struct type construction

std/meta/meta.bro

@@ -39,3 +39,20 @@ TypeInfo :: union(enum) {
 	fallible void
 	distinct void
 }
+
+EnumFieldStruct func($E, $Field type, $default ?Field) type {
+	match typeinfo!(E) {
+		.enum |info|: {
+			names [field!(typeinfo!(E), "enum").fields.len]mut []u8 = undefined
+			field_types [field!(typeinfo!(E), "enum").fields.len]mut type = undefined
+			defaults [field!(typeinfo!(E), "enum").fields.len]mut ?Field = undefined
+			expand for info.fields |field, index| {
+				names[index] = field.name
+				field_types[index] = Field
+				defaults[index] = default
+			}
+			return struct_type!(.auto, names, field_types, defaults)
+		}
+		else: compile_error!("EnumFieldStruct key must be an enum")
+	}
+}

std/meta/meta.test.bro

@@ -0,0 +1,34 @@
+testing :: import "@std/testing"
+
+TestTokenKind :: enum(u8) {
+	ident = 3
+	int = 8
+	eof = 21
+}
+
+TestNames :: alias EnumFieldStruct(TestTokenKind, ?[]u8, some!(none))
+
+enum_field_struct_defaults test {
+	names TestNames = {
+		ident = "identifier",
+		int = "integer",
+	}
+	if field!(names, "ident") |value| {
+		try testing.expect(value.len == 10)
+	} else {
+		try testing.expect(false)
+	}
+	if field!(names, "int") |value| {
+		try testing.expect(value.len == 7)
+	} else {
+		try testing.expect(false)
+	}
+	if field!(names, "eof") |_| {
+		try testing.expect(false)
+	}
+
+	empty TestNames = {}
+	if field!(empty, "ident") |_| {
+		try testing.expect(false)
+	}
+}