first pass at migrating to dataclasses

In some cases, init variables that accept None as a sentinel and
immediately overwrite with [], are migrated to dataclass field
factories. \o/

Note: dataclasses by default cannot provide eq methods, as they then
become unhashable. In the future we may wish to opt into declaring them
frozen, instead/additionally.

7 files changed, 259 insertions, 281 deletions

diff --git a/mesonbuild/backend/backends.py b/mesonbuild/backend/backends.py
index 89febcb..957b259 100644
--- a/mesonbuild/backend/backends.py
+++ b/mesonbuild/backend/backends.py
@@ -13,6 +13,7 @@
 # limitations under the License.
 
 from collections import OrderedDict
+from dataclasses import dataclass, InitVar
 from functools import lru_cache
 from itertools import chain
 from pathlib import Path
@@ -61,11 +62,11 @@ if T.TYPE_CHECKING:
 # Assembly files cannot be unitified and neither can LLVM IR files
 LANGS_CANT_UNITY = ('d', 'fortran', 'vala')
 
+@dataclass(eq=False)
 class RegenInfo:
-    def __init__(self, source_dir: str, build_dir: str, depfiles: T.List[str]):
-        self.source_dir = source_dir
-        self.build_dir = build_dir
-        self.depfiles = depfiles
+    source_dir: str
+    build_dir: str
+    depfiles: T.List[str]
 
 class TestProtocol(enum.Enum):
 
@@ -97,28 +98,30 @@ class TestProtocol(enum.Enum):
         return 'tap'
 
 
+@dataclass(eq=False)
 class CleanTrees:
     '''
     Directories outputted by custom targets that have to be manually cleaned
     because on Linux `ninja clean` only deletes empty directories.
     '''
-    def __init__(self, build_dir: str, trees: T.List[str]):
-        self.build_dir = build_dir
-        self.trees = trees
+    build_dir: str
+    trees: T.List[str]
 
+@dataclass(eq=False)
 class InstallData:
-    def __init__(self, source_dir: str, build_dir: str, prefix: str, libdir: str,
-                 strip_bin: T.List[str], install_umask: T.Union[str, int],
-                 mesonintrospect: T.List[str], version: str,
-                 is_cross_build: bool):
-        # TODO: in python 3.8 or with typing_Extensions install_umask could be:
-        # `T.Union[T.Literal['preserve'], int]`, which would be more accurate.
-        self.source_dir = source_dir
-        self.build_dir = build_dir
-        self.prefix = prefix
-        self.libdir = libdir
-        self.strip_bin = strip_bin
-        self.install_umask = install_umask
+    source_dir: str
+    build_dir: str
+    prefix: str
+    libdir: str
+    strip_bin: T.List[str]
+    # TODO: in python 3.8 or with typing_Extensions this could be:
+    # `T.Union[T.Literal['preserve'], int]`, which would be more accurate.
+    install_umask: T.Union[str, int]
+    mesonintrospect: T.List[str]
+    version: str
+    is_cross_build: bool
+
+    def __post_init__(self) -> None:
         self.targets: T.List[TargetInstallData] = []
         self.headers: T.List[InstallDataBase] = []
         self.man: T.List[InstallDataBase] = []
@@ -127,59 +130,52 @@ class InstallData:
         self.symlinks: T.List[InstallSymlinkData] = []
         self.install_scripts: T.List[ExecutableSerialisation] = []
         self.install_subdirs: T.List[SubdirInstallData] = []
-        self.mesonintrospect = mesonintrospect
-        self.version = version
-        self.is_cross_build = is_cross_build
 
+@dataclass(eq=False)
 class TargetInstallData:
-
+    fname: str
+    outdir: str
+    outdir_name: InitVar[str]
+    aliases: T.Dict[str, str]
+    strip: bool
+    install_name_mappings: T.Mapping[str, str]
+    rpath_dirs_to_remove: T.Set[bytes]
+    install_rpath: str
     # TODO: install_mode should just always be a FileMode object
+    install_mode: T.Optional['FileMode']
+    subproject: str
+    optional: bool = False
+    tag: T.Optional[str] = None
 
