From 5702e0289f7d19f0ea133d43da7dcd7cbfc5b557 Mon Sep 17 00:00:00 2001
From: Gary Guo <gary@garyguo.net>
Date: Mon, 6 Jul 2020 20:42:19 +0100
Subject: [PATCH 1/2] Only allow `repr(i128/u128)` on enum

---
 src/librustc_passes/check_attr.rs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/librustc_passes/check_attr.rs b/src/librustc_passes/check_attr.rs
index ef84f251390..fee63b1ee52 100644
--- a/src/librustc_passes/check_attr.rs
+++ b/src/librustc_passes/check_attr.rs
@@ -292,6 +292,8 @@ fn check_repr(
                 | sym::u32
                 | sym::i64
                 | sym::u64
+                | sym::i128
+                | sym::u128
                 | sym::isize
                 | sym::usize => {
                     int_reprs += 1;

From 97867bbe5cd09df7754864c826f58d3029f4422e Mon Sep 17 00:00:00 2001
From: Gary Guo <gary@garyguo.net>
Date: Mon, 6 Jul 2020 21:04:54 +0100
Subject: [PATCH 2/2] Add UI test for issue 74082

---
 src/test/ui/issues/issue-74082.rs     |  9 +++++++++
 src/test/ui/issues/issue-74082.stderr | 19 +++++++++++++++++++
 2 files changed, 28 insertions(+)
 create mode 100644 src/test/ui/issues/issue-74082.rs
 create mode 100644 src/test/ui/issues/issue-74082.stderr

diff --git a/src/test/ui/issues/issue-74082.rs b/src/test/ui/issues/issue-74082.rs
new file mode 100644
index 00000000000..982f8ef0253
--- /dev/null
+++ b/src/test/ui/issues/issue-74082.rs
@@ -0,0 +1,9 @@
+#![allow(dead_code)]
+
+#[repr(i128)] //~ ERROR: attribute should be applied to enum
+struct Foo;
+
+#[repr(u128)] //~ ERROR: attribute should be applied to enum
+struct Bar;
+
+fn main() {}
diff --git a/src/test/ui/issues/issue-74082.stderr b/src/test/ui/issues/issue-74082.stderr
new file mode 100644
index 00000000000..08fe415513d
--- /dev/null
+++ b/src/test/ui/issues/issue-74082.stderr
@@ -0,0 +1,19 @@
+error[E0517]: attribute should be applied to enum
+  --> $DIR/issue-74082.rs:3:8
+   |
+LL | #[repr(i128)]
+   |        ^^^^
+LL | struct Foo;
+   | ----------- not an enum
+
+error[E0517]: attribute should be applied to enum
+  --> $DIR/issue-74082.rs:6:8
+   |
+LL | #[repr(u128)]
+   |        ^^^^
+LL | struct Bar;
+   | ----------- not an enum
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0517`.