Add comment and exception for problematic edge case in from_any()

1 files changed, 25 insertions, 0 deletions

diff --git a/polymatrix/expression/from_.py b/polymatrix/expression/from_.py
index 65b636d..a3ee56e 100644
--- a/polymatrix/expression/from_.py
+++ b/polymatrix/expression/from_.py
@@ -7,12 +7,14 @@ from typing import Iterable, Any
 
 import polymatrix.expression.init as init
 
+from polymatrix.expression.init import init_variable_expr
 from polymatrix.expression.mixins.expressionbasemixin import ExpressionBaseMixin
 from polymatrix.expression.typing import FromSupportedTypes
 from polymatrix.expressionstate import ExpressionState
 from polymatrix.statemonad import StateMonad
 from polymatrix.polymatrix.mixins import PolyMatrixMixin
 from polymatrix.utils.deprecation import deprecated
+from polymatrix.variable import Variable
 
 from polymatrix.expression.expression import (
     init_expression, Expression,
@@ -43,6 +45,29 @@ def from_any_or(value: FromSupportedTypes, value_if_not_supported: Any) -> Expre
     elif isinstance(value, ExpressionBaseMixin):
         return init_expression(value)
 
+    elif isinstance(value, Variable) and not isinstance(value, ExpressionBaseMixin):
+        # This happens when a variable is constructed somewhere using
+        # polymatrix.variable.init_variable. What should happen here?
+
+        # This is problematic because if there is already another variable in
+        # the state with the same name, but different type (eg a VariableExpr)
+        # it will throw an error.
+
+        # Also we need to consider the case when a variable was created by
+        # another package, e.g. is an optimization variable. What happens then?
+
+        # Should polymatrix.variable.VariableImpl even exist in the first
+        # place? It was part of the proposed architecture but I think it causes
+        # more problems than it is solving.
+
+        # Commented code below won't work
+
+        # value = init_variable_expr(value.name, shape=value.shape)
+        # return init_variable_expression(value)
+
+        raise NotImplementedError("You have encountered a convoluted edge case. "
+                                  "I'm very sorry it doesn't work yet.")
+
     elif isinstance(value, int | float):
         return from_number(value)