spanify: Adjust url_canon_ip

When arrayified, compilation breaks when one tries to index a
`std::array` with a signed type (in this case, `int`).

*   Change problematic values to be an unsigned type and add
    compile-time assertions that they have suitable range.

*   Don't use `StrictNumeric` and friends for now, since we intend
    on converting the indexees to `std::array`, which will give us
    bounds checks for free.

*   Don't use `std::extent_v` in the `static_asserts` for similar
    reasons, since it will silently fail when indexees are arrayified.
    For example, `std::extent_v<some_std_array>` yields `0` in my build.

Bug: 406029216
Change-Id: Icadb0bd39148da5f58c64878f711052689946ad9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6415469
Reviewed-by: Mike West <mkwst@chromium.org>
Commit-Queue: Kalvin Lee <kdlee@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1440729}

url/url_canon_ip.h

@@ -10,6 +10,10 @@
 #ifndef URL_URL_CANON_IP_H_
 #define URL_URL_CANON_IP_H_
 
+#include <cstdint>
+#include <limits>
+#include <type_traits>
+
 #include "base/component_export.h"
 #include "url/third_party/mozilla/url_parse.h"
 #include "url/url_canon.h"
@@ -154,7 +158,11 @@ constexpr CanonHostInfo::Family DoIPv4AddressToNumber(
   // component, which allows for early exit if the last component isn't a
   // number.
   uint32_t component_values[4];
-  int existing_components = 0;
+  uint8_t existing_components = 0;
+  // `existing_components` is used to index `component_values`.
+  // All possible values must be in range.
+  static_assert(std::numeric_limits<decltype(existing_components)>::max() >=
+                sizeof(component_values) / sizeof(component_values[0]));
 
   int current_component_end = host.end();
   int current_position = current_component_end;
@@ -202,7 +210,7 @@ constexpr CanonHostInfo::Family DoIPv4AddressToNumber(
 
   // First, process all components but the last, while making sure each fits
   // within an 8-bit field.
-  for (int i = existing_components - 1; i > 0; i--) {
+  for (decltype(existing_components) i = existing_components - 1; i > 0; --i) {
     if (component_values[i] > std::numeric_limits<uint8_t>::max()) {
       return CanonHostInfo::BROKEN;
     }
@@ -277,7 +285,9 @@ struct IPv6Parsed {
   Component hex_components[8];
 
   // The count of hex components present. Ranges from [0,8].
-  int num_hex_components;
+  uint8_t num_hex_components;
+  static_assert(std::numeric_limits<decltype(num_hex_components)>::max() >=
+                sizeof(hex_components) / sizeof(hex_components[0]));
 
   // The index of the hex component that the "::" contraction precedes, or
   // -1 if there is no contraction.
@@ -479,7 +489,8 @@ constexpr bool DoIPv6AddressToNumber(const CHAR* spec,
   int cur_index_in_address = 0;
 
   // Loop through each hex components, and contraction in order.
-  for (int i = 0; i <= ipv6_parsed.num_hex_components; ++i) {
+  for (decltype(ipv6_parsed.num_hex_components) i = 0;
+       i <= ipv6_parsed.num_hex_components; ++i) {
     // Append the contraction if it appears before this component.
     if (i == ipv6_parsed.index_of_contraction) {
       for (int j = 0; j < num_bytes_of_contraction; ++j) {