Add impls for serde_json and rmp-serde

Cargo.toml

@@ -28,6 +28,8 @@ numpy = { version = "0.21", optional = true }
 pyo3 = { version = ">=0.21", optional = true }
 uuid = { version = "1", optional = true }
 either = { version = ">=1", default-features = false, optional = true }
+serde_json = { version = ">=1", default-features = false, optional = true, features = ["std"] }
+rmp-serde = { version = ">=1", default-features = false, optional = true }
 
 [dev-dependencies]
 trybuild = { version = "1.0", features = ["diff"] }
@@ -53,6 +55,12 @@ uuid = ["dep:uuid"]
 # Provides `Transient` implementations for `either` types
 either = ["dep:either"]
 
+# Provides `Transient` implementations for `serde_json` types
+serde_json = ["dep:serde_json"]
+
+# Provides `Transient` implementations for `rmp_serde` types
+rmp-serde = ["dep:rmp-serde"]
+
 [workspace.lints.clippy]
 let_unit_value = "warn"
 manual_assert = "warn"

src/transient.rs

@@ -691,3 +691,18 @@ mod either_impls {
  type Transience = (Covariant<L>, Covariant<R>);
  }
 }
+
+#[cfg(feature = "serde_json")]
+mod serde_json_impls {
+ use serde_json::Error;
+
+ impl crate::Static for Error {}
+}
+
+#[cfg(feature = "rmp-serde")]
+mod rmp_serde_impls {
+ use rmp_serde::{decode, encode};
+
+ impl crate::Static for encode::Error {}
+ impl crate::Static for decode::Error {}
+}

tests/fail/invariance-bad-function.rs

@@ -11,7 +11,7 @@ unsafe impl<'a> Transient for S<'a> {
 
 // This function requires `long` to shorten its lifetime from 'b to 'a, and
 // should be *rejected* if the type is considered to be *invariant*.
-fn shrink<'a, 'b: 'a>(long: Box<S<'b>>) -> Box<dyn Any<Inv<'a>> + '_> {
+fn shrink<'a, 'b: 'a>(long: Box<S<'b>>) -> Box<dyn Any<Inv<'a>> + 'b> {
  long
 }
 

tests/fail/invariance-bad-function.stderr

@@ -1,7 +1,7 @@
 error: lifetime may not live long enough
  --> tests/fail/invariance-bad-function.rs:15:5
  |
-14 | fn shrink<'a, 'b: 'a>(long: Box<S<'b>>) -> Box<dyn Any<Inv<'a>> + '_> {
+14 | fn shrink<'a, 'b: 'a>(long: Box<S<'b>>) -> Box<dyn Any<Inv<'a>> + 'b> {
  | -- -- lifetime `'b` defined here
  | |
  | lifetime `'a` defined here