Destructor invocation is not implemented; only empty drop bodies are accepted

LIMIT-EVALUATION-005

Drop bodies never run, so only an empty drop body is accepted.

Lifecycle

planned

Owner

metel-interpreter

Scope

architecture/spec/evaluation.md#evaluation

Origin

metel-core#1211 limitation analysis; skipped fixture evaluator/closures/v0_13_0_captured_drop_order.toml

Affects · linked records

arch.evaluation.requirement-1architecture requirement

arch.type-construction.requirement-5architecture requirement

reject_inert_destructor metel-frontend/src/pipeline/type_checking/construction/declarations.rscode

limitationKnown limitations ↗

Limitation

The evaluator never runs a Drop implementation. Because a drop body would then silently never execute, the typechecker rejects any drop body that is not empty. Reproduced against current develop:

struct G { n: i64 }
extend G: Drop { fun drop(&var self) { println("dropped"); } }
fun main() { let g := G { n = 1 }; }

[T0001] type error: a `drop` body cannot run yet: destructor invocation is not implemented (metel-core#261), so this cleanup would silently never happen. Leave the body …

The Language Spec specifies drop order and explicit drop (spec.ownership.drop-order.*, spec.ownership.explicit-drop.*), so this is an implementation shortfall against the spec, not a spec gap.

Impact

Visible to Metel programmers: no user-defined cleanup logic can run, so resource-owning types cannot release resources through Drop. The one skipped fixture in the tree, v0_13_0_captured_drop_order, is skipped for this reason and should be enabled when the limitation is lifted.

Affects

• arch.evaluation.requirement-1
• arch.type-construction.requirement-5

• metel-frontend/src/pipeline/type_checking/construction/declarations.rs::reject_inert_destructor

Resolution

Planned: tracked as metel-core#261 (RFC-0071 3/4: drop order and explicit drop, milestone v0.15.0).