Extend proven fragment to cover the full CompilationModel language surface

[Th0rgal]

Goal

Widen the generic Layer 2 whole-contract preservation theorem from the current SupportedSpec fragment to the full CompilationModel language surface, so that every construct expressible through the verity_contract macro is covered by the generic compile-preservation proof — no unsupported-surface exclusions remain.

Background

The generic whole-contract theorem (compile_preserves_semantics in Contract.lean) is currently proved only for the SupportedSpec fragment. Six independent exclusion surfaces gate what enters the theorem:

Surface	Gate function	What it excludes
Core	stmtTouchesUnsupportedCoreSurface	Complex expression forms: mapping, mappingWord, mappingPackedWord, mapping2, mappingChain, structMember, keccak256, call/staticcall/delegatecall, returndataSize, extcodesize, returndataOptionalBoolAt, externalCall, internalCall, arrayLength, arrayElement, storageArrayLength, storageArrayElement, dynamicBytesEq, constructorArg
State	stmtTouchesUnsupportedStateSurface	Storage-rich forms: storage, storageAddr, all mapping* reads, structMember* reads, storageArray* reads, setMapping*, setStructMember*, storageArrayPush/storageArrayPop/setStorageArrayElement
Calls	stmtTouchesUnsupportedCallSurface	internalCall, internalCallAssign, externalCallBind, ecm, calldatacopy, returndataCopy, revertReturndata, mappingChain
Helpers	stmtTouchesUnsupportedHelperSurface	internalCall, internalCallAssign, mappingChain in certain positions
Effects	stmtTouchesUnsupportedEffectSurface	requireError, revertError, returnValues, returnArray, returnBytes, returnStorageWords, emit, rawLog, externalCallBind, ecm
Foreign	stmtTouchesUnsupportedForeignSurface	externalCallBind, ecm, mappingChain
Low-level	stmtTouchesUnsupportedLowLevelSurface	calldatacopy, returndataCopy, revertReturndata, low-level call/staticcall/delegatecall in expressions

Each surface represents a family of CompilationModel constructs that compile and execute correctly (tested by differential and property tests) but lack formal compile-preservation proofs. The task is to prove preservation for each family and thread the proof through the generic theorem.

What's Already in the Proven Fragment

The current proven fragment covers:

Expressions (proven in generic induction core)

• Literals, parameters, local variables
• Arithmetic: add, sub, mul, div, mod, sdiv, smod
• Comparison: eq, lt, gt, le, ge, slt, sgt
• Bitwise: bitAnd, bitOr, bitXor, bitNot, shl, shr, sar, signextend
• Logic: logicalAnd, logicalOr, logicalNot
• Higher-level: min, max, ceilDiv, ite, wMulDown, wDivUp, mulDivDown, mulDivUp
• Environment: caller, contractAddress, chainid, msgValue, blockTimestamp, blockNumber, blobbasefee, calldatasize
• Memory: mload, tload, calldataload

Statements (proven in generic induction core)

• letVar, assignVar
• setStorage (simple slot write)
• setStorageAddr
• require (with string message)
• return (single value)
• mstore, tstore
• stop
• ite (if/else branching — recursive into both branches)
• forEach (bounded loops — recursive into body)

Layer 3 (all 8 Yul statement types fully proved)

Layer 3 (IR → Yul) is already generic for all statement types. The bottleneck is Layer 2 (CompilationModel → IR).

Detailed Widening Plan

Tier 1: Storage and Mapping Operations (highest impact)

Target: Eliminate stmtTouchesUnsupportedStateSurface entirely.

