Point incompatible assignment errors to rvalue instead of lvalue (python#7569)

JukkaL · web-flow · commit e88ff4c4caa0 · 2019-09-27T15:15:27.000+03:00
This seems more logical. If there is a tuple lvalue, we point to the
incompatible tuple item.

Note that this may break some `# type: ignore` statements since
the reported line number may change (but it usually doesn't).
diff --git a/mypy/checker.py b/mypy/checker.py
@@ -1986,7 +1986,7 @@ def check_assignment(self, lvalue: Lvalue, rvalue: Expression, infer_lvalue_type
                          new_syntax: bool = False) -> None:
         """Type check a single assignment: lvalue = rvalue."""
         if isinstance(lvalue, TupleExpr) or isinstance(lvalue, ListExpr):
-            self.check_assignment_to_multiple_lvalues(lvalue.items, rvalue, lvalue,
+            self.check_assignment_to_multiple_lvalues(lvalue.items, rvalue, rvalue,
                                                       infer_lvalue_type)
         else:
             lvalue_type, index_lvalue, inferred = self.check_lvalue(lvalue)
@@ -2056,9 +2056,9 @@ def check_assignment(self, lvalue: Lvalue, rvalue: Expression, infer_lvalue_type
                         lvalue.kind is None):  # Ignore member access to modules
                     instance_type = self.expr_checker.accept(lvalue.expr)
                     rvalue_type, lvalue_type, infer_lvalue_type = self.check_member_assignment(
-                        instance_type, lvalue_type, rvalue, lvalue)
+                        instance_type, lvalue_type, rvalue, context=rvalue)
                 else:
-                    rvalue_type = self.check_simple_assignment(lvalue_type, rvalue, lvalue,
+                    rvalue_type = self.check_simple_assignment(lvalue_type, rvalue, context=rvalue,
                                                                code=codes.ASSIGNMENT)
 
                 # Special case: only non-abstract non-protocol classes can be assigned to
@@ -2196,7 +2196,7 @@ def check_compatibility_super(self, lvalue: RefExpr, lvalue_type: Optional[Type]
                 if base_static and compare_static:
                     lvalue_node.is_staticmethod = True
 
-            return self.check_subtype(compare_type, base_type, lvalue,
+            return self.check_subtype(compare_type, base_type, rvalue,
                                       message_registry.INCOMPATIBLE_TYPES_IN_ASSIGNMENT,
                                       'expression has type',
                                       'base class "%s" defined the type as' % base.name(),
diff --git a/mypy/fastparse.py b/mypy/fastparse.py
@@ -729,11 +729,14 @@ def visit_Assign(self, n: ast3.Assign) -> AssignmentStmt:
 
     # AnnAssign(expr target, expr annotation, expr? value, int simple)
     def visit_AnnAssign(self, n: ast3.AnnAssign) -> AssignmentStmt:
+        line = n.lineno
         if n.value is None:  # always allow 'x: int'
             rvalue = TempNode(AnyType(TypeOfAny.special_form), no_rhs=True)  # type: Expression
+            rvalue.line = line
+            rvalue.column = n.col_offset
         else:
             rvalue = self.visit(n.value)
-        typ = TypeConverter(self.errors, line=n.lineno).visit(n.annotation)
+        typ = TypeConverter(self.errors, line=line).visit(n.annotation)
         assert typ is not None
         typ.column = n.annotation.col_offset
         s = AssignmentStmt([self.visit(n.target)], rvalue, type=typ, new_syntax=True)
diff --git a/test-data/unit/check-columns.test b/test-data/unit/check-columns.test
@@ -81,18 +81,44 @@ y = 'hello'
 if int():
     x = 2; y = x; y += 1
 [out]
-main:4:12: error: Incompatible types in assignment (expression has type "int", variable has type "str")
+main:4:16: error: Incompatible types in assignment (expression has type "int", variable has type "str")
 main:4:24: error: Unsupported operand types for + ("str" and "int")
 
+[case testColumnsAssignment]
+class A:
+    x = 0
+
+A().x = ''  # E:9: Incompatible types in assignment (expression has type "str", variable has type "int")
+a = [0]
+a[0] = ''  # E:8: Incompatible types in assignment (expression has type "str", target has type "int")
+b = 0
+c = 0
+b, c = 0, ''  # E:11: Incompatible types in assignment (expression has type "str", variable has type "int")
+b, c = '', 0  # E:8: Incompatible types in assignment (expression has type "str", variable has type "int")
+
+t = 0, ''
+b, c = t  # E:8: Incompatible types in assignment (expression has type "str", variable has type "int")
+
+class B(A):
+    x = ''  # E:9: Incompatible types in assignment (expression has type "str", base class "A" defined the type as "int")
+[builtins fixtures/list.pyi]
+
+[case testColumnsAttributeIncompatibleWithBaseClassUsingAnnotation]
+class A:
+    x: str
+
+class B(A):
+    x: int  # E:5: Incompatible types in assignment (expression has type "int", base class "A" defined the type as "str")
+
 [case testColumnsSimpleIsinstance]
 import typing
 def f(x: object, n: int, s: str) -> None:
     if int():
-        n = x # E:9: Incompatible types in assignment (expression has type "object", variable has type "int")
+        n = x # E:13: Incompatible types in assignment (expression has type "object", variable has type "int")
         if isinstance(x, int):
             n = x
-            s = x # E:13: Incompatible types in assignment (expression has type "int", variable has type "str")
-        n = x # E:9: Incompatible types in assignment (expression has type "object", variable has type "int")
+            s = x # E:17: Incompatible types in assignment (expression has type "int", variable has type "str")
+        n = x # E:13: Incompatible types in assignment (expression has type "object", variable has type "int")
 [builtins fixtures/isinstance.pyi]
 
