diff --git a/README.md b/README.md
index 2d7b33c..ba6a853 100644
--- a/README.md
+++ b/README.md
@@ -77,7 +77,7 @@ cat tests/test_reduced.c
 
 ```sh
 # Ubuntu 20.04
-sudo apt install -y make cmake python3 csmith libcsmith-dev creduce
+sudo apt install -y build-essential clang make cmake python3 csmith libcsmith-dev creduce
 ```
 
 ### Run
diff --git a/rust-toolchain b/rust-toolchain
index 373aea9..bb120e8 100644
--- a/rust-toolchain
+++ b/rust-toolchain
@@ -1 +1 @@
-1.57.0
+1.59.0
diff --git a/src/asm/write_asm.rs b/src/asm/write_asm.rs
index c64b6b8..4b61735 100644
--- a/src/asm/write_asm.rs
+++ b/src/asm/write_asm.rs
@@ -272,8 +272,7 @@ impl WriteString for RType {
                         "w"
                     } else {
                         "l"
-                    }
-                    .to_string(),
+                    },
                     if *is_signed { "" } else { "u" },
                     float_data_size.write_string()
                 )
@@ -292,8 +291,7 @@ impl WriteString for RType {
                         "w"
                     } else {
                         "l"
-                    }
-                    .to_string(),
+                    },
                     if *is_signed { "" } else { "u" }
                 )
             }
diff --git a/src/ir/dtype.rs b/src/ir/dtype.rs
index 948ffab..a83861d 100644
--- a/src/ir/dtype.rs
+++ b/src/ir/dtype.rs
@@ -881,6 +881,7 @@ impl Dtype {
         }
     }
 
+    #[must_use]
     pub fn set_const(self, is_const: bool) -> Self {
         match self {
             Self::Unit { .. } => Self::Unit { is_const },
@@ -998,6 +999,7 @@ impl Dtype {
         }
     }
 
+    #[must_use]
     pub fn set_signed(self, is_signed: bool) -> Self {
         match self {
             Self::Int {
diff --git a/src/ir/interp.rs b/src/ir/interp.rs
index 1d1bfeb..078166d 100644
--- a/src/ir/interp.rs
+++ b/src/ir/interp.rs
@@ -1037,12 +1037,11 @@ impl Byte {
                 let padding = std::cmp::max(inner_size, inner_align) - inner_size;
                 values
                     .iter()
-                    .map(|v| {
+                    .flat_map(|v| {
                         let mut result = Self::value_to_bytes(v, structs);
                         result.extend(iter::repeat(Byte::Undef).take(padding));
                         result
                     })
-                    .flatten()
                     .collect()
             }
             Value::Struct { name, fields } => {
diff --git a/src/ir/mod.rs b/src/ir/mod.rs
index 38e2d43..8a1872f 100644
--- a/src/ir/mod.rs
+++ b/src/ir/mod.rs
@@ -740,6 +740,7 @@ impl Constant {
         matches!(self, Self::Undef { .. })
     }
 
+    #[must_use]
     pub fn typecast(self, target_dtype: Dtype) -> Self {
         if self.dtype() == target_dtype {
             return self;
diff --git a/src/ir/write_ir.rs b/src/ir/write_ir.rs
index 09226d7..454d075 100644
--- a/src/ir/write_ir.rs
+++ b/src/ir/write_ir.rs
@@ -28,7 +28,7 @@ impl WriteLine for TranslationUnit {
                             } else {
                                 "%anon"
                             },
-                            f.deref().to_string()
+                            f.deref()
                         )
                     })
                     .collect::<Vec<_>>()