checker: check struct reference fields uninitialized (fix #19559)

doc/docs.md

@@ -5933,7 +5933,7 @@ cause a panic.
 
 ```v
 struct Node {
-	a &Node
+	a &Node = unsafe { nil } // Auto-initialized to nil, use with caution!
 	b &Node = unsafe { nil } // Auto-initialized to nil, use with caution!
 }
 

vlib/v/checker/struct.v

@@ -686,7 +686,7 @@ or use an explicit `unsafe{ a[..] }`, if you do not want a copy of the slice.',
 				if field.name in inited_fields {
 					continue
 				}
-				sym := c.table.sym(field.typ)
+				sym := c.table.final_sym(field.typ)
 				if field.name.len > 0 && field.name[0].is_capital() && sym.info is ast.Struct
 					&& sym.language == .v {
 					// struct embeds
@@ -712,6 +712,10 @@ or use an explicit `unsafe{ a[..] }`, if you do not want a copy of the slice.',
 							}
 						}
 					}
+					if sym.kind == .struct_ {
+						c.check_ref_fields_initialized(sym, mut checked_types, '${type_sym.name}.${field.name}',
+							node)
+					}
 					continue
 				}
 				if field.typ.is_ptr() && !field.typ.has_flag(.shared_f)
@@ -724,12 +728,6 @@ or use an explicit `unsafe{ a[..] }`, if you do not want a copy of the slice.',
 				if sym.kind == .struct_ {
 					c.check_ref_fields_initialized(sym, mut checked_types, '${type_sym.name}.${field.name}',
 						node)
-				} else if sym.kind == .alias {
-					parent_sym := c.table.sym((sym.info as ast.Alias).parent_type)
-					if parent_sym.kind == .struct_ {
-						c.check_ref_fields_initialized(parent_sym, mut checked_types,
-							'${type_sym.name}.${field.name}', node)
-					}
 				}
 				// Do not allow empty uninitialized interfaces
 				mut has_noinit := false
@@ -858,6 +856,9 @@ fn (mut c Checker) check_ref_fields_initialized(struct_sym &ast.TypeSymbol, mut
 		} else if sym.kind == .alias {
 			psym := c.table.sym((sym.info as ast.Alias).parent_type)
 			if psym.kind == .struct_ {
+				if field.typ in checked_types {
+					continue
+				}
 				checked_types << field.typ
 				c.check_ref_fields_initialized(psym, mut checked_types, '${linked_name}.${field.name}',
 					node)

vlib/v/checker/tests/struct_ref_fields_uninitialized_err_a.out

@@ -0,0 +1,33 @@
+vlib/v/checker/tests/struct_ref_fields_uninitialized_err_a.vv:25:7: error: reference field `Outer.c1.b` must be initialized (part of struct `ContainsRef`)
+   23 |
+   24 | fn main() {
+   25 |     _ := Outer{}
+      |          ~~~~~~~
+   26 |     _ := Struct{}
+   27 | }
+vlib/v/checker/tests/struct_ref_fields_uninitialized_err_a.vv:25:7: error: reference field `ContainsRef.b` must be initialized
+   23 |
+   24 | fn main() {
+   25 |     _ := Outer{}
+      |          ~~~~~~~
+   26 |     _ := Struct{}
+   27 | }
+vlib/v/checker/tests/struct_ref_fields_uninitialized_err_a.vv:25:7: error: reference field `Outer.c2.b` must be initialized (part of struct `ContainsRef`)
+   23 |
+   24 | fn main() {
+   25 |     _ := Outer{}
+      |          ~~~~~~~
+   26 |     _ := Struct{}
+   27 | }
+vlib/v/checker/tests/struct_ref_fields_uninitialized_err_a.vv:26:7: error: reference field `Struct.ref2` must be initialized
+   24 | fn main() {
+   25 |     _ := Outer{}
+   26 |     _ := Struct{}
+      |          ~~~~~~~~
+   27 | }
+vlib/v/checker/tests/struct_ref_fields_uninitialized_err_a.vv:26:7: error: reference field `EmbedStruct.ref2` must be initialized
+   24 | fn main() {
+   25 |     _ := Outer{}
+   26 |     _ := Struct{}
+      |          ~~~~~~~~
+   27 | }

vlib/v/checker/tests/struct_ref_fields_uninitialized_err_b.out

@@ -0,0 +1,26 @@
+vlib/v/checker/tests/struct_ref_fields_uninitialized_err_b.vv:8:32: warning: unnecessary default value of `none`: struct fields are zeroed by default
+    6 | pub struct Window {
+    7 | mut:
+    8 |     desktop_viewport ?&Viewport = none
+      |                                   ~~~~
+    9 |     phone_viewport   ?&Viewport = none
+   10 | }
+vlib/v/checker/tests/struct_ref_fields_uninitialized_err_b.vv:9:32: warning: unnecessary default value of `none`: struct fields are zeroed by default
+    7 | mut:
+    8 |     desktop_viewport ?&Viewport = none
+    9 |     phone_viewport   ?&Viewport = none
+      |                                   ~~~~
+   10 | }
+   11 |
+vlib/v/checker/tests/struct_ref_fields_uninitialized_err_b.vv:13:8: error: reference field `Window.desktop_viewport.parent` must be initialized (part of struct `Viewport`)
+   11 |
+   12 | fn main() {
+   13 |     _ := &Window{}
+      |           ~~~~~~~~
+   14 | }
+vlib/v/checker/tests/struct_ref_fields_uninitialized_err_b.vv:13:8: error: reference field `Window.phone_viewport.parent` must be initialized (part of struct `Viewport`)
+   11 |
+   12 | fn main() {
+   13 |     _ := &Window{}
+      |           ~~~~~~~~
+   14 | }

vlib/v/checker/tests/struct_ref_fields_uninitialized_err_b.vv

@@ -0,0 +1,14 @@
+struct Viewport {
+mut:
+	parent &Window
+}
+
+pub struct Window {
+mut:
+	desktop_viewport ?&Viewport = none
+	phone_viewport   ?&Viewport = none
+}
+
+fn main() {
+	_ := &Window{}
+}