engine: remove AST interpreter and testing Cargo feature

docs/architecture.md

@@ -14,7 +14,6 @@ Core simulation engine. Compiles, type-checks, unit-checks, and simulates SD mod
 - Primary compilation path is `db::compile_project_incremental()` using salsa tracked functions for fine-grained incrementality (`db.rs`, `db_analysis.rs`, `db_ltm.rs`)
 - Equation text is parsed via recursive descent parser (`parser/mod.rs`)
 - Simulations run on a stack-based bytecode VM (`vm.rs`) with `PREVIOUS`/`INIT` intrinsic opcodes
-- AST-walking `interpreter.rs` is deprecated for production; retained as a reference spec for VM correctness
 - `builtins.rs` defines builtin functions (including `PREVIOUS`, `INIT`); stateful module functions (TREND, SMOOTH3) are model definitions in `stdlib/*.stmx`, generated into `stdlib.gen.rs`
 - Native Vensim MDL parser in `mdl/` (replaces C++ xmutil); see [docs/design/mdl-parser.md](/docs/design/mdl-parser.md)
 

docs/array-design.md

@@ -112,7 +112,7 @@ Indexed dimensions (e.g., numeric dimensions like `Periods(5)`) can use position
 - Broadcasting: `BeginBroadcastIter`, `LoadBroadcastElement`, `StoreBroadcastElement`
 - Sparse iteration support via pre-computed flat offsets
 
-#### Array Builtins (in both interpreter and VM)
+#### Array Builtins
 - `SUM(array)` - Sum all elements
 - `MEAN(array)` - Arithmetic mean
 - `STDDEV(array)` - Standard deviation

src/simlin-engine/CLAUDE.md

@@ -22,17 +22,16 @@ Equation text flows through these stages in order:
    - `pretty.rs` - Debug pretty-printing
 6. **`src/bytecode.rs`** - Instruction set definition, opcodes, type aliases (`LiteralId`, `ModuleId`, `DimId`, `TempId`, etc.). Includes `LoadPrev`/`LoadInitial` opcodes for `PREVIOUS()`/`INIT()` intrinsics and vector operation opcodes (`VectorSelect`, `VectorElmMap`, `VectorSortOrder`, `Rank`, `AllocateAvailable`, `AllocateByPriority`) that operate on view-stack arrays and write results to temp storage.
 7. **`src/vm.rs`** - Stack-based bytecode VM. Hot loop uses proven-safe unchecked array access validated at compile time by `ByteCodeBuilder`. Maintains `prev_values` and `initial_values` snapshot buffers for `LoadPrev`/`LoadInitial` opcodes. Implements vector operation dispatch (VectorSelect, VectorElmMap, VectorSortOrder, Rank, AllocateAvailable, AllocateByPriority). Array reducers (ArrayMax, ArrayMin, ArrayMean, ArrayStddev) return NaN for empty views; ArraySum returns 0.0 (additive identity).
-8. **`src/interpreter.rs`** - AST-walking interpreter. Retained as a reference spec for VM correctness verification via `Simulation::new()` + `run_to_end()`. Production compilation uses `db::compile_project_incremental`.
-9. **`src/alloc.rs`** - Allocation helpers shared by interpreter and VM: `allocate_available()` (bisection-based priority allocation), `alloc_curve()` (per-requester allocation curves for 6 profile types), `normal_cdf()`/`erfc_approx()`.
+8. **`src/alloc.rs`** - Allocation helpers for VM priority allocation: `allocate_available()` (bisection-based priority allocation), `alloc_curve()` (per-requester allocation curves for 6 profile types), `normal_cdf()`/`erfc_approx()`.
 
