diff --git a/README.md b/README.md
index 952d9bf3..681ae280 100644
--- a/README.md
+++ b/README.md
@@ -26,7 +26,7 @@ Features
 * Freely pass Rust variables/constants into a script via an external [`Scope`](https://schungx.github.io/rhai/rust/scope.html).
 * Easily [call a script-defined function](https://schungx.github.io/rhai/engine/call-fn.html) from Rust.
 * Fairly low compile-time overhead.
-* Fairly efficient evaluation (1 million iterations in 0.25 sec on a single core, 2.3 GHz Linux VM).
+* Fairly efficient evaluation (1 million iterations in 0.4 sec on a single core, 2.3 GHz Linux VM).
 * Relatively little `unsafe` code (yes there are some for performance reasons, and most `unsafe` code is limited to
   one single source file, all with names starting with `"unsafe_"`).
 * Re-entrant scripting engine can be made `Send + Sync` (via the [`sync`] feature).
diff --git a/doc/src/about/features.md b/doc/src/about/features.md
index c012353a..0768115f 100644
--- a/doc/src/about/features.md
+++ b/doc/src/about/features.md
@@ -22,7 +22,7 @@ Fast
 
 * Fairly low compile-time overhead.
 
-* Fairly efficient evaluation (1 million iterations in 0.25 sec on a single core, 2.3 GHz Linux VM).
+* Fairly efficient evaluation (1 million iterations in 0.4 sec on a single core, 2.3 GHz Linux VM).
 
 * Scripts are [optimized][script optimization] (useful for template-based machine-generated scripts) for repeated evaluations.
 
diff --git a/src/error.rs b/src/error.rs
index 58423ef9..61f2c58f 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -49,7 +49,7 @@ impl fmt::Display for LexError {
                 "Length of string literal exceeds the maximum limit ({})",
                 max
             ),
-            Self::ImproperSymbol(s) => write!(f, "{}", s),
+            Self::ImproperSymbol(s) => f.write_str(s),
         }
     }
 }
@@ -185,18 +185,16 @@ impl fmt::Display for ParseErrorType {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
             Self::BadInput(s) | ParseErrorType::MalformedCallExpr(s) => {
-                write!(f, "{}", if s.is_empty() { self.desc() } else { s })
+                f.write_str(if s.is_empty() { self.desc() } else { s })
             }
             Self::ForbiddenConstantExpr(s) => {
                 write!(f, "Expecting a constant to assign to '{}'", s)
             }
             Self::UnknownOperator(s) => write!(f, "{}: '{}'", self.desc(), s),
 
-            Self::MalformedIndexExpr(s) => {
-                write!(f, "{}", if s.is_empty() { self.desc() } else { s })
-            }
+            Self::MalformedIndexExpr(s) => f.write_str(if s.is_empty() { self.desc() } else { s }),
 
-            Self::MalformedInExpr(s) => write!(f, "{}", if s.is_empty() { self.desc() } else { s }),
+            Self::MalformedInExpr(s) => f.write_str(if s.is_empty() { self.desc() } else { s }),
 
             Self::DuplicatedProperty(s) => {
                 write!(f, "Duplicated property '{}' for object map literal", s)
@@ -222,12 +220,12 @@ impl fmt::Display for ParseErrorType {
 
