Feat: Implement return value.

Author: dylan-sutton-chavez

compiler/src/main.rs

@@ -29,7 +29,7 @@ fn main() {
 
     initialize_logger();
 
-    let source = "result = 2 + 3 * 7";
+    let source = "def add(a, b): return a + b\nresult = add(1, 2)";
 
     let chunk = modules::parser::Parser::new(source, modules::lexer::lexer(source)).parse();
 

compiler/src/modules/parser.rs

@@ -188,6 +188,15 @@ impl<'src, I: Iterator<Item = Token>> Parser<'src, I> {
             Some(TokenType::For)   => self.for_stmt(),
             Some(TokenType::Name)  => { let t = self.advance(); self.name_stmt(t); }
             Some(TokenType::Def)   => { self.advance(); self.func_def(); }
+            Some(TokenType::Return) => {
+                self.advance();
+                if matches!(self.peek(), Some(TokenType::Newline | TokenType::Endmarker)) {
+                    self.emit_const(Value::None);
+                } else {
+                    self.expr();
+                }
+                self.chunk.emit(OpCode::ReturnValue, 0);
+            }
             _ => self.expr()
         }
     }
@@ -532,12 +541,17 @@ impl<'src, I: Iterator<Item = Token>> Parser<'src, I> {
         if matches!(self.peek(), Some(TokenType::Colon)) { self.advance(); }
         params
     }
-
+        
     fn compile_body(&mut self, params: &[String]) -> SSAChunk {
         let (saved_chunk, saved_ver) = (std::mem::take(&mut self.chunk), std::mem::take(&mut self.ssa_versions));
         for p in params { self.ssa_versions.insert(p.clone(), 0); }
-        self.stmt();
-        self.chunk.emit(OpCode::ReturnValue, 0);
+        
+        loop {
+            let is_return = matches!(self.peek(), Some(TokenType::Return));
+            self.stmt();
+            if is_return || self.at_end() { break; }
+        }
+        
         let body = std::mem::take(&mut self.chunk);
         (self.chunk, self.ssa_versions) = (saved_chunk, saved_ver);
         body

compiler/tests/cases/parser_cases.json

@@ -31,7 +31,7 @@
     "src": "range(4)",
     "constants": ["4"],
     "names": [],
-    "instructions": [["LoadConst", 0], ["CallRange", 1], ["PopTop", 0], ["ReturnValue", 0]],
+    "instructions": [["LoadConst",0], ["CallRange",1], ["PopTop",0], ["ReturnValue",0]],
     "annotations": {}
   },
   {
@@ -42,7 +42,7 @@
     "annotations": {}
   },
   {
-    "src": "def add(a, b): a + b\nresult = add(1, 2)",
+    "src": "def add(a, b): return a + b\nresult = add(1, 2)",
     "constants": ["1", "2"],
     "names": ["add_1", "result_1"],
     "instructions": [["MakeFunction",0], ["StoreName",0], ["LoadName",0], ["LoadConst",0], ["LoadConst",1], ["Call",2], ["StoreName",1], ["PopTop",0], ["ReturnValue",0]],