SourceFile

A single parsed source file (the root of the typed AST).

SourceMap

Maps CstNodeIds to their source Spans.

Enums

AstDecl

A top-level PL/SQL declaration.

AstExpr

A PL/SQL expression node.

AstStatement

A statement inside a routine / anonymous block body.

AstTypeDecl

A type declaration.

Traits

Spanned

Every AST node must implement this trait.