Function entry_module_source_path 

pub fn entry_module_source_path(
    root: &Path,
    entry_module: &str,
) -> Result<PathBuf, ToolchainError>

Resolves the on-disk source path for entry_module under <root>/src, confining it to that directory.

Gleam’s internal nested-module separator @ maps to a path separator under src/ (demo@nested -> src/demo/nested.gleam); source-style / separators are also accepted. Every component must match [a-z][a-z0-9_]*, the exact module grammar this toolchain supports, before any path is built.

Errors

Returns ToolchainError::InvalidProject when the module name is not a supported Gleam logical name or the resolved path escapes <root>/src.