Upgrade to Rust 1.42 (#8836)

* Upgrade to Rust 1.42

* deref

* parens

Co-authored-by: Trent Nelson <trent@solana.com>

ci/docker-rust-nightly/Dockerfile

@@ -1,4 +1,4 @@
-FROM solanalabs/rust:1.41.1
+FROM solanalabs/rust:1.42.0
 ARG date
 
 RUN set -x \

ci/docker-rust-nightly/README.md

@@ -15,6 +15,8 @@ To update the pinned version:
 1. Run `ci/docker-rust-nightly/build.sh` to rebuild the nightly image locally,
    or potentially `ci/docker-rust-nightly/build.sh YYYY-MM-DD` if there's a
    specific YYYY-MM-DD that is desired (default is today's build).
+   Check https://rust-lang.github.io/rustup-components-history/ for build
+   status
 1. Update `ci/rust-version.sh` to reflect the new nightly `YYY-MM-DD`
 1. Run `SOLANA_DOCKER_RUN_NOSETUID=1 ci/docker-run.sh --nopull solanalabs/rust-nightly:YYYY-MM-DD ci/test-coverage.sh`
    to confirm the new nightly image builds.  Fix any issues as needed

ci/docker-rust/Dockerfile

@@ -1,6 +1,6 @@
 # Note: when the rust version is changed also modify
 # ci/rust-version.sh to pick up the new image tag
-FROM rust:1.41.1
+FROM rust:1.42.0
 
 # Add Google Protocol Buffers for Libra's metrics library.
 ENV PROTOC_VERSION 3.8.0

ci/rust-version.sh

@@ -16,13 +16,13 @@
 if [[ -n $RUST_STABLE_VERSION ]]; then
   stable_version="$RUST_STABLE_VERSION"
 else
-  stable_version=1.41.1
+  stable_version=1.42.0
 fi
 
 if [[ -n $RUST_NIGHTLY_VERSION ]]; then
   nightly_version="$RUST_NIGHTLY_VERSION"
 else
-  nightly_version=2020-02-27
+  nightly_version=2020-03-12
 fi
 
 

ledger/src/blockstore.rs

@@ -3947,7 +3947,7 @@ pub mod tests {
                     .flat_map(|k| {
                         let begin = k * gap + 1;
                         let end = (k + 1) * gap;
-                        (begin..end)
+                        begin..end
                     })
                     .collect();
                 assert_eq!(

runtime/src/bank.rs

@@ -1005,7 +1005,7 @@ impl Bank {
         let results = self
             .rc
             .accounts
-            .lock_accounts(txs, iteration_order.as_ref().map(|v| v.as_slice()));
+            .lock_accounts(txs, iteration_order.as_deref());
         TransactionBatch::new(results, &self, txs, iteration_order)
     }
 

runtime/src/transaction_batch.rs

@@ -39,7 +39,7 @@ impl<'a, 'b> TransactionBatch<'a, 'b> {
     }
 
     pub fn iteration_order(&self) -> Option<&[usize]> {
-        self.iteration_order.as_ref().map(|v| v.as_slice())
+        self.iteration_order.as_deref()
     }
     pub fn bank(&self) -> &Bank {
         self.bank