try_from_expr_derive

The procedural macro implementation for try_from_expr. This crate provides the TryFromExpr derive macro.

Usage

This crate is typically not used directly. Instead, use the main try_from_expr crate which re-exports this macro:

[dependencies]
try_from_expr = "0.1.0"

Implementation Details

This crate implements the TryFromExpr derive macro that generates TryFrom<&syn::Expr> implementations for enums. It handles:

• Variant Detection: Analyzes enum variants (unit, tuple, struct)
• Mode Detection: Automatically determines if an enum is a "wrapper" or "leaf" enum
• Parser Generation: Creates type-specific parsers for each field
• Error Handling: Generates helpful error messages for parsing failures

Wrapper vs Leaf Enums

The macro distinguishes between two types of enums:

Leaf Enums: Enums with concrete values

• Parse exact variant names
• Validate enum membership
• Extract and parse parameters

Wrapper Enums: Enums that contain other enum types

• Try type-directed dispatch first
• Fall back to trying each child type
• Aggregate error messages

Generated Code

For each enum, the macro generates:

1. TryFrom<&syn::Expr> implementation
2. Helper methods for expression unwrapping
3. Type-specific parsing functions
4. Error aggregation logic

License

MIT