interpreter: move deprecation validation for *_pch to the interpreter

Author: dcbaker

mesonbuild/build.py

@@ -1610,8 +1610,6 @@ def add_pch(self, language: str, pchlist: T.List[str]) -> None:
             if os.path.dirname(pchlist[0]) != os.path.dirname(pchlist[1]):
                 raise InvalidArguments('PCH files must be stored in the same folder.')
 
-            FeatureDeprecated.single_use('PCH source files', '0.50.0', self.subproject,
-                                         'Only a single header file should be used.')
         for f in pchlist:
             if not os.path.isfile(os.path.join(self.environment.source_dir, self.subdir, f)):
                 raise MesonException(f'File {f} does not exist.')

mesonbuild/interpreter/type_checking.py

@@ -13,7 +13,7 @@
                      BothLibraries, SharedLibrary, StaticLibrary, Jar, Executable, StructuredSources)
 from ..options import OptionKey, UserFeatureOption
 from ..dependencies import Dependency, DependencyMethods, InternalDependency
-from ..interpreterbase.decorators import KwargInfo, ContainerTypeInfo, FeatureBroken
+from ..interpreterbase.decorators import KwargInfo, ContainerTypeInfo, FeatureBroken, FeatureDeprecated
 from ..mesonlib import (File, FileMode, MachineChoice, has_path_sep, listify, stringlistify,
                         EnvironmentVariables)
 from ..programs import ExternalProgram
@@ -658,12 +658,18 @@ def _pch_validator(args: T.List[str]) -> T.Optional[str]:
     return None
 
 
+def _pch_feature_validator(args: T.List[str]) -> T.Iterable[FeatureCheckBase]:
+    if len(args) > 1:
+        yield FeatureDeprecated('PCH source files', '0.50.0', 'Only a single header file should be used.')
+
+
 _PCH_ARGS: KwargInfo[T.List[str]] = KwargInfo(
     'pch',
     ContainerTypeInfo(list, str),
     listify=True,
     default=[],
     validator=_pch_validator,
+    feature_validator=_pch_feature_validator,
 )