feat: add integration tests and lint script for examples

- Add 30 integration tests that verify all examples and projects
  parse and type-check correctly
- Add scripts/lint-examples.sh for quick pre-commit validation
- Tests will catch regressions like missing `run ... with {}` syntax
  or broken escape sequences

Run with: cargo test example_tests
Or quick check: ./scripts/lint-examples.sh

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

scripts/lint-examples.sh

@@ -0,0 +1,71 @@
+#!/usr/bin/env bash
+# Lint all Lux example and project files
+# Run this before committing to catch parse/type errors early
+
+set -e
+
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+NC='\033[0m' # No Color
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+ROOT_DIR="$(dirname "$SCRIPT_DIR")"
+LUX="${ROOT_DIR}/target/release/lux"
+
+# Build if needed
+if [ ! -f "$LUX" ]; then
+    echo "Building lux..."
+    cd "$ROOT_DIR" && cargo build --release
+fi
+
+FAILED=0
+PASSED=0
+
+check_file() {
+    local file="$1"
+    local output
+    # Run the file and capture output, timeout after 10s
+    if output=$(timeout 10 "$LUX" "$file" 2>&1); then
+        echo -e "${GREEN}OK${NC}: $file"
+        ((PASSED++)) || true
+    else
+        # Check if it's just a runtime error vs parse/type error
+        if echo "$output" | grep -q "Parse error\|Type error\|Type Error\|Type Mismatch"; then
+            echo -e "${RED}FAIL${NC}: $file"
+            echo "$output" | head -20
+            echo ""
+            ((FAILED++)) || true
+        else
+            # Runtime errors are OK for linting (file parses and type checks)
+            echo -e "${GREEN}OK${NC}: $file (runtime error expected)"
+            ((PASSED++)) || true
+        fi
+    fi
+}
+
+echo "=== Linting Lux Examples ==="
+echo ""
+
+for file in "$ROOT_DIR"/examples/*.lux; do
+    check_file "$file"
+done
+
+echo ""
+echo "=== Linting Lux Projects ==="
+echo ""
+
+for file in "$ROOT_DIR"/projects/*/main.lux; do
+    check_file "$file"
+done
+
+echo ""
+echo "=== Summary ==="
+echo "Passed: $PASSED"
+echo "Failed: $FAILED"
+
+if [ $FAILED -gt 0 ]; then
+    exit 1
+fi
+
+echo ""
+echo "All files pass parse and type checking!"

src/main.rs

@@ -2814,4 +2814,177 @@ c")"#;
             assert_eq!(eval(source).unwrap(), "42");
         }
     }
+
+    // Integration tests for example files
+    mod example_tests {
+        use super::*;
+        use std::fs;
+        use std::path::Path;
+
+        fn check_file(path: &str) -> Result<(), String> {
+            let source = fs::read_to_string(path)
+                .map_err(|e| format!("Failed to read {}: {}", path, e))?;
+
+            let program = Parser::parse_source(&source)
+                .map_err(|e| format!("Parse error in {}: {}", path, e))?;
+
+            let mut checker = TypeChecker::new();
+            checker.check_program(&program).map_err(|errors| {
+                format!("Type errors in {}:\n{}", path,
+                    errors.iter().map(|e| e.to_string()).collect::<Vec<_>>().join("\n"))
+            })?;
+
+            Ok(())
+        }
+
+        #[test]
+        fn test_example_hello() {
+            check_file("examples/hello.lux").unwrap();
+        }
+
+        #[test]
+        fn test_example_factorial() {
+            check_file("examples/factorial.lux").unwrap();
+        }
+
+        #[test]
+        fn test_example_functional() {
+            check_file("examples/functional.lux").unwrap();
+        }
+
+        #[test]
+        fn test_example_pipelines() {
+            check_file("examples/pipelines.lux").unwrap();
+        }
+
+        #[test]
+        fn test_example_tailcall() {
+            check_file("examples/tailcall.lux").unwrap();
+        }
+
+        #[test]
+        fn test_example_effects() {
+            check_file("examples/effects.lux").unwrap();
+        }
+
+        #[test]
+        fn test_example_handlers() {
+            check_file("examples/handlers.lux").unwrap();
+        }
+
+        #[test]
+        fn test_example_builtin_effects() {
+            check_file("examples/builtin_effects.lux").unwrap();
+        }
+
+        #[test]
+        fn test_example_datatypes() {
+            check_file("examples/datatypes.lux").unwrap();
+        }
+
+        #[test]
+        fn test_example_generics() {
+            check_file("examples/generics.lux").unwrap();
+        }
+
+        #[test]
+        fn test_example_traits() {
+            check_file("examples/traits.lux").unwrap();
+        }
+
+        #[test]
+        fn test_example_interpolation() {
+            check_file("examples/interpolation.lux").unwrap();
+        }
+
+        #[test]
+        fn test_example_behavioral() {
+            check_file("examples/behavioral.lux").unwrap();
+        }
+
+        #[test]
+        fn test_example_behavioral_types() {
+            check_file("examples/behavioral_types.lux").unwrap();
+        }
+
+        #[test]
+        fn test_example_versioning() {
+            check_file("examples/versioning.lux").unwrap();
+        }
+
+        #[test]
+        fn test_example_schema_evolution() {
+            check_file("examples/schema_evolution.lux").unwrap();
+        }
+
+        #[test]
+        fn test_example_file_io() {
+            check_file("examples/file_io.lux").unwrap();
+        }
+
+        #[test]
+        fn test_example_json() {
+            check_file("examples/json.lux").unwrap();
+        }
+
+        #[test]
+        fn test_example_random() {
+            check_file("examples/random.lux").unwrap();
+        }
+
+        #[test]
+        fn test_example_statemachine() {
+            check_file("examples/statemachine.lux").unwrap();
+        }
+
+        #[test]
+        fn test_example_shell() {
+            check_file("examples/shell.lux").unwrap();
+        }
+
+        #[test]
+        fn test_example_http() {
+            check_file("examples/http.lux").unwrap();
+        }
+
+        #[test]
+        fn test_example_http_server() {
+            check_file("examples/http_server.lux").unwrap();
+        }
+
+        #[test]
+        fn test_example_jit_test() {
+            check_file("examples/jit_test.lux").unwrap();
+        }
+
+        #[test]
+        fn test_project_json_parser() {
+            check_file("projects/json-parser/main.lux").unwrap();
+        }
+
+        #[test]
+        fn test_project_markdown_converter() {
+            check_file("projects/markdown-converter/main.lux").unwrap();
+        }
+
+        #[test]
+        fn test_project_todo_app() {
+            check_file("projects/todo-app/main.lux").unwrap();
+        }
+
+        #[test]
+        fn test_project_mini_interpreter() {
+            check_file("projects/mini-interpreter/main.lux").unwrap();
+        }
+
+        #[test]
+        fn test_project_guessing_game() {
+            check_file("projects/guessing-game/main.lux").unwrap();
+        }
+
+        #[test]
+        fn test_project_rest_api() {
+            check_file("projects/rest-api/main.lux").unwrap();
+        }
+    }
 }