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TYPE_E_DUPLICATEID
Type inheritance hierarchy contains a duplicate member ID
TYPE_E_DUPLICATEID is HRESULT 2147649734 (0x800288C6) from winerror.h. AllStat describes it as “Duplicate ID in inheritance hierarchy.” The value must be interpreted at type-library construction or validation of inherited interfaces and Automation DISPIDs, because the same high-level symptom can come from a different contract boundary and require different cleanup.
Boundary to preserve: The documented condition is “Duplicate ID in inheritance hierarchy.” A comparison run should change that state, not an unrelated component setting.
The decisive Interpretation is that the inheritance graph exposes the same identifier more than once where uniqueness is required. When this result crosses a language or process boundary, preserve its original numeric form before projections replace it with a broad exception class.
Where the result appears
- This result belongs to type-library and metadata processing around type-library construction or validation of inherited interfaces and Automation DISPIDs.
- identify the LIBID, major/minor version, LCID, SYSKIND, file path, resource ID, and the specific ITypeLib or ITypeInfo operation.
- Metadata consumers should treat this result as a contract-version or construction problem until file integrity, registry view, import dependencies, TYPEKIND, and builder phase are verified.
Triage of this result starts by locating the exact owner of the failing state, including object identity, apartment, package, and deployment generation.
Typical causes and interpretation boundary
Common cause categories for this HRESULT are: two bases reuse an ID; a derived member collides with an inherited member; generated IDs are unstable across builds. Do not treat the cause list for this HRESULT as a checklist of simultaneous failures; use traces and postconditions to select the matching branch.
The check that separates it from nearby HRESULTs is: the inheritance graph exposes the same identifier more than once where uniqueness is required. A recovery decision for this HRESULT should wait until the decisive condition is observed in call data, component state, or metadata.
Evidence and telemetry
- Record it with the type-library path and hash, LIBID and version, LCID, architecture, source package, and producer toolchain.
- capture duplicate MEMBERID or DISPID; base-interface chain; overriding member; imported library versions; generator allocation scheme.
- Retain the exact type, member, field, name, MEMBERID, HREFTYPE, TYPEKIND, or registry path involved in it.
- When it is produced during generation, record construction order, imported libraries, layout/finalization state, and output TLB hash.
- After it, release TYPEATTR, FUNCDESC, VARDESC, BSTR, and interface resources using the matching API even when parsing or lookup fails.
When recording it, retain structural metadata and redact content-bearing arguments, authentication material, and personal data.
Diagnostic sequence
- Capture it (0x800288C6) before a compiler, importer, or language runtime reduces it to a generic metadata error.
- Verify the exact type-library identity, file/resource loaded, registry view, architecture, and operation that returned it.
- Prove the decisive metadata condition for this HRESULT: the inheritance graph exposes the same identifier more than once where uniqueness is required.
- Test the likely causes independently for this HRESULT: two bases reuse an ID; a derived member collides with an inherited member; generated IDs are unstable across builds.
- For <code>it</code>, enumerate the relevant TYPEATTR, members, imports, names, IDs, locales, and builder state instead of assuming source declarations match deployed metadata.
- Rebuild or reload one corrected metadata generation and verify that it disappears without introducing a different identity or compatibility break.
Correct handling and recovery
The appropriate recovery is to assign stable nonconflicting IDs, preserve published DISPIDs, validate the full inheritance graph, and regenerate dependent proxies and wrappers. A retry policy for this HRESULT needs a bounded attempt count, a state refresh step, and a rule for reconciling work that may already have completed.
Cleanup following it must be generation-aware: do not destroy shared state or outputs owned by an earlier successful operation.
Practical scenario
Two generated base interfaces both assign DISPID 7; the ID allocator reserves inherited ranges before adding derived members.
Coverage for this HRESULT should include the exact failure, a corrected success case, and the closest related HRESULT so classification remains stable.
Difference from related HRESULTs
TYPE_E_INVALIDID concerns an incorrectly formed inheritance-depth ID; it specifically detects reuse within the hierarchy.
Tests and telemetry should encode the boundary around it so future wrappers do not flatten it into an ambiguous generic exception.
Developer and administrator guidance
Tools handling it should pin type-library identity and version, avoid caching raw indices across versions, and preserve stable GUIDs and DISPIDs for published contracts. Repair for <code>it</code> should be performed by the metadata producer or installer, not by ad hoc registry edits in the consuming process.
Administrators should compare installed files and registration against the product manifest, repair the matching package, and keep 32-bit and 64-bit registry views explicit. For <code>it</code>, copying a TLB from another machine can silence lookup while creating a more dangerous ABI mismatch.
References
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