Remove unnecessary lifetimes of CRC digest (#129)

The CRC digest lifetime was too strict for using it in a method and it can be elided.

src/ser/flavors.rs

@@ -638,10 +638,10 @@ pub mod crc {
                     ///
                     /// When successful, this function returns the slice containing the
                     /// serialized and encoded message.
-                    pub fn [<to_slice_ $int>]<'a, 'b, T>(
-                        value: &'b T,
+                    pub fn [<to_slice_ $int>]<'a, T>(
+                        value: &T,
                         buf: &'a mut [u8],
-                        digest: Digest<'a, $int>,
+                        digest: Digest<'_, $int>,
                     ) -> Result<&'a mut [u8]>
                     where
                         T: Serialize + ?Sized,
@@ -653,9 +653,9 @@ pub mod crc {
                     /// data followed by a CRC. The CRC bytes are included in the output `Vec`.
                     #[cfg(feature = "heapless")]
                     #[cfg_attr(doc_cfg, doc(cfg(feature = "heapless")))]
-                    pub fn [<to_vec_ $int>]<'a, T, const B: usize>(
+                    pub fn [<to_vec_ $int>]<T, const B: usize>(
                         value: &T,
-                        digest: Digest<'a, $int>,
+                        digest: Digest<'_, $int>,
                     ) -> Result<heapless::Vec<u8, B>>
                     where
                         T: Serialize + ?Sized,
@@ -669,7 +669,7 @@ pub mod crc {
                     /// data followed by a CRC. The CRC bytes are included in the output `Vec`.
                     #[cfg(feature = "alloc")]
                     #[cfg_attr(doc_cfg, doc(cfg(feature = "alloc")))]
-                    pub fn [<to_allocvec_ $int>]<'a, T>(value: &T, digest: Digest<'a, $int>) -> Result<alloc::vec::Vec<u8>>
+                    pub fn [<to_allocvec_ $int>]<T>(value: &T, digest: Digest<'_, $int>) -> Result<alloc::vec::Vec<u8>>
                     where
                         T: Serialize + ?Sized,
                     {

src/ser/mod.rs

@@ -339,10 +339,10 @@ where
 #[cfg(feature = "use-crc")]
 #[cfg_attr(doc_cfg, doc(cfg(feature = "use-crc")))]
 #[inline]
-pub fn to_slice_crc32<'a, 'b, T>(
-    value: &'b T,
+pub fn to_slice_crc32<'a, T>(
+    value: &T,
     buf: &'a mut [u8],
-    digest: crc::Digest<'a, u32>,
+    digest: crc::Digest<'_, u32>,
 ) -> Result<&'a mut [u8]>
 where
     T: Serialize + ?Sized,
@@ -375,9 +375,9 @@ where
 #[cfg(all(feature = "use-crc", feature = "heapless"))]
 #[cfg_attr(doc_cfg, doc(cfg(all(feature = "use-crc", feature = "heapless"))))]
 #[inline]
-pub fn to_vec_crc32<'a, T, const B: usize>(
+pub fn to_vec_crc32<T, const B: usize>(
     value: &T,
-    digest: crc::Digest<'a, u32>,
+    digest: crc::Digest<'_, u32>,
 ) -> Result<heapless::Vec<u8, B>>
 where
     T: Serialize + ?Sized,
@@ -409,7 +409,7 @@ where
 #[cfg(all(feature = "use-crc", feature = "use-std"))]
 #[cfg_attr(doc_cfg, doc(cfg(all(feature = "use-crc", feature = "use-std"))))]
 #[inline]
-pub fn to_stdvec_crc32<'a, T>(value: &T, digest: crc::Digest<'a, u32>) -> Result<std::vec::Vec<u8>>
+pub fn to_stdvec_crc32<T>(value: &T, digest: crc::Digest<'_, u32>) -> Result<std::vec::Vec<u8>>
 where
     T: Serialize + ?Sized,
 {
@@ -440,9 +440,9 @@ where
 #[cfg(all(feature = "use-crc", feature = "alloc"))]
 #[cfg_attr(doc_cfg, doc(cfg(all(feature = "use-crc", feature = "alloc"))))]
 #[inline]
-pub fn to_allocvec_crc32<'a, T>(
+pub fn to_allocvec_crc32<T>(
     value: &T,
-    digest: crc::Digest<'a, u32>,
+    digest: crc::Digest<'_, u32>,
 ) -> Result<alloc::vec::Vec<u8>>
 where
     T: Serialize + ?Sized,

tests/crc.rs

@@ -58,3 +58,28 @@ fn test_crc_error() {
 
     assert_eq!(res, Err(postcard::Error::DeserializeBadCrc));
 }
+
+#[test]
+#[cfg(feature = "use-crc")]
+fn test_crc_in_method() {
+    use crc::{Crc, CRC_32_ISCSI};
+    use postcard::{to_slice_crc32, Result};
+    use serde::Serialize;
+
+    #[derive(Debug, Serialize)]
+    pub struct Thing {
+        value: u32,
+    }
+
+    impl Thing {
+        pub fn to_bytes<'a>(&self, buf: &'a mut [u8]) -> Result<&'a mut [u8]> {
+            let crc = Crc::<u32>::new(&CRC_32_ISCSI);
+            to_slice_crc32(self, buf, crc.digest())
+        }
+    }
+
+    let buffer = &mut [0u8; 5];
+    let thing = Thing { value: 42 };
+    let slice = thing.to_bytes(buffer).unwrap();
+    assert_eq!(slice, &[0x2A, 0xB7, 0xF5, 0x22, 0x19]);
+}