eiffel-implement

name	eiffel-implement
description	Phase 4 of Eiffel Spec Kit. Writes feature bodies while keeping contracts FROZEN. Detects unauthorized contract changes. Use with /eiffel.implement command.
allowed-tools	Read, Grep, Glob, Edit, Write, Bash, Task

/eiffel.implement - Phase 4: Implementation

Purpose: Write feature bodies that satisfy contracts. Contracts are FROZEN - no modifications allowed.

Usage

/eiffel.implement <project-path>

Project Scoping

<project-path>/
├── .eiffel-workflow/
│   ├── tasks.md (from Phase 3)
│   └── evidence/
│       ├── phase4-contracts-before.txt
│       ├── phase4-contracts-after.txt
│       └── phase4-compile.txt
├── src/*.e (implementation goes here)

Prerequisites

• Phase 3 complete: <project-path>/.eiffel-workflow/tasks.md approved

Critical Rule: CONTRACTS ARE FROZEN

DO NOT modify require/ensure/invariant clauses.

If implementation seems impossible without changing contracts:

1. STOP
2. Document why
3. Return to Phase 1 (/eiffel.contracts)
4. Re-run Phase 2 review after changes

Workflow

Step 1: Snapshot Contracts

grep -n "require\|ensure\|invariant" <project-path>/src/*.e > <project-path>/.eiffel-workflow/evidence/phase4-contracts-before.txt

Step 2: Implement Tasks

For each task in tasks.md:

1. Read the feature contracts
2. Read the approach from approach.md
3. Write feature body between do and ensure
4. Compile after each feature

Step 3: Compile After Each Task

CRITICAL: You MUST cd to the project directory before compiling. The EIFGENs folder is created in the current working directory, not where the ECF file is located. Compiling from the wrong directory pollutes other folders with build artifacts.

cd <project-path> && /d/prod/ec.sh -batch -config <project>.ecf -target <project>_tests -c_compile

ZERO WARNINGS POLICY: If the compiler reports obsolete call warnings or any other warnings, FIX THEM IMMEDIATELY. Do not note them and move on. Do not defer them. Fix them right now before proceeding. Common fixes:

• Obsolete as_string_8: Use explicit {STRING_32} "literal" manifest type or .to_string_8
• Obsolete feature calls: Replace with the suggested alternative in the warning message

Step 4: Detect Contract Changes

grep -n "require\|ensure\|invariant" <project-path>/src/*.e > <project-path>/.eiffel-workflow/evidence/phase4-contracts-after.txt
diff <project-path>/.eiffel-workflow/evidence/phase4-contracts-before.txt <project-path>/.eiffel-workflow/evidence/phase4-contracts-after.txt

If contracts changed: STOP and notify human.

Step 5: Save Evidence

Save to <project-path>/.eiffel-workflow/evidence/phase4-compile.txt:

# Phase 4 Implementation Evidence
# Project: <project-path>
# Date: [timestamp]

[Paste compilation output]

Contract changes detected: [yes/no]
# Status: PASS / FAIL

Context Management (RLM Pattern)

This skill focuses ONLY on: <project-path>

DO NOT:

• Read files outside this project directory
• Load entire ecosystem or multiple libraries into context
• Keep large file contents in working memory

DO:

• Use Task tool with Explore agent for ecosystem questions
• Ask targeted questions when implementation needs external API details
• Release context after getting answers

Example - Ecosystem Query:

Need to call simple_json from your implementation? Don't read all its files.
Instead: Task(subagent_type=Explore) → "How do I serialize an object to JSON string with simple_json?"

The sub-agent searches, summarizes, and returns ONLY what you need. Your context stays focused on this project.

Completion

Phase 4 COMPLETE: Implementation done.
Project: <project-path>

- All features implemented
- Contracts unchanged
- Compilation: PASS

Next: Run /eiffel.verify <project-path> to generate and run tests.