-    def __init__(self, fname: str, outdir: str, outdir_name: str, aliases: T.Dict[str, str],
-                 strip: bool, install_name_mappings: T.Mapping[str, str], rpath_dirs_to_remove: T.Set[bytes],
-                 install_rpath: str, install_mode: T.Optional['FileMode'],
-                 subproject: str, optional: bool = False, tag: T.Optional[str] = None):
-        self.fname = fname
-        self.outdir = outdir
-        self.out_name = os.path.join(outdir_name, os.path.basename(fname))
-        self.aliases = aliases
-        self.strip = strip
-        self.install_name_mappings = install_name_mappings
-        self.rpath_dirs_to_remove = rpath_dirs_to_remove
-        self.install_rpath = install_rpath
-        self.install_mode = install_mode
-        self.subproject = subproject
-        self.optional = optional
-        self.tag = tag
+    def __post_init__(self, outdir_name: str) -> None:
+        self.out_name = os.path.join(outdir_name, os.path.basename(self.fname))
 
+@dataclass(eq=False)
 class InstallEmptyDir:
-    def __init__(self, path: str, install_mode: 'FileMode', subproject: str, tag: T.Optional[str] = None):
-        self.path = path
-        self.install_mode = install_mode
-        self.subproject = subproject
-        self.tag = tag
+    path: str
+    install_mode: 'FileMode'
+    subproject: str
+    tag: T.Optional[str] = None
 
+@dataclass(eq=False)
 class InstallDataBase:
-    def __init__(self, path: str, install_path: str, install_path_name: str,
-                 install_mode: 'FileMode', subproject: str, tag: T.Optional[str] = None,
-                 data_type: T.Optional[str] = None):
-        self.path = path
-        self.install_path = install_path
-        self.install_path_name = install_path_name
-        self.install_mode = install_mode
-        self.subproject = subproject
-        self.tag = tag
-        self.data_type = data_type
-
+    path: str
+    install_path: str
+    install_path_name: str
+    install_mode: 'FileMode'
+    subproject: str
+    tag: T.Optional[str] = None
+    data_type: T.Optional[str] = None
+
+@dataclass(eq=False)
 class InstallSymlinkData:
-    def __init__(self, target: str, name: str, install_path: str,
-                 subproject: str, tag: T.Optional[str] = None):
-        self.target = target
-        self.name = name
-        self.install_path = install_path
-        self.subproject = subproject
-        self.tag = tag
+    target: str
+    name: str
+    install_path: str
+    subproject: str
+    tag: T.Optional[str] = None
 
+# cannot use dataclass here because "exclude" is out of order
 class SubdirInstallData(InstallDataBase):
     def __init__(self, path: str, install_path: str, install_path_name: str,
                  install_mode: 'FileMode', exclude: T.Tuple[T.Set[str], T.Set[str]],
@@ -187,64 +183,53 @@ class SubdirInstallData(InstallDataBase):
         super().__init__(path, install_path, install_path_name, install_mode, subproject, tag, data_type)
         self.exclude = exclude
 
+@dataclass(eq=False)
 class ExecutableSerialisation:
 
     # XXX: should capture and feed default to False, instead of None?
 
-    def __init__(self, cmd_args: T.List[str],
-                 env: T.Optional[build.EnvironmentVariables] = None,
-                 exe_wrapper: T.Optional['programs.ExternalProgram'] = None,
-                 workdir: T.Optional[str] = None,
-                 extra_paths: T.Optional[T.List] = None,
-                 capture: T.Optional[bool] = None,
-                 feed: T.Optional[bool] = None,
-                 tag: T.Optional[str] = None,
-                 verbose: bool = False,
-                 ) -> None:
-        self.cmd_args = cmd_args
-        self.env = env
-        if exe_wrapper is not None:
-            assert isinstance(exe_wrapper, programs.ExternalProgram)
-        self.exe_wrapper = exe_wrapper
-        self.workdir = workdir
-        self.extra_paths = extra_paths
-        self.capture = capture
-        self.feed = feed
+    cmd_args: T.List[str]
+    env: T.Optional[build.EnvironmentVariables] = None
+    exe_wrapper: T.Optional['programs.ExternalProgram'] = None
+    workdir: T.Optional[str] = None
+    extra_paths: T.Optional[T.List] = None
+    capture: T.Optional[bool] = None
+    feed: T.Optional[bool] = None
+    tag: T.Optional[str] = None
+    verbose: bool = False
+
+    def __post_init__(self) -> None:
+        if self.exe_wrapper is not None:
+            assert isinstance(self.exe_wrapper, programs.ExternalProgram)
         self.pickled = False
         self.skip_if_destdir = False
-        self.verbose = verbose
         self.subproject = ''
-        self.tag = tag
 
