From 698f8c2f01ea549d77d7dc3338a12e04c11057b9 Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Wed, 17 Apr 2024 14:02:58 +0200
Subject: Adding upstream version 1.64.0+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 .../rustc_error_codes/src/error_codes/E0128.md     | 25 ++++++++++++++++++++++
 1 file changed, 25 insertions(+)
 create mode 100644 compiler/rustc_error_codes/src/error_codes/E0128.md

(limited to 'compiler/rustc_error_codes/src/error_codes/E0128.md')

diff --git a/compiler/rustc_error_codes/src/error_codes/E0128.md b/compiler/rustc_error_codes/src/error_codes/E0128.md
new file mode 100644
index 000000000..2ea8ae68e
--- /dev/null
+++ b/compiler/rustc_error_codes/src/error_codes/E0128.md
@@ -0,0 +1,25 @@
+A type parameter with default value is using forward declared identifier.
+
+Erroneous code example:
+
+```compile_fail,E0128
+struct Foo<T = U, U = ()> {
+    field1: T,
+    field2: U,
+}
+// error: generic parameters with a default cannot use forward declared
+//        identifiers
+```
+
+Type parameter defaults can only use parameters that occur before them. Since
+type parameters are evaluated in-order, this issue could be fixed by doing:
+
+```
+struct Foo<U = (), T = U> {
+    field1: T,
+    field2: U,
+}
+```
+
+Please also verify that this wasn't because of a name-clash and rename the type
+parameter if so.
-- 
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