interpreterbase: Fix version checking for deprecation

Currently deprecation features use the same logic as new features, but
that doesn't work correctly. FeatureNew wants to warn about cases where
you claim to support >= 0.40, but use a feature from 0.42; deprecation
wants to warn when you claim to support >= 0.50, but use a feature that
was replaced in 0.45.

To make this work we need to invert the version check in the deprecation
function, so that if the deprecation is 0.45, and the supported version
is >= 0.50, we get a true not a false.

mesonbuild/interpreterbase.py

@@ -18,6 +18,7 @@
 from . import mparser, mesonlib, mlog
 from . import environment, dependencies
 
+import abc
 import os, copy, re
 import collections.abc
 from functools import wraps
@@ -212,7 +213,7 @@ class permittedKwargs:
             return f(*wrapped_args, **wrapped_kwargs)
         return wrapped
 
-class FeatureCheckBase:
+class FeatureCheckBase(metaclass=abc.ABCMeta):
     "Base class for feature version checks"
 
     # In python 3.6 we can just forward declare this, but in 3.5 we can't
@@ -230,13 +231,18 @@ class FeatureCheckBase:
             return ''
         return mesonlib.project_meson_versions[subproject]
 
+    @staticmethod
+    @abc.abstractmethod
+    def check_version(target_version: str, feature_Version: str) -> bool:
+        pass
+
     def use(self, subproject: str) -> None:
         tv = self.get_target_version(subproject)
         # No target version
         if tv == '':
             return
         # Target version is new enough
-        if mesonlib.version_compare_condition_with_min(tv, self.feature_version):
+        if self.check_version(tv, self.feature_version):
             return
         # Feature is too new for target version, register it
         if subproject not in self.feature_registry:
@@ -287,6 +293,10 @@ class FeatureNew(FeatureCheckBase):
     # Format: {subproject: {feature_version: set(feature_names)}}
     feature_registry = {}  # type: T.ClassVar[T.Dict[str, T.Dict[str, T.Set[str]]]]
 
+    @staticmethod
+    def check_version(target_version: str, feature_version: str) -> bool:
+        return mesonlib.version_compare_condition_with_min(target_version, feature_version)
+
     @staticmethod
     def get_warning_str_prefix(tv: str) -> str:
         return 'Project specifies a minimum meson_version \'{}\' but uses features which were added in newer versions:'.format(tv)
@@ -303,6 +313,11 @@ class FeatureDeprecated(FeatureCheckBase):
     # Format: {subproject: {feature_version: set(feature_names)}}
     feature_registry = {}  # type: T.ClassVar[T.Dict[str, T.Dict[str, T.Set[str]]]]
 
+    @staticmethod
+    def check_version(target_version: str, feature_version: str) -> bool:
+        # For deprecatoin checks we need to return the inverse of FeatureNew checks
+        return not mesonlib.version_compare_condition_with_min(target_version, feature_version)
+
     @staticmethod
     def get_warning_str_prefix(tv: str) -> str:
         return 'Deprecated features used:'