Skip to content

11_interpreter_design.md

Latest commit

 

History

History
80 lines (57 loc) · 3.11 KB

11_interpreter_design.md

File metadata and controls

80 lines (57 loc) · 3.11 KB
Raw

11 — TechScript 2.0 Interpreter Design

Status: Authoritative Specification Version: 2.0.0 Last Updated: 2026-07-15 Related Documents: 05 AST Design · 09 Runtime Design · 10 Semantic Analysis · 14 Error Codes

1. Execution Model

The interpreter evaluates AST nodes sequentially, using the CheckedProgram and SymbolTable to resolve scopes.

flowchart TD
    CP["CheckedProgram"]
    WALK["Walk AST\nTop-to-Bottom"]
    EVAL_STMT["evaluate_statement()"]
    EVAL_EXPR["evaluate_expression()"]
    ENV["Environment\n(read/write)"]
    RESULT["Value or RuntimeError"]

    CP --> WALK
    WALK --> EVAL_STMT
    EVAL_STMT --> EVAL_EXPR
    EVAL_EXPR --> ENV
    EVAL_STMT --> ENV
    EVAL_EXPR --> RESULT
    EVAL_STMT --> RESULT

    style CP fill:#ff6b6b,color:#fff
    style RESULT fill:#6bcb77,color:#fff
Loading

2. Expression Evaluation

Expressions are evaluated by type. Sub-expressions (arithmetic, comparison, logic) map to Rust operations on Value variants. Logical operators support short-circuiting.

3. Statement Execution

Statements alter the environment state. Mutable declarations update the innermost environment scope. Jump instructions (break, continue, return) return control signals.

4. Function & Method Dispatch

Functions evaluate into Value::Function closures. When a method is accessed on an instance, the interpreter retrieves the MethodDecl AST node and invokes it inside a local scope with self bound to the object:

execute_method(obj, method_name, args):
    method = obj.methods.get(method_name)
    // Invokes the method body regardless of whether it was defined
    // using 'build' or 'fun' keyword in the source code.
    eval_function_body(method, args, bound_self = obj)

5. Compatibility & Evolution Analysis

5.1 Compatibility Notes

  • Unified Dispatch: The interpreter evaluates both build and fun method declarations identically. Both compile to standard method bindings at runtime.
  • Dynamic Scoping: Environment lookup chains match Version 1 scoping rules, preventing binding capture regressions.

5.2 Migration Notes

  • All modules imported during execution are resolved using .txs file extensions.
  • If a script relies on importing legacy .tech files, rename the files before execution.
  • Auto-fixing linter tasks bypass the interpreter, transforming source code files directly.

5.3 Rationale

  • Uniform Evaluation: Handling build and fun identically in the execution path avoids duplicating frame-pushing logic and simplifies debugging.
  • Zero-allocation Signals: Using Rust's Result<T, Signal> enum for control flow signals (Break, Continue, Return) avoids allocation overhead during loop execution.

5.4 Future Roadmap

  • v2.1: The AST interpreter will be replaced by a flat bytecode execution loop (techscript_vm), running VM instructions sequentially.
  • v3.0: Functions and methods will compile directly to LLVM instructions, removing interpreter frame push overhead.