rewriter: Accept UnknownValue() in more places

Fixes #14840

2 files changed, 10 insertions, 5 deletions

diff --git a/mesonbuild/ast/interpreter.py b/mesonbuild/ast/interpreter.py
index 62c4839a7..86b644259 100644
--- a/mesonbuild/ast/interpreter.py
+++ b/mesonbuild/ast/interpreter.py
@@ -692,8 +692,11 @@ class AstInterpreter(InterpreterBase):
     def func_get_variable(self, node: BaseNode, args: T.List[TYPE_var], kwargs: T.Dict[str, TYPE_var]) -> T.Any:
         assert isinstance(node, FunctionNode)
         var_name = args[0]
-        assert isinstance(var_name, str)
-        val = self.get_cur_value(var_name)
+        if isinstance(var_name, UnknownValue):
+            val: T.Union[UnknownValue, BaseNode] = UnknownValue()
+        else:
+            assert isinstance(var_name, str)
+            val = self.get_cur_value(var_name)
         self.dataflow_dag.add_edge(val, node)
         return val
 
diff --git a/mesonbuild/ast/introspection.py b/mesonbuild/ast/introspection.py
index decce4b3a..6ffc6adbe 100644
--- a/mesonbuild/ast/introspection.py
+++ b/mesonbuild/ast/introspection.py
@@ -203,9 +203,11 @@ class IntrospectionInterpreter(AstInterpreter):
         has_fallback = 'fallback' in kwargs
         required = kwargs.get('required', True)
         version = kwargs.get('version', [])
-        if not isinstance(version, UnknownValue):
-            if not isinstance(version, list):
-                version = [version]
+        if not isinstance(version, list):
+            version = [version]
+        if any(isinstance(el, UnknownValue) for el in version):
+            version = UnknownValue()
+        else:
             assert all(isinstance(el, str) for el in version)
             version = T.cast(T.List[str], version)
         assert isinstance(required, (bool, UnknownValue))