Enum RunError 

pub enum RunError {
    Parse(String),
    Types(Vec<String>),
    Lower(String),
    Eval(String),
    Import(String),
}

Why a run stopped short.

Variants

Parse(String)

Types(Vec<String>)

The type checker rejected the program. Carries every diagnostic, not just the first: a caller fixing one error wants to see the rest.

Each one is already rendered file:line:col: message against the file the offending form came from — which, in a program with imports, is frequently not the file the user named. The rendering happens here rather than at the consumer because here is where the file table exists; see uses::ResolvedProgram::locate.

Lower(String)

No longer reachable, and that is the point. This reported “blue emitted a tree the reader could not read back” — a failure only a print-then-reparse hop could have. crate::lower_to_spanned deleted the hop, so there is nothing left to fail: the tree the evaluator gets IS the tree erasure produced, not a re-reading of its text.

Kept rather than removed because it is public API on a released crate and a consumer may still match on it, per ★★ MODULARIZE, DON’T DELETE. It is retired, not orphaned — if a future stage ever serialises again it has a typed home. Nothing constructs it today; do not read its presence as evidence the pipeline can still fail this way.

Eval(String)

The program ran and raised.

Rendered file:line:col: message against the file the failing form’s top-level form came from — the same uses::ResolvedProgram::locate machinery, the same file table and the same join key the type errors above use. Until erasure learned to carry spans this was a bare message, because the evaluator was handed a tree whose every node had been stamped Span::synthetic() on the way in.

The honest limit, stated so nobody reads more into a position than is there. The index names the top-level form that was EXECUTING; the span names where the failing text SITS. Those agree on the file whenever the failing code is in the same file as the top-level form that reached it — which is every single-file program, and an imported package whose own top-level code raises. They can disagree when a top-level form in file A calls a function defined in file B and the raise happens inside B: the path reported is A’s. locate refuses to print a line:col it cannot justify (the span must be a real range in that file), so the usual shape of that case is a file with no position rather than a precise-looking wrong one — but a same-length pair of files can still put a plausible number on the wrong file. Closing it needs per-frame file identity at the evaluator, which is a call stack blue does not have.

Import(String)

A use("name") could not be resolved.

Its own variant rather than folded into Parse, because the reader’s next action is different: a parse error is in the source in front of them, an import error is in their packaging — a missing bidama, a BLUE_PATH that does not contain it, or no loader at all.

Trait Implementations

impl Debug for RunError

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

Formats the value using the given formatter.

impl Display for RunError

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

Formats the value using the given formatter.

impl Error for RunError

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0:

use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.