Field-wise Clone is not entailed for a borrowed open row

LIMIT-TYPE-INFERENCE-008

A where all R: Clone grant on a borrowed open-row parameter is rejected before its body can be checked.

Lifecycle

resolved

Owner

metel-frontend

Scope

architecture/spec/type-inference.md#type-inference

Origin

v0.14.0 sensitive release-matrix probe; metel-core#1412

Affects · linked records

spec.types.generics.field-wise-row-constraints.legality-1language spec rule

spec.types.generics.open-rows.legality-4language spec rule

limitationKnown limitations ↗

Limitation

A function accepting &{ ..R } with where all R: Clone was rejected with T0012 before the body was checked. The parameter lowering now preserves the reference while collecting its open-row bound, and borrowed rows no longer get the by-value Copy width check. The regression evaluator/records/release_matrix_borrowed_all_clone.mtl passes without a skip. The fix merged in metel-core PR #1422.

Impact

Previously, generic code could not express this borrowed-row cloning operation with the field-wise bound that worked for owned open rows.

Affects

• spec.types.generics.field-wise-row-constraints.legality-1
• spec.types.generics.open-rows.legality-4

Resolution

Implemented in metel-core commit 5f038b189cb67c5ec40e51d16a3e11a831a4535e (PR #1422), with empty/nonempty borrowed-row cloning and retained source ownership covered by the executable fixture above; tracked by metel-core#1412. Diagnostics for unused row constraints now state the required row context without referring to the closed implementation tracker metel-core#1302.