Construct	What to prove	Complexity
Expr.storage / Stmt.setStorage (already partial)	Storage read is sload(slot); write is sstore(slot, val)	Low — extend existing proof
Expr.storageAddr / Stmt.setStorageAddr	Same as storage but with address masking	Low
Expr.mapping / Stmt.setMapping	sload(keccak256(abi.encode(key, base)))	Medium — needs mappingSlot lemma
Expr.mappingWord / Stmt.setMappingWord	mappingSlot + word offset	Medium
Expr.mappingPackedWord / Stmt.setMappingPackedWord	mappingSlot + word offset + bit masking	Medium-High
Expr.mapping2 / Stmt.setMapping2	Double keccak nesting	Medium
Expr.mapping2Word / Stmt.setMapping2Word	Double keccak + word offset	Medium
Expr.mappingUint / Stmt.setMappingUint	Uint256-keyed variant	Medium
Expr.mappingChain / Stmt.setMappingChain	Arbitrary-depth nesting (recursive)	High
Expr.structMember / Stmt.setStructMember	Resolves to mappingPackedWord at compile time	Medium (reduces to packed word case)
Expr.structMember2 / Stmt.setStructMember2	Double mapping variant	Medium
Expr.storageArrayLength / Expr.storageArrayElement	Dynamic array header + element access	Medium
Stmt.storageArrayPush / Stmt.storageArrayPop / Stmt.setStorageArrayElement	Dynamic array mutations	Medium-High

Strategy: The mappingSlot kernel Keccak engine is already proven (solidityMappingSlot_lt_evmModulus is now a theorem). Build the storage-mapping bridge lemma library:

1. Prove compileMapping correctness: compiled Yul sload(mappingSlot(base, key)) = source evalMapping field key
2. Extend to word offsets and packed words via arithmetic lemmas
3. Prove array operations via length-slot and element-slot arithmetic

Tier 2: Internal Helper Calls (already extensively scaffolded)

Target: Eliminate stmtTouchesUnsupportedHelperSurface entirely.

The proof infrastructure is already built — this is the most scaffolded gap:

• SourceSemantics.lean defines execStmtListWithHelpers, evalExprWithHelpers, interpretInternalFunctionFuel
• SupportedSpec.lean defines InternalHelperSummaryContract, helper-rank interfaces, expression-position world-preservation obligations
• GenericInduction.lean defines the helper-aware induction seam (CompiledStmtStepWithHelpersAndHelperIR / StmtListGenericWithHelpersAndHelperIR) and all split bridges
• The helper-free conservative extension is closed (interpretIRWithInternalsZeroConservativeExtensionGoal_closed)
• The whole-contract helper-aware wrappers exist (compile_preserves_semantics_with_helper_proofs_and_helper_ir_supported)

What remains:

1. Prove SupportedFunctionBodyWithHelpersAndHelperIRPreservationGoal for the four genuine internal-helper cases:
   • StmtListDirectInternalHelperCallStepInterface — void helper calls
   • StmtListDirectInternalHelperAssignStepInterface — helper-return bindings
   • StmtListExprInternalHelperStepInterface — expression-position helper calls
   • StmtListStructuralInternalHelperStepInterface — structural recursion through helpers
2. Consume helper-summary soundness + decreasing rank evidence end-to-end
3. Remove the SupportedStmtList.helperSurfaceClosed gate

Tier 3: Effects and Observables

Target: Eliminate stmtTouchesUnsupportedEffectSurface entirely.

Construct	What to prove	Complexity
Stmt.emit	Event emission = LOG opcode sequence	Medium — needs memory/ABI encoding bridge
Stmt.rawLog	Raw log emission = LOG0–LOG4	Medium
Stmt.requireError	ABI-encoded typed revert	Medium-High — needs ABI encoding correctness
Stmt.revertError	ABI-encoded typed revert (unconditional)	Medium
Stmt.returnValues	Multi-value ABI return encoding	Medium-High
Stmt.returnArray	Dynamic array ABI return encoding	High
Stmt.returnBytes	Dynamic bytes ABI return encoding	High
Stmt.returnStorageWords	Storage-read + ABI return	High (combines storage + ABI)

Strategy: Build an ABI encoding correctness library first:

1. Prove scalar ABI encoding (uint256, address, bool, bytes32)
2. Prove dynamic offset/length encoding for bytes/arrays
3. Compose with mstore correctness to show memory layout matches ABI spec
4. Thread through event emission (topics = indexed args, data = non-indexed ABI encoding)

Tier 4: External Calls and Low-Level Mechanics

Target: Eliminate stmtTouchesUnsupportedCallSurface, stmtTouchesUnsupportedForeignSurface, and stmtTouchesUnsupportedLowLevelSurface.

