Refine inlining.

examples/custom_types.rs

@@ -36,6 +36,8 @@ fn main() -> Result<(), Box<EvalAltResult>> {
         type Item = i64;
         type IntoIter = std::vec::IntoIter<Self::Item>;
 
+        #[inline]
+        #[must_use]
         fn into_iter(self) -> Self::IntoIter {
             vec![self.x - 1, self.x, self.x + 1].into_iter()
         }

src/api/custom_syntax.rs

@@ -157,7 +157,6 @@ impl Deref for Expression<'_> {
     type Target = Expr;
 
     #[inline(always)]
-    #[must_use]
     fn deref(&self) -> &Self::Target {
         self.0
     }

src/api/definitions/mod.rs

@@ -77,6 +77,7 @@ pub struct DefinitionsConfig {
 
 impl Default for DefinitionsConfig {
     #[inline(always)]
+    #[must_use]
     fn default() -> Self {
         Self {
             write_headers: false,

src/api/limits.rs

@@ -75,6 +75,7 @@ impl Limits {
 
 impl Default for Limits {
     #[inline(always)]
+    #[must_use]
     fn default() -> Self {
         Self::new()
     }

src/ast/ast.rs

@@ -36,6 +36,7 @@ pub struct AST {
 
 impl Default for AST {
     #[inline(always)]
+    #[must_use]
     fn default() -> Self {
         Self::empty()
     }

src/ast/expr.rs

@@ -75,8 +75,8 @@ impl CustomExpr {
     /// Is this custom syntax self-terminated (i.e. no need for a semicolon terminator)?
     ///
     /// A self-terminated custom syntax always ends in `$block$`, `}` or `;`
-    #[must_use]
     #[inline(always)]
+    #[must_use]
     pub const fn is_self_terminated(&self) -> bool {
         self.self_terminated
     }
@@ -281,7 +281,6 @@ impl<F: Float> Deref for FloatWrapper<F> {
     type Target = F;
 
     #[inline(always)]
-    #[must_use]
     fn deref(&self) -> &Self::Target {
         &self.0
     }
@@ -290,7 +289,6 @@ impl<F: Float> Deref for FloatWrapper<F> {
 #[cfg(not(feature = "no_float"))]
 impl<F: Float> DerefMut for FloatWrapper<F> {
     #[inline(always)]
-    #[must_use]
     fn deref_mut(&mut self) -> &mut Self::Target {
         &mut self.0
     }
@@ -447,6 +445,7 @@ pub enum Expr {
 
 impl Default for Expr {
     #[inline(always)]
+    #[must_use]
     fn default() -> Self {
         Self::Unit(Position::NONE)
     }

src/ast/ident.rs

@@ -40,7 +40,6 @@ impl Deref for Ident {
     type Target = ImmutableString;
 
     #[inline(always)]
-    #[must_use]
     fn deref(&self) -> &Self::Target {
         &self.name
     }
@@ -48,7 +47,6 @@ impl Deref for Ident {
 
 impl DerefMut for Ident {
     #[inline(always)]
-    #[must_use]
     fn deref_mut(&mut self) -> &mut Self::Target {
         &mut self.name
     }

src/ast/namespace.rs

@@ -72,7 +72,6 @@ impl Deref for Namespace {
     type Target = StaticVec<Ident>;
 
     #[inline(always)]
-    #[must_use]
     fn deref(&self) -> &Self::Target {
         &self.path
     }
@@ -80,7 +79,6 @@ impl Deref for Namespace {
 
 impl DerefMut for Namespace {
     #[inline(always)]
-    #[must_use]
     fn deref_mut(&mut self) -> &mut Self::Target {
         &mut self.path
     }

src/ast/stmt.rs

@@ -209,6 +209,7 @@ impl IntoIterator for RangeCase {
     type IntoIter = Box<dyn Iterator<Item = Self::Item>>;
 
     #[inline(always)]
+    #[must_use]
     fn into_iter(self) -> Self::IntoIter {
         match self {
             Self::ExclusiveInt(r, ..) => Box::new(r),
@@ -426,7 +427,6 @@ impl Deref for StmtBlock {
     type Target = StmtBlockContainer;
 
