feat: add support for else-if chains

- Update parser to handle 'else if' syntax
- Allow chaining multiple else-if conditions
- Convert else-if to nested if statements in else block
- Add comprehensive tests for else-if functionality
- All tests pass including transpiler support

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: fcoury

src/parser.rs

@@ -1818,24 +1818,31 @@ impl Parser {
         if self.current_token().kind == TokenKind::Else {
             self.advance(); // Consume 'else'
 
-            if self.current_token().kind != TokenKind::LBrace {
-                return Err(Error::new_parse(
-                    "Expected '{' after else".to_string(),
-                    self.current_token().span,
-                ));
-            }
-
-            self.advance(); // Consume '{'
-            else_block = self.parse_block()?;
+            // Check if this is an 'else if'
+            if self.current_token().kind == TokenKind::If {
+                // Parse the if expression as a single statement in the else block
+                let else_if_expr = self.parse_if_expression()?;
+                end_span = else_if_expr.span().end;
+                else_block = vec![Stmt::Expression(else_if_expr, false)];
+            } else if self.current_token().kind == TokenKind::LBrace {
+                // Regular else block
+                self.advance(); // Consume '{'
+                else_block = self.parse_block()?;
 
-            if self.current_token().kind != TokenKind::RBrace {
+                if self.current_token().kind != TokenKind::RBrace {
+                    return Err(Error::new_parse(
+                        "Expected '}' after else block".to_string(),
+                        self.current_token().span,
+                    ));
+                }
+                end_span = self.current_token().span.end;
+                self.advance(); // Consume '}'
+            } else {
                 return Err(Error::new_parse(
-                    "Expected '}' after else block".to_string(),
+                    "Expected '{' or 'if' after else".to_string(),
                     self.current_token().span,
                 ));
             }
-            end_span = self.current_token().span.end;
-            self.advance(); // Consume '}'
         }
 
         Ok(Expr::If(

tests/scripts/else-if-complex.hk

@@ -0,0 +1,44 @@
+// Test multiple else-if chains
+let score = 85;
+
+if score >= 90 {
+    println!("Grade: A");
+} else if score >= 80 {
+    println!("Grade: B");
+} else if score >= 70 {
+    println!("Grade: C");
+} else if score >= 60 {
+    println!("Grade: D");
+} else {
+    println!("Grade: F");
+}
+
+// Test else-if without final else
+let temp = 25;
+if temp < 0 {
+    println!("Freezing");
+} else if temp < 10 {
+    println!("Cold");
+} else if temp < 20 {
+    println!("Cool");
+} else if temp < 30 {
+    println!("Warm");
+}
+
+// Test nested else-if in else-if
+let x = 15;
+let y = 20;
+
+if x > 20 {
+    println!("x > 20");
+} else if x > 10 {
+    if y > 25 {
+        println!("x > 10 and y > 25");
+    } else if y > 15 {
+        println!("x > 10 and y > 15");
+    } else {
+        println!("x > 10 and y <= 15");
+    }
+} else {
+    println!("x <= 10");
+}

tests/scripts/else-if-complex.hk.err

@@ -0,0 +1,3 @@
+Grade: B
+Warm
+x > 10 and y > 15

tests/scripts/else-if-complex.hk.out

@@ -0,0 +1,3 @@
+Grade: B
+Warm
+x > 10 and y > 15

tests/scripts/else-if-complex.hk.tr.err

@@ -0,0 +1,6 @@
+let a = 1;
+if a == 2 {
+  println!("a is 2");
+} else if a == 1 {
+  println!("a is 1");
+}

tests/scripts/else-if-complex.hk.tr.out

@@ -0,0 +1 @@
+a is 1