Add missing_const_for_fn clippy lint (#8498)

bin/reth/src/commands/db/checksum.rs

@@ -55,7 +55,7 @@ pub(crate) struct ChecksumViewer<'a, DB: Database> {
 }
 
 impl<DB: Database> ChecksumViewer<'_, DB> {
-    pub(crate) fn new(tool: &'_ DbTool<DB>) -> ChecksumViewer<'_, DB> {
+    pub(crate) const fn new(tool: &'_ DbTool<DB>) -> ChecksumViewer<'_, DB> {
         ChecksumViewer { tool, start_key: None, end_key: None, limit: None }
     }
 

bin/reth/src/commands/db/diff.rs

@@ -418,7 +418,7 @@ enum ExtraTableElement<T: Table> {
 
 impl<T: Table> ExtraTableElement<T> {
     /// Return the key for the extra element
-    fn key(&self) -> &T::Key {
+    const fn key(&self) -> &T::Key {
         match self {
             Self::First { key, .. } => key,
             Self::Second { key, .. } => key,

bin/reth/src/commands/db/tui.rs

@@ -55,7 +55,7 @@ enum Entries<T: Table> {
 impl<T: Table> Entries<T> {
     /// Creates new empty [Entries] as [Entries::RawValues] if `raw_values == true` and as
     /// [Entries::Values] if `raw == false`.
-    fn new_with_raw_values(raw_values: bool) -> Self {
+    const fn new_with_raw_values(raw_values: bool) -> Self {
         if raw_values {
             Self::RawValues(Vec::new())
         } else {
@@ -85,7 +85,7 @@ impl<T: Table> Entries<T> {
 
     /// Returns an iterator over keys of the internal [Vec]. For both [Entries::RawValues] and
     /// [Entries::Values], this iterator will yield [Table::Key].
-    fn iter_keys(&self) -> EntriesKeyIter<'_, T> {
+    const fn iter_keys(&self) -> EntriesKeyIter<'_, T> {
         EntriesKeyIter { entries: self, index: 0 }
     }
 }

bin/reth/src/sigsegv_handler.rs

@@ -148,6 +148,6 @@ fn min_sigstack_size() -> usize {
 
 /// Not all OS support hardware where this is needed.
 #[cfg(not(any(target_os = "linux", target_os = "android")))]
-fn min_sigstack_size() -> usize {
+const fn min_sigstack_size() -> usize {
     libc::MINSIGSTKSZ
 }