From fde951652c7983d13036b59b8150e61ae00069e9 Mon Sep 17 00:00:00 2001
From: Jose Mendoza <56417208+StunxFS@users.noreply.github.com>
Date: Tue, 15 Oct 2024 16:06:45 -0400
Subject: [PATCH] checker: clarify error message about using empty map literal
 to initialize structs (fix #22498) (#22534)

---
 vlib/v/checker/containers.v                   | 19 ++++++++++++-------
 ...iteral_to_initialize_anon_struct_error.out |  7 +++++++
 ...literal_to_initialize_anon_struct_error.vv | 11 +++++++++++
 3 files changed, 30 insertions(+), 7 deletions(-)
 create mode 100644 vlib/v/checker/tests/use_empty_map_literal_to_initialize_anon_struct_error.out
 create mode 100644 vlib/v/checker/tests/use_empty_map_literal_to_initialize_anon_struct_error.vv

diff --git a/vlib/v/checker/containers.v b/vlib/v/checker/containers.v
index c5ae14777..8ff9283f9 100644
--- a/vlib/v/checker/containers.v
+++ b/vlib/v/checker/containers.v
@@ -432,16 +432,21 @@ fn (mut c Checker) map_init(mut node ast.MapInit) ast.Type {
 			node.key_type = info.key_type
 			node.value_type = info.value_type
 			return node.typ
-		} else {
-			if sym.kind == .struct {
-				c.error('`{}` can not be used for initialising empty structs any more. Use `${c.table.type_to_str(c.expected_type)}{}` instead.',
-					node.pos)
+		} else if sym.info is ast.Struct {
+			msg := if sym.info.is_anon {
+				'`{}` cannot be used to initialize anonymous structs. Use `struct{}` instead.'
 			} else {
-				c.error('invalid empty map initialisation syntax, use e.g. map[string]int{} instead',
-					node.pos)
+				'`{}` can not be used for initialising empty structs any more. Use `${c.table.type_to_str(c.expected_type)}{}` instead.'
 			}
-			return ast.void_type
+			c.error(msg, node.pos)
+			if sym.info.is_anon {
+				return c.expected_type
+			}
+		} else {
+			c.error('invalid empty map initialisation syntax, use e.g. map[string]int{} instead',
+				node.pos)
 		}
+		return ast.void_type
 	}
 	// `x := map[string]string` - set in parser
 	if node.typ != 0 {
diff --git a/vlib/v/checker/tests/use_empty_map_literal_to_initialize_anon_struct_error.out b/vlib/v/checker/tests/use_empty_map_literal_to_initialize_anon_struct_error.out
new file mode 100644
index 000000000..7f5410f08
--- /dev/null
+++ b/vlib/v/checker/tests/use_empty_map_literal_to_initialize_anon_struct_error.out
@@ -0,0 +1,7 @@
+vlib/v/checker/tests/use_empty_map_literal_to_initialize_anon_struct_error.vv:9:22: error: `{}` cannot be used to initialize anonymous structs. Use `struct{}` instead.
+    7 | 
+    8 | fn main() {
+    9 |     s := AStructName{5, {}}
+      |                         ~~
+   10 |     println(s)
+   11 | }
diff --git a/vlib/v/checker/tests/use_empty_map_literal_to_initialize_anon_struct_error.vv b/vlib/v/checker/tests/use_empty_map_literal_to_initialize_anon_struct_error.vv
new file mode 100644
index 000000000..81f99bd9b
--- /dev/null
+++ b/vlib/v/checker/tests/use_empty_map_literal_to_initialize_anon_struct_error.vv
@@ -0,0 +1,11 @@
+struct AStructName {
+	foo  int
+	anon struct {
+		bar int
+	}
+}
+
+fn main() {
+	s := AStructName{5, {}}
+	println(s)
+}
-- 
2.39.5