Construct	What to prove	Complexity
Expr.call / staticcall / delegatecall	Low-level EVM call = compiled Yul call instruction	High — needs full call-frame semantics
Expr.returndataSize	returndatasize() extraction	Low once call-frame exists
Expr.returndataOptionalBoolAt	Compound returndata check	Medium
Expr.extcodesize	extcodesize(addr) extraction	Low
Stmt.calldatacopy / returndataCopy	Memory copy operations	Medium
Stmt.revertReturndata	Forward returndata as revert	Medium
Stmt.externalCallBind	ABI-decoded external call	High — needs ABI encode/decode roundtrip
Stmt.ecm	External Call Module dispatch	High — needs per-module correctness
Expr.externalCall	Linked external function call	Medium-High

Strategy: This tier requires modeling cross-contract call semantics. The recommended approach:

1. Model calls as opaque state transitions with pre/post conditions (matching the ECM assumption pattern)
2. Prove that the compiled Yul call sequence satisfies those pre/post conditions
3. The actual external contract behavior remains an assumption (as it must — we can't prove other contracts correct)

Tier 5: Remaining Core Expressions

Target: Eliminate exprTouchesUnsupportedCoreSurface entirely.

Construct	What to prove	Complexity
Expr.constructorArg	Constructor argument loading from bytecode	Medium
Expr.keccak256	keccak256(offset, size) on memory region	Medium — needs memory model
Expr.arrayLength / Expr.arrayElement	Calldata array access with bounds checking	Medium
Expr.dynamicBytesEq	Dynamic bytes equality comparison	Medium

Tier 6: Parameter Profile Widening

Target: Widen SupportedExternalParamType and SupportedExternalReturnProfile.

Currently supported	To add
uint256, int256, uint8, address, bytes32, bool	bytes, string, array, fixedArray, tuple
Zero-return or single-scalar return	Multi-value returns, dynamic returns

Strategy: Each new parameter type needs:

1. ABI decoding correctness from calldata
2. ABI encoding correctness for return values
3. Composition with the dispatch theorem

Execution Order

Tier 2 (helpers) ←── Already scaffolded, highest leverage
  ↓
Tier 1 (storage/mappings) ←── Highest contract coverage impact
  ↓
Tier 3 (effects) ←── Requires ABI library from Tier 1 work
  ↓
Tier 5 (remaining core exprs) ←── Small, can parallelize
  ↓
Tier 4 (external calls) ←── Most complex, benefits from all prior work
  ↓
Tier 6 (param widening) ←── Final step to full EDSL coverage

Tiers 1 and 2 can be parallelized. Tier 5 can be parallelized with Tier 3.

Success Criteria

• stmtTouchesUnsupportedCoreSurface returns false for all CompilationModel constructs (function deleted or always-false)
• stmtTouchesUnsupportedStateSurface eliminated
• stmtTouchesUnsupportedCallSurface eliminated
• stmtTouchesUnsupportedHelperSurface eliminated
• stmtTouchesUnsupportedEffectSurface eliminated
• stmtTouchesUnsupportedForeignSurface eliminated
• stmtTouchesUnsupportedLowLevelSurface eliminated
• SupportedExternalParamType accepts all ParamType constructors
• SupportedExternalReturnProfile accepts all return configurations
• The generic whole-contract theorem covers every verity_contract-generated CompilationModel
• 0 sorry in proof modules
• make check passes, no differential test regressions

Related Issues

• Layer 2 follow-on: replace SupportedSpec feature exclusions with compositional proof interfaces and widen coverage toward the full EDSL image #1630 — Layer 2 widening/completeness tracking
• Proof: model IR internal helper composition for the generic Layer 2 theorem #1638 — Compiled-side helper blocker
• Layer 2: replace the theorem spine with a real generic CompilationModel→IR semantic preservation theorem #1510 — Theorem-shape milestone (complete)
• proof: split Layer 2 body support into feature interfaces #1633 — Helper boundary interface refactor
• [Compiler Enhancement] P2: Solidity interop profile for incremental migration #586 — Solidity interop support matrix

Estimated Effort

3–6 months total across all tiers, with Tiers 1–2 deliverable in 4–8 weeks.