astral-sh/ruff · error

Cannot find `:` in `else` statement

Error message

Cannot find `:` in `else` statement

What it means

Internal guard in Ruff's fixer for flake8-return rules (RET505 `superfluous-else-return` and siblings). When inlining an `else:` clause, `remove_else` tokenizes source starting at the `else` keyword to locate the colon that terminates the `else` header. If the tokenizer reaches the end of the token stream without a `Colon`, fix construction is aborted; the diagnostic is still reported, just without an autofix.

Source

Thrown at crates/ruff_linter/src/rules/flake8_return/rules/function.rs:836

    if elif_else.test.is_some() {
        // Ex) `elif` -> `if`
        Ok(Fix::safe_edit(Edit::deletion(
            elif_else.start(),
            elif_else.start() + TextSize::from(2),
        )))
    } else {
        // the start of the line where the `else`` is
        let else_line_start = locator.line_start(elif_else.start());

        // making a tokenizer to find the Colon for the `else`, not always on the same line!
        let mut else_line_tokenizer =
            SimpleTokenizer::starts_at(elif_else.start(), locator.contents());

        // find the Colon for the `else`
        let Some(else_colon) =
            else_line_tokenizer.find(|token| token.kind == SimpleTokenKind::Colon)
        else {
            return Err(anyhow::anyhow!("Cannot find `:` in `else` statement"));
        };

        // get the indentation of the `else`, since that is the indent level we want to end with
        let Some(desired_indentation) = indentation(locator.contents(), elif_else) else {
            return Err(anyhow::anyhow!("Compound statement cannot be inlined"));
        };

        // If the statement is on the same line as the `else`, just remove the `else: `.
        // Ex) `else: return True` -> `return True`
        if let Some(first) = elif_else.body.first() {
            if indexer.preceded_by_multi_statement_line(first, locator.contents()) {
                return Ok(Fix::safe_edit(Edit::deletion(
                    elif_else.start(),
                    first.start(),
                )));
            }
        }

View on GitHub (pinned to 26f38c119c)

Solutions

1. Reformat the `if/else` normally (colon directly after `else`) and re-run `ruff --fix`.
2. Minimize with `ruff check --isolated --fix path/to/file.py`; if it persists on valid input, file a bug at https://github.com/astral-sh/ruff — this is an internal invariant failure, not user error.
3. Work around by disabling the triggering RET rule (e.g. `lint.ignore = ["RET505"]`) or fixing the code manually.
4. Update Ruff to the latest version; tokenizer edge cases are fixed regularly.

Example fix

// before (edge-case layout that stalls the fixer)
if cond:
    return a
else \
    : return b
// after (normal layout the fixer handles)
if cond:
    return a
else:
    return b

import re

def else_clause_is_fixable(source: str) -> bool:
    # a normal `else:` header on its own line is safe to autofix
    return bool(re.search(r'^[ \t]*else[ \t]*:[ \t]*', source, re.MULTILINE))

def has_plain_else_colon(source: str) -> bool:
    return any(line.lstrip().startswith('else:') for line in source.splitlines())

try:
    subprocess.run(['ruff', 'check', '--fix', '--select', 'RET505', path], check=True)
except subprocess.CalledProcessError:
    print(f'autofix failed for {path}; reformat else: headers manually and retry')

When it happens

Trigger: `remove_else` (via `superfluous_else_node`) invoked on an `else` clause whose header colon cannot be found by `SimpleTokenizer::starts_at(elif_else.start(), ...)` — e.g. unusual source layout where `else` is not followed by a colon token in the linear stream.

Common situations: Applying `ruff --fix` to RET505-RET508 hits with exotic but parseable formatting or generated code; a Ruff parser/tokenizer or `ElifElseClause` range edge case; `else` keywords in unexpected positions such as line continuations.

Related errors

• Fix introduced a syntax error
• Unable to rename any references to `{name}`
• Compound statement cannot be inlined
• Positional argument {index} is missing
• Expected dictionary argument to be kwarg

AI-assisted analysis of astral-sh/ruff@26f38c119c (2026-09-05). Data as JSON: /api/errors/9f31d14dd1e3f328. Report an issue: GitHub.