From 30ac2e8763a1b21bab003e4d596333725d04d862 Mon Sep 17 00:00:00 2001
From: Swastik Baranwal <swstkbaranwal@gmail.com>
Date: Thu, 27 Apr 2023 20:24:26 +0530
Subject: [PATCH] checker: disallow assigning anon `struct` to typed `struct`
 (#18017)

---
 vlib/v/checker/struct.v                          |  8 ++++++++
 .../assign_anon_struct_to_typed_struct_err.out   |  7 +++++++
 .../assign_anon_struct_to_typed_struct_err.vv    | 16 ++++++++++++++++
 3 files changed, 31 insertions(+)
 create mode 100644 vlib/v/checker/tests/assign_anon_struct_to_typed_struct_err.out
 create mode 100644 vlib/v/checker/tests/assign_anon_struct_to_typed_struct_err.vv

diff --git a/vlib/v/checker/struct.v b/vlib/v/checker/struct.v
index 337d76fa3..766fcc1ff 100644
--- a/vlib/v/checker/struct.v
+++ b/vlib/v/checker/struct.v
@@ -574,6 +574,14 @@ fn (mut c Checker) struct_init(mut node ast.StructInit, is_field_zero_struct_ini
 						}
 					}
 				}
+
+				if field_type_sym.kind == .struct_ && !(field_type_sym.info as ast.Struct).is_anon
+					&& mut field.expr is ast.StructInit {
+					if field.expr.is_anon {
+						c.error('cannot assign anonymous `struct` to a typed `struct`',
+							field.expr.pos)
+					}
+				}
 			}
 			// Check uninitialized refs/sum types
 			// The variable `fields` contains two parts, the first part is the same as info.fields,
diff --git a/vlib/v/checker/tests/assign_anon_struct_to_typed_struct_err.out b/vlib/v/checker/tests/assign_anon_struct_to_typed_struct_err.out
new file mode 100644
index 000000000..9d2cf1528
--- /dev/null
+++ b/vlib/v/checker/tests/assign_anon_struct_to_typed_struct_err.out
@@ -0,0 +1,7 @@
+vlib/v/checker/tests/assign_anon_struct_to_typed_struct_err.vv:11:18: error: cannot assign anonymous `struct` to a typed `struct`
+    9 |
+   10 | f := Fax{
+   11 |     message: struct {
+      |                     ^
+   12 |         a: 'A'
+   13 |     }
diff --git a/vlib/v/checker/tests/assign_anon_struct_to_typed_struct_err.vv b/vlib/v/checker/tests/assign_anon_struct_to_typed_struct_err.vv
new file mode 100644
index 000000000..f8daedd5b
--- /dev/null
+++ b/vlib/v/checker/tests/assign_anon_struct_to_typed_struct_err.vv
@@ -0,0 +1,16 @@
+struct Message {
+	a string
+	b string
+}
+
+struct Fax {
+	message Message
+}
+
+f := Fax{
+	message: struct {
+		a: 'A'
+	}
+}
+
+dump(f)
-- 
2.39.5