Improve error message for implicitly abstract functions (#13776)

Fixes #13770
python · Sep 30, 2022 · 7819085 · 7819085
1 parent a1eeddb
commit 7819085
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Showing 2 changed files with 7 additions and 6 deletions.
diff --git a/mypy/messages.py b/mypy/messages.py
@@ -1341,15 +1341,16 @@ def cannot_instantiate_abstract_class(
  return
  if len(attrs_with_none) == 1:
  note = (
- "The following method was marked implicitly abstract because it has an empty "
- "function body: {}. If it is not meant to be abstract, explicitly return None."
+ f"{attrs_with_none[0]} is implicitly abstract because it has an empty function "
+ "body. If it is not meant to be abstract, explicitly `return` or `return None`."
  )
  else:
  note = (
  "The following methods were marked implicitly abstract because they have empty "
- "function bodies: {}. If they are not meant to be abstract, explicitly return None."
+ f"function bodies: {format_string_list(attrs_with_none)}. "
+ "If they are not meant to be abstract, explicitly `return` or `return None`."
  )
- self.note(note.format(format_string_list(attrs_with_none)), context, code=codes.ABSTRACT)
+ self.note(note, context, code=codes.ABSTRACT)
 
  def base_class_definitions_incompatible(
  self, name: str, base1: TypeInfo, base2: TypeInfo, context: Context

diff --git a/test-data/unit/check-protocols.test b/test-data/unit/check-protocols.test
@@ -3105,14 +3105,14 @@ class NoneCompatible(Protocol):
 
 class A(NoneCompatible): ...
 A() # E: Cannot instantiate abstract class "A" with abstract attributes "f", "g", "h", "i" and "j" \
- # N: The following methods were marked implicitly abstract because they have empty function bodies: "f", "g", "h", "i" and "j". If they are not meant to be abstract, explicitly return None.
+ # N: The following methods were marked implicitly abstract because they have empty function bodies: "f", "g", "h", "i" and "j". If they are not meant to be abstract, explicitly `return` or `return None`.
 
 class NoneCompatible2(Protocol):
  def f(self, x: int): ...
 
 class B(NoneCompatible2): ...
 B() # E: Cannot instantiate abstract class "B" with abstract attribute "f" \
- # N: The following method was marked implicitly abstract because it has an empty function body: "f". If it is not meant to be abstract, explicitly return None.
+ # N: "f" is implicitly abstract because it has an empty function body. If it is not meant to be abstract, explicitly `return` or `return None`.
 
 class NoneCompatible3(Protocol):
  @abstractmethod