             Self::MissingToken(token, s) => write!(f, "Expecting '{}' {}", token, s),
 
-            Self::AssignmentToConstant(s) if s.is_empty() => write!(f, "{}", self.desc()),
+            Self::AssignmentToConstant(s) if s.is_empty() => f.write_str(self.desc()),
             Self::AssignmentToConstant(s) => write!(f, "Cannot assign to constant '{}'", s),
             Self::LiteralTooLarge(typ, max) => {
                 write!(f, "{} exceeds the maximum limit ({})", typ, max)
             }
-            _ => write!(f, "{}", self.desc()),
+            _ => f.write_str(self.desc()),
         }
     }
 }
diff --git a/src/module.rs b/src/module.rs
index 3cdeb711..c7198d83 100644
--- a/src/module.rs
+++ b/src/module.rs
@@ -876,12 +876,10 @@ impl Module {
                 .functions
                 .iter()
                 .filter(|(_, (_, _, _, v))| match v {
-                    CallableFunction::Pure(_)
-                    | CallableFunction::Method(_)
-                    | CallableFunction::Iterator(_) => true,
                     CallableFunction::Script(ref f) => {
                         filter(f.access, f.name.as_str(), f.params.len())
                     }
+                    _ => true,
                 })
                 .map(|(&k, v)| (k, v.clone())),
         );
@@ -897,10 +895,8 @@ impl Module {
     /// Filter out the functions, retaining only some based on a filter predicate.
     pub(crate) fn retain_functions(&mut self, filter: impl Fn(FnAccess, &str, usize) -> bool) {
         self.functions.retain(|_, (_, _, _, v)| match v {
-            CallableFunction::Pure(_)
-            | CallableFunction::Method(_)
-            | CallableFunction::Iterator(_) => true,
             CallableFunction::Script(ref f) => filter(f.access, f.name.as_str(), f.params.len()),
+            _ => true,
         });
 
         self.all_functions.clear();
diff --git a/src/result.rs b/src/result.rs
index 06bc80d3..d6351b25 100644
--- a/src/result.rs
+++ b/src/result.rs
@@ -197,16 +197,16 @@ impl fmt::Display for EvalAltResult {
             | Self::ErrorTooManyOperations(_)
             | Self::ErrorTooManyModules(_)
             | Self::ErrorStackOverflow(_)
-            | Self::ErrorTerminated(_) => write!(f, "{}", desc)?,
+            | Self::ErrorTerminated(_) => f.write_str(desc)?,
 
-            Self::ErrorRuntime(s, _) => write!(f, "{}", if s.is_empty() { desc } else { s })?,
+            Self::ErrorRuntime(s, _) => f.write_str(if s.is_empty() { desc } else { s })?,
 
             Self::ErrorAssignmentToConstant(s, _) => write!(f, "{}: '{}'", desc, s)?,
             Self::ErrorMismatchOutputType(s, _) => write!(f, "{}: {}", desc, s)?,
-            Self::ErrorArithmetic(s, _) => write!(f, "{}", s)?,
+            Self::ErrorArithmetic(s, _) => f.write_str(s)?,
 
-            Self::ErrorLoopBreak(_, _) => write!(f, "{}", desc)?,
-            Self::Return(_, _) => write!(f, "{}", desc)?,
+            Self::ErrorLoopBreak(_, _) => f.write_str(desc)?,
+            Self::Return(_, _) => f.write_str(desc)?,
 
             Self::ErrorBooleanArgMismatch(op, _) => {
                 write!(f, "{} operator expects boolean operands", op)?
@@ -215,7 +215,7 @@ impl fmt::Display for EvalAltResult {
             Self::ErrorArrayBounds(_, index, _) if *index < 0 => {
                 write!(f, "{}: {} < 0", desc, index)?
             }
-            Self::ErrorArrayBounds(0, _, _) => write!(f, "{}", desc)?,
+            Self::ErrorArrayBounds(0, _, _) => f.write_str(desc)?,
             Self::ErrorArrayBounds(1, index, _) => write!(
                 f,
                 "Array index {} is out of bounds: only one element in the array",
@@ -229,7 +229,7 @@ impl fmt::Display for EvalAltResult {
             Self::ErrorStringBounds(_, index, _) if *index < 0 => {
                 write!(f, "{}: {} < 0", desc, index)?
             }
-            Self::ErrorStringBounds(0, _, _) => write!(f, "{}", desc)?,
+            Self::ErrorStringBounds(0, _, _) => f.write_str(desc)?,
             Self::ErrorStringBounds(1, index, _) => write!(
                 f,
                 "String index {} is out of bounds: only one character in the string",