 ## Data model and project structure
 
 - **`src/common.rs`** - Error types (`ErrorCode` with 100+ variants), `Result`, identifier types (`RawIdent`, `Ident<Canonical>`, dimension/element name types), canonicalization
 - **`src/datamodel.rs`** - Core structures: `Project`, `Model`, `Variable`, `Equation` (including `Arrayed` variant with `default_equation` for EXCEPT semantics and `has_except_default` bool flag), `Dimension` (with `mappings: Vec<DimensionMapping>` replacing the old `maps_to` field, and `parent: Option<String>` for indexed subdimension relationships), `DimensionMapping`, `DataSource`/`DataSourceKind`, `UnitMap`. View element types (`Aux`, `Stock`, `Flow`, `Alias`, `Cloud`) carry an optional `ViewElementCompat` with original Vensim sketch dimensions/bits for MDL roundtrip fidelity. `StockFlow` has an optional `font` string for the Vensim default font spec.
-- **`src/variable.rs`** - Variable variants (`Stock`, `Flow`, `Aux`, `Module`), `ModuleInput`, `Table` (graphical functions). `classify_dependencies()` is the primary API for extracting dependency categories from an AST in a single walk, returning a `DepClassification` with five sets: `all` (every referenced ident), `init_referenced`, `previous_referenced`, `previous_only` (idents only inside PREVIOUS), and `init_only` (idents only inside INIT/PREVIOUS). The older single-purpose functions (`identifier_set`, `init_referenced_idents`, etc.) remain as thin wrappers. `parse_var_with_module_context` accepts a `module_idents` set so `PREVIOUS(module_var)` rewrites through a scalar helper aux instead of `LoadPrev`.
+- **`src/variable.rs`** - Variable variants (`Stock`, `Flow`, `Aux`, `Module`), `ModuleInput`, `Table` (graphical functions). `classify_dependencies()` is the primary API for extracting dependency categories from an AST in a single walk, returning a `DepClassification` with five sets: `all` (every referenced ident), `init_referenced`, `previous_referenced`, `previous_only` (idents only inside PREVIOUS), and `init_only` (idents only inside INIT/PREVIOUS). `parse_var_with_module_context` accepts a `module_idents` set so `PREVIOUS(module_var)` rewrites through a scalar helper aux instead of `LoadPrev`.
 - **`src/dimensions.rs`** - `DimensionsContext` for dimension matching, subdimension detection, and element-level mappings. Supports indexed subdimensions via `parent` field (child maps to first N elements of parent). `has_mapping_to()` checks for element-level dimension mappings between two dimensions. `SubdimensionRelation` caches parent-child offset mappings for both named (element containment) and indexed (declared parent) dimensions
-- **`src/model.rs`** - Model compilation stages (`ModelStage0` -> `ModelStage1` -> `ModuleStage2`), dependency resolution, topological sort. `collect_module_idents` pre-scans datamodel variables to identify which names will expand to modules (preventing incorrect `LoadPrev` compilation). `init_referenced_vars` extends the Initials runlist to include variables referenced by `INIT()` calls, ensuring their values are captured in the `initial_values` snapshot. `check_units` is gated behind `cfg(any(test, feature = "testing"))` (production unit checking uses salsa tracked functions).
-- **`src/project.rs`** - `Project` struct aggregating models. `from_salsa(datamodel, db, source_project, cb)` builds a Project from a pre-synced salsa database (all variable parsing comes from salsa-cached results). `from_datamodel(datamodel)` is a convenience wrapper that creates a local DB and syncs. `From<datamodel::Project>` and `from_datamodel` are gated behind `cfg(any(test, feature = "testing"))` (retained only for tests and the AST interpreter cross-validation path); production code uses `db::compile_project_incremental` with `ltm_enabled`/`ltm_discovery_mode` on `SourceProject`.
+- **`src/model.rs`** - Model compilation stages (`ModelStage0` -> `ModelStage1` -> `ModuleStage2`), dependency resolution, topological sort. `collect_module_idents` pre-scans datamodel variables to identify which names will expand to modules (preventing incorrect `LoadPrev` compilation). `init_referenced_vars` extends the Initials runlist to include variables referenced by `INIT()` calls, ensuring their values are captured in the `initial_values` snapshot. Unit checking uses salsa tracked functions in `db.rs`.
+- **`src/project.rs`** - `Project` struct aggregating models. `from_salsa(datamodel, db, source_project, cb)` builds a Project from a pre-synced salsa database (all variable parsing comes from salsa-cached results). `from_datamodel(datamodel)` is a convenience wrapper that creates a local DB and syncs. Production code uses `db::compile_project_incremental` with `ltm_enabled`/`ltm_discovery_mode` on `SourceProject`.
 - **`src/results.rs`** - `Results` (variable offsets + timeseries data), `Specs` (time/integration config)
 - **`src/patch.rs`** - `ModelPatch`/`ProjectPatch` (both `Clone`) for representing and applying model changes. `ModelPatch` is consumed by `incremental_layout()` to determine what variables were added/removed/renamed
 
@@ -86,7 +85,6 @@ The primary compilation path uses salsa tracked functions for fine-grained incre
 
 ## Cargo features
 
-- **`testing`** - Exposes the monolithic `Project::from` construction path and associated test helpers (`check_units`, etc.). Required by `simulate`, `simulate_ltm`, and `compiler_vector` integration tests. Production code uses `compile_project_incremental` instead.
 - **`file_io`** - Filesystem-based data providers (CSV/Excel). Required by `simulate` and `simulate_ltm` tests.
 - **`schema`** - JSON Schema derivation via `schemars`.
 - **`ai_info`** - AI metadata signing.

src/simlin-engine/Cargo.toml

@@ -14,10 +14,6 @@ default = ["schema", "ai_info", "debug-derive"]
 # are used with .unwrap(), or appear in assert_eq!() keep unconditional Debug.
 # New types should use: #[cfg_attr(feature = "debug-derive", derive(Debug))]
 debug-derive = []
-# Exposes the monolithic Project::from construction path and associated
-# test helpers (compile, build_sim, run_interpreter, etc.) for integration
-# tests. Production code uses compile_project_incremental instead.
-testing = []
 schema = ["dep:schemars"]
 ai_info = ["dep:ed25519", "dep:base64"]
 file_io = ["dep:csv"]
@@ -66,19 +62,19 @@ tempfile = "3"
 
 [[test]]
 name = "simulate"
-required-features = ["file_io", "testing"]
+required-features = ["file_io"]
 
 [[test]]
 name = "simulate_ltm"
-required-features = ["file_io", "testing"]
+required-features = ["file_io"]
 
 [[test]]
 name = "simulate_systems"
-required-features = ["file_io", "testing"]
+required-features = ["file_io"]
 
 [[test]]
 name = "systems_roundtrip"
-required-features = ["file_io", "testing"]
+required-features = ["file_io"]
 
 [[test]]
 name = "roundtrip"
@@ -91,7 +87,6 @@ name = "json_roundtrip"
 
 [[test]]
 name = "compiler_vector"
-required-features = ["testing"]
 
 [[bench]]
 name = "array_ops"