 [case testColumnHasNoAttribute]
@@ -247,9 +273,9 @@ class C:
 
 p: P
 if int():
-    p = C() # E:5: Incompatible types in assignment (expression has type "C", variable has type "P") \
-      # N:5: 'C' is missing following 'P' protocol member: \
-      # N:5:     y
+    p = C() # E:9: Incompatible types in assignment (expression has type "C", variable has type "P") \
+      # N:9: 'C' is missing following 'P' protocol member: \
+      # N:9:     y
 
 [case testColumnRedundantCast]
 # flags: --warn-redundant-casts
@@ -354,6 +380,6 @@ def f(x: T) -> T:
     # XXX: Disabled because the column differs in 3.8
     # aa: List[int] = ['' for x in [1]] # :22: List comprehension has incompatible type List[str]; expected List[int]
     cc = (1).bad # E:11: "int" has no attribute "bad"
-    n: int = '' # E:5: Incompatible types in assignment (expression has type "str", variable has type "int")
+    n: int = '' # E:14: Incompatible types in assignment (expression has type "str", variable has type "int")
     return x
 [builtins fixtures/list.pyi]
diff --git a/test-data/unit/check-inference-context.test b/test-data/unit/check-inference-context.test
@@ -656,10 +656,10 @@ f = lambda x: A() # type: Callable[[], A]
 f2 = lambda: A() # type: Callable[[A], A]
 class A: pass
 [out]
-main:2: error: Incompatible types in assignment (expression has type "Callable[[Any], A]", variable has type "Callable[[], A]")
 main:2: error: Cannot infer type of lambda
-main:3: error: Incompatible types in assignment (expression has type "Callable[[], A]", variable has type "Callable[[A], A]")
+main:2: error: Incompatible types in assignment (expression has type "Callable[[Any], A]", variable has type "Callable[[], A]")
 main:3: error: Cannot infer type of lambda
+main:3: error: Incompatible types in assignment (expression has type "Callable[[], A]", variable has type "Callable[[A], A]")
 
 [case testEllipsisContextForLambda]
 from typing import Callable
diff --git a/test-data/unit/check-literal.test b/test-data/unit/check-literal.test
@@ -2582,8 +2582,9 @@ class Foo:
         self.instancevar3: Final[Literal[False]] = True    # E: Incompatible types in assignment (expression has type "Literal[True]", variable has type "Literal[False]")
 
 # TODO: Fix the order in which these error messages are shown to be more consistent.
-var1 = 10                # E: Incompatible types in assignment (expression has type "Literal[10]", variable has type "Literal[4]") \
-                         # E: Cannot assign to final name "var1"
+var1 = 10                # E: Cannot assign to final name "var1" \
+                         # E: Incompatible types in assignment (expression has type "Literal[10]", variable has type "Literal[4]")
+
 
 Foo.classvar1 = 10       # E: Cannot assign to final attribute "classvar1" \
                          # E: Incompatible types in assignment (expression has type "Literal[10]", variable has type "Literal[4]")
diff --git a/test-data/unit/cmdline.test b/test-data/unit/cmdline.test
@@ -1408,8 +1408,8 @@ some_file.py:3: error: Unsupported operand types for + ("int" and "str")
          ^
 some_file.py:11: error: Incompatible types in assignment (expression has type
 "AnotherCustomClassDefinedBelow", variable has type "OneCustomClassName")
-            self.very_important_attribute_with_long_name: OneCustomClassNa...
-            ^
+    ...t_attribute_with_long_name: OneCustomClassName = OneCustomClassName()....
+                                                        ^
 some_file.py:11: error: Argument 1 to "some_interesting_method" of
 "OneCustomClassName" has incompatible type "Union[int, str, float]"; expected
 "AnotherCustomClassDefinedBelow"
diff --git a/test-data/unit/semanal-typeddict.test b/test-data/unit/semanal-typeddict.test
@@ -52,6 +52,6 @@ MypyFile:1(
       StrExpr(foo))
     AssignmentStmt:4(
       NameExpr(x)
-      TempNode:-1(
+      TempNode:4(
         Any)
       str?)))
diff --git a/test-data/unit/semenal-literal.test b/test-data/unit/semenal-literal.test
@@ -6,11 +6,11 @@ MypyFile:1(
   ImportFrom:1(typing_extensions, [Literal])
   AssignmentStmt:2(
     NameExpr(foo [__main__.foo])
-    TempNode:-1(
+    TempNode:2(
       Any)
     Literal[3]))
 
-[case testLiteralSemenalInFunction]
+[case testLiteralSemanalInFunction]
 from typing_extensions import Literal
 def foo(a: Literal[1], b: Literal["  foo  "]) -> Literal[True]: pass
 [builtins fixtures/bool.pyi]