+@dataclass(eq=False)
 class TestSerialisation:
-    def __init__(self, name: str, project_name: str, suite: T.List[str], fname: T.List[str],
-                 is_cross_built: bool, exe_wrapper: T.Optional[programs.ExternalProgram],
-                 needs_exe_wrapper: bool, is_parallel: bool, cmd_args: T.List[str],
-                 env: build.EnvironmentVariables, should_fail: bool,
-                 timeout: T.Optional[int], workdir: T.Optional[str],
-                 extra_paths: T.List[str], protocol: TestProtocol, priority: int,
-                 cmd_is_built: bool, depends: T.List[str], version: str):
-        self.name = name
-        self.project_name = project_name
-        self.suite = suite
-        self.fname = fname
-        self.is_cross_built = is_cross_built
-        if exe_wrapper is not None:
-            assert isinstance(exe_wrapper, programs.ExternalProgram)
-        self.exe_wrapper = exe_wrapper
-        self.is_parallel = is_parallel
-        self.cmd_args = cmd_args
-        self.env = env
-        self.should_fail = should_fail
-        self.timeout = timeout
-        self.workdir = workdir
-        self.extra_paths = extra_paths
-        self.protocol = protocol
-        self.priority = priority
-        self.needs_exe_wrapper = needs_exe_wrapper
-        self.cmd_is_built = cmd_is_built
-        self.depends = depends
-        self.version = version
+    name: str
+    project_name: str
+    suite: T.List[str]
+    fname: T.List[str]
+    is_cross_built: bool
+    exe_wrapper: T.Optional[programs.ExternalProgram]
+    needs_exe_wrapper: bool
+    is_parallel: bool
+    cmd_args: T.List[str]
+    env: build.EnvironmentVariables
+    should_fail: bool
+    timeout: T.Optional[int]
+    workdir: T.Optional[str]
+    extra_paths: T.List[str]
+    protocol: TestProtocol
+    priority: int
+    cmd_is_built: bool
+    depends: T.List[str]
+    version: str
+
+    def __post_init__(self) -> None:
+        if self.exe_wrapper is not None:
+            assert isinstance(self.exe_wrapper, programs.ExternalProgram)
 
 
 def get_backend_from_name(backend: str, build: T.Optional[build.Build] = None, interpreter: T.Optional['Interpreter'] = None) -> T.Optional['Backend']:
diff --git a/mesonbuild/build.py b/mesonbuild/build.py
index d8002bf..93bf29d 100644
--- a/mesonbuild/build.py
+++ b/mesonbuild/build.py
@@ -13,6 +13,7 @@
 # limitations under the License.
 
 from collections import OrderedDict
+from dataclasses import dataclass, field
 from functools import lru_cache
 import copy
 import hashlib
@@ -130,22 +131,19 @@ def get_target_macos_dylib_install_name(ld) -> str:
 class InvalidArguments(MesonException):
     pass
 
+@dataclass(eq=False)
 class DependencyOverride(HoldableObject):
-    def __init__(self, dep: dependencies.Dependency, node: 'BaseNode', explicit: bool = True):
-        self.dep = dep
-        self.node = node
-        self.explicit = explicit
+    dep: dependencies.Dependency
+    node: 'BaseNode'
+    explicit: bool = True
 
+@dataclass(eq=False)
 class Headers(HoldableObject):
-
-    def __init__(self, sources: T.List[File], install_subdir: T.Optional[str],
-                 custom_install_dir: T.Optional[str], custom_install_mode: 'FileMode',
-                 subproject: str):
-        self.sources = sources
-        self.install_subdir = install_subdir
-        self.custom_install_dir = custom_install_dir
-        self.custom_install_mode = custom_install_mode
-        self.subproject = subproject
+    sources: T.List[File]
+    install_subdir: T.Optional[str]
+    custom_install_dir: T.Optional[str]
+    custom_install_mode: 'FileMode'
+    subproject: str
 
