Use const fn where possible (RustPython#5894)

Author: ShaharNaveh

common/src/cformat.rs

@@ -136,7 +136,7 @@ bitflags! {
 
 impl CConversionFlags {
     #[inline]
-    pub fn sign_string(&self) -> &'static str {
+    pub const fn sign_string(&self) -> &'static str {
         if self.contains(Self::SIGN_CHAR) {
             "+"
         } else if self.contains(Self::BLANK_SIGN) {

common/src/encodings.rs

@@ -137,7 +137,11 @@ struct DecodeError<'a> {
 
 /// # Safety
 /// `v[..valid_up_to]` must be valid utf8
-unsafe fn make_decode_err(v: &[u8], valid_up_to: usize, err_len: Option<usize>) -> DecodeError<'_> {
+const unsafe fn make_decode_err(
+    v: &[u8],
+    valid_up_to: usize,
+    err_len: Option<usize>,
+) -> DecodeError<'_> {
     let (valid_prefix, rest) = unsafe { v.split_at_unchecked(valid_up_to) };
     let valid_prefix = unsafe { core::str::from_utf8_unchecked(valid_prefix) };
     DecodeError {

common/src/hash.rs

@@ -164,7 +164,7 @@ pub fn lcg_urandom(mut x: u32, buf: &mut [u8]) {
 }
 
 #[inline]
-pub fn hash_object_id_raw(p: usize) -> PyHash {
+pub const fn hash_object_id_raw(p: usize) -> PyHash {
     // TODO: Use commented logic when below issue resolved.
     // Ref: https://github.com/RustPython/RustPython/pull/3951#issuecomment-1193108966
 
@@ -175,7 +175,7 @@ pub fn hash_object_id_raw(p: usize) -> PyHash {
 }
 
 #[inline]
-pub fn hash_object_id(p: usize) -> PyHash {
+pub const fn hash_object_id(p: usize) -> PyHash {
     fix_sentinel(hash_object_id_raw(p))
 }
 

common/src/linked_list.rs

@@ -193,7 +193,7 @@ impl<L: Link> LinkedList<L, L::Target> {
     // }
 
     /// Returns whether the linked list does not contain any node
-    pub fn is_empty(&self) -> bool {
+    pub const fn is_empty(&self) -> bool {
         self.head.is_none()
         // if self.head.is_some() {
         //     return false;
@@ -284,7 +284,7 @@ pub struct DrainFilter<'a, T: Link, F> {
 }
 
 impl<T: Link> LinkedList<T, T::Target> {
-    pub fn drain_filter<F>(&mut self, filter: F) -> DrainFilter<'_, T, F>
+    pub const fn drain_filter<F>(&mut self, filter: F) -> DrainFilter<'_, T, F>
     where
         F: FnMut(&mut T::Target) -> bool,
     {
@@ -323,7 +323,7 @@ where
 
 impl<T> Pointers<T> {
     /// Create a new set of empty pointers
-    pub fn new() -> Self {
+    pub const fn new() -> Self {
         Self {
             inner: UnsafeCell::new(PointersInner {
                 prev: None,
@@ -333,15 +333,15 @@ impl<T> Pointers<T> {
         }
     }
 
-    fn get_prev(&self) -> Option<NonNull<T>> {
+    const fn get_prev(&self) -> Option<NonNull<T>> {
         // SAFETY: prev is the first field in PointersInner, which is #[repr(C)].
         unsafe {
             let inner = self.inner.get();
             let prev = inner as *const Option<NonNull<T>>;
             ptr::read(prev)
         }
     }
-    fn get_next(&self) -> Option<NonNull<T>> {
+    const fn get_next(&self) -> Option<NonNull<T>> {
         // SAFETY: next is the second field in PointersInner, which is #[repr(C)].
         unsafe {
             let inner = self.inner.get();
@@ -351,15 +351,15 @@ impl<T> Pointers<T> {
         }
     }
 
