Introducing pg.Inferential: a new interface for symbolic value infe…

…rence.

This CL introduces interface `pg.Inferentiable` for representing symbolic nodes that could be inferred dynamically upon read. Based this new design, we were able to get rid of `pg.ContextualValue` and its leaky implementation (e.g. `sym_contextual_getattr`). As a result, we replaced `sym_value` with `sym_inferred`, and removed `sym_contextual_getattr/hasattr`, together with `pg.ContextualValue` and `pg.symbolic.GetAttributeContext`.

PiperOrigin-RevId: 552091721

pyglove/core/__init__.py

@@ -165,15 +165,9 @@
 Insertion = symbolic.Insertion
 WritePermissionError = symbolic.WritePermissionError
 
-# Contextual value marker.
-ContextualValue = symbolic.ContextualValue
-ContextualGetter = symbolic.ContextualGetter
-
-# Decorator for making contextual getters.
-contextual_getter = symbolic.contextual_getter
-
-# Context object for computing contextual attribute.
-GetAttributeContext = symbolic.GetAttributeContext
+# Inferentiable classes.
+Inferentiable = symbolic.Inferential
+InferredValue = symbolic.InferredValue
 
 #
 # Symbols from 'typing.py'

pyglove/core/symbolic/__init__.py

@@ -60,13 +60,11 @@
 from pyglove.core.symbolic.flags import auto_call_functors
 from pyglove.core.symbolic.flags import should_call_functors_during_init
 
-# Marker for contextual values.
-from pyglove.core.symbolic.base import ContextualValue
-from pyglove.core.symbolic.contextual import ContextualGetter
-from pyglove.core.symbolic.contextual import contextual_getter
+# Inferential values
+from pyglove.core.symbolic.base import Inferential
 
-# GetAttribute context for computing contextual values.
-from pyglove.core.symbolic.base import GetAttributeContext
+from pyglove.core.symbolic.inferred import InferredValue
+from pyglove.core.symbolic.inferred import ValueFromParentChain
 
 # Symbolic types and their definition helpers.
 from pyglove.core.symbolic.base import Symbolic