Enum NixTraceFrame 

pub enum NixTraceFrame {
    Eager {
        file: Option<String>,
        description: String,
    },
    Lambda {
        closure_env: Env,
        current_file: Option<PathBuf>,
    },
}

A single frame in the Nix-level error trace.

The frame is only ever observed on the cold error path (via attach_trace). To keep the hot lambda-call path allocation-free, the per-call lambda frame stores the raw ingredients (a cheap Rc-clone of the closure env + the raw current-eval-file PathBuf) and defers the format! / path-strip work into attach_trace. The rendered (description, file) pair is byte-identical to the eager form either way (see the description() / file() accessors).

Variants

Eager

Pre-formatted frame (the builtin-call path — kept eager because the builtin name is already a &'static str, so there is no per-call heap-String to defer).

Fields

file: Option<String>

description: String

Lambda

Lazy per-lambda-call frame. The description string and the stripped file string are built on demand in attach_trace.

• closure_env provides the description’s file (from closure.env.eval_file()) — an O(1) Rc refcount bump.
• current_file is the raw current_eval_file() snapshot taken at push time (the stack top after the file guard pushed the closure’s file), used verbatim for the frame’s file field so the rendered loc matches the eager form byte-for-byte.

Fields

closure_env: Env

current_file: Option<PathBuf>

Trait Implementations

impl Clone for NixTraceFrame

fn clone(&self) -> NixTraceFrame

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for NixTraceFrame

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for NixTraceFrame

The frame’s rendered description IS its Display — the typed emission surface for the trace message (write!, never format!()). The Lambda arm defers the path-strip to this cold error-path render.

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.