Fix AST cloning in loop vectorizer. Add missing docstring.

src/pystencils/backend/ast/vector.py

@@ -50,6 +50,8 @@ class PsVecMemAcc(PsExpression, PsLvalue, PsVectorOp):
         offset: Offset inside the memory region
         vector_entries: Number of elements to access
         stride: Optional integer step size for strided access, or ``None`` for contiguous access
+        aligned: For contiguous accesses, whether the access is guaranteed to be naturally aligned
+            according to the vector data type
     """
 
     __match_args__ = ("pointer", "offset", "vector_entries", "stride", "aligned")

src/pystencils/backend/transformations/loop_vectorizer.py

@@ -187,13 +187,13 @@ class LoopVectorizer:
 
                 trailing_ctr = self._ctx.duplicate_symbol(scalar_ctr)
                 trailing_loop_body = substitute_symbols(
-                    loop.body, {scalar_ctr: PsExpression.make(trailing_ctr)}
+                    loop.body.clone(), {scalar_ctr: PsExpression.make(trailing_ctr)}
                 )
                 trailing_loop = PsLoop(
                     PsExpression.make(trailing_ctr),
                     PsExpression.make(trailing_start),
-                    loop.stop,
-                    loop.step,
+                    loop.stop.clone(),
+                    loop.step.clone(),
                     trailing_loop_body,
                 )