Narrow down cast operators on IntType

Say for USHORT, we were implementing casts from and to unsigned.
With this change, we cast from and to uint16_t only.  This allows
compiler more opportunities to catch possible narrowing issues in
the code.

It needed a couple of fixes in the codebase though, because
previously, if a USHORT was participating in arithmetic with signed
numbers, eg. "u + 1", the result would have been unsigned.  With
this change, it would be signed.  The correct fix is to update the
code to read "u + 1u".

That said, I think about conditionally adding back the cast
out to signed/unsigned, to facilitate better type deduction.
But I couldn't think of a real situation where that would help
with anything.  So I didn't add.  Here's what it was:

  template <typename Type2 = hb_conditional<hb_is_signed (Type), signed, unsigned>,
           hb_enable_if (sizeof (Type) < sizeof (Type2))>
  operator hb_type_identity_t<Type2> () const { return v; }

https://github.com/harfbuzz/harfbuzz/pull/2875

src/hb-aat-layout-common.hh

@@ -576,7 +576,7 @@ struct StateTable
 	  if (unlikely (stop > states))
 	    return_trace (false);
 	  for (const HBUSHORT *p = states; stop < p; p--)
-	    num_entries = hb_max (num_entries, *(p - 1) + 1);
+	    num_entries = hb_max (num_entries, *(p - 1) + 1u);
 	  state_neg = min_state;
 	}
       }
@@ -597,7 +597,7 @@ struct StateTable
 	  if (unlikely (stop < states))
 	    return_trace (false);
 	  for (const HBUSHORT *p = &states[state_pos * num_classes]; p < stop; p++)
-	    num_entries = hb_max (num_entries, *p + 1);
+	    num_entries = hb_max (num_entries, *p + 1u);
 	  state_pos = max_state + 1;
 	}
       }

src/hb-aat-layout-morx-table.hh

@@ -337,9 +337,9 @@ struct ContextualSubtable
       const EntryData &data = entries[i].data;
 
       if (data.markIndex != 0xFFFF)
-	num_lookups = hb_max (num_lookups, 1 + data.markIndex);
+	num_lookups = hb_max (num_lookups, 1u + data.markIndex);
       if (data.currentIndex != 0xFFFF)
-	num_lookups = hb_max (num_lookups, 1 + data.currentIndex);
+	num_lookups = hb_max (num_lookups, 1u + data.currentIndex);
     }
 
     return_trace (substitutionTables.sanitize (c, this, num_lookups));

src/hb-open-type.hh

@@ -54,16 +54,15 @@ namespace OT {
 
 /* Integer types in big-endian order and no alignment requirement */
 template <typename Type,
-	  unsigned int Size = sizeof (Type),
+	  unsigned int Size = sizeof (Type)>
-	  typename Wide = hb_conditional<hb_is_signed (Type), signed, unsigned>>
 struct IntType
 {
   typedef Type type;
 
   IntType () = default;
-  explicit constexpr IntType (Wide V) : v {V} {}
+  explicit constexpr IntType (Type V) : v {V} {}
-  IntType& operator = (Wide i) { v = i; return *this; }
+  IntType& operator = (Type i) { v = i; return *this; }
-  operator Wide () const { return v; }
+  operator Type () const { return v; }
 
   bool operator == (const IntType &o) const { return (Type) v == (Type) o.v; }
   bool operator != (const IntType &o) const { return !(*this == o); }