interpreter: add cm_interpreter to SubprojectHolder

This is used in the cmake module, as an extra attribute we just tack on.
Instead, let's actually define and type it.

mesonbuild/interpreter/interpreterobjects.py

@@ -1,3 +1,4 @@
+from __future__ import annotations
 import os
 import shlex
 import subprocess
@@ -29,9 +30,10 @@ import typing as T
 
 if T.TYPE_CHECKING:
     from . import kwargs
-    from .interpreter import Interpreter
+    from ..cmake.interpreter import CMakeInterpreter
     from ..envconfig import MachineInfo
     from ..interpreterbase import SubProject
+    from .interpreter import Interpreter
 
     from typing_extensions import TypedDict
 
@@ -678,6 +680,7 @@ class SubprojectHolder(MesonInterpreterObject):
         self.disabled_feature = disabled_feature
         self.exception = exception
         self.subdir = PurePath(subdir).as_posix()
+        self.cm_interpreter: T.Optional[CMakeInterpreter] = None
         self.methods.update({'get_variable': self.get_variable_method,
                              'found': self.found_method,
                              })

mesonbuild/modules/cmake.py

@@ -104,9 +104,10 @@ endmacro()
 class CMakeSubproject(ModuleObject):
     def __init__(self, subp: SubprojectHolder):
         assert isinstance(subp, SubprojectHolder)
-        assert hasattr(subp, 'cm_interpreter')
+        assert subp.cm_interpreter is not None
         super().__init__()
         self.subp = subp
+        self.cm_interpreter = subp.cm_interpreter
         self.methods.update({'get_variable': self.get_variable,
                              'dependency': self.dependency,
                              'include_directories': self.include_directories,
@@ -121,7 +122,7 @@ class CMakeSubproject(ModuleObject):
             raise InterpreterException('Exactly one argument is required.')
 
         tgt = args[0]
-        res = self.subp.cm_interpreter.target_info(tgt)
+        res = self.cm_interpreter.target_info(tgt)
         if res is None:
             raise InterpreterException(f'The CMake target {tgt} does not exist\n' +
                                        '  Use the following command in your meson.build to list all available targets:\n\n' +
@@ -172,7 +173,7 @@ class CMakeSubproject(ModuleObject):
     @noPosargs
     @noKwargs
     def target_list(self, state, args, kwargs):
-        return self.subp.cm_interpreter.target_list()
+        return self.cm_interpreter.target_list()
 
     @noPosargs
     @noKwargs