Fold LSP - Scheme Code Intelligence

Fold LSP - Scheme Code Intelligence

Overview

The Fold includes an LSP (Language Server Protocol) server that provides rich code intelligence for Scheme files. The MCP server exposes these capabilities as tools that can be used to understand and navigate Scheme code.

Use LSP tools for:

• Getting type information and documentation for symbols
• Finding where functions are defined
• Finding all usages of a function or variable
• Checking files for syntax errors and warnings
• Searching for symbols by name

Available Tools

Usage Patterns

When Editing Scheme Files

1. Before modifying a function, use fold_lsp_hover to understand:

   • The function's type signature
   • What parameters it expects
   • What it returns

2. After editing, use fold_lsp_diagnostics to:

   • Verify no syntax errors were introduced
   • Check for unbalanced parentheses
   • Identify any type issues

When Understanding Code

Use fold_lsp_lookup for comprehensive symbol analysis:

• Combines type info, definition location, and all references
• More efficient than calling each tool separately
• Useful for understanding a symbol's role in the codebase

When Refactoring

1. Use fold_lsp_references to find all usages of a symbol
2. Review each usage to understand the impact
3. Make changes incrementally
4. Use fold_lsp_diagnostics after each change

When Searching

Use fold_lsp_symbols when:

• Looking for a function by partial name
• Exploring available functions in a module
• Finding where a concept is implemented

Position Parameters

LSP tools use 0-indexed positions:

• line: Line number starting from 0
• character: Column position starting from 0

To find the position of a symbol in a file:

1. Read the file content
2. Count lines (0-indexed)
3. Count characters from line start (0-indexed)

Examples

Get Type Information

To understand what vec3-add does:

fold_lsp_hover(file: "lattice/​linalg/​vec.ss", line: 42, character: 8)

Returns type signature and documentation if available.

Find Definition

To navigate to where matrix-multiply is defined:

fold_lsp_definition(file: "lattice/​linalg/​matrix.ss", line: 100, character: 12)

Returns file path and line number of definition.

Check for Errors

After editing a file, verify it's correct:

fold_lsp_diagnostics(file: "lattice/​linalg/​vec.ss")

Returns list of errors/​warnings or "File looks clean!"

Search for Symbols

Find all functions related to "parse":

fold_lsp_symbols(query: "parse")

Returns matching function names with their locations.

Best Practices

1. Use proactively: Check types before modifying unfamiliar code
2. Verify edits: Run diagnostics after any .ss file changes
3. Understand impact: Check references before renaming or removing
4. Combine tools: Use lookup for comprehensive understanding
5. Trust but verify: LSP type inference is best-effort, not guaranteed

Integration with Other Tools

LSP tools complement other The Fold tools:

• With lattice search (lf, li, le): LSP provides position-specific info, lattice provides module-level discovery
• With REPL (fold_eval): LSP shows types, REPL executes code
• With Read tool: LSP shows semantics, Read shows raw content

Troubleshooting

LSP not responding:

1. Check status with fold_lsp_status
2. The LSP starts automatically on first use
3. If issues persist, restart the MCP server

No results:

• Ensure file path is correct (absolute or relative to project root)
• Position must be on a symbol, not whitespace
• Some symbols may not have type information

Wrong results:

• LSP uses heuristic type inference, not formal type checking
• Built-in primitives have predefined types
• User-defined functions get inferred types when possible