fix various __str__ and __repr__ implementations

sx/core/expr.py

@@ -269,7 +269,7 @@ class ProxyExpr(G[T], Expr[T]):
         return put(self.__source, value, pop=pop)
 
     def __str__(self) -> str:
-        return f'${self.__name}:{self.__source}'
+        return f'${self.__name}'
 
     def __repr__(self) -> str:
         return f'${self.__name}(=> {self.__source!r})'

sx/types/seq.py

@@ -120,7 +120,7 @@ class Arr(G[T], Type[List[T]]):
 
     def __str__(self) -> str:
         if self.count is not None:
-            count = repr(self.count)
+            count = str(self.count)
         else:
             count = ''
         return f'{self.child}[{count}]'

sx/types/transforms.py

@@ -192,8 +192,9 @@ class Mapped(G[T, V], Transform[T, V]):
         super().__init__(child,
             parse=mapping.__getitem__,
             dump=reverse.__getitem__,
+            context=False,
             str=str or f'{mapping}[{child}]',
-            repr=repr or f'<{__name__}.Mapped({child!r}, {mapping!r})>'
+            repr=repr or f'{__name__}.Mapped({child!r}, {mapping!r})'
         )