sumtype: put private matchImpl helpers together

std/sumtype.d

@@ -1860,33 +1860,6 @@ private template Iota(size_t n)
     assert(Iota!3 == AliasSeq!(0, 1, 2));
 }
 
-/* The number that the dim-th argument's tag is multiplied by when
- * converting TagTuples to and from case indices ("caseIds").
- *
- * Named by analogy to the stride that the dim-th index into a
- * multidimensional static array is multiplied by to calculate the
- * offset of a specific element.
- */
-private size_t stride(size_t dim, lengths...)()
-{
-    import core.checkedint : mulu;
-
-    size_t result = 1;
-    bool overflow = false;
-
-    static foreach (i; 0 .. dim)
-    {
-        result = mulu(result, lengths[i], overflow);
-    }
-
-    /* The largest number matchImpl uses, numCases, is calculated with
-     * stride!(SumTypes.length), so as long as this overflow check
-     * passes, we don't need to check for overflow anywhere else.
-     */
-    assert(!overflow, "Integer overflow");
-    return result;
-}
-
 private template matchImpl(Flag!"exhaustive" exhaustive, handlers...)
 {
     auto ref matchImpl(SumTypes...)(auto ref SumTypes args)
@@ -2029,10 +2002,11 @@ private template matchImpl(Flag!"exhaustive" exhaustive, handlers...)
     }
 }
 
+// Predicate for staticMap
 private enum typeCount(SumType) = SumType.Types.length;
 
-/* A TagTuple represents a single possible set of tags that `args`
- * could have at runtime.
+/* A TagTuple represents a single possible set of tags that the arguments to
+ * `matchImpl` could have at runtime.
  *
  * Because D does not allow a struct to be the controlling expression
  * of a switch statement, we cannot dispatch on the TagTuple directly.
@@ -2104,6 +2078,33 @@ private struct TagTuple(SumTypes...)
     }
 }
 
+/* The number that the dim-th argument's tag is multiplied by when
+ * converting TagTuples to and from case indices ("caseIds").
+ *
+ * Named by analogy to the stride that the dim-th index into a
+ * multidimensional static array is multiplied by to calculate the
+ * offset of a specific element.
+ */
+private size_t stride(size_t dim, lengths...)()
+{
+    import core.checkedint : mulu;
+
+    size_t result = 1;
+    bool overflow = false;
+
+    static foreach (i; 0 .. dim)
+    {
+        result = mulu(result, lengths[i], overflow);
+    }
+
+    /* The largest number matchImpl uses, numCases, is calculated with
+     * stride!(SumTypes.length), so as long as this overflow check
+     * passes, we don't need to check for overflow anywhere else.
+     */
+    assert(!overflow, "Integer overflow");
+    return result;
+}
+
 // Matching
 @safe unittest
 {