Don't avoid sign-extension when hashing byte/short/int

There is not a reason to keep this and removing it lets us remove a
template.

Author: n8sh

src/core/internal/hash.d

@@ -129,25 +129,6 @@ private template canBitwiseHash(T)
     }
 }
 
-private template UnqualUnsigned(T) if (__traits(isIntegral, T) && !is(T == __vector))
-{
-    static if (T.sizeof == ubyte.sizeof) alias UnqualUnsigned = ubyte;
-    else static if (T.sizeof == ushort.sizeof) alias UnqualUnsigned = ushort;
-    else static if (T.sizeof == uint.sizeof) alias UnqualUnsigned = uint;
-    else static if (T.sizeof == ulong.sizeof) alias UnqualUnsigned = ulong;
-    else static if (T.sizeof == ulong.sizeof * 2)
-    {
-        static assert(T.sizeof == ucent.sizeof);
-        alias UnqualUnsigned = ucent;
-    }
-    else
-    {
-        static assert(0, "No known unsigned equivalent of " ~ T.stringof);
-    }
-
-    static assert(UnqualUnsigned.sizeof == T.sizeof && __traits(isUnsigned, UnqualUnsigned));
-}
-
 // Overly restrictive for simplicity: has false negatives but no false positives.
 private template useScopeConstPassByValue(T)
 {
@@ -344,7 +325,7 @@ if (!is(T == enum) && !is(T : typeof(null)) && is(T S: S[]) && !__traits(isStati
 size_t hashOf(T)(scope const T val) if (!is(T == enum) && __traits(isArithmetic, T)
     && __traits(isIntegral, T) && T.sizeof <= size_t.sizeof && !is(T == __vector))
 {
-    return cast(UnqualUnsigned!T) val;
+    return val;
 }
 
 //arithmetic type hash
@@ -371,10 +352,10 @@ size_t hashOf(T)(scope const T val, size_t seed) if (!is(T == enum) && __traits(
         enum uint r1 = 31;
         enum uint r2 = 27;
     }
-    auto h = c1 * cast(UnqualUnsigned!T) val;
-    h = (h << r1) | (h >>> (typeof(h).sizeof * 8 - r1));
+    size_t h = c1 * val;
+    h = (h << r1) | (h >>> (size_t.sizeof * 8 - r1));
     h = (h * c2) ^ seed;
-    h = (h << r2) | (h >>> (typeof(h).sizeof * 8 - r2));
+    h = (h << r2) | (h >>> (size_t.sizeof * 8 - r2));
     return h * 5 + c3;
 }
 

src/rt/typeinfo/ti_byte.d

@@ -26,8 +26,7 @@ class TypeInfo_g : TypeInfo
 
     override size_t getHash(scope const void* p)
     {
-        // Hash as if unsigned.
-        return *cast(const ubyte *)p;
+        return *cast(const byte *)p;
     }
 
     override bool equals(in void* p1, in void* p2)

src/rt/typeinfo/ti_cent.d

@@ -28,7 +28,7 @@ class TypeInfo_zi : TypeInfo
 
     override size_t getHash(scope const void* p)
     {
-        // Hash as if unsigned.
+        // cent & ucent hash the same if ucent.sizeof >= size_t.sizeof.
         return hashOf(*cast(const ucent*) p);
     }
 

src/rt/typeinfo/ti_int.d

@@ -26,8 +26,7 @@ class TypeInfo_i : TypeInfo
 
     override size_t getHash(scope const void* p)
     {
-        // Hash as if unsigned.
-        return *cast(const uint *)p;
+        return *cast(const int *)p;
     }
 
     override bool equals(in void* p1, in void* p2)

src/rt/typeinfo/ti_long.d

@@ -26,10 +26,10 @@ class TypeInfo_l : TypeInfo
 
     override size_t getHash(scope const void* p)
     {
-        // Hash as if unsigned.
         static if (ulong.sizeof <= size_t.sizeof)
-            return *cast(const ulong*)p;
+            return *cast(const long*)p;
         else
+            // long & ulong hash the same if ulong.sizeof > size_t.sizeof.
             return hashOf(*cast(const ulong*)p);
     }
 

src/rt/typeinfo/ti_short.d

@@ -26,8 +26,7 @@ class TypeInfo_s : TypeInfo
 
     override size_t getHash(scope const void* p)
     {
-        // Hash as if unsigned.
-        return *cast(const ushort *)p;
+        return *cast(const short *)p;
     }
 
     override bool equals(in void* p1, in void* p2)