Merge pull request #2195 from n8sh/core-hash-18918

Fix Issue 18918 - core.internal.hash should perform memberwise hashing of structs with references
merged-on-behalf-of: Sebastian Wilzbach <sebi.wilzbach@gmail.com>

src/core/internal/convert.d

@@ -603,15 +603,18 @@ nothrow pure @safe unittest
     enum ctfe_works = (() => { Month x = Month.jan; return toUbyte(x).length > 0; })();
 }
 
-private bool isNonReference(T)()
+package(core.internal) bool isNonReference(T)()
 {
     static if (is(T == struct) || is(T == union))
     {
         return isNonReferenceStruct!T();
     }
     else static if (__traits(isStaticArray, T))
     {
-      return isNonReference!(typeof(T.init[0]))();
+        static if (T.length > 0)
+            return isNonReference!(typeof(T.init[0]))();
+        else
+            return true;
     }
     else static if (is(T E == enum))
     {
@@ -637,9 +640,9 @@ private bool isNonReference(T)()
 
 private bool isNonReferenceStruct(T)() if (is(T == struct) || is(T == union))
 {
-    foreach (cur; T.init.tupleof)
+    static foreach (cur; T.tupleof)
     {
-        static if (!isNonReference!(typeof(cur))()) return false;
+        if (!isNonReference!(typeof(cur))()) return false;
     }
 
     return true;

src/core/internal/hash.d

@@ -43,9 +43,11 @@ if (!is(T == enum) && !is(T : typeof(null)) && is(T S: S[]) && !__traits(isStati
 {
     alias ElementType = typeof(val[0]);
     static if (is(ElementType == interface) || is(ElementType == class) ||
+                   (is(ElementType == struct) && !isNonReference!ElementType) ||
                    ((is(ElementType == struct) || is(ElementType == union))
                        && is(typeof(val[0].toHash()) == size_t)))
     //class or interface array or struct array with toHash(); CTFE depend on toHash() method
+    //also do this for arrays of structs whose hashes would be calculated in a memberwise fashion
     {
         size_t hash = seed;
         foreach (o; val)
@@ -135,7 +137,15 @@ size_t hashOf(T)(auto ref T val, size_t seed = 0) if (!is(T == enum) && (is(T ==
             pragma(msg, "Warning: struct "~__traits(identifier, T)~" has method toHash, however it cannot be called with "~T.stringof~" this.");
         }
 
-        static if (is(typeof(toUbyte(val)) == const(ubyte)[]))//CTFE ready for structs without reference fields
+        static if (is(T == struct) && !isNonReference!T) // Memberwise hashing.
+        {
+            static foreach (i, F; typeof(val.tupleof))
+            {
+                seed = hashOf(val.tupleof[i], seed);
+            }
+            return seed;
+        }
+        else static if (is(typeof(toUbyte(val)) == const(ubyte)[]))//CTFE ready for structs without reference fields
         {
             return bytesHash(toUbyte(val), seed);
         }
@@ -446,6 +456,16 @@ unittest // issue 15111
     testAlias!(int[8]);
 }
 
+nothrow pure @system unittest // issue 18918
+{
+    static struct S { string array; }
+    auto s1 = S("abc");
+    auto s2 = S(s1.array.idup);
+    assert(hashOf(s1) == hashOf(s2));
+    enum e = hashOf(S("abc"));
+    assert(hashOf(s1) == e);
+}
+
 // MurmurHash3 was written by Austin Appleby, and is placed in the public
 // domain. The author hereby disclaims copyright to this source code.