add return statements

examples/hello.v

@@ -30,4 +30,8 @@ fn main(a int) int {
 	loop a > 2 {
 		println('skirts')
 	}
+
+	cock_and_ball_torture('cbt', 1, 2, 3)
+
+	return 23
 }

src/ast.zig

@@ -76,6 +76,7 @@ pub const ExprType = enum {
     Logical,
     Literal,
     Variable,
+    Call,
     Grouping,
 };
 
@@ -84,6 +85,12 @@ pub const VarDecl = struct {
     mutable: bool = false,
 };
 
+pub const CallExpr = struct {
+    callee: *Expr,
+    paren: Token,
+    arguments: ExprList,
+};
+
 pub const Expr = union(ExprType) {
     Assign: AssignExpr,
     VarDecl: VarDecl,
@@ -95,6 +102,7 @@ pub const Expr = union(ExprType) {
 
     Variable: Token,
     Grouping: *Expr,
+    Call: CallExpr,
 };
 
 pub const Block = std.ArrayList(*Stmt);
@@ -117,6 +125,13 @@ pub const Stmt = union(enum) {
     If: IfStmt,
     Loop: LoopStmt,
 
+    Return: ReturnStmt,
+
+    pub const ReturnStmt = struct {
+        keyword: Token,
+        value: *Expr,
+    };
+
     pub fn mkPrintln(allocator: *std.mem.Allocator, expr: *Expr) !*Stmt {
         var stmt = try allocator.create(Stmt);
         stmt.* = Stmt{ .Println = expr };
@@ -156,6 +171,18 @@ pub const Stmt = union(enum) {
 
         return stmt;
     }
+
+    pub fn mkReturn(allocator: *std.mem.Allocator, tok: Token, value: *Expr) !*Stmt {
+        var stmt = try allocator.create(Stmt);
+        stmt.* = Stmt{
+            .Return = ReturnStmt{
+                .keyword = tok,
+                .value = value,
+            },
+        };
+
+        return stmt;
+    }
 };
 
 pub const Node = union(NodeType) {
@@ -305,6 +332,18 @@ pub fn printExpr(expr: *Expr) void {
             std.debug.warn(")");
         },
 
+        .Call => |call| {
+            std.debug.warn("(");
+            printExpr(call.callee);
+
+            for (call.arguments.toSlice()) |arg| {
+                std.debug.warn(" ");
+                printExpr(arg);
+            }
+
+            std.debug.warn(")");
+        },
+
         else => std.debug.warn("UnknownExpr-{}", @tagName(expr.*)),
     }
 }
@@ -341,6 +380,12 @@ pub fn printStmt(ident: usize, stmt: *Stmt) void {
             std.debug.warn(")\n");
         },
 
+        .Return => |ret| {
+            std.debug.warn("(return ");
+            printExpr(ret.value);
+            std.debug.warn(")\n");
+        },
+
         else => std.debug.warn("UnknownStmt-{}", @tagName(stmt.*)),
     }
 }

src/parser.zig

@@ -241,6 +241,19 @@ pub const Parser = struct {
         return vardecl;
     }
 
+    fn mkCall(self: *@This(), callee: *Expr, paren: Token, args: ast.ExprList) !*Expr {
+        var expr = try self.allocator.create(Expr);
+        expr.* = Expr{
+            .Call = ast.CallExpr{
+                .callee = callee,
+                .paren = paren,
+                .arguments = args,
+            },
+        };
+
+        return expr;
+    }
+
     fn mkBool(self: *Parser, val: bool) !*ast.Expr {
         var expr = try self.allocator.create(Expr);
         expr.* = Expr{
@@ -451,6 +464,7 @@ pub const Parser = struct {
             .If => try self.parseIfStmt(),
             .Loop => try self.parseLoop(),
             .Println => try self.parsePrintln(),
+            .Return => try self.parseReturn(),
 
             // TODO make newlines tokens and consume newline?
             else => try self.parseStmtExpr(),
@@ -512,14 +526,20 @@ pub const Parser = struct {
         return try Stmt.mkLoop(self.allocator, expr, body);
     }
 
+    fn parseReturn(self: *@This()) !*Stmt {
+        const tok = try self.consumeSingle(.Return);
+        const expr = (try self.parseExpr()).Expr;
+        return try Stmt.mkReturn(self.allocator, tok, expr);
+    }
+
     fn parsePrintln(self: *@This()) !*Stmt {
         _ = try self.consumeSingle(.Println);
 
         _ = try self.consumeSingle(.LeftParen);
-        var expr = try self.parseExpr();
+        var expr = (try self.parseExpr()).Expr;
         _ = try self.consumeSingle(.RightParen);
 
-        return try Stmt.mkPrintln(self.allocator, expr.Expr);
+        return try Stmt.mkPrintln(self.allocator, expr);
     }
 
     fn parseStmtExpr(self: *@This()) !*Stmt {
@@ -676,10 +696,58 @@ pub const Parser = struct {
             return try self.mkUnary(op, right);
         }
 
-        var expr = try self.parsePrimary();
+        var expr = try self.parseCall();
         return expr;
     }
 
+    fn parseCall(self: *@This()) !*Expr {
+        // we parse a primary expression instead of consuming a .Identifier
+        // since parseCall is connected to the rest of the parser. doing
+        // identifiers would break the rest of the rules that want primaries.
+
+        // nothing stops us from ensuring expr is a Variable though ;)
+        var expr = try self.parsePrimary();
+
+        while (true) {
+            if (self.check(.LeftParen)) {
+                if (ast.ExprType(expr.*) != .Variable) {
+                    self.doError("cannot call non-variable{}", ast.ExprType(expr.*));
+                    return Result.CompileError;
+                }
+
+                _ = try self.consumeSingle(.LeftParen);
+                expr = try self.finishCall(expr);
+            } else {
+                break;
+            }
+        }
+
+        return expr;
+    }
+
+    fn finishCall(self: *@This(), callee: *Expr) !*Expr {
+        var args = ast.ExprList.init(self.allocator);
+        errdefer args.deinit();
+
+        if (!self.check(.RightParen)) {
+
+            // emulating do-while really badly
+            var arg = (try self.parseExpr()).Expr;
+            try args.append(arg);
+
+            while (self.check(.Comma)) {
+                _ = try self.consumeSingle(.Comma);
+
+                arg = (try self.parseExpr()).Expr;
+                try args.append(arg);
+            }
+        }
+
+        var paren = try self.consume(.RightParen, "Expected ')' after arguments");
+
+        return self.mkCall(callee, paren, args);
+    }
+
     fn parsePrimary(self: *@This()) !*Expr {
         const curtype = self.peek().ttype;
         const lexeme = self.peek().lexeme;