Normalize function signature in function casting check

src/librustc_typeck/check/cast.rs

@@ -536,7 +536,10 @@ impl<'a, 'tcx> CastCheck<'tcx> {
                 match self.expr_ty.kind {
                     ty::FnDef(..) => {
                         // Attempt a coercion to a fn pointer type.
-                        let f = self.expr_ty.fn_sig(fcx.tcx);
+                        let f = fcx.normalize_associated_types_in(
+                            self.expr.span,
+                            &self.expr_ty.fn_sig(fcx.tcx),
+                        );
                         let res = fcx.try_coerce(
                             self.expr,
                             self.expr_ty,

src/test/ui/issues/issue-54094.rs

@@ -0,0 +1,14 @@
+// check-pass
+trait Zoo {
+    type X;
+}
+
+impl Zoo for u16 {
+    type X = usize;
+}
+
+fn foo(abc: <u16 as Zoo>::X) {}
+
+fn main() {
+    let x: *const u8 = foo as _;
+}