     #[inline(always)]
-    #[must_use]
     fn deref(&self) -> &Self::Target {
         &self.block
     }
@@ -434,7 +434,6 @@ impl Deref for StmtBlock {
 
 impl DerefMut for StmtBlock {
     #[inline(always)]
-    #[must_use]
     fn deref_mut(&mut self) -> &mut Self::Target {
         &mut self.block
     }
@@ -607,6 +606,7 @@ pub enum Stmt {
 
 impl Default for Stmt {
     #[inline(always)]
+    #[must_use]
     fn default() -> Self {
         Self::Noop(Position::NONE)
     }

src/engine.rs

@@ -190,6 +190,7 @@ impl fmt::Debug for Engine {
 
 impl Default for Engine {
     #[inline(always)]
+    #[must_use]
     fn default() -> Self {
         Self::new()
     }

src/eval/debugger.rs

@@ -48,6 +48,7 @@ pub enum DebuggerCommand {
 
 impl Default for DebuggerCommand {
     #[inline(always)]
+    #[must_use]
     fn default() -> Self {
         Self::Continue
     }

src/eval/global_state.rs

@@ -316,7 +316,6 @@ impl IntoIterator for GlobalRuntimeState<'_> {
         std::iter::Rev<smallvec::IntoIter<[crate::Shared<crate::Module>; 3]>>,
     >;
 
-    #[inline]
     fn into_iter(self) -> Self::IntoIter {
         self.keys
             .into_iter()
@@ -333,10 +332,8 @@ impl<'a> IntoIterator for &'a GlobalRuntimeState<'_> {
         std::iter::Rev<std::slice::Iter<'a, crate::Shared<crate::Module>>>,
     >;
 
-    #[inline]
     fn into_iter(self) -> Self::IntoIter {
-        let x = self.keys.iter().rev().zip(self.modules.iter().rev());
-        x
+        self.keys.iter().rev().zip(self.modules.iter().rev())
     }
 }
 

src/eval/target.rs

@@ -399,7 +399,6 @@ impl Deref for Target<'_> {
     type Target = Dynamic;
 
     #[inline]
-    #[must_use]
     fn deref(&self) -> &Dynamic {
         match self {
             Self::RefMut(r) => r,
@@ -425,7 +424,6 @@ impl AsRef<Dynamic> for Target<'_> {
 
 impl DerefMut for Target<'_> {
     #[inline]
-    #[must_use]
     fn deref_mut(&mut self) -> &mut Dynamic {
         match self {
             Self::RefMut(r) => r,

src/func/func.rs

@@ -46,6 +46,7 @@ pub trait Func<ARGS, RET> {
     /// func(123, "hello")? == false;           // call the anonymous function
     /// # Ok(())
     /// # }
+    #[must_use]
     fn create_from_ast(self, ast: AST, entry_point: &str) -> Self::Output;
 
     /// Create a Rust closure from a script.
@@ -79,6 +80,7 @@ pub trait Func<ARGS, RET> {
     /// # Ok(())
     /// # }
     /// ```
+    #[must_use]
     fn create_from_script(self, script: &str, entry_point: &str) -> ParseResult<Self::Output>;
 }
 

src/func/hashing.rs

@@ -41,6 +41,7 @@ pub struct StraightHasher(u64);
 
 impl Hasher for StraightHasher {
     #[inline(always)]
+    #[must_use]
     fn finish(&self) -> u64 {
         self.0
     }
@@ -66,6 +67,7 @@ impl BuildHasher for StraightHasherBuilder {
     type Hasher = StraightHasher;
 
     #[inline(always)]
+    #[must_use]
     fn build_hasher(&self) -> Self::Hasher {
         StraightHasher(ALT_ZERO_HASH)
     }

src/func/register.rs

@@ -86,8 +86,11 @@ pub trait RegisterNativeFunction<ARGS, RET, RESULT> {
     /// _(metadata)_ Get the type name of this function's return value.
     /// Exported under the `metadata` feature only.
     #[cfg(feature = "metadata")]
+    #[inline(always)]
     #[must_use]
-    fn return_type_name() -> &'static str;
+    fn return_type_name() -> &'static str {
+        std::any::type_name::<RET>()
+    }
 }
 
