From 7b2fe92241d55bf552db31644878c17888646feb Mon Sep 17 00:00:00 2001
From: Christoffer Lerno <christoffer@aegik.com>
Date: Wed, 15 Jan 2025 10:54:50 +0100
Subject: [PATCH] Improve error message on incorrect inner struct/union name
 #1847.

---
 releasenotes.md                             | 1 +
 src/compiler/parse_global.c                 | 5 +++++
 test/test_suite/struct/inner_struct_name.c3 | 5 +++++
 3 files changed, 11 insertions(+)
 create mode 100644 test/test_suite/struct/inner_struct_name.c3

diff --git a/releasenotes.md b/releasenotes.md
index 2615194b4..00265e3ce 100644
--- a/releasenotes.md
+++ b/releasenotes.md
@@ -177,6 +177,7 @@
 - `io::print` will now print structs.
 - Improve error message when using `void` aliases as variable storage type.
 - Add a target type: "prepare" which doesn't compile anything (but may run `exec`)
+- Improve error message on incorrect inner struct/union name #1847.
 
 ### Fixes
 - `Unsupported int[*] $x = { 1, 2, 3, 4 }` #1489.
diff --git a/src/compiler/parse_global.c b/src/compiler/parse_global.c
index e2868ac2f..9ad9ed0f3 100644
--- a/src/compiler/parse_global.c
+++ b/src/compiler/parse_global.c
@@ -1546,6 +1546,11 @@ bool parse_struct_body(ParseContext *c, Decl *parent)
 			{
 				member = decl_new_with_type(NULL, c->span, decl_kind);
 				advance(c);
+				if (token_is_some_ident(c->tok))
+				{
+					RETURN_PRINT_ERROR_HERE("The name of an inner struct or union must be a name starting with a lowercase letter.");
+					return decl_poison(parent);
+				}
 			}
 			else
 			{
diff --git a/test/test_suite/struct/inner_struct_name.c3 b/test/test_suite/struct/inner_struct_name.c3
new file mode 100644
index 000000000..01d8fa6f1
--- /dev/null
+++ b/test/test_suite/struct/inner_struct_name.c3
@@ -0,0 +1,5 @@
+struct Foo {
+    union Bar { // #error: name of an inner struct
+        int a;
+    }
+}