     # TODO: we really don't need any of these methods, but they're preserved to
     # keep APIs relying on them working.
@@ -166,16 +164,13 @@ class Headers(HoldableObject):
         return self.custom_install_mode
 
 
+@dataclass(eq=False)
 class Man(HoldableObject):
-
-    def __init__(self, sources: T.List[File], custom_install_dir: T.Optional[str],
-                 custom_install_mode: 'FileMode', subproject: str,
-                 locale: T.Optional[str]):
-        self.sources = sources
-        self.custom_install_dir = custom_install_dir
-        self.custom_install_mode = custom_install_mode
-        self.subproject = subproject
-        self.locale = locale
+    sources: T.List[File]
+    custom_install_dir: T.Optional[str]
+    custom_install_mode: 'FileMode'
+    subproject: str
+    locale: T.Optional[str]
 
     def get_custom_install_dir(self) -> T.Optional[str]:
         return self.custom_install_dir
@@ -187,40 +182,30 @@ class Man(HoldableObject):
         return self.sources
 
 
+@dataclass(eq=False)
 class EmptyDir(HoldableObject):
-
-    def __init__(self, path: str, install_mode: 'FileMode', subproject: str,
-                 install_tag: T.Optional[str] = None):
-        self.path = path
-        self.install_mode = install_mode
-        self.subproject = subproject
-        self.install_tag = install_tag
+    path: str
+    install_mode: 'FileMode'
+    subproject: str
+    install_tag: T.Optional[str] = None
 
 
+@dataclass(eq=False)
 class InstallDir(HoldableObject):
+    source_subdir: str
+    installable_subdir: str
+    install_dir: str
+    install_mode: 'FileMode'
+    exclude: T.Tuple[T.Set[str], T.Set[str]]
+    strip_directory: bool
+    subproject: str
+    from_source_dir: bool = True
+    install_tag: T.Optional[str] = None
 
-    def __init__(self, source_subdir: str, installable_subdir: str, install_dir: str,
-                 install_mode: 'FileMode',
-                 exclude: T.Tuple[T.Set[str], T.Set[str]],
-                 strip_directory: bool, subproject: str,
-                 from_source_dir: bool = True,
-                 install_tag: T.Optional[str] = None):
-        self.source_subdir = source_subdir
-        self.installable_subdir = installable_subdir
-        self.install_dir = install_dir
-        self.install_mode = install_mode
-        self.exclude = exclude
-        self.strip_directory = strip_directory
-        self.from_source_dir = from_source_dir
-        self.subproject = subproject
-        self.install_tag = install_tag
-
-
+@dataclass(eq=False)
 class DepManifest:
-
-    def __init__(self, version: str, license: T.List[str]):
-        self.version = version
-        self.license = license
+    version: str
+    license: T.List[str]
 
     def to_json(self) -> T.Dict[str, T.Union[str, T.List[str]]]:
         return {
@@ -229,6 +214,7 @@ class DepManifest:
         }
 
 
+# literally everything isn't dataclass stuff
 class Build:
     """A class that holds the status of one build including
     all dependencies and so on.
@@ -363,18 +349,17 @@ class Build:
 
         return link_args.get(compiler.get_language(), [])
 
+@dataclass(eq=False)
 class IncludeDirs(HoldableObject):
 
     """Internal representation of an include_directories call."""
 
-    def __init__(self, curdir: str, incdirs: T.List[str], is_system: bool, extra_build_dirs: T.Optional[T.List[str]] = None):
-        self.curdir = curdir
-        self.incdirs = incdirs
-        self.is_system = is_system
-
-        # Interpreter has validated that all given directories
-        # actually exist.
-        self.extra_build_dirs: T.List[str] = extra_build_dirs or []
+    curdir: str
+    incdirs: T.List[str]
+    is_system: bool
+    # Interpreter has validated that all given directories
+    # actually exist.
+    extra_build_dirs: T.List[str] = field(default_factory=list)
 
     def __repr__(self) -> str:
         r = '<{} {}/{}>'
@@ -404,21 +389,18 @@ class IncludeDirs(HoldableObject):
                 strlist.append(os.path.join(builddir, self.curdir, idir))
         return strlist
 
