--- /dev/null
+// https://github.com/rust-lang/rust/issues/69228
+// Used to give bogus suggestion about T not being Sized.
+
+use std::mem::size_of;
+
+fn foo<T>() {
+ let _arr: [u8; size_of::<T>()];
+ //~^ ERROR generic parameters may not be used in const operations
+ //~| NOTE cannot perform const operation
+ //~| NOTE type parameters may not be used in const expressions
+}
+
+fn main() {}
--- /dev/null
+error: generic parameters may not be used in const operations
+ --> $DIR/size-of-t.rs:7:30
+ |
+LL | let _arr: [u8; size_of::<T>()];
+ | ^ cannot perform const operation using `T`
+ |
+ = note: type parameters may not be used in const expressions
+ = help: use `#![feature(generic_const_exprs)]` to allow generic const expressions
+
+error: aborting due to previous error
+