Update exhaustive matching to syn 1.0.90

serde_derive/src/bound.rs

@@ -184,9 +184,7 @@ pub fn with_bound(
 
                 syn::Type::Infer(_) | syn::Type::Never(_) | syn::Type::Verbatim(_) => {}
 
-                #[cfg(test)]
-                syn::Type::__TestExhaustive(_) => unimplemented!(),
-                #[cfg(not(test))]
+                #[cfg_attr(all(test, exhaustive), deny(non_exhaustive_omitted_patterns))]
                 _ => {}
             }
         }

serde_derive/src/internals/attr.rs

@@ -1912,9 +1912,7 @@ fn collect_lifetimes(ty: &syn::Type, out: &mut BTreeSet<syn::Lifetime>) {
         | syn::Type::Infer(_)
         | syn::Type::Verbatim(_) => {}
 
-        #[cfg(test)]
-        syn::Type::__TestExhaustive(_) => unimplemented!(),
-        #[cfg(not(test))]
+        #[cfg_attr(all(test, exhaustive), deny(non_exhaustive_omitted_patterns))]
         _ => {}
     }
 }

serde_derive/src/internals/receiver.rs

@@ -147,9 +147,7 @@ impl ReplaceReceiver<'_> {
 
             Type::Infer(_) | Type::Never(_) | Type::Verbatim(_) => {}
 
-            #[cfg(test)]
-            Type::__TestExhaustive(_) => unimplemented!(),
-            #[cfg(not(test))]
+            #[cfg_attr(all(test, exhaustive), deny(non_exhaustive_omitted_patterns))]
             _ => {}
         }
     }

serde_derive/src/lib.rs

@@ -60,6 +60,7 @@
     clippy::use_self,
     clippy::wildcard_imports
 )]
+#![cfg_attr(all(test, exhaustive), feature(non_exhaustive_omitted_patterns_lint))]
 
 #[macro_use]
 extern crate quote;