Refactor regex compilation and use is_some_and

This commit introduces several improvements:

- Pre-compiles regular expressions in `ast/tester.rs` to avoid redundant
  compilation, improving performance.
- Replaces `.extension().map_or(false, |ext| ext == "myc")` with the
  more concise and readable `.extension().is_some_and(|ext| ext ==
  "myc")`.
- Simplifies upvalue capture logic by using `.or_default()` instead of
  `.or_insert_with(HashSet::new)`.
- Adds a `Default` implementation for `TracingObserver`.
- Optimizes string literal parsing in `highlight_myc` to correctly
  handle escape sequences.
- Uses `saturating_sub` for bracket depth to prevent underflow.

src/ast/compiler/upvalues.rs

@@ -35,7 +35,7 @@ impl UpvalueAnalyzer {
                             // Captured from an outer scope!
                             if let Some(lambda_id) = &current_lambda {
                                 capture_map.entry(decl_id.clone())
-                                    .or_insert_with(HashSet::new)
+                                    .or_default()
                                     .insert(lambda_id.clone());
                             }
                         }

src/ast/tester.rs

@@ -21,14 +21,15 @@ pub fn run_functional_tests() -> Vec<TestResult> {
     let mut results = Vec::new();
     let entries = fs::read_dir("examples").unwrap();
     let env = Environment::new();
+    let output_re = Regex::new(r";; Output: (.*)").unwrap();
 
     for entry in entries.filter_map(|e| e.ok()) {
         let path = entry.path();
-        if path.extension().map_or(false, |ext| ext == "myc") {
+        if path.extension().is_some_and(|ext| ext == "myc") {
             let content = fs::read_to_string(&path).unwrap();
             let name = path.file_name().unwrap().to_string_lossy().to_string();
             
-            let expected_output = Regex::new(r";; Output: (.*)").unwrap()
+            let expected_output = output_re
                 .captures(&content)
                 .map(|m| m.get(1).unwrap().as_str().trim().to_string());
 
@@ -55,15 +56,15 @@ pub fn run_benchmarks(update: bool) -> Vec<BenchmarkResult> {
     let entries = fs::read_dir("examples").unwrap();
     let env = Environment::new();
     let is_release = !cfg!(debug_assertions);
+    let baseline_re = Regex::new(r";; Benchmark: ([\d\.]+\w+)").unwrap();
 
     for entry in entries.filter_map(|e| e.ok()) {
         let path = entry.path();
-        if path.extension().map_or(false, |ext| ext == "myc") {
+        if path.extension().is_some_and(|ext| ext == "myc") {
             let content = fs::read_to_string(&path).unwrap();
             let name = path.file_name().unwrap().to_string_lossy().to_string();
             
-            let baseline_pattern = Regex::new(r";; Benchmark: ([\d\.]+\w+)").unwrap();
-            let baseline_match = baseline_pattern.captures(&content);
+            let baseline_match = baseline_re.captures(&content);
             
