interpreter: remove current_lineno

This was only used in a couple of places, and requires extra tracking to
ensure it is correct, while we already have `current_node.lineno`, which
is always accurate and up to date.

I have also fixed a potential strict-null issue by using a sentinel node
for `current_node`

mesonbuild/interpreter/interpreter.py

@@ -2701,11 +2701,11 @@ class Interpreter(InterpreterBase, HoldableObject):
         ofile_rpath = os.path.join(self.subdir, output)
         if ofile_rpath in self.configure_file_outputs:
             mesonbuildfile = os.path.join(self.subdir, 'meson.build')
-            current_call = f"{mesonbuildfile}:{self.current_lineno}"
+            current_call = f"{mesonbuildfile}:{self.current_node.lineno}"
             first_call = "{}:{}".format(mesonbuildfile, self.configure_file_outputs[ofile_rpath])
             mlog.warning('Output file', mlog.bold(ofile_rpath, True), 'for configure_file() at', current_call, 'overwrites configure_file() output at', first_call)
         else:
-            self.configure_file_outputs[ofile_rpath] = self.current_lineno
+            self.configure_file_outputs[ofile_rpath] = self.current_node.lineno
         (ofile_path, ofile_fname) = os.path.split(os.path.join(self.subdir, output))
         ofile_abs = os.path.join(self.environment.build_dir, ofile_path, ofile_fname)
 

mesonbuild/interpreterbase/interpreterbase.py

@@ -82,7 +82,7 @@ class InterpreterBase:
         self.current_lineno = -1
         # Current node set during a function call. This can be used as location
         # when printing a warning message during a method call.
-        self.current_node: mparser.BaseNode = None
+        self.current_node = mparser.BaseNode(-1, -1, 'sentinel')
         # This is set to `version_string` when this statement is evaluated:
         # meson.version().compare_version(version_string)
         # If it was part of a if-clause, it is used to temporally override the
@@ -183,7 +183,6 @@ class InterpreterBase:
         while i < len(statements):
             cur = statements[i]
             try:
-                self.current_lineno = cur.lineno
                 self.evaluate_statement(cur)
             except Exception as e:
                 if getattr(e, 'lineno', None) is None:

mesonbuild/modules/__init__.py

@@ -38,7 +38,7 @@ class ModuleState:
         self.subproject = interpreter.subproject
         self.subdir = interpreter.subdir
         self.root_subdir = interpreter.root_subdir
-        self.current_lineno = interpreter.current_lineno
+        self.current_lineno = interpreter.current_node.lineno
         self.environment = interpreter.environment
         self.project_name = interpreter.build.project_name
         self.project_version = interpreter.build.dep_manifest[interpreter.active_projectname].version