bhc-span

Source location tracking and span management for the Basel Haskell Compiler.

Overview

This crate provides types for tracking source locations throughout the compilation pipeline, enabling accurate error reporting and source mapping.

Key Types

Usage

use bhc_span::{Span, BytePos, SourceFile, FileId};

// Create a span from byte positions
let span = Span::new(BytePos::new(10), BytePos::new(20));
assert_eq!(span.len(), 10);

// Create a source file and look up line/column
let file = SourceFile::new(
    FileId::new(0),
    "example.hs".to_string(),
    "main = putStrLn \"Hello\"".to_string()
);

let loc = file.lookup_line_col(BytePos::new(7));
assert_eq!(loc.line, 1);
assert_eq!(loc.col, 8);

// Merge spans
let span1 = Span::from_raw(10, 20);
let span2 = Span::from_raw(15, 30);
let merged = span1.merge(span2);
assert_eq!(merged, Span::from_raw(10, 30));

Features

• Zero-cost span representation (just two u32 values)
• Efficient line/column lookup with precomputed line starts
• Span merging and manipulation operations
• Serialization support via serde

Design Notes

• Spans use byte offsets rather than character offsets for efficiency
• The DUMMY span ([0, 0)) is used for generated code or when location is irrelevant
• Line and column numbers are 1-indexed to match editor conventions

Related Crates

• bhc-diagnostics - Uses spans for error reporting
• bhc-lexer - Attaches spans to tokens
• bhc-parser - Attaches spans to AST nodes