 const EXPECT_ARGS: &str = "arguments";
@@ -138,7 +141,6 @@ macro_rules! def_register {
             #[inline(always)] fn param_types() -> Box<[TypeId]> { vec![$(TypeId::of::<$par>()),*].into_boxed_slice() }
             #[cfg(feature = "metadata")] #[inline(always)] fn param_names() -> Box<[&'static str]> { vec![$(std::any::type_name::<$param>()),*].into_boxed_slice() }
             #[cfg(feature = "metadata")] #[inline(always)] fn return_type() -> TypeId { TypeId::of::<RET>() }
-            #[cfg(feature = "metadata")] #[inline(always)] fn return_type_name() -> &'static str { std::any::type_name::<RET>() }
             #[inline(always)] fn into_callable_function(self) -> CallableFunction {
                 CallableFunction::$abi(Shared::new(move |_ctx: NativeCallContext, args: &mut FnCallArgs| {
                     // The arguments are assumed to be of the correct number and types!
@@ -164,7 +166,6 @@ macro_rules! def_register {
             #[inline(always)] fn param_types() -> Box<[TypeId]> { vec![$(TypeId::of::<$par>()),*].into_boxed_slice() }
             #[cfg(feature = "metadata")] #[inline(always)] fn param_names() -> Box<[&'static str]> { vec![$(std::any::type_name::<$param>()),*].into_boxed_slice() }
             #[cfg(feature = "metadata")] #[inline(always)] fn return_type() -> TypeId { TypeId::of::<RET>() }
-            #[cfg(feature = "metadata")] #[inline(always)] fn return_type_name() -> &'static str { std::any::type_name::<RET>() }
             #[inline(always)] fn into_callable_function(self) -> CallableFunction {
                 CallableFunction::$abi(Shared::new(move |ctx: NativeCallContext, args: &mut FnCallArgs| {
                     // The arguments are assumed to be of the correct number and types!

src/func/script.rs

@@ -251,13 +251,10 @@ impl Engine {
             // Then check sub-modules
             || self.global_sub_modules.values().any(|m| m.contains_qualified_fn(hash_script));
 
-        if !result {
-            if cache.filter.is_absent(hash_script) {
-                cache.filter.mark(hash_script);
-            } else {
+        if !result && !cache.filter.is_absent_and_set(hash_script) {
+            // Do not cache "one-hit wonders"
             cache.map.insert(hash_script, None);
         }
-        }
 
         result
     }

src/module/mod.rs

@@ -196,6 +196,7 @@ pub struct Module {
 
 impl Default for Module {
     #[inline(always)]
+    #[must_use]
     fn default() -> Self {
         Self::new()
     }

src/module/resolvers/collection.rs

@@ -42,7 +42,7 @@ impl ModuleResolversCollection {
     /// ```
     #[inline(always)]
     #[must_use]
-    pub fn new() -> Self {
+    pub const fn new() -> Self {
         Self(Vec::new())
     }
     /// Append a [module resolver][ModuleResolver] to the end.
@@ -112,6 +112,7 @@ impl IntoIterator for ModuleResolversCollection {
     type IntoIter = IntoIter<Box<dyn ModuleResolver>>;
 
     #[inline(always)]
+    #[must_use]
     fn into_iter(self) -> Self::IntoIter {
         self.0.into_iter()
     }

src/module/resolvers/file.rs

@@ -56,6 +56,7 @@ pub struct FileModuleResolver {
 
 impl Default for FileModuleResolver {
     #[inline(always)]
+    #[must_use]
     fn default() -> Self {
         Self::new()
     }

src/module/resolvers/stat.rs

@@ -134,6 +134,7 @@ impl IntoIterator for StaticModuleResolver {
     type IntoIter = IntoIter<SmartString, Shared<Module>>;
 
     #[inline(always)]
+    #[must_use]
     fn into_iter(self) -> Self::IntoIter {
         self.0.into_iter()
     }

src/optimizer.rs

@@ -38,6 +38,7 @@ pub enum OptimizationLevel {
 
 impl Default for OptimizationLevel {
     #[inline(always)]
+    #[must_use]
     fn default() -> Self {
         Self::Simple
     }

src/packages/mod.rs

@@ -45,11 +45,14 @@ pub use time_basic::BasicTimePackage;
 pub trait Package {
     /// Initialize the package.
     /// Functions should be registered into `module` here.
+    #[cold]
     fn init(module: &mut Module);
 
     /// Initialize the package with an [`Engine`].
     ///
     /// Perform tasks such as registering custom operators/syntax.
+    #[cold]
+    #[inline]
     #[allow(unused_variables)]
     fn init_engine(engine: &mut Engine) {}
 
