[Bug] Trailing backslash degrades the whole bash parse to a single ERROR node

What version of Kimi Code is running?

Reproduced on main at commit d1a46db94 (package @moonshot-ai/tree-sitter-bash).

Which open platform/subscription were you using?

N/A — this is a code-level correctness bug in the @moonshot-ai/tree-sitter-bash parser, found by source review and reproduced with a unit test. It is not tied to a plan or model.

Which model were you using?

N/A

What platform is your computer?

macOS (Darwin arm64). The bug is platform-independent — the parser is pure TypeScript.

What issue are you seeing?

parse() degrades a perfectly valid command whose scan range ends in a lone backslash into a single whole-source ERROR node (hasError: true), losing all structure.

On current main:

• parse('echo \') returns a root that is a single ERROR [0,6) instead of command(command_name(word "echo"), word "\"). Internally SyntaxNodeBuilder throws RangeError: invalid node range [0, 7) for source of length 6, and parse()'s last-resort catch in src/parse.ts converts that into the whole-source ERROR node.
• The same happens for \, [[ -f x && \, and case x in a\.

What steps can reproduce the bug?

In packages/tree-sitter-bash:

import { parse } from '#/parse';

const r = parse('echo \\'); // the string: echo, space, one backslash
// expected: ok:true, hasError:false — a command with a trailing word "\"
// actual:   ok:true, hasError:true — root is a single whole-source ERROR node

This is not fuzzer-only: test/fixtures/corpus/statements.txt already contains a real line ending in a continuation backslash, so any consumer that parses a single line before the following newline arrives hits it.

What is the expected behavior?

A lone trailing backslash is kept as word text — which is exactly what scanWord's own comment in src/lexer.ts says should happen. echo \ should parse to a normal command with a trailing word "\" and hasError: false; the test-command and case inputs should error-recover locally rather than collapsing the whole tree.

Additional information

Root cause: four character scanners skip an escaped character with idx += 2. When the backslash is the last character of the scan range, that overshoots to end + 1, so the emitted node endIndex exceeds the source length (or the parent's end) and SyntaxNodeBuilder rejects it. The four sites are scanWord (src/lexer.ts) and scanCasePatternEnd / scanTestToken / scanTestCloser (src/parser.ts).

Proposed fix: clamp the skip to the scan bound, idx = Math.min(idx + 2, end). The clamp is a no-op unless the backslash is the final character, so no other parse changes. I verified locally that the full tree-sitter-bash suite — including the differential comparison against the reference tree-sitter-bash corpus — stays green, and added regression cases that fail before the change and pass after it.

I'm happy to open the PR once this is approved.

Contribution

• I am willing to submit a PR for this bug fix myself (please wait for maintainer approval in this issue first)

Start in packages/tree-sitter-bash/src/lexer.ts and src/parser.ts, focusing on the four character scanners named in the issue, then inspect the regression cases in test/fixtures/corpus/statements.txt. Run the tree-sitter-bash test suite and confirm trailing backslashes preserve the command structure while malformed test-command and case inputs recover locally instead of becoming one whole-source ERROR node.