Add test for issue 151048

Author: mu001999

tests/ui/const-generics/mgca/tuple_expr_arg_bad-issue-151048.rs

@@ -0,0 +1,8 @@
+#![feature(min_generic_const_args)]
+#![expect(incomplete_features)]
+
+struct Y {
+    stuff: [u8; { ([1, 2], 3, [4, 5]) }], //~ ERROR expected `usize`, found const tuple
+}
+
+fn main() {}

tests/ui/const-generics/mgca/tuple_expr_arg_bad-issue-151048.stderr

@@ -0,0 +1,8 @@
+error: expected `usize`, found const tuple
+  --> $DIR/tuple_expr_arg_bad-issue-151048.rs:5:19
+   |
+LL |     stuff: [u8; { ([1, 2], 3, [4, 5]) }],
+   |                   ^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+