rewriter: Replace assignments with cur_assignments

Replace the variable tracking of `AstInterpreter.assignments`
with a slightly better variable tracking called
`AstInterpreter.cur_assignments`.
We now have a class `UnknownValue` for more explicit handling
of situations that are too complex/impossible.

1 files changed, 6 insertions, 0 deletions

diff --git a/mesonbuild/interpreterbase/baseobjects.py b/mesonbuild/interpreterbase/baseobjects.py
index a5ccccedc..7cda5729f 100644
--- a/mesonbuild/interpreterbase/baseobjects.py
+++ b/mesonbuild/interpreterbase/baseobjects.py
@@ -121,6 +121,12 @@ class MesonInterpreterObject(InterpreterObject):
 class MutableInterpreterObject:
     ''' Dummy class to mark the object type as mutable '''
 
+class UnknownValue(MesonInterpreterObject):
+    '''This class is only used for the rewriter/static introspection tool and
+    indicates that a value cannot be determined statically, either because of
+    limitations in our code or because the value differs from machine to
+    machine.'''
+
 HoldableTypes = (HoldableObject, int, bool, str, list, dict)
 TYPE_HoldableTypes = T.Union[TYPE_var, HoldableObject]
 InterpreterObjectTypeVar = T.TypeVar('InterpreterObjectTypeVar', bound=TYPE_HoldableTypes)