# Zexus Blockchain Bug Fixes - Summary

**Date**: January 1, 2026  
**Issues Fixed**: 6 critical blockchain-blocking bugs  
**Status**: ✅ ALL RESOLVED

---

## Overview

This document summarizes the fixes applied to resolve 6 critical bugs in the Zexus interpreter that were blocking blockchain functionality. All fixes have been tested and verified.

---

## Issues Fixed

### 1. Entity Property Access Returns Null (Issue 1.1)

**Problem**: `Block{index: 42, data: "test"}` syntax was not recognized by parser.

**Solution**: 
- Added `LBRACE` as infix operator in parser precedences
- Created `parse_constructor_call_expression()` method to handle Entity{...} syntax
- Modified entity constructor in evaluator to accept Map as single argument
- Enhanced strategy_context.py to properly parse Entity{...} expressions

**Files Modified**:
- `src/zexus/parser/parser.py`
- `src/zexus/parser/strategy_context.py` 
- `src/zexus/evaluator/functions.py`

**Test**: `test_entity_debug.zx` ✅

---

### 2. Contract State Assignment Failure (Issues 1.2, 2.2)

**Problem**: Contract state variables like `state balances = {}` were storing AST nodes instead of evaluated values.

**Solution**:
- Modified parser to evaluate map/list literals in state variable declarations
- Updated `deploy()` in security.py to accept evaluated storage values
- Fixed `instantiate()` to properly copy storage from parent contract
- Changed contract evaluation to pass evaluated storage dict to deploy()

**Files Modified**:
- `src/zexus/parser/strategy_context.py`
- `src/zexus/security.py`
- `src/zexus/evaluator/statements.py`

**Test**: `test_contract_debug.zx` ✅

---

### 3. len() Not Supported for Maps (Issue 2.1)

**Problem**: Builtin `len()` function only worked on String and List types.

**Solution**:
- Added Map type check in `_len()` builtin function
- Returns `Integer(len(map.pairs))` for Map objects

**Files Modified**:
- `src/zexus/evaluator/functions.py`

**Test**: `test_map_len.zx` ✅

---

### 4. State Variable Type Preservation (Issue 3.1)

**Problem**: Integer state variables like `min_stake = 1000` were being converted to strings.

**Solution**:
- Automatically fixed by Issue 1.2 solution
- Contract state initialization now properly evaluates and preserves types

**Test**: `test_state_variable_type.zx` ✅

---

### 5. Nested Map Assignment in Contracts (Issue 3.2)

**Problem**: Cannot assign complex nested structures like `validators[addr] = {stake: 1000, active: true}`.

**Solution**:
- Automatically fixed by combination of Issue 1.2 and Issue 4.1 solutions
- Contract state initialization handles map literals
- Computed property access evaluates variable keys correctly

**Test**: `test_nested_map_assignment.zx` ✅

---

### 6. Map State Not Persisting Across Function Calls (Issue 4.1)

**Problem**: When writing `balances[from_addr] = value`, the interpreter was using the literal string "from_addr" as a key instead of evaluating the `from_addr` variable.

**Solution**:
- Added `computed` flag to `PropertyAccessExpression` AST node
  - `computed=False` for `obj.prop` syntax (literal property name)
  - `computed=True` for `obj[expr]` syntax (evaluated expression)
- Updated both parsers to set the flag appropriately
  - `parse_index_expression()` sets `computed=True` for bracket notation
  - `parse_method_call_expression()` sets `computed=False` for dot notation
- Modified evaluator to check the flag:
  - When `computed=True`: Evaluate the property expression to get the key
  - When `computed=False`: Use the identifier name directly as literal string key

**Files Modified**:
- `src/zexus/zexus_ast.py`
- `src/zexus/parser/parser.py`
- `src/zexus/parser/strategy_context.py`
- `src/zexus/evaluator/core.py`
- `src/zexus/evaluator/statements.py`

**Test**: `test_map_persistence.zx` ✅

---

## Technical Details

### Property Access Semantics

The key insight for Issue 4.1 was understanding the difference between:

```zexus
# Literal property access (computed=False)
obj.property       // Use string "property" as key

# Computed property access (computed=True)
obj[expression]    // Evaluate expression first, use result as key
```

Both are represented as `PropertyAccessExpression` in the AST, but they need different evaluation strategies.

### Map Literal Evaluation in State

For Issue 1.2, the parser was creating AST nodes for map literals but not evaluating them:

```python
# Before (wrong):
state balances = MapLiteral([...])  # AST node stored

# After (correct):
state balances = Map({...})  # Evaluated object stored
```

---

## Test Suite

All tests passing:

```bash
✓ test_entity_debug.zx          # Entity{...} syntax works
✓ test_contract_debug.zx        # Contract state initialization
✓ test_map_len.zx               # len() on maps
✓ test_map_persistence.zx       # Map modifications persist
✓ test_state_variable_type.zx   # Type preservation
✓ test_nested_map_assignment.zx # Nested structures
```

**Example Output**:
```
=== Test 1: Entity Syntax ===
Outside action - my_block.index: 42
Outside action - my_block.data: test

=== Test 2: Contract State ===
Genesis balance: 1000000

=== Test 3: Map len() ===
Count: 3

=== Test 4: Map Persistence ===
Alice balance: 925000
Bob balance: 50000
Charlie balance: 25000

=== Test 5: State Type ===
✓ Stake is sufficient

=== Test 6: Nested Maps ===
✓ Validator registered
```

---

## Impact

### Before Fixes
- ❌ Token transfers broken
- ❌ Validator registration failed
- ❌ Block storage not working
- ❌ Smart contract state unusable
- ❌ Account balances couldn't persist
- ❌ No stateful blockchain operations

### After Fixes
- ✅ Token transfers working
- ✅ Validator registration successful
- ✅ Block storage functional
- ✅ Smart contract state fully operational
- ✅ Account balances persist correctly
- ✅ All stateful blockchain operations enabled

---

## Files Modified Summary

**Parser**:
- `src/zexus/parser/parser.py`
- `src/zexus/parser/strategy_context.py`

**AST**:
- `src/zexus/zexus_ast.py`

**Evaluator**:
- `src/zexus/evaluator/core.py`
- `src/zexus/evaluator/expressions.py`
- `src/zexus/evaluator/statements.py`
- `src/zexus/evaluator/functions.py`

**Security/Contracts**:
- `src/zexus/security.py`

**Environment** (debug logs removed):
- `src/zexus/environment.py`

---

## Lessons Learned

1. **Parser-Evaluator Separation**: AST nodes must be evaluated before storage, not stored directly
2. **Property Access Semantics**: Need to distinguish literal vs computed property access in the AST
3. **Type Preservation**: Initial value evaluation is critical for maintaining type consistency
4. **Testing Strategy**: Small, focused test files help isolate issues better than large test suites

---

## Future Considerations

While all issues are now fixed, consider:

1. **Property Access Syntax**: Document the `computed` flag for future parser maintainers
2. **Type System**: Consider adding explicit type annotations to catch these issues earlier
3. **Test Coverage**: Add these test cases to the automated test suite
4. **Performance**: The computed flag check adds minimal overhead but could be optimized if needed

---

**Conclusion**: All 6 critical blockchain bugs have been successfully resolved. The Zexus interpreter now fully supports stateful blockchain applications with proper contract state management, entity syntax, map operations, and type preservation.
