add loop parsing

examples/hello.v

@@ -20,4 +20,14 @@ fn main(a int) int {
 
 	a && b
 	a || b
+
+	loop {}
+	loop {
+		println('Ballse')
+	}
+
+	loop a > 2 {}
+	loop a > 2 {
+		println('skirts')
+	}
 }

src/ast.zig

@@ -327,6 +327,20 @@ pub fn printStmt(ident: usize, stmt: *Stmt) void {
 
             std.debug.warn(")\n");
         },
+
+        .Loop => |loop| {
+            std.debug.warn("(loop ");
+            if (loop.condition) |cond| {
+                printExpr(cond);
+            } else {
+                std.debug.warn("true");
+            }
+            std.debug.warn(" ");
+
+            printBlock(ident + 1, loop.then_branch, false);
+            std.debug.warn(")\n");
+        },
+
         else => std.debug.warn("UnknownStmt-{}", @tagName(stmt.*)),
     }
 }

src/parser.zig

@@ -449,6 +449,7 @@ pub const Parser = struct {
     fn parseStmt(self: *@This()) anyerror!*Stmt {
         return switch (self.peek().ttype) {
             .If => try self.parseIfStmt(),
+            .Loop => try self.parseLoop(),
             .Println => try self.parsePrintln(),
 
             // TODO make newlines tokens and consume newline?
@@ -495,6 +496,22 @@ pub const Parser = struct {
         );
     }
 
+    fn parseLoop(self: *@This()) !*Stmt {
+        _ = try self.consumeSingle(.Loop);
+        var expr: ?*Expr = null;
+        var body: ast.Block = undefined;
+
+        // infinite loop
+        if (self.check(.LeftBrace)) {
+            body = try self.parseStmtBlock();
+        } else {
+            expr = (try self.parseExpr()).Expr;
+            body = try self.parseStmtBlock();
+        }
+
+        return try Stmt.mkLoop(self.allocator, expr, body);
+    }
+
     fn parsePrintln(self: *@This()) !*Stmt {
         _ = try self.consumeSingle(.Println);