Use MatrixGenExpr view for GenExpr arrays

Author: Zeroto521

CHANGELOG.md

@@ -8,6 +8,7 @@
 ### Fixed
 - Removed `Py_INCREF`/`Py_DECREF` on `Model` in `catchEvent`/`dropEvent` that caused memory leak for imbalanced usage
 - Used `getIndex()` instead of `ptr()` for sorting nonlinear expression terms to avoid nondeterministic behavior 
+- Return `MatrixGenExpr` in `buildGenExprObj` instead of `MatrixExpr`
 ### Changed
 - Speed up `constant * Expr` via C-level API
 ### Removed

src/pyscipopt/expr.pxi

@@ -210,7 +210,7 @@ def buildGenExprObj(expr):
         GenExprs = np.empty(expr.shape, dtype=object)
         for idx in np.ndindex(expr.shape):
             GenExprs[idx] = buildGenExprObj(expr[idx])
-        return GenExprs.view(MatrixExpr)
+        return GenExprs.view(MatrixGenExpr)
 
     else:
         assert isinstance(expr, GenExpr)