@@ -65,6 +68,8 @@ pub trait Package {
     ///
     /// package.register_into_engine(&mut engine);
     /// ```
+    #[cold]
+    #[inline]
     fn register_into_engine(&self, engine: &mut Engine) -> &Self {
         Self::init_engine(engine);
         engine.register_global_module(self.as_shared_module());
@@ -84,6 +89,8 @@ pub trait Package {
     /// package.register_into_engine_as(&mut engine, "core");
     /// ```
     #[cfg(not(feature = "no_module"))]
+    #[cold]
+    #[inline]
     fn register_into_engine_as(&self, engine: &mut Engine, name: &str) -> &Self {
         Self::init_engine(engine);
         engine.register_static_module(name, self.as_shared_module());
@@ -133,7 +140,6 @@ macro_rules! def_package {
             fn as_shared_module(&self) -> $crate::Shared<$crate::Module> {
                 self.0.clone()
             }
-            #[inline]
             fn init($lib: &mut $crate::Module) {
                 $($(
                     $(#[$base_meta])* { <$base_pkg>::init($lib); }
@@ -141,7 +147,6 @@ macro_rules! def_package {
 
                 $block
             }
-            #[inline]
             fn init_engine(_engine: &mut $crate::Engine) {
                 $($(
                     $(#[$base_meta])* { <$base_pkg>::init_engine(_engine); }
@@ -156,6 +161,7 @@ macro_rules! def_package {
 
         impl Default for $package {
             #[inline(always)]
+            #[must_use]
             fn default() -> Self {
                 Self::new()
             }
@@ -193,12 +199,16 @@ macro_rules! def_package {
         }
 
         impl Default for $package {
+            #[inline(always)]
+            #[must_use]
             fn default() -> Self {
                 Self::new()
             }
         }
 
         impl $package {
+            #[inline]
+            #[must_use]
             pub fn new() -> Self {
                 let mut module = $root::Module::new();
                 <Self as $root::packages::Package>::init(&mut module);
@@ -229,12 +239,16 @@ macro_rules! def_package {
         }
 
         impl Default for $package {
+            #[inline(always)]
+            #[must_use]
             fn default() -> Self {
                 Self::new()
             }
         }
 
         impl $package {
+            #[inline]
+            #[must_use]
             pub fn new() -> Self {
                 let mut module = $root::Module::new();
                 <Self as $root::packages::Package>::init(&mut module);

src/parser.rs

@@ -110,7 +110,7 @@ impl fmt::Debug for ParseState<'_> {
 
 impl<'e> ParseState<'e> {
     /// Create a new [`ParseState`].
-    #[inline(always)]
+    #[inline]
     #[must_use]
     pub fn new(
         engine: &Engine,
@@ -183,7 +183,6 @@ impl<'e> ParseState<'e> {
     ///
     /// * `is_func_name`: `true` if the variable is actually the name of a function
     ///                   (in which case it will be converted into a function pointer).
-    #[inline]
     #[must_use]
     pub fn access_var(
         &mut self,
@@ -235,7 +234,6 @@ impl<'e> ParseState<'e> {
     ///
     /// Panics when called under `no_module`.
     #[cfg(not(feature = "no_module"))]
-    #[inline]
     #[must_use]
     pub fn find_module(&self, name: &str) -> Option<NonZeroUsize> {
         self.imports
@@ -258,7 +256,7 @@ impl<'e> ParseState<'e> {
 
     /// Get an interned property getter, creating one if it is not yet interned.
     #[cfg(not(feature = "no_object"))]
-    #[inline(always)]
+    #[inline]
     #[must_use]
     pub fn get_interned_getter(
         &mut self,
@@ -273,7 +271,7 @@ impl<'e> ParseState<'e> {
 
     /// Get an interned property setter, creating one if it is not yet interned.
     #[cfg(not(feature = "no_object"))]
-    #[inline(always)]
+    #[inline]
     #[must_use]
     pub fn get_interned_setter(
         &mut self,
@@ -313,7 +311,7 @@ struct ParseSettings {
 
 impl ParseSettings {
     /// Create a new `ParseSettings` with one higher expression level.
-    #[inline(always)]
+    #[inline]
     #[must_use]
     pub const fn level_up(&self) -> Self {
         Self {
@@ -417,7 +415,6 @@ impl Expr {
 }
 
