checker: check struct embed required field (#17595)

vlib/v/checker/struct.v

@@ -656,6 +656,13 @@ fn (mut c Checker) struct_init(mut node ast.StructInit, is_field_zero_struct_ini
 					c.struct_init(mut zero_struct_init, true)
 				}
 			}
+			for embed in info.embeds {
+				mut zero_struct_init := ast.StructInit{
+					pos: node.pos
+					typ: embed
+				}
+				c.struct_init(mut zero_struct_init, true)
+			}
 			// println('>> checked_types.len: $checked_types.len | checked_types: $checked_types | type_sym: $type_sym.name ')
 		}
 		else {}

vlib/v/checker/tests/struct_embed_required_field_err.out

@@ -0,0 +1,7 @@
+vlib/v/checker/tests/struct_embed_required_field_err.vv:11:7: error: field `Foo.foo` must be initialized
+    9 |
+   10 | fn main() {
+   11 |     b := Bar {
+      |          ~~~~~
+   12 |         foo: 1
+   13 |     }

vlib/v/checker/tests/struct_embed_required_field_err.vv

@@ -0,0 +1,15 @@
+struct Foo {
+	foo u8 [required]
+}
+
+struct Bar {
+	Foo
+	foo u8 [required]
+}
+
+fn main() {
+	b := Bar {
+		foo: 1
+	}
+	println(b)
+}

vlib/v/checker/tests/struct_ref_fields_uninitialized_err.out

@@ -25,3 +25,9 @@ vlib/v/checker/tests/struct_ref_fields_uninitialized_err.vv:26:7: warning: refer
    26 |     _ := Struct{}
       |          ~~~~~~~~
    27 | }
+vlib/v/checker/tests/struct_ref_fields_uninitialized_err.vv:26:7: warning: reference field `EmbedStruct.ref2` must be initialized
+   24 | fn main() {
+   25 |     _ := Outer{}
+   26 |     _ := Struct{}
+      |          ~~~~~~~~
+   27 | }