fix(php-shim): accept negative offsets in substr_replace

The signature took usize, so PHP's negative $start and $length, which
count from the end of the string, could not be expressed. Take i64 and
an optional length, and apply PHP's clamping rules.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

2 files changed, 7 insertions, 5 deletions

diff --git a/crates/shirabe/src/package/version/version_bumper.rs b/crates/shirabe/src/package/version/version_bumper.rs
index c0e76520..fcdbf246 100644
--- a/crates/shirabe/src/package/version/version_bumper.rs
+++ b/crates/shirabe/src/package/version/version_bumper.rs
@@ -112,10 +112,12 @@ impl VersionBumper {
                     } else {
                         format!("{}{}", new_pretty_constraint, suffix)
                     };
-                let offset = match_offset as usize;
-                let length = Platform::strlen(match_str) as usize;
-                modified =
-                    shirabe_php_shim::substr_replace(&modified, &replacement, offset, length);
+                modified = shirabe_php_shim::substr_replace(
+                    &modified,
+                    &replacement,
+                    match_offset,
+                    Some(Platform::strlen(match_str)),
+                );
             }
 
             let new_constraint = parser.parse_constraints(&modified)?;
diff --git a/crates/shirabe/src/util/process_executor.rs b/crates/shirabe/src/util/process_executor.rs
index 00091029..875c8810 100644
--- a/crates/shirabe/src/util/process_executor.rs
+++ b/crates/shirabe/src/util/process_executor.rs
@@ -224,7 +224,7 @@ impl ProcessExecutor {
                         &command_str,
                         &Self::escape(&Self::get_executable(&m1)),
                         0,
-                        strlen(&m1) as usize,
+                        Some(strlen(&m1)),
                     );
                 }
             }