+@dataclass(eq=False)
 class ExtractedObjects(HoldableObject):
     '''
     Holds a list of sources for which the objects must be extracted
     '''
-    def __init__(self, target: 'BuildTarget',
-                 srclist: T.Optional[T.List[File]] = None,
-                 genlist: T.Optional[T.List['GeneratedTypes']] = None,
-                 objlist: T.Optional[T.List[T.Union[str, 'File', 'ExtractedObjects']]] = None,
-                 recursive: bool = True):
-        self.target = target
-        self.recursive = recursive
-        self.srclist: T.List[File] = srclist if srclist is not None else []
-        self.genlist: T.List['GeneratedTypes'] = genlist if genlist is not None else []
-        self.objlist: T.Optional[T.List[T.Union[str, 'File', 'ExtractedObjects']]] = \
-             objlist if objlist is not None else []
+    target: 'BuildTarget'
+    srclist: T.List[File] = field(default_factory=list)
+    genlist: T.List['GeneratedTypes'] = field(default_factory=list)
+    objlist: T.List[T.Union[str, 'File', 'ExtractedObjects']] = field(default_factory=list)
+    recursive: bool = True
+
+    def __post_init__(self) -> None:
         if self.target.is_unity:
             self.check_unity_compatible()
 
@@ -523,23 +505,25 @@ class EnvironmentVariables(HoldableObject):
             env[name] = method(env, name, values, separator)
         return env
 
+@dataclass(eq=False)
 class Target(HoldableObject):
 
     # TODO: should Target be an abc.ABCMeta?
 
-    def __init__(self, name: str, subdir: str, subproject: str, build_by_default: bool, for_machine: MachineChoice):
-        if has_path_sep(name):
+    name: str
+    subdir: str
+    subproject: str
+    build_by_default: bool
+    for_machine: MachineChoice
+
+    def __post_init__(self) -> None:
+        if has_path_sep(self.name):
             # Fix failing test 53 when this becomes an error.
             mlog.warning(textwrap.dedent(f'''\
-                Target "{name}" has a path separator in its name.
+                Target "{self.name}" has a path separator in its name.
                 This is not supported, it can cause unexpected failures and will become
                 a hard error in the future.\
             '''))
-        self.name = name
-        self.subdir = subdir
-        self.subproject = subproject
-        self.build_by_default = build_by_default
-        self.for_machine = for_machine
         self.install = False
         self.build_always_stale = False
         self.option_overrides_base: T.Dict[OptionKey, str] = {}
@@ -548,6 +532,7 @@ class Target(HoldableObject):
         if not hasattr(self, 'typename'):
             raise RuntimeError(f'Target type is not set for target class "{type(self).__name__}". This is a bug')
 
+    # dataclass comparators?
     def __lt__(self, other: object) -> bool:
         if not isinstance(other, Target):
             return NotImplemented
@@ -1619,6 +1604,7 @@ class Generator(HoldableObject):
     def __init__(self, exe: T.Union['Executable', programs.ExternalProgram],
                  arguments: T.List[str],
                  output: T.List[str],
+                 # how2dataclass
                  *,
                  depfile: T.Optional[str] = None,
                  capture: bool = False,
@@ -1691,24 +1677,27 @@ class Generator(HoldableObject):
         return output
 
 
+@dataclass(eq=False)
 class GeneratedList(HoldableObject):
 
     """The output of generator.process."""
 
-    def __init__(self, generator: Generator, subdir: str,
-                 preserve_path_from: T.Optional[str],
-                 extra_args: T.List[str]):
-        self.generator = generator
-        self.name = generator.exe
+    generator: Generator
+    subdir: str
+    preserve_path_from: T.Optional[str]
+    extra_args: T.List[str]
+
+    def __post_init__(self) -> None:
+        self.name = self.generator.exe
         self.depends: T.Set['CustomTarget'] = set() # Things this target depends on (because e.g. a custom target was used as input)
-        self.subdir = subdir
         self.infilelist: T.List['File'] = []
         self.outfilelist: T.List[str] = []
         self.outmap: T.Dict[File, T.List[str]] = {}
         self.extra_depends = []  # XXX: Doesn't seem to be used?
         self.depend_files: T.List[File] = []
-        self.preserve_path_from = preserve_path_from
-        self.extra_args: T.List[str] = extra_args if extra_args is not None else []
+
+        if self.extra_args is None:
+            self.extra_args: T.List[str] = []
 
         if isinstance(self.generator.exe, programs.ExternalProgram):
             if not self.generator.exe.found():
@@ -2712,6 +2701,7 @@ class Jar(BuildTarget):
             return ['-cp', os.pathsep.join(cp_paths)]
         return []
 
