cgen: fix codegen for generic struct field array option (fix #25093) (#25097)

vlib/v/gen/c/cgen.v

@@ -5444,7 +5444,7 @@ fn (mut g Gen) ident(node ast.Ident) {
 						}
 						if i == 0 && node.obj.ct_type_var != .smartcast && node.obj.is_unwrapped {
 							dot := if (!node.obj.ct_type_unwrapped && !node.obj.orig_type.is_ptr()
-								&& obj_sym.is_heap())
+								&& !node.obj.orig_type.has_flag(.generic) && obj_sym.is_heap())
 								|| node.obj.orig_type.has_flag(.option_mut_param_t) {
 								'->'
 							} else {
@@ -6727,7 +6727,7 @@ fn (mut g Gen) write_types(symbols []&ast.TypeSymbol) {
 					for opt_field in opt_fields {
 						field_sym := g.table.final_sym(opt_field.typ)
 						arr := field_sym.info as ast.ArrayFixed
-						if !arr.elem_type.has_flag(.option) {
+						if !arr.elem_type.has_flag(.option) || arr.elem_type.has_flag(.generic) {
 							continue
 						}
 						styp := field_sym.cname

vlib/v/tests/options/option_generic_array_field_test.v

@@ -0,0 +1,39 @@
+module main
+
+@[heap]
+struct FLQueue[T] {
+mut:
+	inner [8]?T
+}
+
+fn (mut f FLQueue[T]) put[T](element T) {
+	for index, item in f.inner {
+		if item == none {
+			f.inner[index] = element
+			return
+		}
+	}
+	panic('put: No free slot')
+}
+
+fn (mut f FLQueue[T]) get[T]() ?T {
+	for item in f.inner {
+		if item != none {
+			return item
+		}
+	}
+	return none
+}
+
+@[heap]
+struct Thread {
+	stack [1024]u8
+}
+
+fn test_main() {
+	mut q := FLQueue[Thread]{}
+	t := Thread{}
+	q.put(t)
+	p := q.get()
+	println(p)
+}