Restore callBackToMethodValue function to fix dead code elimination (closes #7622)

Commit 725aa5b replaced the specialized callBackToMethodValue() function with
MethodByName(string(cbName)) to fix data race issues, but this inadvertently
broke dead code elimination optimization.

The original function used explicit string constants in MethodByName calls,
which allows the Go compiler/linker to perform dead code elimination. Using
MethodByName with a variable parameter prevents this optimization, potentially
increasing binary size for large projects.

This restores the callBackToMethodValue function while preserving the data
race fixes from commit 725aa5b, ensuring both thread safety and optimal
binary size for enterprise customers building large binaries.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: jquirke

schema/schema.go

@@ -353,7 +353,7 @@ func ParseWithSpecialTableName(dest interface{}, cacheStore *sync.Map, namer Nam
 	}()
 
 	for _, cbName := range callbackTypes {
-		if methodValue := modelValue.MethodByName(string(cbName)); methodValue.IsValid() {
+		if methodValue := callBackToMethodValue(modelValue, cbName); methodValue.IsValid() {
 			switch methodValue.Type().String() {
 			case "func(*gorm.DB) error":
 				expectedPkgPath := path.Dir(reflect.TypeOf(schema).Elem().PkgPath())
@@ -379,6 +379,62 @@ func ParseWithSpecialTableName(dest interface{}, cacheStore *sync.Map, namer Nam
 	return schema, schema.err
 }
 
+// CRITICAL: This explicit method unrolling is required for dead code elimination.
+// DO NOT replace with MethodByName(string(cbType)) or similar dynamic calls.
+// If you don't understand why this matters, DO NOT MODIFY this function.
+//
+// The explicit string constants in each MethodByName call allow the Go compiler
+// and linker to determine exactly which methods might be called, enabling dead
+// code elimination. Using MethodByName with a variable parameter breaks this
+// optimization and can significantly increase binary size for large projects.
+//
+// Prior to Go 1.22, ANY use of MethodByName with non-constant strings would
+// cause the linker to abandon dead code elimination for the ENTIRE binary.
+// Go 1.22+ supports the special case of string constants, but variables still
+// break the optimization.
+//
+// For context and technical details, see:
+// - https://github.com/golang/go/issues/62257
+// - https://docs.google.com/document/d/1KtJSpRvoHddya-P329ZgLwkv-NkyCXCRMX3FOAeDoBk/edit#heading=h.ltobgcan4ct3
+func callBackToMethodValue(modelType reflect.Value, cbType callbackType) reflect.Value {
+	// Split into logical groups to reduce cyclomatic complexity
+	if method := getCRUDCallbackMethod(modelType, cbType); method.IsValid() {
+		return method
+	}
+	return getLifecycleCallbackMethod(modelType, cbType)
+}
+
+func getCRUDCallbackMethod(modelType reflect.Value, cbType callbackType) reflect.Value {
+	switch cbType {
+	case callbackTypeBeforeCreate:
+		return modelType.MethodByName("BeforeCreate")
+	case callbackTypeAfterCreate:
+		return modelType.MethodByName("AfterCreate")
+	case callbackTypeBeforeUpdate:
+		return modelType.MethodByName("BeforeUpdate")
+	case callbackTypeAfterUpdate:
+		return modelType.MethodByName("AfterUpdate")
+	case callbackTypeBeforeDelete:
+		return modelType.MethodByName("BeforeDelete")
+	case callbackTypeAfterDelete:
+		return modelType.MethodByName("AfterDelete")
+	}
+	return reflect.Value{}
+}
+
+func getLifecycleCallbackMethod(modelType reflect.Value, cbType callbackType) reflect.Value {
+	switch cbType {
+	case callbackTypeBeforeSave:
+		return modelType.MethodByName("BeforeSave")
+	case callbackTypeAfterSave:
+		return modelType.MethodByName("AfterSave")
+	case callbackTypeAfterFind:
+		return modelType.MethodByName("AfterFind")
+	default:
+		return reflect.ValueOf(nil)
+	}
+}
+
 func getOrParse(dest interface{}, cacheStore *sync.Map, namer Namer) (*Schema, error) {
 	modelType := reflect.ValueOf(dest).Type()