[attrs] Fix incorrect handling of attrib with init=False and default

mypy/plugins/attrs.py

@@ -240,11 +240,12 @@ def _analyze_class(ctx: 'mypy.plugin.ClassDefContext', auto_attribs: bool) -> Li
     # attributes for all classes have been read, because subclasses can override parents.
     last_default = False
     for attribute in attributes:
-        if attribute.init and not attribute.has_default and last_default:
-            ctx.api.fail(
-                "Non-default attributes not allowed after default attributes.",
-                attribute.context)
-        last_default = attribute.has_default
+        if attribute.init:
+            if not attribute.has_default and last_default:
+                ctx.api.fail(
+                    "Non-default attributes not allowed after default attributes.",
+                    attribute.context)
+            last_default |= attribute.has_default
 
     return attributes
 

test-data/unit/check-attr.test

@@ -844,3 +844,16 @@ class A:
     x: int = attr.ib(factory=list)  # E: Incompatible types in assignment (expression has type "List[T]", variable has type "int")
     y: str = attr.ib(factory=my_factory) # E: Incompatible types in assignment (expression has type "int", variable has type "str")
 [builtins fixtures/list.pyi]
+
+[case testAttrsDefaultAndInit]
+import attr
+
+@attr.s
+class C:
+   a = attr.ib(init=False, default=42)
+   b = attr.ib()  # Ok because previous attribute is init=False
+   c = attr.ib(default=44)
+   d = attr.ib(init=False)  # Ok because this attribute is init=False
+   e = attr.ib()  # E: Non-default attributes not allowed after default attributes.
+
+[builtins fixtures/bool.pyi]