RFC-0173 generic-body checking was incomplete

LIMIT-TYPES-004

Resolved: generic bodies retain declared bounds and row facts, and report rigidity failures at the causal expression.

Lifecycle

resolved

Owner

metel-frontend

Scope

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

Origin

RFC-0173 entering 3-integrated with no implementation yet; metel-core#1320, #1323

Affects · linked records

spec.types.generics.rigid-type-parameters.legality-1language spec rule

spec.types.generics.rigid-type-parameters.legality-2language spec rule

spec.types.generics.rigid-type-parameters.dynamics-1language spec rule

limitationKnown limitations ↗

Limitation

RFC-0173 makes the definition-time check the contract for a generic body: each declared parameter is rigid, and a use is allowed only if the declared bounds entail it. The completed implementation (metel-core#1364) keeps row decompositions as symbolic facts through generic calls and generalized schemes; checks direct and where each bound forwarding; makes conditional-impl visibility depend on declared entailment; and records solver provenance so a rigidity mismatch (T0001) points at the causal expression. A construction disagreement is I0010, never a call-site type error. Operators on bare parameters remain the separate language-level gap GAP-TYPES-005.

Impact

At the time, a generic function could over-constrain its parameters or use an entitlement that only a concrete caller supplied. Row-polymorphic code was affected most because a remainder could collapse into its source row. The completed implementation enforces the RFC-0173 contract at the definition.

Affects

• spec.types.generics.rigid-type-parameters.legality-1
• spec.types.generics.rigid-type-parameters.legality-2
• spec.types.generics.rigid-type-parameters.dynamics-1

Resolution

Resolved by metel-core#1364 and ADR-0058. LIMIT-EVALUATION-001 (the per-call reconstruction) remains a separate implementation boundary; its failure mode is guarded by I0010 and the differential fixture sweep specified in ADR-0058.