Map actual 0 hash to 42.

src/fn_call.rs

@@ -20,6 +20,7 @@ use crate::stdlib::{
     string::ToString,
     vec::Vec,
 };
+use crate::utils::combine_hashes;
 use crate::{
     calc_native_fn_hash, calc_script_fn_hash, Dynamic, Engine, EvalAltResult, FnPtr,
     ImmutableString, Module, ParseErrorType, Position, Scope, StaticVec, INT,
@@ -1177,9 +1178,8 @@ impl Engine {
                 //    and the actual list of argument `TypeId`'.s
                 let hash_fn_args =
                     calc_native_fn_hash(empty(), "", args.iter().map(|a| a.type_id())).unwrap();
-                // 3) The final hash is the XOR of the two hashes.
-                let hash_qualified_fn =
-                    NonZeroU64::new(hash_script.get() ^ hash_fn_args.get()).unwrap();
+                // 3) The two hashes are combined.
+                let hash_qualified_fn = combine_hashes(hash_script, hash_fn_args);
 
                 module.get_qualified_fn(hash_qualified_fn)
             }

src/module/mod.rs

@@ -17,7 +17,7 @@ use crate::stdlib::{
     vec::Vec,
 };
 use crate::token::Token;
-use crate::utils::StraightHasherBuilder;
+use crate::utils::{combine_hashes, StraightHasherBuilder};
 use crate::{
     Dynamic, EvalAltResult, ImmutableString, NativeCallContext, Position, Shared, StaticVec,
 };
@@ -1823,10 +1823,9 @@ impl Module {
                                 param_types.iter().cloned(),
                             )
                             .unwrap();
-                            // 3) The final hash is the XOR of the two hashes.
+                            // 3) The two hashes are combined.
                             let hash_qualified_fn =
-                                NonZeroU64::new(hash_qualified_script.get() ^ hash_fn_args.get())
-                                    .unwrap();
+                                combine_hashes(hash_qualified_script, hash_fn_args);
 
                             functions.insert(hash_qualified_fn, func.clone());
                         } else if cfg!(not(feature = "no_function")) {

src/parser.rs

@@ -2797,17 +2797,14 @@ fn make_curry_from_externals(fn_expr: Expr, externals: StaticVec<Ident>, pos: Po
 
     #[cfg(not(feature = "no_closure"))]
     externals.iter().for_each(|x| {
-        args.push(Expr::Variable(Box::new((
-            None,
-            None,
-            None,
-            x.clone().into(),
-        ))));
+        let expr = Expr::Variable(Box::new((None, None, None, x.clone().into())));
+        args.push(expr);
     });
 
     #[cfg(feature = "no_closure")]
     externals.into_iter().for_each(|x| {
-        args.push(Expr::Variable(Box::new((None, None, 0, x.clone().into()))));
+        let expr = Expr::Variable(Box::new((None, None, None, x.clone().into())));
+        args.push(expr);
     });
 
     let curry_func = crate::engine::KEYWORD_FN_PTR_CURRY;

src/utils.rs

@@ -22,18 +22,23 @@ use crate::Shared;
 ///
 /// Panics when hashing any data type other than a [`NonZeroU64`].
 #[derive(Debug, Clone, Copy, Eq, PartialEq, Ord, PartialOrd, Hash)]
-pub struct StraightHasher(NonZeroU64);
+pub struct StraightHasher(u64);
 
 impl Hasher for StraightHasher {
     #[inline(always)]
     fn finish(&self) -> u64 {
-        self.0.get()
+        self.0
     }
     #[inline(always)]
     fn write(&mut self, bytes: &[u8]) {
         let mut key = [0_u8; 8];
         key.copy_from_slice(&bytes[..8]); // Panics if fewer than 8 bytes
-        self.0 = NonZeroU64::new(u64::from_le_bytes(key)).unwrap();
+        self.0 = u64::from_le_bytes(key);
+
+        // HACK - If it so happens to hash directly to zero (OMG!) then change it to 42...
+        if self.0 == 0 {
+            self.0 = 42;
+        }
     }
 }
 
@@ -46,10 +51,20 @@ impl BuildHasher for StraightHasherBuilder {
 
     #[inline(always)]
     fn build_hasher(&self) -> Self::Hasher {
-        StraightHasher(NonZeroU64::new(1).unwrap())
+        StraightHasher(1)
     }
 }
 
+/// Create an instance of the default hasher.
+pub fn get_hasher() -> impl Hasher {
+    #[cfg(feature = "no_std")]
+    let s: ahash::AHasher = Default::default();
+    #[cfg(not(feature = "no_std"))]
+    let s = crate::stdlib::collections::hash_map::DefaultHasher::new();
+
+    s
+}
+
 /// _(INTERNALS)_ Calculate a [`NonZeroU64`] hash key from a namespace-qualified function name and parameter types.
 /// Exported under the `internals` feature only.
 ///
@@ -87,16 +102,6 @@ pub fn calc_script_fn_hash<'a>(
     calc_fn_hash(modules, fn_name, Some(num), empty())
 }
 
-/// Create an instance of the default hasher.
-pub fn get_hasher() -> impl Hasher {
-    #[cfg(feature = "no_std")]
-    let s: ahash::AHasher = Default::default();
-    #[cfg(not(feature = "no_std"))]
-    let s = crate::stdlib::collections::hash_map::DefaultHasher::new();
-
-    s
-}
-
 /// Calculate a [`NonZeroU64`] hash key from a namespace-qualified function name and parameter types.
 ///
 /// Module names are passed in via `&str` references from an iterator.
@@ -123,7 +128,15 @@ fn calc_fn_hash<'a>(
     } else {
         params.for_each(|t| t.hash(s));
     }
-    NonZeroU64::new(s.finish())
+    // HACK - If it so happens to hash directly to zero (OMG!) then change it to 42...
+    NonZeroU64::new(s.finish()).or_else(|| NonZeroU64::new(42))
+}
+
+/// Combine two [`NonZeroU64`] hashes by taking the XOR of them.
+#[inline(always)]
+pub(crate) fn combine_hashes(a: NonZeroU64, b: NonZeroU64) -> NonZeroU64 {
+    // HACK - If it so happens to hash directly to zero (OMG!) then change it to 42...
+    NonZeroU64::new(a.get() ^ b.get()).unwrap_or_else(|| NonZeroU64::new(42).unwrap())
 }
 
 /// The system immutable string type.