Builder & Error Remapping

The builder module (builder.mist in the mist_api crate) wraps cargo to:

1. Spawn cargo with --message-format=json
2. Parse JSON compiler messages
3. For each diagnostic span, look up the corresponding .map.json file
4. Remap Rust line/column to Mist line/column using the mapping
5. Display errors/warnings with Mist source locations and context lines

pub fn build(args: Vec<String>, root: PathBuf) -> bool {
    // Spawn cargo with JSON output
    // Parse CompilerMessage for each span
    // Look up rev_mapper::Mapping from .map.json
    // Remap to Mist positions
    // Print diagnostics
}

Diagnostic Output

Errors and warnings are displayed with Mist source context:

src/main.mist:10:5
 Error: mismatched types
    let x: i32 = "hello";
                ^^^^^^^