Add loop captures to capture struct

src/template/lib.zig

@@ -39,12 +39,12 @@ fn executeStatement(writer: anytype, comptime stmt: Statement, args: anytype, ca
             const iterable = deref(args, fields);
             const subtemplate = loop.subtemplate;
             try writer.writeAll("capture on " ++ loop.capture ++ ": ");
-            for (iterable) |_| {
+            for (iterable) |v| {
                 try executeTemplate(
                     writer,
                     subtemplate,
                     args,
-                    captures,
+                    addCapture(captures, loop.capture, v),
                 );
             }
         },
@@ -74,6 +74,29 @@ fn deref(arg: anytype, comptime names: []const []const u8) Deref(@TypeOf(arg), n
     return deref(@field(arg, names[0]), names[1..]);
 }
 
+fn AddCapture(comptime Root: type, comptime name: []const u8, comptime Val: type) type {
+    var fields = std.meta.fields(Root) ++ [_]std.builtin.Type.StructField{.{
+        .name = name,
+        .field_type = Val,
+        .default_value = null,
+        .is_comptime = false,
+        .alignment = @alignOf(Val),
+    }};
+
+    return @Type(.{ .Struct = .{
+        .layout = .Auto,
+        .fields = fields,
+        .decls = &.{},
+        .is_tuple = false,
+    } });
+}
+
+fn addCapture(root: anytype, comptime name: []const u8, val: anytype) AddCapture(@TypeOf(root), name, @TypeOf(val)) {
+    var result = std.mem.zeroInit(AddCapture(@TypeOf(root), name, @TypeOf(val)), root);
+    @field(result, name) = val;
+    return result;
+}
+
 const TemplateType = enum {
     root,
     subtemplate,

src/template/test.tmp.html

@@ -10,7 +10,7 @@
 
     <section>
       {$bar}
-      {#for .foo |$f|}a testing thing {#end_for}
+      {#for .foo |$f|}a testing thing: {$f} {#end_for}
       {{#for args.notes |$note, $i|}}
         <h3>Note no. {{$i}}</h3>
         {{#template note_display ($note)}}