Agent Skills: Smalltalk Implementation Finder

Smalltalk Implementation Finder

Find and analyze method implementations across class hierarchies to understand abstract methods, implementation patterns, and assess refactoring opportunities.

Purpose

Use this skill to:

• Learn implementation idioms by studying existing code
• Assess refactoring impact before making changes
• Discover implementation patterns across class hierarchies
• Find duplicate implementations that could be consolidated
• Understand subclass responsibilities for abstract methods

Core Workflow

1. Find implementors → search_implementors(method_name)
2. Get source code → get_method_source(class, method)
3. Analyze patterns → Compare implementations
4. Apply learnings → Use discovered idioms in your code

Primary Use Cases

1. Learning Implementation Idioms

When to use: Implementing a method for the first time and want to follow conventions.

Quick workflow:

1. search_implementors("methodName")
2. Sample 5-10 well-known classes
3. get_method_source for each
4. Identify common pattern
5. Apply to your implementation

Common idioms:

• hash → Combine fields with bitXor:
• initialize → Call super initialize first
• = → Check class equality, then compare fields
• printOn: → Use class identifier + element printing

Example: Learning hash implementation

Point>>hash → "^ x hash bitXor: y hash"
Association>>hash → "^ key hash bitXor: value hash"

Pattern: field1 hash bitXor: field2 hash

2. Assessing Refactoring Impact

When to use: Planning to change a method signature or refactor implementations.

Quick workflow:

1. Count implementors: search_implementors(method)
2. Count references: search_references(method)
3. Assess impact: Low (<5 impl, <20 refs) / Medium (5-20, 20-100) / High (20+, 100+)
4. Decide: Proceed / Add new method / Don't change

Example: Changing at:put:

Implementors: 50+ classes
References: 500+ call sites
Impact: VERY HIGH
Decision: Don't change. Add new method instead.

3. Finding Duplicate Code

When to use: Suspect multiple classes have identical implementations.

Quick workflow:

1. Find implementors in same hierarchy
2. Get source for each
3. Compare for duplicates
4. Refactor identical code to superclass

Example: Consolidating isEmpty

Array>>isEmpty → "^ self size = 0"
Set>>isEmpty → "^ self size = 0"
OrderedCollection>>isEmpty → "^ self size = 0"

Action: Pull up to Collection superclass

4. Understanding Abstract Methods

When to use: Encountering self subclassResponsibility and need to see concrete implementations.

Quick workflow:

1. Check abstract definition in superclass
2. Find all implementors
3. Study 3-5 concrete implementations
4. Understand expected behavior

Example: Understanding Collection>>do:

Collection>>do: → "self subclassResponsibility"
Array>>do: → "1 to: self size do: [:i | aBlock value: (self at: i)]"
LinkedList>>do: → "[node notNil] whileTrue: [aBlock value: node value. ...]"

Understanding: Each uses its own iteration strategy

5. Narrowing Usage Search

When to use: Finding references to a specific class's implementation, not all implementations.

Quick workflow:

1. Find implementors
2. Find all references
3. Filter by receiver type/context
4. Focus on relevant usage

Example: Finding Collection>>select: usage (not Dictionary>>select:)

Implementors: [Collection, Dictionary, Interval, ...]
References: 1000+ call sites

Filter by variable context:
  "myArray select: [...]" → Collection implementation
  "myDict select: [...]" → Dictionary implementation

MCP Tools

search_implementors

mcp__smalltalk-interop__search_implementors: 'methodName'

Returns all classes implementing the method.

get_method_source

mcp__smalltalk-interop__get_method_source: class: 'ClassName' method: 'methodName'

Gets source code for a specific implementation.

eval (for hierarchy exploration)

mcp__smalltalk-interop__eval: 'Collection allSubclasses'

Useful for scoping analysis to specific hierarchies.

search_references

mcp__smalltalk-interop__search_references: 'methodName'

Finds all senders (combines well with implementor analysis).

Quick Reference

| Goal | Tools | Pattern | |------|-------|---------| | Learn idiom | search_implementors → get_method_source | Sample 5-10, identify pattern | | Assess impact | search_implementors + search_references | Count both, assess risk | | Find duplicates | search_implementors → get_method_source | Compare, find identical | | Narrow usage | search_implementors → search_references | Filter by receiver type |

Best Practices

✅ Do

• Scope by hierarchy: Focus on relevant class hierarchies using eval("ClassA allSubclasses")
• Sample wisely: Choose well-known, well-implemented classes (Array, Dictionary, Point)
• Count first: Get overview before analyzing 500+ implementations
• Check super: Understand inherited behavior

❌ Don't

• Analyze all implementors without filtering
• Use obscure classes as examples
• Ignore superclass implementations
• Assume same method name = same behavior

Common Workflows

Workflow: Implement Abstract Method

Problem: Need to implement printOn: in new class

1. search_implementors("printOn:")
2. Filter to similar classes
3. get_method_source for 3-5 examples
4. Identify pattern
5. Apply to your class

Workflow: Assess Refactoring

Problem: Want to change at:put: signature

1. search_implementors("at:put:") → Count implementations
2. search_references("at:put:") → Count call sites
3. Assess impact (High/Medium/Low)
4. Decide: Change / Add new / Don't change

Workflow: Find Duplication

Problem: Suspect duplicate isEmpty implementations

1. search_implementors("isEmpty")
2. Focus on Collection hierarchy
3. get_method_source for subclasses
4. Compare for identical code
5. Refactor to superclass if identical

Detailed Resources

For comprehensive analysis techniques and real-world scenarios, see:

• Implementation Analysis Reference - Detailed techniques for analyzing implementations, MCP tools reference, advanced patterns, and performance considerations
• Implementation Scenarios - Real-world examples including implementing abstract methods, assessing refactoring impact, finding duplicate code, learning idioms, and understanding template method patterns

Summary

Key principle: Implementations across a hierarchy reveal design patterns and idioms. Use them to write better, more idiomatic code.

Primary workflow: Find implementors → Get source → Analyze patterns → Apply learnings

Remember: Always scope your analysis to relevant hierarchies and representative classes to avoid information overload.