add adt_expr_unit_enum_extra-field test

Author: Shourya742

tests/ui/const-generics/mgca/adt_expr_unit_enum_extra_field.rs

@@ -0,0 +1,13 @@
+#![feature(min_generic_const_args, adt_const_params)]
+
+#[derive(Eq, PartialEq, std::marker::ConstParamTy)]
+enum E {
+    S {}
+}
+
+fn foo<const N: E>() {}
+
+fn main() {
+    E::S { x: const { 1 } };
+        //~^ ERROR variant `E::S` has no field named `x` [E0559]
+}

tests/ui/const-generics/mgca/adt_expr_unit_enum_extra_field.stderr

@@ -0,0 +1,11 @@
+error[E0559]: variant `E::S` has no field named `x`
+  --> $DIR/adt_expr_unit_enum_extra_field.rs:11:12
+   |
+LL |     E::S { x: const { 1 } };
+   |            ^ `E::S` does not have this field
+   |
+   = note: all struct fields are already assigned
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0559`.