# Advanced Parser Fix - Complete Summary

## Problem
The advanced strategy-based parser (ContextStackParser + StructuralAnalyzer) was not working correctly for:
1. Top-level assignments (`x = 5`)
2. Function declarations (`function add(a, b) { ... }`)
3. Function expressions/literals (`function(x) { return x * 2; }`)

## Root Causes
1. **Structural Analyzer Issues**:
   - Was creating separate blocks for semicolons, treating them as statements
   - Not properly handling closing braces in function/action blocks
   - LET/CONST statements not allowing FUNCTION keyword on RHS (for function expressions)

2. **Strategy Context Parser Issues**:
   - Generic block handler returned empty BlockStatement for unknown types
   - No detection logic for assignments, LET, CONST, return statements
   - No function literal parser implementation
   - Expression parser didn't recognize FUNCTION keyword

## Solutions Implemented

### 1. Structural Analyzer Fixes (strategy_structural.py)
- **Semicolon Handling**: Skip trailing semicolons instead of treating them as separate statements
- **Nesting Level Tracking**: Improved logic for statement starters to properly close braces
- **Found Brace Block Detection**: Stop collecting tokens after closing a brace block
- **LET/CONST Exception**: Allow FUNCTION keyword as RHS of assignment for function expressions

### 2. Strategy Context Parser Enhancements (strategy_context.py)
- **Intelligent Generic Block Parser**: 
  - Detects LET, CONST, assignments, print, return statements
  - Delegates to appropriate parser methods
  - Falls back to expression parsing for unknown types

- **Function Literal Parser** (`_parse_function_literal`):
  - Parses anonymous functions: `function(x) { return x * 2; }`
  - Returns ActionLiteral for proper function semantics
  - Properly handles parameters and body blocks

- **Expression Parser Enhancement**:
  - Added FUNCTION token detection in special cases
  - Calls _parse_function_literal when FUNCTION encountered

- **Return Statement Parser** (`_parse_return_statement`):
  - New method to parse return statements
  - Handles return value expressions

### 3. zx-run Script
- Enabled advanced strategies: `enable_advanced_strategies=True`
- Proper error handling for evaluation

## Test Results
All tests pass successfully:

✅ **Test 1: Simple Assignment**
```
x = 5;
print(x);
```
Output: `5`

✅ **Test 2: Function Declaration**
```
function add(a, b) {
    return a + b;
}
result = add(3, 4);
print(result);
```
Output: `7`

✅ **Test 3: Function Expression**
```
let f = function(x) { return x * 2; };
print(f(5));
```
Output: `10`

## Files Modified
1. `src/zexus/parser/strategy_structural.py` - Fixed block collection logic
2. `src/zexus/parser/strategy_context.py` - Added parsers for functions and assignments
3. `zx-run` - Enabled advanced parsing

## Key Improvements
- Advanced parser now handles complex Zexus syntax correctly
- Proper nesting level tracking prevents incorrect block boundaries
- Function expressions work as expected (ActionLiteral)
- Assignment statements properly recognized and executed
- Return statements properly evaluated within function scopes
