Avoid recomputing TypeCode in integral-float checks

Add a TypeCode-based IsInteger overload and reuse the TypeCode already
computed by the callers in Converter.ToPrimitive and MethodBinder,
instead of fetching it again inside IsInteger(Type).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: jhonabreul

src/runtime/Converter.cs

@@ -900,7 +900,7 @@ internal static bool ToPrimitive(BorrowedReference value, Type obType, out objec
             // accepted. This keeps single- and multi-overload binding consistent:
             // MethodBinder only treats integral floats as candidates for integer
             // parameters, and this guard enforces the same rule at conversion time.
-            if (obType.IsInteger() && Runtime.PyFloat_Check(value))
+            if (tc.IsInteger() && Runtime.PyFloat_Check(value))
             {
                 double dbl = Runtime.PyFloat_AsDouble(value);
                 if (double.IsNaN(dbl) || double.IsInfinity(dbl) || Math.Truncate(dbl) != dbl)

src/runtime/MethodBinder.cs

@@ -683,7 +683,7 @@ internal Binding Bind(BorrowedReference inst, BorrowedReference args, BorrowedRe
                                         // parameters. Converter.ToManaged rejects non-integral floats
                                         // (e.g. 5.5) so we don't silently truncate. Enums are excluded
                                         // on purpose.
-                                        else if (Runtime.PyFloat_Check(op) && underlyingType.IsInteger() && !underlyingType.IsEnum)
+                                        else if (Runtime.PyFloat_Check(op) && argtypecode.IsInteger() && !underlyingType.IsEnum)
                                         {
                                             clrtype = parameter.ParameterType;
                                             typematch = Converter.ToManaged(op, clrtype, out arg, false);

src/runtime/Util/Util.cs

@@ -311,7 +311,17 @@ public static bool IsDelegate(this Type type)
         /// </summary>
         public static bool IsInteger(this Type type)
         {
-            switch (Type.GetTypeCode(type))
+            return Type.GetTypeCode(type).IsInteger();
+        }
+
+        /// <summary>
+        /// Determines whether the specified type code is a CLR integer type (signed or unsigned).
+        /// Enums report an integral <see cref="TypeCode"/> too, so callers that want to
+        /// exclude them must check <see cref="Type.IsEnum"/> separately.
+        /// </summary>
+        public static bool IsInteger(this TypeCode typeCode)
+        {
+            switch (typeCode)
             {
                 case TypeCode.Byte:
                 case TypeCode.SByte: