# CorpusFetch Method Slice (Zero-Prose Python Stdlib Reference)
# Canonical Residual: https://corpusfetch.com/c/what-in-stream-verification-checkpoints-prevent-autoregressive-error-cascade-during-long-form-symbolic-and-code-generation.md
# Remnant Warrant:    https://corpusfetch.com/c/what-in-stream-verification-checkpoints-prevent-autoregressive-error-cascade-during-long-form-symbolic-and-code-generation.warrant.json
# Markdown SHA-256:   423140c796cb4286707cab26c4dbcccb93c9dcc8e8d67d4423db768001590381
# Code AST SHA-256:   9e10043852308f14b4bb060b4b3a9d90738a792b75b8cfb0d44141e10463c8c1
# Verified Classes:   InstreamCheckpointError, InstreamVerificationGate
# Defensive Guards:   1 fail-closed invariants (zero external deps)

from dataclasses import dataclass
from typing import Callable, Any


class InstreamCheckpointError(RuntimeError):
    """Raised when an in-stream syntactic or semantic checkpoint fails during generation."""
    pass


class InstreamVerificationGate:
    @classmethod
    def verify_chunk(cls, chunk_content: str, checker_fn: Callable[[str], bool]) -> str:
        if not checker_fn(chunk_content):
            raise InstreamCheckpointError("Instream verification checkpoint failed.")
        return chunk_content