Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 42 insertions, 0 deletions

diff --git a/compiler/rustc_error_codes/src/error_codes/E0493.md b/compiler/rustc_error_codes/src/error_codes/E0493.md
new file mode 100644
index 000000000..e891129ef
--- /dev/null
+++ b/compiler/rustc_error_codes/src/error_codes/E0493.md
@@ -0,0 +1,42 @@
+A value with a custom `Drop` implementation may be dropped during const-eval.
+
+Erroneous code example:
+
+```compile_fail,E0493
+enum DropType {
+    A,
+}
+
+impl Drop for DropType {
+    fn drop(&mut self) {}
+}
+
+struct Foo {
+    field1: DropType,
+}
+
+static FOO: Foo = Foo { field1: (DropType::A, DropType::A).1 }; // error!
+```
+
+The problem here is that if the given type or one of its fields implements the
+`Drop` trait, this `Drop` implementation cannot be called within a const
+context since it may run arbitrary, non-const-checked code. To prevent this
+issue, ensure all values with a custom `Drop` implementation escape the
+initializer.
+
+```
+enum DropType {
+    A,
+}
+
+impl Drop for DropType {
+    fn drop(&mut self) {}
+}
+
+struct Foo {
+    field1: DropType,
+}
+
+static FOO: Foo = Foo { field1: DropType::A }; // We initialize all fields
+                                               // by hand.
+```