+@dataclass(eq=False)
 class CustomTargetIndex(HoldableObject):
 
     """A special opaque object returned by indexing a CustomTarget. This object
@@ -2720,11 +2710,12 @@ class CustomTargetIndex(HoldableObject):
     the sources.
     """
 
-    def __init__(self, target: CustomTarget, output: str):
+    target: CustomTarget
+    output: str
+
+    def __post_init__(self) -> None:
         self.typename = 'custom'
-        self.target = target
-        self.output = output
-        self.for_machine = target.for_machine
+        self.for_machine = self.target.for_machine
 
     @property
     def name(self) -> str:
@@ -2800,45 +2791,41 @@ class ConfigurationData(HoldableObject):
 
 # A bit poorly named, but this represents plain data files to copy
 # during install.
+@dataclass(eq=False)
 class Data(HoldableObject):
-    def __init__(self, sources: T.List[File], install_dir: str, install_dir_name: str,
-                 install_mode: 'FileMode', subproject: str,
-                 rename: T.List[str] = None,
-                 install_tag: T.Optional[str] = None,
-                 data_type: str = None):
-        self.sources = sources
-        self.install_dir = install_dir
-        self.install_dir_name = install_dir_name
-        self.install_mode = install_mode
-        self.install_tag = install_tag
-        if rename is None:
+    sources: T.List[File]
+    install_dir: str
+    install_dir_name: str
+    install_mode: 'FileMode'
+    subproject: str
+    rename: T.List[str] = None
+    install_tag: T.Optional[str] = None
+    data_type: str = None
+
+    def __post_init__(self) -> None:
+        if self.rename is None:
             self.rename = [os.path.basename(f.fname) for f in self.sources]
-        else:
-            self.rename = rename
-        self.subproject = subproject
-        self.data_type = data_type
 
+@dataclass(eq=False)
 class SymlinkData(HoldableObject):
-    def __init__(self, target: str, name: str, install_dir: str,
-                 subproject: str, install_tag: T.Optional[str] = None):
-        self.target = target
-        if name != os.path.basename(name):
-            raise InvalidArguments(f'Link name is "{name}", but link names cannot contain path separators. '
+    target: str
+    name: str
+    install_dir: str
+    subproject: str
+    install_tag: T.Optional[str] = None
+
+    def __post_init__(self) -> None:
+        if self.name != os.path.basename(self.name):
+            raise InvalidArguments(f'Link name is "{self.name}", but link names cannot contain path separators. '
                                    'The dir part should be in install_dir.')
-        self.name = name
-        self.install_dir = install_dir
-        self.subproject = subproject
-        self.install_tag = install_tag
 
+@dataclass(eq=False)
 class TestSetup:
-    def __init__(self, exe_wrapper: T.List[str], gdb: bool,
-                 timeout_multiplier: int, env: EnvironmentVariables,
-                 exclude_suites: T.List[str]):
-        self.exe_wrapper = exe_wrapper
-        self.gdb = gdb
-        self.timeout_multiplier = timeout_multiplier
-        self.env = env
-        self.exclude_suites = exclude_suites
+    exe_wrapper: T.List[str]
+    gdb: bool
+    timeout_multiplier: int
+    env: EnvironmentVariables
+    exclude_suites: T.List[str]
 
 def get_sources_string_names(sources, backend):
     '''
diff --git a/mesonbuild/envconfig.py b/mesonbuild/envconfig.py
index 3a2923b..1b5f728 100644
--- a/mesonbuild/envconfig.py
+++ b/mesonbuild/envconfig.py
@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from dataclasses import dataclass
 import subprocess
 import typing as T
 from enum import Enum
@@ -234,27 +235,15 @@ class Properties:
     def get(self, key: str, default: T.Optional[T.Union[str, bool, int, T.List[str]]] = None) -> T.Optional[T.Union[str, bool, int, T.List[str]]]:
         return self.properties.get(key, default)
 
