Module compile_path 

FHIRPath expression → SqlExpr compiler.

Walks the AST produced by helios_fhirpath::parser::parser() and emits a dialect-independent SqlExpr. The translation covers the subset needed by the SoF v2 conformance corpus, expanded one feature at a time across stages 2–5.

Coverage by stage

• Stage 2 (this file’s current state): literals, member navigation, bracket indexing, comparison & logical operators, polarity, basic function calls (exists, empty, count, first, last, iif, not, ofType primitive), $this.
• Stage 3: focus-as-collection threading (.where(...).select(...) chains that nest into lateral subqueries).
• Stage 4: %name constants bound as parameters, extension(url), reference keys, ofType(complex), join(sep).
• Stage 5: lowBoundary / highBoundary.

Structs

CompileEnv

Compile-time environment threaded through expression lowering.

Constant

A ViewDefinition.constant[] entry resolved to a typed value.

Functions

compile_fhirpath_expr

Parse src and compile it to SqlExpr.