Report note about binary operation on the same location as error (#8936)

This way we also suppress the note when ignoring the error.

Author: JukkaL

mypy/checkexpr.py

@@ -2680,12 +2680,16 @@ def check_op(self, method: str, base_type: Type,
 
             if msg.is_errors():
                 self.msg.add_errors(msg)
+                # Point any notes to the same location as an existing message.
+                recent_context = msg.most_recent_context()
                 if len(left_variants) >= 2 and len(right_variants) >= 2:
-                    self.msg.warn_both_operands_are_from_unions(context)
+                    self.msg.warn_both_operands_are_from_unions(recent_context)
                 elif len(left_variants) >= 2:
-                    self.msg.warn_operand_was_from_union("Left", base_type, context=right_expr)
+                    self.msg.warn_operand_was_from_union(
+                        "Left", base_type, context=recent_context)
                 elif len(right_variants) >= 2:
-                    self.msg.warn_operand_was_from_union("Right", right_type, context=right_expr)
+                    self.msg.warn_operand_was_from_union(
+                        "Right", right_type, context=recent_context)
 
             # See the comment in 'check_overload_call' for more details on why
             # we call 'combine_function_signature' instead of just unioning the inferred

mypy/errors.py

@@ -405,6 +405,10 @@ def is_errors_for_file(self, file: str) -> bool:
         """Are there any errors for the given file?"""
         return file in self.error_info_map
 
+    def most_recent_error_location(self) -> Tuple[int, int]:
+        info = self.error_info_map[self.file][-1]
+        return info.line, info.column
+
     def raise_error(self, use_stdout: bool = True) -> None:
         """Raise a CompileError with the generated messages.
 

mypy/messages.py

@@ -31,7 +31,7 @@
     FuncDef, reverse_builtin_aliases,
     ARG_POS, ARG_OPT, ARG_NAMED, ARG_NAMED_OPT, ARG_STAR, ARG_STAR2,
     ReturnStmt, NameExpr, Var, CONTRAVARIANT, COVARIANT, SymbolNode,
-    CallExpr, SymbolTable
+    CallExpr, SymbolTable, TempNode
 )
 from mypy.subtypes import (
     is_subtype, find_member, get_member_flags,
@@ -145,6 +145,14 @@ def enable_errors(self) -> None:
     def is_errors(self) -> bool:
         return self.errors.is_errors()
 
+    def most_recent_context(self) -> Context:
+        """Return a dummy context matching the most recent generated error in current file."""
+        line, column = self.errors.most_recent_error_location()
+        node = TempNode(NoneType())
+        node.line = line
+        node.column = column
+        return node
+
     def report(self,
                msg: str,
                context: Optional[Context],

test-data/unit/check-errorcodes.test

@@ -736,3 +736,15 @@ class C:
     def __rsub__(self, x): pass
 
 x - C()  # type: ignore[operator]
+
+[case testErrorCodeMultiLineBinaryOperatorOperand]
+# flags: --strict-optional
+from typing import Optional
+
+class C: pass
+
+def f() -> Optional[C]:
+    return None
+
+f(  # type: ignore[operator]
+) + C()

test-data/unit/check-isinstance.test

@@ -974,8 +974,8 @@ def foo() -> Union[int, str, A]: pass
 def bar() -> None:
     x = foo()
     x + 1  # E: Unsupported left operand type for + ("A") \
-           # E: Unsupported operand types for + ("str" and "int") \
-           # N: Left operand is of type "Union[int, str, A]"
+           # N: Left operand is of type "Union[int, str, A]" \
+           # E: Unsupported operand types for + ("str" and "int")
     if isinstance(x, A):
        x.a
     else:

test-data/unit/check-unions.test

@@ -303,9 +303,9 @@ from typing import Union
 class A: pass
 def f(x: Union[int, str, A]):
     x + object() # E: Unsupported left operand type for + ("A") \
+                 # N: Left operand is of type "Union[int, str, A]" \
                  # E: Unsupported operand types for + ("int" and "object") \
-                 # E: Unsupported operand types for + ("str" and "object") \
-                 # N: Left operand is of type "Union[int, str, A]"
+                 # E: Unsupported operand types for + ("str" and "object")
 [builtins fixtures/primitives.pyi]
 
 [case testNarrowingDownNamedTupleUnion]