+@dataclass(unsafe_hash=True)
 class MachineInfo(HoldableObject):
-    def __init__(self, system: str, cpu_family: str, cpu: str, endian: str):
-        self.system = system
-        self.cpu_family = cpu_family
-        self.cpu = cpu
-        self.endian = endian
-        self.is_64_bit = cpu_family in CPU_FAMILIES_64_BIT  # type: bool
+    system: str
+    cpu_family: str
+    cpu: str
+    endian: str
 
-    def __eq__(self, other: object) -> bool:
-        if not isinstance(other, MachineInfo):
-            return NotImplemented
-        return \
-            self.system == other.system and \
-            self.cpu_family == other.cpu_family and \
-            self.cpu == other.cpu and \
-            self.endian == other.endian
-
-    def __ne__(self, other: object) -> bool:
-        if not isinstance(other, MachineInfo):
-            return NotImplemented
-        return not self.__eq__(other)
+    def __post_init__(self) -> None:
+        self.is_64_bit: bool = self.cpu_family in CPU_FAMILIES_64_BIT
 
     def __repr__(self) -> str:
         return f'<MachineInfo: {self.system} {self.cpu_family} ({self.cpu})>'
diff --git a/mesonbuild/interpreterbase/decorators.py b/mesonbuild/interpreterbase/decorators.py
index 0f493f2..c6fcaa0 100644
--- a/mesonbuild/interpreterbase/decorators.py
+++ b/mesonbuild/interpreterbase/decorators.py
@@ -19,6 +19,7 @@ from .exceptions import InterpreterException, InvalidArguments
 from .operator import MesonOperator
 from ._unholder import _unholder
 
+from dataclasses import dataclass
 from functools import wraps
 import abc
 import itertools
@@ -99,10 +100,9 @@ def disablerIfNotFound(f: TV_func) -> TV_func:
         return ret
     return T.cast(TV_func, wrapped)
 
+@dataclass(repr=False, eq=False)
 class permittedKwargs:
-
-    def __init__(self, permitted: T.Set[str]):
-        self.permitted = permitted  # type: T.Set[str]
+    permitted: T.Set[str]
 
     def __call__(self, f: TV_func) -> TV_func:
         @wraps(f)
@@ -575,6 +575,7 @@ def typed_kwargs(name: str, *types: KwargInfo) -> T.Callable[..., T.Any]:
     return inner
 
 
+# This cannot be a dataclass due to https://github.com/python/mypy/issues/5374
 class FeatureCheckBase(metaclass=abc.ABCMeta):
     "Base class for feature version checks"
 
@@ -738,6 +739,7 @@ class FeatureDeprecated(FeatureCheckBase):
         mlog.warning(*args, location=self.location)
 
 
+# This cannot be a dataclass due to https://github.com/python/mypy/issues/5374
 class FeatureCheckKwargsBase(metaclass=abc.ABCMeta):
 
     @property
diff --git a/mesonbuild/mparser.py b/mesonbuild/mparser.py
index c470e29..735766e 100644
--- a/mesonbuild/mparser.py
+++ b/mesonbuild/mparser.py
@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from dataclasses import dataclass
 import re
 import codecs
 import textwrap
@@ -87,15 +88,15 @@ class BlockParseException(MesonException):
 
 TV_TokenTypes = T.TypeVar('TV_TokenTypes', int, str, bool)
 
+@dataclass(eq=False)
 class Token(T.Generic[TV_TokenTypes]):
-    def __init__(self, tid: str, filename: str, line_start: int, lineno: int, colno: int, bytespan: T.Tuple[int, int], value: TV_TokenTypes):
-        self.tid = tid                # type: str
-        self.filename = filename      # type: str
-        self.line_start = line_start  # type: int
-        self.lineno = lineno          # type: int
-        self.colno = colno            # type: int
-        self.bytespan = bytespan      # type: T.Tuple[int, int]
-        self.value = value            # type: TV_TokenTypes
+    tid: str
+    filename: str
+    line_start: int
+    lineno: int
+    colno: int
+    bytespan: T.Tuple[int, int]
+    value: TV_TokenTypes
 
     def __eq__(self, other: object) -> bool:
         if isinstance(other, str):
@@ -237,13 +238,19 @@ class Lexer:
             if not matched:
                 raise ParseException('lexer', self.getline(line_start), lineno, col)
 
