fix #103783, fix ICE checking transmutability of NaughtyLenArray

src/test/ui/transmutability/arrays/issue-103783-array-length.rs

@@ -0,0 +1,24 @@
+#![crate_type = "lib"]
+#![feature(transmutability)]
+#![allow(dead_code)]
+
+mod assert {
+    use std::mem::{Assume, BikeshedIntrinsicFrom};
+    pub struct Context;
+
+    pub fn is_maybe_transmutable<Src, Dst>()
+    where
+        Dst: BikeshedIntrinsicFrom<
+            Src,
+            Context,
+            { Assume { alignment: true, lifetimes: true, safety: true, validity: true } },
+        >,
+    {
+    }
+}
+
+fn test() {
+    type NaughtyLenArray = [u32; 3.14159]; //~ ERROR mismatched types
+    type JustUnit = ();
+    assert::is_maybe_transmutable::<JustUnit, NaughtyLenArray>();
+}

src/test/ui/transmutability/arrays/issue-103783-array-length.stderr

@@ -0,0 +1,9 @@
+error[E0308]: mismatched types
+  --> $DIR/issue-103783-array-length.rs:21:34
+   |
+LL |     type NaughtyLenArray = [u32; 3.14159];
+   |                                  ^^^^^^^ expected `usize`, found floating-point number
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.