return_self_not_must_use

youknowone · Jun 10, 2026 · Jun 5, 2026 · Jun 5, 2026 · Jun 5, 2026 · Jun 5, 2026
commit 3b462daa12d9bb7376795aeeb7a31a00517e9d48
diff --git a/Cargo.toml b/Cargo.toml
@@ -409,6 +409,7 @@ needless_for_each = "warn"
 option_as_ref_cloned = "warn"
 ptr_offset_by_literal = "warn"
 redundant_else = "warn"
+return_self_not_must_use = "warn"
 uninlined_format_args = "warn"
 unnecessary_wraps = "warn"
 unnested_or_patterns = "warn"
diff --git a/crates/common/src/cformat.rs b/crates/common/src/cformat.rs
@@ -160,16 +160,22 @@ pub trait FormatBuf:
     Extend<Self::Char> + Default + FromIterator<Self::Char> + From<String>
 {
     type Char: FormatChar;
+
     fn chars(&self) -> impl Iterator<Item = Self::Char>;
+
     fn len(&self) -> usize;
+
     fn is_empty(&self) -> bool {
         self.len() == 0
     }
+
+    #[must_use]
     fn concat(self, other: Self) -> Self;
 }
 
 pub trait FormatChar: Copy + Into<CodePoint> + From<u8> {
     fn to_char_lossy(self) -> char;
+
     fn eq_char(self, c: char) -> bool;
 }
 

diff --git a/crates/vm/src/builtins/dict.rs b/crates/vm/src/builtins/dict.rs
@@ -342,10 +342,10 @@ impl PyDict {
         default: OptionalArg<PyObjectRef>,
         vm: &VirtualMachine,
     ) -> PyResult {
-        match self.entries.get(vm, &*key)? {
-            Some(value) => Ok(value),
-            None => Ok(default.unwrap_or_none(vm)),
-        }
+        Ok(self
+            .entries
+            .get(vm, &*key)?
+            .unwrap_or_else(|| default.unwrap_or_none(vm)))
     }
 
     #[pymethod]
@@ -360,6 +360,7 @@ impl PyDict {
     }
 
     #[pymethod]
+    #[must_use]
     pub fn copy(&self) -> Self {
         Self {
             entries: self.entries.clone(),

diff --git a/crates/vm/src/builtins/getset.rs b/crates/vm/src/builtins/getset.rs
@@ -70,6 +70,7 @@ impl GetDescriptor for PyGetSet {
 }
 
 impl PyGetSet {
+    #[must_use]
     pub fn new(name: String, class: &'static Py<PyType>) -> Self {
         Self {
             name,
@@ -79,6 +80,7 @@ impl PyGetSet {
         }
     }
 
+    #[must_use]
     pub fn with_get<G, X>(mut self, getter: G) -> Self
     where
         G: IntoPyGetterFunc<X>,
@@ -87,6 +89,7 @@ impl PyGetSet {
         self
     }
 
+    #[must_use]
     pub fn with_set<S, X>(mut self, setter: S) -> Self
     where
         S: IntoPySetterFunc<X>,

diff --git a/crates/vm/src/builtins/memory.rs b/crates/vm/src/builtins/memory.rs
@@ -117,7 +117,8 @@ impl PyMemoryView {
         Ok(zelf)
     }
 
-    /// this should be the only way to create a memoryview from another memoryview
+    /// this should be the only way to create a memoryview from another memoryview.
+    #[must_use]
     pub fn new_view(&self) -> Self {
         let zelf = Self {
             buffer: self.buffer.clone(),

diff --git a/crates/vm/src/vm/interpreter.rs b/crates/vm/src/vm/interpreter.rs
@@ -229,6 +229,7 @@ impl InterpreterBuilder {
     ///     })
     ///     .build();
     /// ```
+    #[must_use]
     pub fn init_hook<F>(mut self, init: F) -> Self
     where
         F: FnOnce(&mut VirtualMachine) + 'static,
@@ -250,6 +251,7 @@ impl InterpreterBuilder {
     ///     // In practice: .add_frozen_modules(rustpython_pylib::FROZEN_STDLIB)
     ///     .build();
     /// ```
+    #[must_use]
     pub fn add_frozen_modules<I>(mut self, frozen: I) -> Self
     where
         I: IntoIterator<Item = (&'static str, FrozenModule)>,