 /// Make sure that the next expression is not a statement expression (i.e. wrapped in `{}`).
-#[inline]
 fn ensure_not_statement_expr(
     input: &mut TokenStream,
     type_name: &(impl ToString + ?Sized),
@@ -429,7 +426,6 @@ fn ensure_not_statement_expr(
 }
 
 /// Make sure that the next expression is not a mis-typed assignment (i.e. `a = b` instead of `a == b`).
-#[inline]
 fn ensure_not_assignment(input: &mut TokenStream) -> ParseResult<()> {
     match input.peek().expect(NEVER_ENDS) {
         (Token::Equals, pos) => Err(LexError::ImproperSymbol(
@@ -446,7 +442,6 @@ fn ensure_not_assignment(input: &mut TokenStream) -> ParseResult<()> {
 /// # Panics
 ///
 /// Panics if the next token is not the expected one.
-#[inline]
 fn eat_token(input: &mut TokenStream, expected_token: Token) -> Position {
     let (t, pos) = input.next().expect(NEVER_ENDS);
 
@@ -462,7 +457,6 @@ fn eat_token(input: &mut TokenStream, expected_token: Token) -> Position {
 }
 
 /// Match a particular [token][Token], consuming it if matched.
-#[inline]
 fn match_token(input: &mut TokenStream, token: Token) -> (bool, Position) {
     let (t, pos) = input.peek().expect(NEVER_ENDS);
     if *t == token {
@@ -473,7 +467,6 @@ fn match_token(input: &mut TokenStream, token: Token) -> (bool, Position) {
 }
 
 /// Parse a variable name.
-#[inline]
 fn parse_var_name(input: &mut TokenStream) -> ParseResult<(SmartString, Position)> {
     match input.next().expect(NEVER_ENDS) {
         // Variable name
@@ -491,7 +484,6 @@ fn parse_var_name(input: &mut TokenStream) -> ParseResult<(SmartString, Position
 
 /// Parse a symbol.
 #[cfg(not(feature = "no_custom_syntax"))]
-#[inline]
 fn parse_symbol(input: &mut TokenStream) -> ParseResult<(SmartString, Position)> {
     match input.next().expect(NEVER_ENDS) {
         // Symbol

src/tokenizer.rs

@@ -32,7 +32,7 @@ pub struct TokenizerControlBlock {
 
 impl TokenizerControlBlock {
     /// Create a new `TokenizerControlBlock`.
-    #[inline(always)]
+    #[inline]
     #[must_use]
     pub const fn new() -> Self {
         Self {
@@ -97,7 +97,7 @@ impl Position {
     /// # Panics
     ///
     /// Panics if `line` is zero.
-    #[inline(always)]
+    #[inline]
     #[must_use]
     pub const fn new(line: u16, position: u16) -> Self {
         assert!(line != 0, "line cannot be zero");
@@ -220,6 +220,7 @@ impl Position {
 
 impl Default for Position {
     #[inline(always)]
+    #[must_use]
     fn default() -> Self {
         Self::START
     }
@@ -299,6 +300,8 @@ pub struct Span {
 }
 
 impl Default for Span {
+    #[inline(always)]
+    #[must_use]
     fn default() -> Self {
         Self::NONE
     }
@@ -315,7 +318,7 @@ impl Span {
         Self { start, end }
     }
     /// Is this [`Span`] non-existent?
-    #[inline(always)]
+    #[inline]
     #[must_use]
     pub const fn is_none(&self) -> bool {
         self.start.is_none() && self.end.is_none()

src/types/dynamic.rs

@@ -153,7 +153,6 @@ impl<'d, T: Any + Clone> Deref for DynamicWriteLock<'d, T> {
     type Target = T;
 
     #[inline]
-    #[must_use]
     fn deref(&self) -> &Self::Target {
         match self.0 {
             DynamicWriteLockInner::Reference(ref reference) => *reference,
@@ -165,7 +164,6 @@ impl<'d, T: Any + Clone> Deref for DynamicWriteLock<'d, T> {
 
 impl<'d, T: Any + Clone> DerefMut for DynamicWriteLock<'d, T> {
     #[inline]
-    #[must_use]
     fn deref_mut(&mut self) -> &mut Self::Target {
         match self.0 {
             DynamicWriteLockInner::Reference(ref mut reference) => *reference,

src/types/immutable_string.rs

@@ -53,7 +53,6 @@ impl Deref for ImmutableString {
     type Target = SmartString;
 
