Add test interactions for PP572 with --allow-redefinition

test-data/unit/check-pep572-redefinition.test

@@ -0,0 +1,72 @@
+-- Test cases for interaction with allow-redefinition flag
+-- and PEP572 (the walrus operator, :=)
+
+-- Base cases for no walrus operator usage & without flag
+[case testRedefine_noUsage]
+# flags: --allow-redefinition
+a: int
+a = 1
+a = 1.0 # E: Incompatible types in assignment (expression has type "float", variable has type "int")
+if (a == 1.0):
+    reveal_type(a) # N: Revealed type is "builtins.int"
+reveal_type(a) # N: Revealed type is "builtins.int"
+
+[builtins fixtures/float.pyi]
+
+[case testRedefine_withUsage]
+# flags: --allow-redefinition
+a: int
+b: int
+a = 1
+b = 2
+b = b + a
+reveal_type(a) # N: Revealed type is "builtins.int"
+a = 1.0
+if (a == 1.0):
+    reveal_type(a) # N: Revealed type is "builtins.float"
+reveal_type(a) # N: Revealed type is "builtins.float"
+
+[builtins fixtures/float.pyi]
+
+[case test_withUsage]
+# flags:
+a: int
+b: int
+a = 1
+b = 2
+b = b + a
+reveal_type(a) # N: Revealed type is "builtins.int"
+a = 1.0 # E: Incompatible types in assignment (expression has type "float", variable has type "int")
+if (a == 1.0):
+    reveal_type(a) # N: Revealed type is "builtins.int"
+reveal_type(a) # N: Revealed type is "builtins.int"
+
+[builtins fixtures/float.pyi]
+
+-- This should error due to no usage before attempted redefinition
+[case testRedefine_PEP572_noUsage]
+# flags: --allow-redefinition
+a: int
+a = 1
+
+if (a := 1.0): # E: Incompatible types in assignment (expression has type "float", variable has type "int")
+    reveal_type(a) # N: Revealed type is "builtins.int"
+reveal_type(a) # N: Revealed type is "builtins.int"
+
+[builtins fixtures/float.pyi]
+
+-- This should pass as 'a' is used before it is attempted to be redefined
+[case testRedefine_PEP572_withUsage]
+# flags: --allow-redefinition
+a: int
+b: int
+a = 1
+b = 2
+b = b + a
+reveal_type(a) # N: Revealed type is "builtins.int"
+
+if (a := 1.0):
+    reveal_type(a) # N: Revealed type is "builtins.float"
+reveal_type(a) # N: Revealed type is "builtins.float"
+
+[builtins fixtures/float.pyi]

test-data/unit/fixtures/float.pyi

@@ -21,13 +21,15 @@ class ellipsis: pass
 
 class int:
     def __abs__(self) -> int: ...
+    def __add__(self, other: int) -> int: ...
     def __float__(self) -> float: ...
     def __int__(self) -> int: ...
     def __mul__(self, x: int) -> int: ...
     def __neg__(self) -> int: ...
     def __rmul__(self, x: int) -> int: ...
 
 class float:
+    def __eq__(self, other: float) -> bool: ...
     def __float__(self) -> float: ...
     def __int__(self) -> int: ...
     def __mul__(self, x: float) -> float: ...