Update toolchain to 10/25 (#3648)

Culprit PR: rust-lang/rust#131985

The automatic PR failed because the culprit PR removed the
`host_param_index` field that we used in the `contract_host_param`
function. We needed the `contract_host_param` function in the first
place because previously, Rust would add a `<const HOST: bool>`
parameter to a function's `GenericArgs` to handle trait constness (c.f.
#3258). The culprit PR [removed that
argument](https://github.com/rust-lang/rust/pull/131985/files#diff-0a61b538a3cec072c76fecae4635af6a12ec3256860029ac70549c2aa53ab394L1527),
so our logic to find and remove this parameter during stubbing is no
longer necessary.

Resolves #3645

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

kani-compiler/src/kani_middle/stubbing/mod.rs

@@ -37,24 +37,6 @@ pub fn harness_stub_map(
     stub_pairs
 }
 
-/// Retrieve the index of the host parameter if old definition has one, but not the new definition.
-///
-/// This is to allow constant functions to be stubbed by non-constant functions when the
-/// `effect` feature is on.
-///
-/// Note that the opposite is not supported today, but users should be able to change their stubs.
-///
-/// Note that this has no effect at runtime.
-pub fn contract_host_param(tcx: TyCtxt, old_def: FnDef, new_def: FnDef) -> Option<usize> {
-    let old_generics = tcx.generics_of(rustc_internal::internal(tcx, old_def.def_id()));
-    let new_generics = tcx.generics_of(rustc_internal::internal(tcx, new_def.def_id()));
-    if old_generics.host_effect_index.is_some() && new_generics.host_effect_index.is_none() {
-        old_generics.host_effect_index
-    } else {
-        None
-    }
-}
-
 /// Checks whether the stub is compatible with the original function/method: do
 /// the arities and types (of the parameters and return values) match up? This
 /// does **NOT** check whether the type variables are constrained to implement
@@ -81,15 +63,12 @@ pub fn check_compatibility(tcx: TyCtxt, old_def: FnDef, new_def: FnDef) -> Resul
     let new_def_id = rustc_internal::internal(tcx, new_def.def_id());
     let old_ty = rustc_internal::stable(tcx.type_of(old_def_id)).value;
     let new_ty = rustc_internal::stable(tcx.type_of(new_def_id)).value;
-    let TyKind::RigidTy(RigidTy::FnDef(_, mut old_args)) = old_ty.kind() else {
+    let TyKind::RigidTy(RigidTy::FnDef(_, old_args)) = old_ty.kind() else {
         unreachable!("Expected function, but found {old_ty}")
     };
     let TyKind::RigidTy(RigidTy::FnDef(_, new_args)) = new_ty.kind() else {
         unreachable!("Expected function, but found {new_ty}")
     };
-    if let Some(idx) = contract_host_param(tcx, old_def, new_def) {
-        old_args.0.remove(idx);
-    }
 
     // TODO: We should check for the parameter type too or replacement will fail.
     if old_args.0.len() != new_args.0.len() {

kani-compiler/src/kani_middle/transform/stubs.rs

@@ -3,7 +3,7 @@
 //! This module contains code related to the MIR-to-MIR pass that performs the
 //! stubbing of functions and methods.
 use crate::kani_middle::codegen_units::Stubs;
-use crate::kani_middle::stubbing::{contract_host_param, validate_stub_const};
+use crate::kani_middle::stubbing::validate_stub_const;
 use crate::kani_middle::transform::body::{MutMirVisitor, MutableBody};
 use crate::kani_middle::transform::{TransformPass, TransformationType};
 use crate::kani_queries::QueryDb;
@@ -46,12 +46,8 @@ impl TransformPass for FnStubPass {
     fn transform(&mut self, tcx: TyCtxt, body: Body, instance: Instance) -> (bool, Body) {
         trace!(function=?instance.name(), "transform");
         let ty = instance.ty();
-        if let TyKind::RigidTy(RigidTy::FnDef(fn_def, mut args)) = ty.kind() {
+        if let TyKind::RigidTy(RigidTy::FnDef(fn_def, args)) = ty.kind() {
             if let Some(replace) = self.stubs.get(&fn_def) {
-                if let Some(idx) = contract_host_param(tcx, fn_def, *replace) {
-                    debug!(?idx, "FnStubPass::transform remove_host_param");
-                    args.0.remove(idx);
-                }
                 let new_instance = Instance::resolve(*replace, &args).unwrap();
                 debug!(from=?instance.name(), to=?new_instance.name(), "FnStubPass::transform");
                 if let Some(body) = FnStubValidator::validate(tcx, (fn_def, *replace), new_instance)

rust-toolchain.toml

@@ -2,5 +2,5 @@
 # SPDX-License-Identifier: Apache-2.0 OR MIT
 
 [toolchain]
-channel = "nightly-2024-10-24"
+channel = "nightly-2024-10-25"
 components = ["llvm-tools", "rustc-dev", "rust-src", "rustfmt"]