     #[inline(always)]
-    #[must_use]
     fn deref(&self) -> &Self::Target {
         &self.0
     }
@@ -148,6 +147,7 @@ impl FromStr for ImmutableString {
     type Err = ();
 
     #[inline(always)]
+    #[must_use]
     fn from_str(s: &str) -> Result<Self, Self::Err> {
         let s: SmartString = s.into();
         Ok(Self(s.into()))
@@ -156,6 +156,7 @@ impl FromStr for ImmutableString {
 
 impl FromIterator<char> for ImmutableString {
     #[inline]
+    #[must_use]
     fn from_iter<T: IntoIterator<Item = char>>(iter: T) -> Self {
         Self(iter.into_iter().collect::<SmartString>().into())
     }
@@ -163,6 +164,7 @@ impl FromIterator<char> for ImmutableString {
 
 impl<'a> FromIterator<&'a char> for ImmutableString {
     #[inline]
+    #[must_use]
     fn from_iter<T: IntoIterator<Item = &'a char>>(iter: T) -> Self {
         Self(iter.into_iter().copied().collect::<SmartString>().into())
     }
@@ -170,6 +172,7 @@ impl<'a> FromIterator<&'a char> for ImmutableString {
 
 impl<'a> FromIterator<&'a str> for ImmutableString {
     #[inline]
+    #[must_use]
     fn from_iter<T: IntoIterator<Item = &'a str>>(iter: T) -> Self {
         Self(iter.into_iter().collect::<SmartString>().into())
     }
@@ -177,6 +180,7 @@ impl<'a> FromIterator<&'a str> for ImmutableString {
 
 impl FromIterator<String> for ImmutableString {
     #[inline]
+    #[must_use]
     fn from_iter<T: IntoIterator<Item = String>>(iter: T) -> Self {
         Self(iter.into_iter().collect::<SmartString>().into())
     }
@@ -184,6 +188,7 @@ impl FromIterator<String> for ImmutableString {
 
 impl FromIterator<SmartString> for ImmutableString {
     #[inline]
+    #[must_use]
     fn from_iter<T: IntoIterator<Item = SmartString>>(iter: T) -> Self {
         Self(iter.into_iter().collect::<SmartString>().into())
     }

src/types/interner.rs

@@ -39,6 +39,7 @@ pub struct StringsInterner<'a> {
 
 impl Default for StringsInterner<'_> {
     #[inline(always)]
+    #[must_use]
     fn default() -> Self {
         Self::new()
     }

src/types/scope.rs

@@ -128,7 +128,7 @@ impl IntoIterator for Scope<'_> {
     type Item = (String, Dynamic, Vec<Identifier>);
     type IntoIter = Box<dyn Iterator<Item = Self::Item>>;
 
-    #[inline]
+    #[must_use]
     fn into_iter(self) -> Self::IntoIter {
         Box::new(
             self.values
@@ -143,7 +143,7 @@ impl<'a> IntoIterator for &'a Scope<'_> {
     type Item = (&'a Identifier, &'a Dynamic, &'a Vec<Identifier>);
     type IntoIter = Box<dyn Iterator<Item = Self::Item> + 'a>;
 
-    #[inline]
+    #[must_use]
     fn into_iter(self) -> Self::IntoIter {
         Box::new(
             self.values
@@ -719,7 +719,6 @@ impl Scope<'_> {
         scope
     }
     /// Get an iterator to entries in the [`Scope`].
-    #[inline]
     #[allow(dead_code)]
     pub(crate) fn into_iter(self) -> impl Iterator<Item = (Identifier, Dynamic, Vec<Identifier>)> {
         self.names

tests/build_type.rs

@@ -49,6 +49,8 @@ fn build_type() -> Result<(), Box<EvalAltResult>> {
         type Item = INT;
         type IntoIter = std::vec::IntoIter<Self::Item>;
 
+        #[inline]
+        #[must_use]
         fn into_iter(self) -> Self::IntoIter {
             vec![self.x, self.y, self.z].into_iter()
         }

tests/for.rs

@@ -337,6 +337,8 @@ impl IntoIterator for MyIterableType {
     type Item = char;
     type IntoIter = std::vec::IntoIter<Self::Item>;
 
+    #[inline]
+    #[must_use]
     fn into_iter(self) -> Self::IntoIter {
         self.0.chars().collect::<Vec<_>>().into_iter()
     }