Use slots=True on all dataclasses. (pelme#112)

No big deal but nicer to be strict/potentially save some memory.

Author: pelme

htpy/__init__.py

@@ -129,7 +129,7 @@ def _attrs_string(attrs: Mapping[str, Attribute]) -> str:
 P = t.ParamSpec("P")
 
 
-@dataclasses.dataclass(frozen=True)
+@dataclasses.dataclass(frozen=True, slots=True)
 class ContextProvider(t.Generic[T]):
     context: Context[T]
     value: T
@@ -154,7 +154,7 @@ def encode(self, encoding: str = "utf-8", errors: str = "strict") -> bytes:
         return str(self).encode(encoding, errors)
 
 
-@dataclasses.dataclass(frozen=True)
+@dataclasses.dataclass(frozen=True, slots=True)
 class ContextConsumer(t.Generic[T]):
     context: Context[T]
     debug_name: str
@@ -183,7 +183,7 @@ class _NO_DEFAULT:
     pass
 
 
-@dataclasses.dataclass(frozen=True)
+@dataclasses.dataclass(frozen=True, slots=True)
 class Context(t.Generic[T]):
     name: str
     _: dataclasses.KW_ONLY

t.py

@@ -10,7 +10,7 @@
     from .conftest import RenderFixture
 
 letter_ctx: Context[t.Literal["a", "b", "c"]] = Context("letter", default="a")
-no_default_ctx = Context[str]("no_default")
+no_default_ctx: Context[str] = Context("no_default")
 
 
 @letter_ctx.consumer