+@dataclass(eq=False)
 class BaseNode:
-    def __init__(self, lineno: int, colno: int, filename: str, end_lineno: T.Optional[int] = None, end_colno: T.Optional[int] = None):
-        self.lineno = lineno      # type: int
-        self.colno = colno        # type: int
-        self.filename = filename  # type: str
-        self.end_lineno = end_lineno if end_lineno is not None else self.lineno
-        self.end_colno = end_colno if end_colno is not None else self.colno
+    lineno: int
+    colno: int
+    filename: str
+    end_lineno: T.Optional[int] = None
+    end_colno: T.Optional[int] = None
+
+    def __post_init__(self) -> None:
+        if self.end_lineno is None:
+            self.end_lineno = self.lineno
+        if self.end_colno is None:
+            self.end_colno = self.colno
 
         # Attributes for the visitors
         self.level = 0            # type: int
diff --git a/mesonbuild/msubprojects.py b/mesonbuild/msubprojects.py
index 67bfca8..4eb3632 100755
--- a/mesonbuild/msubprojects.py
+++ b/mesonbuild/msubprojects.py
@@ -1,3 +1,4 @@
+from dataclasses import dataclass, InitVar
 import os, subprocess
 import argparse
 import asyncio
@@ -94,18 +95,22 @@ class Logger:
             self.print_progress()
 
 
+@dataclass(eq=False)
 class Runner:
-    def __init__(self, logger: Logger, r: Resolver, wrap: PackageDefinition, repo_dir: str, options: 'Arguments') -> None:
+    logger: Logger
+    r: InitVar[Resolver]
+    wrap: PackageDefinition
+    repo_dir: str
+    options: 'Arguments'
+
+    def __post_init__(self, r: Resolver) -> None:
         # FIXME: Do a copy because Resolver.resolve() is stateful method that
         # cannot be called from multiple threads.
         self.wrap_resolver = copy.copy(r)
-        self.wrap_resolver.dirname = os.path.join(r.subdir_root, wrap.directory)
-        self.wrap = self.wrap_resolver.wrap = wrap
-        self.repo_dir = repo_dir
-        self.options = options
-        self.run_method: T.Callable[[], bool] = options.subprojects_func.__get__(self) # type: ignore
+        self.wrap_resolver.dirname = os.path.join(r.subdir_root, self.wrap.directory)
+        self.wrap_resolver.wrap = self.wrap
+        self.run_method: T.Callable[[], bool] = self.options.subprojects_func.__get__(self) # type: ignore
         self.log_queue: T.List[T.Tuple[mlog.TV_LoggableList, T.Any]] = []
-        self.logger = logger
 
     def log(self, *args: mlog.TV_Loggable, **kwargs: T.Any) -> None:
         self.log_queue.append((list(args), kwargs))
diff --git a/mesonbuild/wrap/wrap.py b/mesonbuild/wrap/wrap.py
index f2b59bd..80756af 100644
--- a/mesonbuild/wrap/wrap.py
+++ b/mesonbuild/wrap/wrap.py
@@ -14,6 +14,7 @@
 
 from .. import mlog
 import contextlib
+from dataclasses import dataclass
 import urllib.request
 import urllib.error
 import urllib.parse
@@ -203,13 +204,15 @@ def verbose_git(cmd: T.List[str], workingdir: str, check: bool = False) -> bool:
     except mesonlib.GitException as e:
         raise WrapException(str(e))
 
+@dataclass(eq=False)
 class Resolver:
-    def __init__(self, source_dir: str, subdir: str, subproject: str = '', wrap_mode: WrapMode = WrapMode.default) -> None:
-        self.source_dir = source_dir
-        self.subdir = subdir
-        self.subproject = subproject
-        self.wrap_mode = wrap_mode
-        self.subdir_root = os.path.join(source_dir, subdir)
+    source_dir: str
+    subdir: str
+    subproject: str = ''
+    wrap_mode: WrapMode = WrapMode.default
+
+    def __post_init__(self) -> None:
+        self.subdir_root = os.path.join(self.source_dir, self.subdir)
         self.cachedir = os.path.join(self.subdir_root, 'packagecache')
         self.wraps = {} # type: T.Dict[str, PackageDefinition]
         self.provided_deps = {} # type: T.Dict[str, PackageDefinition]