             // Measure
             let mut runs = Vec::new();
@@ -80,24 +81,21 @@ pub fn run_benchmarks(update: bool) -> Vec<BenchmarkResult> {
                 let updated_content = if let Some(m) = baseline_match {
                     content.replace(m.get(0).unwrap().as_str(), &format!(";; Benchmark: {}", new_val))
                 } else {
-                    format!(";; Benchmark: {}
-{}", new_val, content)
+                    format!(";; Benchmark: {}\n{}", new_val, content)
                 };
                 fs::write(&path, updated_content).unwrap();
                 results.push(BenchmarkResult { name, median, baseline: None, diff_pct: None, status: format!("UPDATED: {}", new_val) });
+            } else if let Some(m) = baseline_match {
+                let baseline_str = m.get(1).unwrap().as_str();
+                let baseline = parse_duration(baseline_str).unwrap();
+                let diff = (median.as_nanos() as f64 / baseline.as_nanos() as f64) - 1.0;
+                
+                let threshold = if is_release { 0.10 } else { 0.25 };
+                let status = if median > baseline && diff > threshold { "FAILED" } else { "OK" };
+                
+                results.push(BenchmarkResult { name, median, baseline: Some(baseline), diff_pct: Some(diff * 100.0), status: status.to_string() });
             } else {
-                if let Some(m) = baseline_match {
-                    let baseline_str = m.get(1).unwrap().as_str();
-                    let baseline = parse_duration(baseline_str).unwrap();
-                    let diff = (median.as_nanos() as f64 / baseline.as_nanos() as f64) - 1.0;
-                    
-                    let threshold = if is_release { 0.10 } else { 0.25 };
-                    let status = if median > baseline && diff > threshold { "FAILED" } else { "OK" };
-                    
-                    results.push(BenchmarkResult { name, median, baseline: Some(baseline), diff_pct: Some(diff * 100.0), status: status.to_string() });
-                } else {
-                    results.push(BenchmarkResult { name, median, baseline: None, diff_pct: None, status: "MISSING BASELINE".to_string() });
-                }
+                results.push(BenchmarkResult { name, median, baseline: None, diff_pct: None, status: "MISSING BASELINE".to_string() });
             }
         }
     }
@@ -112,8 +110,11 @@ fn format_duration(d: Duration) -> String {
 }
 
 fn parse_duration(s: &str) -> Option<Duration> {
-    let re = Regex::new(r"([\d\.]+)(\w+)").unwrap();
-    let caps = re.captures(s)?;
+    use lazy_static::lazy_static;
+    lazy_static! {
+        static ref RE: Regex = Regex::new(r"([\d\.]+)(\w+)").unwrap();
+    }
+    let caps = RE.captures(s)?;
     let val: f64 = caps[1].parse().ok()?;
     let unit = &caps[2];
     match unit {

src/ast/vm.rs

@@ -53,6 +53,12 @@ impl TracingObserver {
     }
 }
 
+impl Default for TracingObserver {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 impl VMObserver for TracingObserver {
     const ACTIVE: bool = true;
     

src/main.rs

@@ -46,7 +46,7 @@ impl Default for CompilerApp {
             .map(|entries| {
                 entries
                     .filter_map(|e| e.ok())
-                    .filter(|e| e.path().extension().map_or(false, |ext| ext == "myc"))
+                    .filter(|e| e.path().extension().is_some_and(|ext| ext == "myc"))
                     .filter_map(|e| {
                         let path = e.path();
                         let name = e.file_name().into_string().ok()?;
@@ -184,7 +184,7 @@ impl CompilerApp {
         if let Ok(entries) = std::fs::read_dir("examples") {
             self.examples = entries
                 .filter_map(|e| e.ok())
-                .filter(|e| e.path().extension().map_or(false, |ext| ext == "myc"))
+                .filter(|e| e.path().extension().is_some_and(|ext| ext == "myc"))
                 .filter_map(|e| {
                     let path = e.path();
                     let name = e.file_name().into_string().ok()?;
@@ -445,8 +445,8 @@ fn highlight_myc(ctx: &egui::Context, code: &str) -> egui::text::LayoutJob {
                 while let Some(next) = chars.next() {
                     text.push(next);
                     if next == '"' { break; }
-                    if next == '\\' {
-                        if let Some(escaped) = chars.next() { text.push(escaped); }
+                    if next == '\\' && let Some(escaped) = chars.next() {
+                        text.push(escaped);
                     }
                 }
                 color = color_str;
@@ -463,7 +463,7 @@ fn highlight_myc(ctx: &egui::Context, code: &str) -> egui::text::LayoutJob {
                 bracket_depth += 1;
             }
             ')' | ']' | '}' => {
-                if bracket_depth > 0 { bracket_depth -= 1; }
+                bracket_depth = bracket_depth.saturating_sub(1);
                 color = color_bracket[bracket_depth % 3];
             }
             '0'..='9' => {