thiserror, docs, remove general Failure case (#9741)

automerge

sdk/src/sanitize.rs

@@ -1,11 +1,22 @@
-#[derive(PartialEq, Debug)]
+use thiserror::Error;
+
+#[derive(PartialEq, Debug, Error, Eq, Clone)]
 pub enum SanitizeError {
-    Failed,
+    #[error("index out of bounds")]
     IndexOutOfBounds,
-    ValueOutOfRange,
+    #[error("value out of bounds")]
+    ValueOutOfBounds,
+    #[error("invalid value")]
     InvalidValue,
 }
 
+/// Trait for sanitizing values and members of over the wire messages.
+/// Implementation should recursively decent through the data structure
+/// and sanitize all struct members and enum clauses.  Sanitize excludes
+/// signature verification checks, those are handled by another pass.
+/// Sanitize checks should include but are not limited too:
+///   * All index values are in range
+///   * All values are within their static max/min bounds
 pub trait Sanitize {
     fn sanitize(&self) -> Result<(), SanitizeError> {
         Ok(())