-    fn set_prev(&mut self, value: Option<NonNull<T>>) {
+    const fn set_prev(&mut self, value: Option<NonNull<T>>) {
         // SAFETY: prev is the first field in PointersInner, which is #[repr(C)].
         unsafe {
             let inner = self.inner.get();
             let prev = inner as *mut Option<NonNull<T>>;
             ptr::write(prev, value);
         }
     }
-    fn set_next(&mut self, value: Option<NonNull<T>>) {
+    const fn set_next(&mut self, value: Option<NonNull<T>>) {
         // SAFETY: next is the second field in PointersInner, which is #[repr(C)].
         unsafe {
             let inner = self.inner.get();

common/src/lock/thread_mutex.rs

@@ -78,7 +78,7 @@ pub struct ThreadMutex<R: RawMutex, G: GetThreadId, T: ?Sized> {
 }
 
 impl<R: RawMutex, G: GetThreadId, T> ThreadMutex<R, G, T> {
-    pub fn new(val: T) -> Self {
+    pub const fn new(val: T) -> Self {
         Self {
             raw: RawThreadMutex::INIT,
             data: UnsafeCell::new(val),

compiler/codegen/src/compile.rs

@@ -282,7 +282,7 @@ impl Default for PatternContext {
 }
 
 impl PatternContext {
-    pub fn new() -> Self {
+    pub const fn new() -> Self {
         Self {
             stores: Vec::new(),
             allow_irrefutable: false,
@@ -4118,7 +4118,7 @@ impl Compiler<'_> {
         code.current_block = block;
     }
 
-    fn set_source_range(&mut self, range: TextRange) {
+    const fn set_source_range(&mut self, range: TextRange) {
         self.current_source_range = range;
     }
 

compiler/codegen/src/string_parser.rs

@@ -28,7 +28,7 @@ struct StringParser {
 }
 
 impl StringParser {
-    fn new(source: Box<str>, flags: AnyStringFlags) -> Self {
+    const fn new(source: Box<str>, flags: AnyStringFlags) -> Self {
         Self {
             source,
             cursor: 0,

compiler/codegen/src/symboltable.rs

@@ -162,18 +162,18 @@ impl Symbol {
         }
     }
 
-    pub fn is_global(&self) -> bool {
+    pub const fn is_global(&self) -> bool {
         matches!(
             self.scope,
             SymbolScope::GlobalExplicit | SymbolScope::GlobalImplicit
         )
     }
 
-    pub fn is_local(&self) -> bool {
+    pub const fn is_local(&self) -> bool {
         matches!(self.scope, SymbolScope::Local | SymbolScope::Cell)
     }
 
-    pub fn is_bound(&self) -> bool {
+    pub const fn is_bound(&self) -> bool {
         self.flags.intersects(SymbolFlags::BOUND)
     }
 }

compiler/codegen/src/unparse.rs

@@ -32,7 +32,7 @@ struct Unparser<'a, 'b, 'c> {
     source: &'c SourceCode<'c>,
 }
 impl<'a, 'b, 'c> Unparser<'a, 'b, 'c> {
-    fn new(f: &'b mut fmt::Formatter<'a>, source: &'c SourceCode<'c>) -> Self {
+    const fn new(f: &'b mut fmt::Formatter<'a>, source: &'c SourceCode<'c>) -> Self {
         Unparser { f, source }
     }
 
@@ -602,7 +602,7 @@ pub struct UnparseExpr<'a> {
     source: &'a SourceCode<'a>,
 }
 
-pub fn unparse_expr<'a>(expr: &'a Expr, source: &'a SourceCode<'a>) -> UnparseExpr<'a> {
+pub const fn unparse_expr<'a>(expr: &'a Expr, source: &'a SourceCode<'a>) -> UnparseExpr<'a> {
     UnparseExpr { expr, source }
 }
 

compiler/src/lib.rs

@@ -62,7 +62,7 @@ impl CompileError {
         }
     }
 
-    pub fn python_location(&self) -> (usize, usize) {
+    pub const fn python_location(&self) -> (usize, usize) {
         match self {
             Self::Codegen(codegen_error) => {
                 if let Some(location) = &codegen_error.location {