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HIR

High-level intermediate representation: analyzed form still close to source structure, ready for MIR lowering.
Status Active — analysis product component (ADR 0012)
Owners echo_hir (built inside echo_pipeline::analyze)
Related docs/sota-gaps.md, docs/semantics.md, docs/mir.md

Scope

HIR is source-shaped IR with import classification, method tables, and expression/statement spans. It is not a VM and does not embed LLVM types.

Facts (current)

  • Entry: lower_file(&File, &HashSet import_module_names) -> HirModule.
  • Function values:
    • Design: nameless closed values; binds name them like any other value.
    • HirModule.bodies = closed code objects (HirBody.symbol = linkage).
    • Bind → FnRef { symbol } → MIR FnValue (runtime: code pointer as i64).
    • Call known bind → Call { symbol } (direct). Call through value (param/local) → CallValue → MIR CallTarget::Indirect. Nested bodies use __n_{id}.
    • Function values carry ret shape (plain/result/option) for indirect calls.
    • Methods remain call-form only (not freestanding values).
  • Top-level executable stmts → entry (includes function-value binds as FnRef).
  • Import names (analysis fact) classify ModuleCall / ModuleField vs MethodCall / Field — MIR must not re-decide import vs value.
  • Methods: %/@ fn members → __m_{struct}_{method} body symbol + HirModule.methods (graph-wide union at MIR lower).
  • Struct lits: tagged name { … } → StructLit with type name; structural { k: v } → StructLit with empty name (not a % type / methods).
  • Match arms: value multi-expr, % Type (HirMatchArm::Type), default, Option/Result $ / ! binds.
  • Every HirExpr has span; stmts carry span for provenance.
  • Built only as part of AnalysisProduct; hosts use echo_pipeline, not raw lower.

Schema / cache

When HIR node shapes change in a way that would invalidate stored lower artifacts, bump HIR_SCHEMA_VERSION / HIR_LOWERER_VERSION in echo_fingerprint (incremental.md).

Open questions

  • How much desugaring stays in HIR vs MIR as surface grows