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RequirementSYS-REQ-063SystemApproved

When ParseString encounters a string literal ending with a lone backslash (the escape sequence is incomplete because there is no character after the backslash), the parser shall return MalformedValueError.

1 open known issue affect this requirement (worst severity: High). Automated checks pass.
PriorityshallTypeguaranteeCategoryfunctionalComponentparserAssuranceEFindingsHighworst open

Specification

The requirement exactly as authored — its complete prose text and, where present, the formal FRETish sentence it compiles to.

Description

When ParseString encounters a string literal ending with a lone backslash (the escape sequence is incomplete because there is no character after the backslash), the parser shall return MalformedValueError.

FRETish formula
the parser shall always satisfy !raw_string_has_backslash_at_end | returns_error_for_backslash_at_end
View full formal model

Rationale & tags

Why this requirement exists, and how it is categorised.

A backslash at the end of a string is the simplest truncated-escape case and exercises the len(in) < 2 guard in unescapeToUTF8.

parsestringescapeedge-case

Verification & provenance

How this requirement was checked: the review trail, edit history, and the machine-analysis status terms (each ⓘ explains what it means).

Assurance levelE
Formalizationvalid
Realizabilityrealizable
Vacuitychecked_ok
Strategyfretish

Review

Status
approved
Reviewer
Buger · lead_engineer
Reviewed
Aug 20, 2026, 13:11 UTC
Spec-conformance reviewed (agent:claude:spec-conformance); approved on owner authorization.

History

Created
Apr 14, 2026, 18:00 UTC · Claude · AI agent
Modified
Aug 20, 2026, 13:11 UTC · Buger

Change history

Every recorded revision of this requirement's source file — newest first, each with its commit message and the diff for that change.

Review history

Human and AI-agent approvals of this requirement — the 'why was this approved' lineage, each with the reviewer's justification and the code it cites.

  1. Claude:spec Conformance · AI agentApprovedSpec conformanceAug 20, 2026 · last monthREVIEW-43

    The requirement demands that a string ending in a lone backslash return MalformedValueError, and the control flow is correctly shaped: ParseString (parser.go:2148) maps any Unescape error to MalformedValueError, and unescapeToUTF8Config is supposed to reject an escape with fewer than two bytes before reading the escape byte at in[1]. KI-6 broke this at escape.go:194 by weakening the guard from len(in) < 2 to len(in) < 1, so a single-byte \ input passes and the switch at escape.go:200 reads in[1] one byte past the slice end, producing an index-out-of-range panic instead of a clean malformed error. I inspected the mutated guard and the immediately-following switch e := in[1] that indexes past the buffer, confirming the OOB read is real and reachable through the public API. The defect is tracked as open KI-6, so the requirement remains approvable while its verification honestly fails.

    Cited code (4)

Open known issues

Findings currently open against this requirement — issues its verification surfaced that are not resolved yet. Each links to the full finding.

Obligations

What this requirement must witness to be considered satisfied — the required evidence, and the tests that discharge each one.

The tests that discharge each obligation aren't available for a historical run

The evidence matrix behind each obligation comes from the live audit index, which can't be rebuilt for a past commit. Nothing here means unknown — not that the requirement has no obligations.

Formula evidence

The formal formula behind this requirement, the variables it is written over, and the tests that exercise it (each term is explained inline).

FRETish formula

the parser shall always satisfy !raw_string_has_backslash_at_end | returns_error_for_backslash_at_end

Variables

NameTypeDirectionDescription
raw_string_has_backslash_at_endTrue when ParseString encounters a string ending with a lone backslash with no character after it.
returns_error_for_backslash_at_endTrue when ParseString returns MalformedValueError for a string ending with a lone backslash.

Witnesses· 3 scenarios total

  • TestMCDC_SYS_REQ_063_Row1_TriggerFalse
    exercises 1 condition scenario
  • TestMCDC_SYS_REQ_063_Row2_InvariantViolation
    exercises 1 condition scenario
  • TestMCDC_SYS_REQ_063_Row3_TrailingBackslashError
    exercises 1 condition scenario

MC/DC truth table· 3 rows

Each row assigns the formula's conditions (T/F) and shows the Result— the formula's value for that input row, not a test pass/fail. A row proves a condition when flipping only that condition flips the outcome. The test that covers each row is linked.

Covereda test exercises this rowExempteda reviewed mcdc:ignoreNo-actionfalse-result row satisfied by designUncoveredneeds a covering test
#raw_string_has_backslash_at_endreturns_error_for_backslash_at_endResultProvesCovering test
1FFTraw_string_has_backslash_at_end
2TFFraw_string_has_backslash_at_end
3TTTreturns_error_for_backslash_at_end

Its place

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Trace evidence

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Impact

Blast radius — authored trace links only (automatically derived links come from the audit index and aren't shown here).

If you change this

Requirements
0
Files
1
Tests
2
At-risk contracts
0

Files to re-check (1)

  • parser.goparser.go

Tests to re-run (2)

  • deep_spec_test.godeep_spec_test.go
  • mcdc_spec_witnesses_test.gomcdc_spec_witnesses_test.go

What this rests on

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