fix: allow prototype method names as object keys#1586
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ssalbdivad merged 1 commit intoJul 7, 2026
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Object.prototype method names like 'constructor', 'hasOwnProperty',
and 'toString' are valid object keys and should not be incorrectly
flagged as duplicate keys.
The issue was that the 'seen' object used for duplicate detection was
initialized with '{}' which has prototype methods. When checking
'key in seen' for these keys, it returned true even though they
weren't explicitly set.
Fix: Use Object.create(null) to create a prototype-free object for
the 'seen' tracking.
Fixes arktypeio#1572
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ssalbdivad
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Jul 7, 2026
Bumps all publishable packages and documents the fixes merged since 2.2.2: - fix type.fn.raw throwing at runtime (#1631, @aarsh767) - anchor versioned UUID validation (#1602, @WolfieLeader) - fix inferred output of declared morphs (#1579, @eralmansouri) - allow Object.prototype method names as keys (#1586, @kaigritun) Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Qk4c4vPUecBDYbd4p3yE1H
ssalbdivad
added a commit
that referenced
this pull request
Jul 7, 2026
Bumps all publishable packages and documents the fixes merged since 2.2.2: - fix type.fn.raw throwing at runtime (#1631, @aarsh767) - anchor versioned UUID validation (#1602, @WolfieLeader) - fix inferred output of declared morphs (#1579, @eralmansouri) - allow Object.prototype method names as keys (#1586, @kaigritun)
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Summary
Fixes #1572
Object.prototype method names like
constructor,hasOwnProperty, andtoStringare valid object keys and should not be incorrectly flagged as duplicate keys.Problem
When defining an object type with a key that matches an
Object.prototypemethod name:This throws a
ParseError: Duplicate key "constructor"even though the key is valid.Root Cause
The
seenobject used for duplicate key detection was initialized with{}, which inherits fromObject.prototype. When checkingkey in seen, it returnedtruefor keys like"constructor"because they exist on the prototype chain.Solution
Use
Object.create(null)to create a prototype-free object for theseentracking. This ensures only explicitly set keys are detected as duplicates.Testing
Added a test case to verify that prototype method names can be used as object keys without error.