Fix compiler warnings.

Author: vecchiot-aws

compiler/rustc_codegen_llvm/src/gotoc/cbmc/goto_program/expr.rs

@@ -710,7 +710,7 @@ impl Expr {
     /// e.g. when extracting the values out of an existing struct expr (see transformer.rs)
     pub fn struct_expr_from_padded_values(
         typ: Type,
-        mut values: Vec<Expr>,
+        values: Vec<Expr>,
         symbol_table: &SymbolTable,
     ) -> Self {
         assert!(

compiler/rustc_codegen_llvm/src/gotoc/cbmc/goto_program/symtab_transformer/identity_transformer.rs

@@ -1,11 +1,8 @@
 // Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
 // SPDX-License-Identifier: Apache-2.0 OR MIT
 
-use super::super::{
-    DatatypeComponent, Expr, Location, Stmt, Symbol, SymbolTable, SymbolValues, Type,
-};
+use super::super::SymbolTable;
 use super::Transformer;
-use std::collections::{BTreeMap, HashSet};
 
 /// Struct for performing the identity transformation on a symbol table.
 /// Mainly used as a demo/for testing.

compiler/rustc_codegen_llvm/src/gotoc/cbmc/goto_program/symtab_transformer/mod.rs

@@ -6,6 +6,5 @@ mod identity_transformer;
 mod passes;
 mod transformer;
 
-use identity_transformer::IdentityTransformer;
 pub use passes::do_passes;
 use transformer::Transformer;

compiler/rustc_codegen_llvm/src/gotoc/cbmc/goto_program/symtab_transformer/transformer.rs

@@ -5,9 +5,8 @@ use super::super::{
     BinaryOperand, CIntType, DatatypeComponent, Expr, ExprValue, Location, Parameter, SelfOperand,
     Stmt, StmtBody, SwitchCase, Symbol, SymbolTable, SymbolValues, Type, UnaryOperand,
 };
-use crate::btree_map;
 use num::bigint::BigInt;
-use std::collections::{BTreeMap, HashSet};
+use rustc_data_structures::fx::FxHashSet;
 
 /// The `Transformer` trait is a visitor pattern for the `SymbolTable`.
 /// To use it, you just need to implement the three symbol table accessor methods,
@@ -709,7 +708,7 @@ pub trait Transformer: Sized {
     fn transform_symbol_table(mut self, orig_symtab: &SymbolTable) -> SymbolTable {
         self.preprocess();
 
-        let mut added: HashSet<String> = HashSet::new();
+        let mut added: FxHashSet<String> = FxHashSet::default();
 
         // New symbol tables come with some items in them by default. Skip over those.
         for (name, _symbol) in self.symbol_table().iter() {