FESADev/phases/1-linear-static-mitc4/step1.md

Step 1: core-types-diagnostics

Sprint Contract

Objective

Add core numeric/id types, shell DOF enumeration, diagnostics primitives, and error-result conventions used by later layers.

Required Reading

• /AGENTS.md
• /PROGRESS.md
• /PLAN.md
• /docs/README.md
• /docs/HARNESS_ENGINEERING.md
• /docs/ARCHITECTURE.md
• /docs/ADR.md
• /docs/NUMERICAL_CONVENTIONS.md
• /phases/1-linear-static-mitc4/step0.md

Scope

• Define int64-based ids, indices, and equation-number types.
• Define double as the default scalar precision.
• Define the six shell DOFs in the documented order: UX, UY, UZ, RX, RY, RZ.
• Add diagnostics/result primitives with enough context for parser, validation, and solver errors.

Allowed Files

• include/**
• src/**
• tests/**
• docs/ADR.md
• PLAN.md
• PROGRESS.md
• phases/1-linear-static-mitc4/index.json

Explicit Non-Goals

• Do not add Domain, parser, DofManager, sparse matrix, or MITC4 element behavior.
• Do not use 32-bit ids, equation numbers, or sparse indices.
• Do not encode global equation ids inside node or element data structures.

Tests To Write First

• Unit tests for id/index/equation type sizes and signedness expectations.
• Unit tests for DOF ordering, component labels, and stable integer mapping.
• Unit tests for diagnostic severity, code, message, and source-location payloads.

Reference Artifacts

• None.

Acceptance Commands

python scripts/validate_workspace.py

Evaluator Checklist

• Core types are reusable without depending on parser, analysis, MKL, TBB, or HDF5.
• DOF labels and order match docs/NUMERICAL_CONVENTIONS.md.
• Diagnostics can carry actionable context for unsupported input and singular systems.
• Tests were added before behavior and pass through validation.

Handoff Requirements

• Record completed work and validation in PROGRESS.md.
• Keep PLAN.md focused on future blockers only.
• Update the matching phase index entry: use completed with a one-line summary, or blocked with blocked_reason, or error with error_message.

Verification

1. Run the acceptance command.
2. Inspect tests for explicit int64 and DOF-order assertions.

Do Not

• Do not infer future element or solver APIs beyond what this contract requires.