fix: ensure table tests pass with miri

We previously assumed that &'static str would always have the same
address, but with miri it seems like this address is not actually stable
(see rust-lang/miri#1955).

So refactor the tests to let it use the StringInterner instead of
constructing InternedString by itself.

Author: tom-anders

lib/strings/src/string_interner.rs

@@ -4,7 +4,7 @@ use crate::table::StringTable;
 
 #[derive(Eq, Clone, Copy)]
 pub struct InternedString {
-    ptr: *const str,
+    pub(crate) ptr: *const str,
     pub(crate) hash: usize,
 }
 
@@ -13,10 +13,6 @@ impl InternedString {
         s.bytes().fold(2166136261, |hash, byte| (hash ^ byte as usize).wrapping_mul(16777619))
     }
 
-    pub fn new(s: &str) -> Self {
-        Self { ptr: s as *const str, hash: Self::hash(s) }
-    }
-
     #[allow(clippy::op_ref)]
     /// Compare actual underlying strings, instead of just comparing pointers.
     /// This is only needed when interning new strings.

lib/strings/src/table.rs

@@ -168,48 +168,59 @@ impl<V> Entry<V> {
 
 #[cfg(test)]
 mod tests {
+    use crate::string_interner::StringInterner;
+
     use super::*;
 
     #[test]
     fn table() {
         let mut table = StringTable::new();
-        table.insert(InternedString::new("hello"), 1);
-        table.insert(InternedString::new("world"), 2);
-        assert_eq!(table.get(InternedString::new("world")), Some(&2));
-        table.insert(InternedString::new("a"), 3);
-        table.insert(InternedString::new("b"), 4);
-        table.insert(InternedString::new("c"), 5);
-        table.insert(InternedString::new("d"), 6);
-        table.insert(InternedString::new("e"), 7);
-        table.insert(InternedString::new("f"), 8);
+        let mut interner = StringInterner::with_capacity(8);
+        table.insert(interner.intern("hello"), 1);
+        table.insert(interner.intern("world"), 2);
+        assert_eq!(table.get(interner.intern("world")), Some(&2));
+        table.insert(interner.intern("a"), 3);
+        table.insert(interner.intern("b"), 4);
+        table.insert(interner.intern("c"), 5);
+        table.insert(interner.intern("d"), 6);
+        table.insert(interner.intern("e"), 7);
+        table.insert(interner.intern("f"), 8);
 
-        assert_eq!(table.get(InternedString::new("world")), Some(&2));
-        assert_eq!(table.get(InternedString::new("nope")), None);
-        assert_eq!(table.get_mut(InternedString::new("world")), Some(&mut 2));
-        assert_eq!(table.get_mut(InternedString::new("nope")), None);
+        assert_eq!(table.get(interner.intern("world")), Some(&2));
+        assert_eq!(table.get(interner.intern("nope")), None);
+        assert_eq!(table.get_mut(interner.intern("world")), Some(&mut 2));
+        assert_eq!(table.get_mut(interner.intern("nope")), None);
 
-        table.insert(InternedString::new("world"), -123);
-        assert_eq!(table.get(InternedString::new("world")), Some(&-123));
+        table.insert(interner.intern("world"), -123);
+        assert_eq!(table.get(interner.intern("world")), Some(&-123));
 
-        *table.get_mut(InternedString::new("e")).unwrap() = 123;
-        assert_eq!(table.get(InternedString::new("e")), Some(&123));
+        *table.get_mut(interner.intern("e")).unwrap() = 123;
+        assert_eq!(table.get(interner.intern("e")), Some(&123));
     }
 
     #[test]
     fn get_str_eq() {
         let s = "s".to_string();
         let mut table = StringTable::new();
-        table.insert(InternedString::new(s.as_str()), 123);
-
-        assert_eq!(table.get(InternedString::new(s.as_str())), Some(&123));
-
-        #[allow(clippy::redundant_clone)]
-        let s2 = s.clone();
-        assert_eq!(table.get(InternedString::new(s2.as_str())), None);
-        assert_eq!(table.get_str_eq(InternedString::new("hkjhkjhkj")), None);
-        assert_eq!(
-            table.get_str_eq(InternedString::new(s2.as_str())),
-            Some(&InternedString::new(s.as_str()))
-        );
+        let mut interner = StringInterner::with_capacity(16);
+
+        let s_internered = interner.intern(s.as_str());
+        table.insert(s_internered, 123);
+
+        assert_eq!(table.get(s_internered), Some(&123));
+        assert_eq!(table.get_str_eq(s_internered), Some(&s_internered));
+        assert_eq!(table.get_str_eq(interner.intern("hkjhkjhkj")), None);
+
+        let mut interner2 = StringInterner::with_capacity(16);
+
+        // Clone the string to give it a different address, and then intern it in a second interner,
+        // such that the resulting interned string has a different address as well.
+        let s_cloned_interned = interner2.intern(&s.clone());
+        assert_ne!(s_internered, s_cloned_interned);
+
+        // Now, normal get() returns None because it only compares the address, but get_str_eq()
+        // findfs the original interned string since it should do full string comparison.
+        assert_eq!(table.get(s_cloned_interned), None);
+        assert_eq!(table.get_str_eq(s_cloned_interned), Some(&s_internered));
     }
 }