Add ui test of duplicate generics in remote derive

test_suite/tests/ui/remote/double_generic.rs

@@ -0,0 +1,17 @@
+use serde_derive::{Deserialize, Serialize};
+
+mod remote {
+    pub struct Struct<T, U> {
+        pub t: T,
+        pub u: U,
+    }
+}
+
+#[derive(Serialize, Deserialize)]
+#[serde(remote = "remote::StructGeneric<u8>")]
+struct StructDef<U> {
+    t: u8,
+    u: U,
+}
+
+fn main() {}

test_suite/tests/ui/remote/double_generic.stderr

@@ -0,0 +1,52 @@
+error: expected one of `:`, `@`, or `|`, found `>`
+  --> tests/ui/remote/double_generic.rs:12:19
+   |
+12 | struct StructDef<U> {
+   |                   ^ expected one of `:`, `@`, or `|`
+
+error: expected one of `!`, `)`, `,`, or `::`, found `<`
+  --> tests/ui/remote/double_generic.rs:12:17
+   |
+11 | #[serde(remote = "remote::StructGeneric<u8>")]
+   |                                             -
+   |                                             |
+   |                                             expected one of `!`, `)`, `,`, or `::`
+   |                                             help: missing `,`
+12 | struct StructDef<U> {
+   |                 ^ unexpected token
+
+error: proc-macro derive produced unparseable tokens
+  --> tests/ui/remote/double_generic.rs:10:10
+   |
+10 | #[derive(Serialize, Deserialize)]
+   |          ^^^^^^^^^
+
+error: expected one of `!`, `+`, `,`, `::`, or `>`, found `<`
+  --> tests/ui/remote/double_generic.rs:12:17
+   |
+10 | #[derive(Serialize, Deserialize)]
+   |                     -----------
+   |                     |
+   |                     while parsing this item list starting here
+   |                     the item list ends here
+11 | #[serde(remote = "remote::StructGeneric<u8>")]
+   |                                             - expected one of `!`, `+`, `,`, `::`, or `>`
+12 | struct StructDef<U> {
+   |                 ^ unexpected token
+   |
+help: you might have meant to end the type parameters here
+   |
+11 | #[serde(remote = "remote::StructGeneric<u8>">)]
+   |                                             +
+
+error: proc-macro derive produced unparseable tokens
+  --> tests/ui/remote/double_generic.rs:10:21
+   |
+10 | #[derive(Serialize, Deserialize)]
+   |                     ^^^^^^^^^^^
+
+error[E0412]: cannot find type `StructGeneric` in module `remote`
+  --> tests/ui/remote/double_generic.rs:11:18
+   |
+11 | #[serde(remote = "remote::StructGeneric<u8>")]
+   |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^ not found in `remote`