[mypyc] Add __repr__ to AssignmentTarget subclasses (#20258)

This makes debugging a little easier, since you can see register names
etc.

Author: JukkaL

mypyc/irbuild/targets.py

@@ -20,6 +20,9 @@ def __init__(self, register: Register) -> None:
         self.register = register
         self.type = register.type
 
+    def __repr__(self) -> str:
+        return f"AssignmentTargetRegister({self.register.name})"
+
 
 class AssignmentTargetIndex(AssignmentTarget):
     """base[index] as assignment target"""
@@ -31,6 +34,9 @@ def __init__(self, base: Value, index: Value) -> None:
         #       lvalue type in mypy and use a better type to avoid unneeded boxing.
         self.type = object_rprimitive
 
+    def __repr__(self) -> str:
+        return f"AssignmentTargetIndex({self.base!r}, {self.index!r})"
+
 
 class AssignmentTargetAttr(AssignmentTarget):
     """obj.attr as assignment target"""
@@ -48,10 +54,17 @@ def __init__(self, obj: Value, attr: str, can_borrow: bool = False) -> None:
             self.obj_type = object_rprimitive
             self.type = object_rprimitive
 
+    def __repr__(self) -> str:
+        can_borrow_str = ", can_borrow=True" if self.can_borrow else ""
+        return f"AssignmentTargetAttr({self.obj!r}.{self.attr}{can_borrow_str})"
+
 
 class AssignmentTargetTuple(AssignmentTarget):
     """x, ..., y as assignment target"""
 
     def __init__(self, items: list[AssignmentTarget], star_idx: int | None = None) -> None:
         self.items = items
         self.star_idx = star_idx
+
+    def __repr__(self) -> str:
+        return f"AssignmentTargetTuple({self.items}, {self.star_idx})"