make error explicit in double_protocol_wrong.py

and other minor fixes

Author: ramalho

Diff for: .gitignore

@@ -1,3 +1,5 @@
+.idea/
+
 # Byte-compiled / optimized / DLL files
 __pycache__/
 *.py[cod]

Diff for: double/double_protocol_ok_py312.py

@@ -0,0 +1,13 @@
+from typing import Protocol
+
+
+# T = TypeVar('T')  # <1>
+
+class Repeatable(Protocol):
+    def __mul__[T](self: T, repeat_count: int) -> T: ...  # <2>
+
+
+# RT = TypeVar('RT', bound=Repeatable)  # <3>
+
+def double[RT: Repeatable](x: RT) -> RT:  # <4>
+    return x * 2

Diff for: double/double_protocol_wrong.py

@@ -2,8 +2,13 @@
 
 T = TypeVar('T')  # <1>
 
+
 class Repeatable(Protocol):
     def __mul__(self: T, repeat_count: int) -> T: ...  # <2>
 
+
 def double(x: Repeatable) -> Repeatable:  # <3>
     return x * 2
+
+
+y = double(3) + 4  # <4>

Diff for: double/double_sequence.py

@@ -1,7 +1,7 @@
-from collections import abc
+from collections.abc import Sequence
 from typing import TypeVar
 
 T = TypeVar('T')
 
-def double(x: abc.Sequence[T]) -> Sequence[T]:
+def double(x: Sequence[T]) -> Sequence[T]:
     return x * 2