utils: Use dataclasses for PerMachine classes

This allows us to simplify the initializers, as well as remove our
custom repr methods.

mesonbuild/utils/universal.py

@@ -502,18 +502,18 @@ def get_prefix(self) -> str:
         return MACHINE_PREFIXES[self.value]
 
 
+@dataclasses.dataclass(eq=False, order=False)
 class PerMachine(T.Generic[_T]):
-    def __init__(self, build: _T, host: _T) -> None:
-        self.build = build
-        self.host = host
+    build: _T
+    host: _T
 
     def __getitem__(self, machine: MachineChoice) -> _T:
         return [self.build, self.host][machine.value]
 
     def __setitem__(self, machine: MachineChoice, val: _T) -> None:
         setattr(self, machine.get_lower_case_name(), val)
 
-    def miss_defaulting(self) -> "PerMachineDefaultable[T.Optional[_T]]":
+    def miss_defaulting(self) -> PerMachineDefaultable[T.Optional[_T]]:
         """Unset definition duplicated from their previous to None
 
         This is the inverse of ''default_missing''. By removing defaulted
@@ -531,20 +531,17 @@ def assign(self, build: _T, host: _T) -> None:
         self.build = build
         self.host = host
 
-    def __repr__(self) -> str:
-        return f'PerMachine({self.build!r}, {self.host!r})'
-
 
+@dataclasses.dataclass(eq=False, order=False)
 class PerThreeMachine(PerMachine[_T]):
     """Like `PerMachine` but includes `target` too.
 
     It turns out just one thing do we need track the target machine. There's no
     need to computer the `target` field so we don't bother overriding the
     `__getitem__`/`__setitem__` methods.
     """
-    def __init__(self, build: _T, host: _T, target: _T) -> None:
-        super().__init__(build, host)
-        self.target = target
+
+    target: _T
 
     def miss_defaulting(self) -> "PerThreeMachineDefaultable[T.Optional[_T]]":
         """Unset definition duplicated from their previous to None
@@ -566,15 +563,14 @@ def miss_defaulting(self) -> "PerThreeMachineDefaultable[T.Optional[_T]]":
     def matches_build_machine(self, machine: MachineChoice) -> bool:
         return self.build == self[machine]
 
-    def __repr__(self) -> str:
-        return f'PerThreeMachine({self.build!r}, {self.host!r}, {self.target!r})'
-
 
+@dataclasses.dataclass(eq=False, order=False)
 class PerMachineDefaultable(PerMachine[T.Optional[_T]]):
     """Extends `PerMachine` with the ability to default from `None`s.
     """
-    def __init__(self, build: T.Optional[_T] = None, host: T.Optional[_T] = None) -> None:
-        super().__init__(build, host)
+
+    build: T.Optional[_T] = None
+    host: T.Optional[_T] = None
 
     def default_missing(self) -> PerMachine[_T]:
         """Default host to build
@@ -585,9 +581,6 @@ def default_missing(self) -> PerMachine[_T]:
         assert self.build is not None, 'Cannot fill in missing when all fields are empty'
         return PerMachine(self.build, self.host if self.host is not None else self.build)
 
-    def __repr__(self) -> str:
-        return f'PerMachineDefaultable({self.build!r}, {self.host!r})'
-
     @classmethod
     def default(cls, is_cross: bool, build: _T, host: _T) -> PerMachine[_T]:
         """Easy way to get a defaulted value
@@ -603,11 +596,12 @@ def default(cls, is_cross: bool, build: _T, host: _T) -> PerMachine[_T]:
         return m.default_missing()
 
 
+@dataclasses.dataclass(eq=False, order=False)
 class PerThreeMachineDefaultable(PerMachineDefaultable[T.Optional[_T]], PerThreeMachine[T.Optional[_T]]):
     """Extends `PerThreeMachine` with the ability to default from `None`s.
     """
-    def __init__(self) -> None:
-        PerThreeMachine.__init__(self, None, None, None)
+
+    target: T.Optional[_T] = None
 
     def default_missing(self) -> PerThreeMachine[_T]:
         """Default host to build and target to host.
@@ -621,9 +615,6 @@ def default_missing(self) -> PerThreeMachine[_T]:
         target = self.target if self.target is not None else host
         return PerThreeMachine(self.build, host, target)
 
-    def __repr__(self) -> str:
-        return f'PerThreeMachineDefaultable({self.build!r}, {self.host!r}, {self.target!r})'
-
 
 def is_sunos() -> bool:
     return platform.system().lower() == 'sunos'