interpreter: use typed_pos_args for func_import

and make the helper method private

mesonbuild/interpreter/interpreter.py

@@ -601,35 +601,33 @@ class Interpreter(InterpreterBase, HoldableObject):
                 dep = df.lookup(kwargs, force_fallback=True)
                 self.build.stdlibs[for_machine][l] = dep
 
-    def import_module(self, modname):
-        if modname in self.modules:
-            return
-        try:
-            module = importlib.import_module('mesonbuild.modules.' + modname)
-        except ImportError:
-            raise InvalidArguments(f'Module "{modname}" does not exist')
-        ext_module = module.initialize(self)
-        assert isinstance(ext_module, ModuleObject)
-        self.modules[modname] = ext_module
-
-    @stringArgs
+    @typed_pos_args('import', str)
     @noKwargs
-    def func_import(self, node, args, kwargs):
-        if len(args) != 1:
-            raise InvalidCode('Import takes one argument.')
+    def func_import(self, node: mparser.BaseNode, args: T.Tuple[str], kwargs) -> ModuleObject:
         modname = args[0]
         if modname.startswith('unstable-'):
             plainname = modname.split('-', 1)[1]
             try:
                 # check if stable module exists
-                self.import_module(plainname)
+                self._import_module(plainname)
                 mlog.warning(f'Module {modname} is now stable, please use the {plainname} module instead.')
                 modname = plainname
             except InvalidArguments:
                 mlog.warning('Module %s has no backwards or forwards compatibility and might not exist in future releases.' % modname, location=node)
                 modname = 'unstable_' + plainname
-        self.import_module(modname)
-        return self.modules[modname]
+
+        if modname in self.modules:
+            return self.modules[modname]
+
+        try:
+            module = importlib.import_module('mesonbuild.modules.' + modname)
+        except ImportError:
+            raise InvalidArguments(f'Module "{modname}" does not exist')
+        ext_module = module.initialize(self)
+        assert isinstance(ext_module, ModuleObject)
+        self.modules[modname] = ext_module
+
+        return ext_module
 
     @stringArgs
     @noKwargs