Disabled toHash in -betterC for now

TypeInfo is part of DRuntime.
See: #5952

Replaced `toHash` with a parameter-less template for codegen on demand.

Author: wilzbach

std/typecons.d

@@ -1169,12 +1169,12 @@ if (distinctFieldNames!(Specs))
             Returns:
                 A `size_t` representing the hash of this `Tuple`.
          */
-        size_t toHash() const nothrow @safe
+        size_t toHash() const nothrow @trusted
         {
             size_t h = 0;
             static foreach (i, T; Types)
             {{
-                const k = typeid(T).getHash((() @trusted => cast(const void*) &field[i])());
+                const k = hashOf(field[i]);
                 static if (i == 0)
                     h = k;
                 else
@@ -1474,6 +1474,19 @@ if (distinctFieldNames!(Specs))
     assert(t == AliasSeq!(1, Bad(1), "asdf"));
 }
 
+// Ensure Tuple.toHash works
+@safe unittest
+{
+    Tuple!(int, int) point;
+    assert(point.toHash == typeof(point).init.toHash);
+    assert(tuple(1, 2) != point);
+    assert(tuple(1, 2) == tuple(1, 2));
+    point[0] = 1;
+    assert(tuple(1, 2) != point);
+    point[1] = 2;
+    assert(tuple(1, 2) == point);
+}
+
 /**
     Creates a copy of a $(LREF Tuple) with its fields in _reverse order.