checker: fix unset type of a pointer field with default value, when a struct contains an embed (fix #16882) (#16883)

vlib/v/ast/ast.v

@@ -2267,6 +2267,18 @@ pub fn (expr Expr) is_literal() bool {
 	}
 }
 
+pub fn (e Expr) is_nil() bool {
+	if e is Nil {
+		return true
+	}
+	if e is UnsafeExpr {
+		if e.expr is Nil {
+			return true
+		}
+	}
+	return false
+}
+
 pub fn type_can_start_with_token(tok &token.Token) bool {
 	match tok.kind {
 		.name {

vlib/v/checker/struct.v

@@ -104,8 +104,7 @@ fn (mut c Checker) struct_decl(mut node ast.StructDecl) {
 					&& c.type_implements(default_expr_type, field.typ, field.pos)
 				c.check_expected(default_expr_type, field.typ) or {
 					if sym.kind == .interface_ && interface_implemented {
-						if !default_expr_type.is_ptr() && !default_expr_type.is_pointer()
-							&& !c.inside_unsafe {
+						if !c.inside_unsafe && !default_expr_type.is_real_pointer() {
 							if c.table.sym(default_expr_type).kind != .interface_ {
 								c.mark_as_referenced(mut &node.fields[i].default_expr,
 									true)
@@ -116,6 +115,11 @@ fn (mut c Checker) struct_decl(mut node ast.StructDecl) {
 							field.default_expr.pos())
 					}
 				}
+				if field.default_expr.is_nil() {
+					if !field.typ.is_real_pointer() && c.table.sym(field.typ).kind != .function {
+						c.error('cannot assign `nil` to a non-pointer field', field.type_pos)
+					}
+				}
 				// Check for unnecessary inits like ` = 0` and ` = ''`
 				if field.typ.is_ptr() {
 					if field.default_expr is ast.IntegerLiteral {
@@ -134,12 +138,6 @@ fn (mut c Checker) struct_decl(mut node ast.StructDecl) {
 						}
 					}
 				}
-				if field.default_expr is ast.UnsafeExpr {
-					if field.default_expr.expr is ast.Nil && !field.typ.is_ptr()
-						&& c.table.sym(field.typ).kind != .function && !field.typ.is_pointer() {
-						c.error('cannot assign `nil` to a non-pointer field', field.type_pos)
-					}
-				}
 				if field.default_expr is ast.IntegerLiteral {
 					if field.default_expr.val == '0' {
 						c.warn('unnecessary default value of `0`: struct fields are zeroed by default',
@@ -444,8 +442,8 @@ fn (mut c Checker) struct_init(mut node ast.StructInit) ast.Type {
 				expr_type_sym := c.table.sym(expr_type)
 				if field_type_sym.kind == .interface_ {
 					if c.type_implements(expr_type, field_info.typ, field.pos) {
-						if !expr_type.is_ptr() && !expr_type.is_pointer()
-							&& expr_type_sym.kind != .interface_ && !c.inside_unsafe {
+						if !c.inside_unsafe && expr_type_sym.kind != .interface_
+							&& !expr_type.is_real_pointer() {
 							c.mark_as_referenced(mut &field.expr, true)
 						}
 					}
@@ -462,7 +460,7 @@ fn (mut c Checker) struct_init(mut node ast.StructInit) ast.Type {
 							field.pos)
 					}
 				} else {
-					if field_info.typ.is_ptr() && !expr_type.is_ptr() && !expr_type.is_pointer()
+					if field_info.typ.is_ptr() && !expr_type.is_real_pointer()
 						&& field.expr.str() != '0' {
 						c.error('reference field must be initialized with reference',
 							field.pos)
@@ -516,6 +514,7 @@ fn (mut c Checker) struct_init(mut node ast.StructInit) ast.Type {
 				sym := c.table.sym(field.typ)
 				if field.name.len > 0 && field.name[0].is_capital() && sym.info is ast.Struct
 					&& sym.language == .v {
+					// struct embeds
 					continue
 				}
 				if field.has_default_expr {
@@ -525,6 +524,10 @@ fn (mut c Checker) struct_init(mut node ast.StructInit) ast.Type {
 							if idx != 0 {
 								info.fields[i].default_expr_typ = ast.new_type(idx)
 							}
+						} else if field.default_expr.is_nil() {
+							if field.typ.is_real_pointer() {
+								info.fields[i].default_expr_typ = field.typ
+							}
 						} else {
 							if const_field := c.table.global_scope.find_const('${field.default_expr}') {
 								info.fields[i].default_expr_typ = const_field.typ

vlib/v/gen/c/struct.v

@@ -167,8 +167,8 @@ fn (mut g Gen) struct_init(node ast.StructInit) {
 					continue
 				}
 			}
-			if field.name in inited_fields {
-				mut sfield := node.fields[inited_fields[field.name]]
+			if already_initalised_node_field_index := inited_fields[field.name] {
+				mut sfield := node.fields[already_initalised_node_field_index]
 				if sfield.typ == 0 {
 					continue
 				}

vlib/v/tests/struct_init_with_interface_pointer_and_embed_test.v

@@ -0,0 +1,28 @@
+pub struct Embed {
+	foo int
+}
+
+pub interface Node {
+	id u32
+mut:
+	parent &Node
+}
+
+pub struct Item {
+	Embed
+pub:
+	id u32
+mut:
+	parent &Node = unsafe { nil }
+}
+
+fn test_struct_with_both_an_embed_and_a_pointer_to_interface_value_fields__initialises_properly() {
+	i := Item{}
+	si := i.str()
+	assert si.contains('Item{')
+	assert si.contains('Embed: Embed{')
+	assert si.contains('foo: 0')
+	assert si.contains('id: 0')
+	assert si.contains('parent: &nil')
+	assert si.contains('}')
+}