feat(ILO-401): VM/JIT codegen for Value::Variant (sum types)#640
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…RECFLD Eliminates the ILO-E803 SumTypeNotSupported bailout that previously caused any program containing a sum-type declaration to fall back to the tree interpreter. The VM compiler now lowers variant construction and pattern-matching using standard record opcodes that Cranelift already handles. Representation: each variant is a 2-field heap record of type `__variant_<typename>` with fields ["tag" (numeric ordinal), "payload"]. - Construction: Expr::Call on a payload variant / Expr::Ref on a no-payload variant both emit emit_variant_record() → OP_LOADK tag + OP_RECNEW. - Pattern matching: Pattern::Variant extracts field 0 (OP_RECFLD), compares to the expected ordinal (OP_EQ + OP_JMPF), and optionally binds field 1. - Cranelift AOT/JIT: no changes needed — it already handles OP_RECNEW, OP_RECFLD, OP_EQ, OP_LOADK. Tests: 4 new vm::tests (zero-payload, payload, VM-vs-interpreter parity, no-E803) and 2 new compile_cranelift::tests (object codegen for both variant shapes). examples/sum-types.ilo verified under --vm and --jit. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
danieljohnmorris
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May 22, 2026
feat(ILO-401): VM/JIT codegen for Value::Variant (sum types)
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Summary
ILO-E803 SumTypeNotSupportedbailout that forced all sum-type programs to fall back to the tree interpreterOP_RECNEW,OP_RECFLD,OP_EQ,OP_LOADK)Codegen strategy
Each variant is stored as a 2-field heap record of type
__variant_<typename>:tag— numeric ordinal (0-based) of the variant within the sum typepayload— constructor argument for payload variants, orNilConstruction (
circle 5→ payload variant,point→ no-payload variant):emit_variant_record(type_id, tag_idx, payload_reg)emitsOP_LOADK(tag constant) +OP_RECNEWExpr::Call(before user-function lookup) andExpr::RefPattern matching (
?s{circle(r):...}):Pattern::VariantemitsOP_RECFLD sub_reg, 0→OP_EQ→OP_JMPF, then optionallyOP_RECFLD sub_reg, 1to bind payloadTest plan
examples/sum-types.iloproduces correct output under--vmand--jitvm::tests::sum_type_vm_zero_payload_variant— no-payload variant constructs and matchesvm::tests::sum_type_vm_payload_variant_match— payload variant carries value through matchvm::tests::sum_type_vm_matches_interpreter— VM result equals tree interpreter resultvm::tests::sum_type_vm_no_e803_bailout— compile no longer returns ILO-E803compile_cranelift::tests::codegen_sum_type_variants_emit_object— Cranelift accepts bytecodecompile_cranelift::tests::codegen_sum_type_zero_payload_variant_emit_object— zero-payload variant codegen🤖 Generated with Claude Code