diff --git a/src/archunitpython/common/fluentapi/checkable.py b/src/archunitpython/common/fluentapi/checkable.py
index 10f216c..ec555fb 100644
--- a/src/archunitpython/common/fluentapi/checkable.py
+++ b/src/archunitpython/common/fluentapi/checkable.py
@@ -9,7 +9,7 @@
 from archunitpython.common.logging.types import LoggingOptions
 
 
-@dataclass(frozen=True)
+@dataclass(frozen=True, slots=True)
 class CheckOptions:
     """Options for controlling rule check execution."""
 
diff --git a/src/archunitpython/common/logging/types.py b/src/archunitpython/common/logging/types.py
index fc0d744..f54eab8 100644
--- a/src/archunitpython/common/logging/types.py
+++ b/src/archunitpython/common/logging/types.py
@@ -8,7 +8,7 @@
 LogLevel = Literal["debug", "info", "warn", "error"]
 
 
-@dataclass(frozen=True)
+@dataclass(frozen=True, slots=True)
 class LoggingOptions:
     """Options for controlling logging during architecture checks."""
 
diff --git a/src/archunitpython/common/types.py b/src/archunitpython/common/types.py
index 4e1839c..24b51c6 100644
--- a/src/archunitpython/common/types.py
+++ b/src/archunitpython/common/types.py
@@ -13,7 +13,7 @@
 MatchType = Literal["exact", "partial"]
 
 
-@dataclass(frozen=True)
+@dataclass(frozen=True, slots=True)
 class PatternMatchingOptions:
     """Options controlling how a pattern is matched against file paths."""
 
@@ -21,7 +21,7 @@ class PatternMatchingOptions:
     matching: MatchType = "partial"
 
 
-@dataclass(frozen=True)
+@dataclass(frozen=True, slots=True)
 class Filter:
     """A compiled regex filter with matching options."""
 
diff --git a/src/archunitpython/common/util/declaration_detector.py b/src/archunitpython/common/util/declaration_detector.py
index 7997eeb..5d85983 100644
--- a/src/archunitpython/common/util/declaration_detector.py
+++ b/src/archunitpython/common/util/declaration_detector.py
@@ -6,7 +6,7 @@
 from dataclasses import dataclass
 
 
-@dataclass
+@dataclass(slots=True)
 class DeclarationCounts:
     """Counts of different declaration types in a Python file."""
 
@@ -88,24 +88,18 @@ def count_declarations(source: str) -> DeclarationCounts:
                     if is_abstract_method(item):
                         counts.abstract_methods += 1
 
-        elif isinstance(node, (ast.FunctionDef, ast.AsyncFunctionDef)):
+    for node in tree.body:
+        if isinstance(node, (ast.FunctionDef, ast.AsyncFunctionDef)):
             # Only count module-level functions
-            if _is_module_level(node, tree):
-                counts.total += 1
-                counts.functions += 1
-
-        elif isinstance(node, ast.Assign) and _is_module_level(node, tree):
+            counts.functions += 1
             counts.total += 1
+        if isinstance(node, ast.Assign):
             counts.variables += 1
+            counts.total += 1
 
     return counts
 
 
-def _is_module_level(node: ast.AST, tree: ast.Module) -> bool:
-    """Check if a node is directly in the module body."""
-    return node in tree.body
-
-
 def _get_name(node: ast.expr) -> str:
     """Extract a name from an AST node."""
     if isinstance(node, ast.Name):