2 files changed, 40 insertions, 0 deletions
diff --git a/src/test/ui/const-generics/issue-86820.rs b/src/test/ui/const-generics/issue-86820.rs
new file mode 100644
index 00000000000..04650403c6b
--- /dev/null
+++ b/src/test/ui/const-generics/issue-86820.rs
@@ -0,0 +1,25 @@
+// Regression test for the ICE described in #86820.
+
+#![allow(unused,dead_code)]
+use std::ops::BitAnd;
+
+const C: fn() = || is_set();
+fn is_set() {
+    0xffu8.bit::<0>();
+}
+
+trait Bits {
+    fn bit<const I : u8>(self) -> bool;
+    //~^ NOTE: the const parameter `I` has type `usize`, but the declaration in trait `Bits::bit` has type `u8`
+}
+
+impl Bits for u8 {
+    fn bit<const I : usize>(self) -> bool {
+    //~^ ERROR: method `bit` has an incompatible const parameter type for trait [E0053]
+        let i = 1 << I;
+        let mask = u8::from(i);
+        mask & self == mask
+    }
+}
+
+fn main() {}
diff --git a/src/test/ui/const-generics/issue-86820.stderr b/src/test/ui/const-generics/issue-86820.stderr
new file mode 100644
index 00000000000..f4396f2f2b0
--- /dev/null
+++ b/src/test/ui/const-generics/issue-86820.stderr
@@ -0,0 +1,15 @@
+error[E0053]: method `bit` has an incompatible const parameter type for trait
+  --> $DIR/issue-86820.rs:17:18
+   |
+LL |     fn bit<const I : usize>(self) -> bool {
+   |                  ^
+   |
+note: the const parameter `I` has type `usize`, but the declaration in trait `Bits::bit` has type `u8`
+  --> $DIR/issue-86820.rs:12:18
+   |
+LL |     fn bit<const I : u8>(self) -> bool;
+   |                  ^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0053`.