Move all compile-fail tests to ui tests

The update-references.sh script makes these much easier to update in
bulk compared to compile-fail tests.

test_suite/tests/ui/transparent/at_most_one.rs

@@ -0,0 +1,19 @@
+// Copyright 2018 Serde Developers
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)]
+#[serde(transparent)]
+struct S {
+    a: u8,
+    b: u8,
+}
+
+fn main() {}

test_suite/tests/ui/transparent/at_most_one.stderr

@@ -0,0 +1,8 @@
+error: #[serde(transparent)] requires struct to have at most one transparent field
+  --> $DIR/at_most_one.rs:12:10
+   |
+12 | #[derive(Serialize)]
+   |          ^^^^^^^^^
+
+error: aborting due to previous error
+

test_suite/tests/ui/transparent/de_at_least_one.rs

@@ -0,0 +1,21 @@
+// Copyright 2018 Serde Developers
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Deserialize)]
+#[serde(transparent)]
+struct S {
+    #[serde(skip)]
+    a: u8,
+    #[serde(default)]
+    b: u8,
+}
+
+fn main() {}

test_suite/tests/ui/transparent/de_at_least_one.stderr

@@ -0,0 +1,8 @@
+error: #[serde(transparent)] requires at least one field that is neither skipped nor has a default
+  --> $DIR/de_at_least_one.rs:12:10
+   |
+12 | #[derive(Deserialize)]
+   |          ^^^^^^^^^^^
+
+error: aborting due to previous error
+

test_suite/tests/ui/transparent/ser_at_least_one.rs

@@ -0,0 +1,19 @@
+// Copyright 2018 Serde Developers
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)]
+#[serde(transparent)]
+struct S {
+    #[serde(skip)]
+    a: u8,
+}
+
+fn main() {}

test_suite/tests/ui/transparent/ser_at_least_one.stderr

@@ -0,0 +1,8 @@
+error: #[serde(transparent)] requires at least one field that is not skipped
+  --> $DIR/ser_at_least_one.rs:12:10
+   |
+12 | #[derive(Serialize)]
+   |          ^^^^^^^^^
+
+error: aborting due to previous error
+