Update Rust toolchain to 2023-11-06 (#2858)

Update to the latest Rust toolchain (2023-11-06).

The relevant changes are:
- rust-lang/rust#117507: this required changing
the import of `Span` from `rustc_span::source_map::Span` to
`rustc_span::Span`.
- rust-lang/rust#114208: this changed the data
field for the `OffsetOf` variant of `NullOp` from `List<FieldIdx>` to
`List<(VariantIdx, FieldIdx)>`, which required updating the relevant
code in `rvalue.rs`.
- rust-lang/rust#115626: the unchecked shift
operators have been separated from the `unchecked_math` feature, so this
required changing the feature annotation in
`tests/ui/should-panic-attribute/unexpected-failures/test.rs`
- Some rustc change (not sure which one) result in a line in
`tests/coverage/unreachable/variant/main.rs` getting optimized out. To
maintain what this test is testing, I changed the `match` to make it a
bit less-prone to optimization.
- A change in `cargo` (rust-lang/cargo#12779)
resulted in an update to Kani's workspace `Cargo.toml` when `cargo add`
is executed inside `tests/script-based-pre/build-cache-bin`. This is
apparently intended behavior, so I had to make the `exclude` in the
`Cargo.toml` more specific to make sure this doesn't happen (I tried
using a glob, but that didn't work, apparently because of
rust-lang/cargo#6009.

Resolves #2848 

By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache 2.0 and MIT licenses.

Cargo.toml

@@ -67,4 +67,6 @@ exclude = [
   "tests/slow",
   "tests/assess-scan-test-scaffold",
   "tests/script-based-pre",
+  "tests/script-based-pre/build-cache-bin/target/new_dep",
+  "tests/script-based-pre/build-cache-dirty/target/new_dep",
 ]

kani-compiler/src/codegen_cprover_gotoc/codegen/rvalue.rs

@@ -727,7 +727,7 @@ impl<'tcx> GotocCtx<'tcx> {
                         .with_size_of_annotation(self.codegen_ty(t)),
                     NullOp::AlignOf => Expr::int_constant(layout.align.abi.bytes(), Type::size_t()),
                     NullOp::OffsetOf(fields) => Expr::int_constant(
-                        layout.offset_of_subfield(self, fields.iter().map(|f| f.index())).bytes(),
+                        layout.offset_of_subfield(self, fields.iter()).bytes(),
                         Type::size_t(),
                     ),
                 }

kani-compiler/src/codegen_cprover_gotoc/context/goto_ctx.rs

@@ -31,7 +31,8 @@ use rustc_middle::ty::layout::{
     TyAndLayout,
 };
 use rustc_middle::ty::{self, Instance, Ty, TyCtxt};
-use rustc_span::source_map::{respan, Span};
+use rustc_span::source_map::respan;
+use rustc_span::Span;
 use rustc_target::abi::call::FnAbi;
 use rustc_target::abi::{HasDataLayout, TargetDataLayout};
 

rust-toolchain.toml

@@ -2,5 +2,5 @@
 # SPDX-License-Identifier: Apache-2.0 OR MIT
 
 [toolchain]
-channel = "nightly-2023-10-31"
+channel = "nightly-2023-11-06"
 components = ["llvm-tools-preview", "rustc-dev", "rust-src", "rustfmt"]

tests/coverage/unreachable/variant/expected

@@ -1,4 +1,4 @@
-coverage/unreachable/variant/main.rs, 15, FULL
+coverage/unreachable/variant/main.rs, 15, PARTIAL
 coverage/unreachable/variant/main.rs, 16, NONE
 coverage/unreachable/variant/main.rs, 17, NONE
 coverage/unreachable/variant/main.rs, 18, FULL

tests/coverage/unreachable/variant/main.rs

@@ -16,9 +16,9 @@ fn print_direction(dir: Direction) {
         Direction::Up => println!("Going up!"),
         Direction::Down => println!("Going down!"),
         Direction::Left => println!("Going left!"),
-        Direction::Right => println!("Going right!"),
+        Direction::Right if 1 == 1 => println!("Going right!"),
         // This part is unreachable since we cover all variants in the match.
-        _ => {}
+        _ => println!("Not going anywhere!"),
     }
 }
 

tests/ui/should-panic-attribute/unexpected-failures/test.rs

@@ -3,7 +3,7 @@
 
 //! Checks that verfication fails when `#[kani::should_panic]` is used but not
 //! all failures encountered are panics.
-#![feature(unchecked_math)]
+#![feature(unchecked_shifts)]
 
 fn trigger_overflow() {
     let x: u32 = kani::any();