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/E0506.md     | 73 ++++++++++++++++++++++
 1 file changed, 73 insertions(+)
 create mode 100644 compiler/rustc_error_codes/src/error_codes/E0506.md

(limited to 'compiler/rustc_error_codes/src/error_codes/E0506.md')

diff --git a/compiler/rustc_error_codes/src/error_codes/E0506.md b/compiler/rustc_error_codes/src/error_codes/E0506.md
new file mode 100644
index 000000000..c312a0460
--- /dev/null
+++ b/compiler/rustc_error_codes/src/error_codes/E0506.md
@@ -0,0 +1,73 @@
+An attempt was made to assign to a borrowed value.
+
+Erroneous code example:
+
+```compile_fail,E0506
+struct FancyNum {
+    num: u8,
+}
+
+let mut fancy_num = FancyNum { num: 5 };
+let fancy_ref = &fancy_num;
+fancy_num = FancyNum { num: 6 };
+// error: cannot assign to `fancy_num` because it is borrowed
+
+println!("Num: {}, Ref: {}", fancy_num.num, fancy_ref.num);
+```
+
+Because `fancy_ref` still holds a reference to `fancy_num`, `fancy_num` can't
+be assigned to a new value as it would invalidate the reference.
+
+Alternatively, we can move out of `fancy_num` into a second `fancy_num`:
+
+```
+struct FancyNum {
+    num: u8,
+}
+
+let mut fancy_num = FancyNum { num: 5 };
+let moved_num = fancy_num;
+fancy_num = FancyNum { num: 6 };
+
+println!("Num: {}, Moved num: {}", fancy_num.num, moved_num.num);
+```
+
+If the value has to be borrowed, try limiting the lifetime of the borrow using
+a scoped block:
+
+```
+struct FancyNum {
+    num: u8,
+}
+
+let mut fancy_num = FancyNum { num: 5 };
+
+{
+    let fancy_ref = &fancy_num;
+    println!("Ref: {}", fancy_ref.num);
+}
+
+// Works because `fancy_ref` is no longer in scope
+fancy_num = FancyNum { num: 6 };
+println!("Num: {}", fancy_num.num);
+```
+
+Or by moving the reference into a function:
+
+```
+struct FancyNum {
+    num: u8,
+}
+
+fn print_fancy_ref(fancy_ref: &FancyNum){
+    println!("Ref: {}", fancy_ref.num);
+}
+
+let mut fancy_num = FancyNum { num: 5 };
+
+print_fancy_ref(&fancy_num);
+
+// Works because function borrow has ended
+fancy_num = FancyNum { num: 6 };
+println!("Num: {}", fancy_num.num);
+```
-- 
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